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The concentration level of cytokeratin fragment antigen 21-1 (CYFRA21-1) can be used as an important indicator for predicting non–small cell lung cancer (NSCLC). Here, a sandwich-type electrochemical immunosensor for ultrasensitive detection of CYFRA21-1 is developed. The sensor based on a combination of gold nanoparticle (AuNPs) decorated Ti3C2Tx-MXene (Au-Ti3C2Tx) as the substrate enhancer, and toluidine blue (TB) modified AuNPs doped covalent organic framework (COF) polymer as the signal tag (TB-Au-COF). The Au-Ti3C2Tx is used to capture numerous primary antibodies and accelerate the electron transfer rate of the substrate, while the TB-Au-COF can be applied to provide a large number of signal units TB and secondary antibodies. These features of composites endow the proposed immunosensor with high sensitivity and current response to CYFRA21-1. Under optimum conditions, the immunosensor offers a wide current response for CYFRA21-1 from 0.5–1.0 × 104 pg·mL−1 with a detection limit of 0.1 pg·mL−1. Furthermore, the biosensing platform can be applied for CYFRA21-1 detection to analyze real serum samples, providing an effective and useful avenue for the applicability of Au-Ti3C2Tx and TB-Au-COF composite materials in biosensing field. [ABSTRACT FROM AUTHOR]

A fluorescence ratio sensor based on dansyl-peptide, Dansyl-Glu-Cys-Glu-Glu-Trp-NH2 (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. The sensor exhibits high selectivity and sensitivity for Ag+ over 16 metal ions in 100 mM sodium perchlorate and 50 mM 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid buffer solution by fluorescence resonance energy transfer. The 1:1 binding stoichiometry of the sensor and Ag+ is measured by fluorescence ratio response and the job's plot. The dissociation constant of the sensor with Ag+ was calculated to be 6.4 × 10−9 M, which indicates that the sensor has an effective binding affinity for Ag+. In addition, the limit of detection of the sensor for Ag+ was determined to be 80 nM, which also indicates that the sensor has a high sensitivity to Ag+. Result showed that the sensor is an excellent Ag+ sensor under neutral condition. Furthermore, this sensor displays good practicality for Ag+ detection in river water samples without performing tedious sample pretreatment, as well as for silver chloride detection. [ABSTRACT FROM AUTHOR]

In this work, a new method of CYFRA21-1 DNA (tDNA) detection based on electrochemically mediated atom transfer radical polymerization (e-ATRP) and surface-initiated reversible addition-fragmentation chain transfer polymerization (SI-RAFT) cascade polymerization and AgNP deposition is proposed. Firstly, the peptide nucleic acid (PNA) probe is captured on a gold electrode by Au-S bonds for specific recognition of tDNA. After hybridization, PNA/DNA strands provide high-density phosphate groups for the subsequent ATRP initiator by the identified carboxylate-Zr4+-phosphate chemistry. Then, a large number of monomers are successfully grafted from the DNA through the e-ATRP reaction. After that, the chain transfer agent of SI-RAFT and methacrylic acid (MAA) are connected by recognized carboxylate-Zr4+-carboxylate chemistry. Subsequently, through SI-RAFT, the resulting polymer introduces numerous aldehyde groups, which could deposit many AgNPs on tDNA through silver mirror reaction, causing significant amplification of the electrochemical signal. Under optimal conditions, this designed method exhibits a low detection limit of 0.487 aM. Moreover, the method enables us to detect DNA at the level of PCR-like and shows high selectivity and strong anti-interference ability in the presence of serum. It suggests that this new sensing signal amplification technology exhibits excellent potential of application in the early diagnosis of non-small cell lung cancer (NSCLC). [ABSTRACT FROM AUTHOR]

An ultrasensitive fluorescence biosensor for detecting cytokeratin fragment antigen 21-1 (CYFRA 21-1) DNA of non-small cell lung carcinoma (NSCLC) is designed using polysaccharide and activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) signal amplification strategy. Thiolated peptide nucleic acid (PNA) is fixed on magnetic nanoparticles (MNPs) by a cross-linking agent and hybridized with CYFRA 21-1 DNA. Hyaluronic acid (HA) is linked to PNA/tDNA heteroduplexes in the form of carboxy-Zr4+-phosphate. Subsequently, multiple 2-bromo-2-methylpropionic acid (BMP) molecules are linked with HA to initiate ARGET ATRP reaction. Finally, a large number of fluorescein o-acrylate (FA) monomers are polymerized on the macro-initiators, and the fluorescence signal is significantly amplified. Under optimal conditions, this biosensor shows a significant linear correlation between the fluorescence intensity and logarithm of CYFRA 21-1 DNA concentration (0.1 fM to 0.1 nM), and the limit of detection is as low as 78 aM. Furthermore, the sensor has a good ability to detect CYFRA 21-1 DNA in serum samples and to recognize mismatched bases. It suggests that the strategy has broad application in early diagnosis by virtue of its high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

An ultrasensitive fluorescence method for early diagnosis of lung cancer via activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) with EDTA as metal ligand was reported. In this paper, we reported a system for the ultrasensitive fluorescence detection of cytokeratin fragment antigen 21–1 DNA (CYFRA21-1 DNA) for the early diagnosis of lung cancer. The approach used electron transfer atom transfer radical polymerization (ARGET-ATRP) with ethylenediaminetetraacetic acid (EDTA) as the metal ligand. Firstly, thiolated peptide nucleic acid (PNA) was linked to aminated magnetic beads solutions (MBs) by a cross-linking agent and then hybridized with CYFRA21-1 DNA (tDNA). Subsequently, Zr4+ was introduced into the MBs by conjugating with the phosphate group of tDNA, and the initiator of ARGET-ATRP was introduced into via phosphate-Zr4+-carboxylate chemistry. Next, Cu(II)Br/EDTA was reduced to Cu(I)/EDTA by ascorbic acid (AA) to trigger ARGET-ATRP and then a large amount of fluorescein-o-acrylate (FA) molecules were grafted from the surface of the MBs, which amplified significantly the fluorescent signal. Under optimal conditions, a strong linear relationship of tDNA over the range from 0.1 fM to 1 nM (R2 = 0.9988). The limit of detection was as low as 23.8 aM (~143 molecules). The fluorescence detection based on the ARGET-ATRP strategy yielded excellent sensitivity, selectivity, outstanding anti-interference properties, and cost-effectiveness. These results indicated that this strategy has considerable potential for biological detection and early clinical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • FADH 2 was used as a catalyst for ATRP system to detect microRNA-21 for the first time. • FADH 2 as ATRP catalyst can reduce the damage of organic reagents to the sandwich structure of nucleic acids. • The mechanism of FADH 2 polymerization in ATRP was studied. • A highly specific and sensitive microRNA-21 biosensor based on FADH 2 was developed. • The applicability of the method was confirmed by the detection of microRNA-21 added to human serum. For early diagnosis of disease, ultrasensitive mircoRNA-21 detection has considerable potential. In this paper, an ultra-sensitive fluorescence detection method for microRNA was developed by atom transfer radical polymerization (ATRP). This ATRP reaction was first initiated by using flavin mononucleotide (FADH 2). The DNA probe 1 modified with amino group was fixed on the magnetic nanoparticle Fe 3 O 4 , and microRNA-21 was added to form the probe 1-microRNA-21. Another carboxy-modified DNA 2 forms a sandwich structure with the bound microRNA-21. Two terminally modified DNA types are used as microRNA probes, using complementary base pairing to form a stable super-sandwich structure between the DNA probe and the microRNA. Under optimal conditions, microRNA was detected in PBS buffer with a detection limit of 0.19 fM. And even in 10% of human serum, microRNA-21 can be detected with a detection limit of 47.8 fM. Results show that this method has high selectivity, efficiency and stability, which broad application prospect in microRNA ultra-sensitive detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vitamin B 12 is milder and more efficient as an electrically initiated catalyst; • Monomer polymerization downed the detection limit to 1.010 fM. • Polymer chains are extremely stable and can be stored for long periods of time. Vitamin B 12 being a natural catalyst in atom transfer radical polymerization (ATRP), has the advantages of mild reaction conditions, good biocompatibility and high catalytic efficiency. In this report, an electrochemical biosensor of the lung cancer biomarker microRNA-21 (miRNA-21) is designed for early screening of lung cancer with high sensitivity at the femtomolar level. In this approach, hairpin DNA with N 3 end group was first attached to the electrode surface. When miRNA-21 was present and paired with hairpin DNA, the N 3 group released and attached to the ATRP initiator through "click reaction". Through eATRP, a large number of FerrocenylMethyl Methacrylate (FcMMA) monomers polymerized into long chains for signal amplification. These long chains had a distinct electrical signal in the square wave voltammetry (SWV), which can detect RNA with high sensitivity. The limit of detection (LOD) goes down to 1.010 fM after ATRP polymerization, which is lower than that of the majority of other ultra-sensitive RNA electrochemical assays. Results also show that the vitamin B 12 -based electrochemical biosensor is highly selective and suitable for RNA detection in complex biological samples. [ABSTRACT FROM AUTHOR]

An ultrasensitive fluorescence method for early diagnosis of lung cancer via Nafion-initiated atom transfer radical polymerization (ATRP) is reported, in this paper. In the proposed method, thiolated peptide nucleic acid (PNA) is modified to amino magnetic beads (MBs) via a cross-linking agent to specifically capture target DNA (tDNA), and the initiator (Nafion) of ATRP is attached to PNA/DNA heteroduplexes based on the phosphate groups of the tDNA and sulfonate groups of Nafion via phosphate-Zr4+-sulfonate chemistry. Nafion as a macroinitiator of ATRP possesses multiple C–F active sites to initiate polymerization, and numerous polymeric chains that significantly amplify the fluorescent signal are formed. Under optimal conditions, a good linear relationship is obtained in the range of 0.1 nM–0.1 fM with correlation coefficients of 0.9975, and the detection limit is as low as 35.5 aM (∼214 molecules). The proposed strategy has several advantages of simplicity, cost-effectiveness, selectivity and sensitivity. More importantly, the anti-interference results demonstrate that the proposed Nafion-initiated ATRP strategy has great potential in bioanalytical applications. An ultrasensitive fluorescence method for early diagnosis of lung cancer via Nafion-initiated atom transfer radical polymerization (ATRP) was reported. Image 1 • Nafion, as the initiator, has multiple active sites to generate free radical and can bind more monomers. • A novel DNA detection for early diagnosis of lung cancer based on Nafion-initiated ATRP was reported for the first time. • This detection has a fairly simple, gentle, cost-effectiveness process with high selectivity and interference immunity. [ABSTRACT FROM AUTHOR]

Sensitive detection of DNA is conducive to enhance the accuracy of diseases diagnosis and risk prediction. In this work, we report the use of activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) as a novel on-chip amplification strategy for the fluorescence detection of DNA. More specifically, the target DNA was captured by the on-chip immobilized hairpin DNA probes. Upon hybridization, exposed 3′-N 3 of the hairpin was used to attach AGET ATRP initiators onto the silicon surface by click chemistry. Then, numerous fluorescent labeling linked to the end of the probes via the formation of long chain polymers of fluorescein o-acrylate, which in turn amplified the fluorescence signal for DNA detection. Under optimal conditions, it showed a good linear range from 100 fM to 1 μM in DNA detection, with the limit of detection as low as 4.3 fM. Moreover, this strategy showed good detection performance in complex real serum samples, the fluorescence intensity of 0.1 nM tDNA in 1% fetal bovine serum samples was 97.6% of that in Tris-EDTA buffer. Based on its high sensitivity, reduced cost and simplicity, the proposed signal amplification strategy displays translational potential in clinical application. Image 1 • Labeling hairpin DNA probes for fluorescence polymers can amplify DNA signals. • The linear range of the method is 100 fM to 1 μM, and the detection limit is 4.3 fM. • The strategy can distinguish single base mismatches of DNA. • The strategy showed good detection capability in serum samples. [ABSTRACT FROM AUTHOR]

Given the gigantic harmfulness of bisphenol A (BPA), a novel and ultrasensitive aptasensor, which employs the truncated BPA aptamer, click chemistry, and activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), was developed herein for the quantitative determination of BPA. Firstly, hairpin DNAs (hairpins) with a thiol at the 5′ end and an azide group at the 3′ end were conjugated with aminated magnetic beads (MBs) through heterobifunctional cross-linkers. BPA truncated aptamer (ssDNA-A) hybridizes with its complementary single-stranded DNA (ssDNA-B) to form double-stranded DNA. In the presence of BPA, ssDNA-A specifically captures BPA, and then ssDNA-B is released. Subsequently, the ssDNA-B hybridizes with hairpins to expose the azide group near the surface of the MBs. Then, propargyl-2-bromoisobutyrate (PBIB), the initiator of AGET ATRP containing alkynyl group, was conjugated with azide group of hairpins via the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Consequently, a large number of fluorescein-o-acrylate (FA) were introduced to the MBs through AGET ATRP, resulting in that the fluorescence intensity was increased dramatically. Obviously, the fluorescence intensity was especially sensitive to the change of BPA concentration, and this method can be used in quantitative determination of BPA. Under optimal conditions, a broad liner range from 100 fM to 100 nM and a low limit of detection (LOD) of 6.6 fM were obtained. Moreover, the method exhibits not only excellent specificity for BPA detection over BPA analogues but high anti-interference ability in real water sample detection, indicating that it has huge application prospect in food safety and environment monitoring. [ABSTRACT FROM AUTHOR]

Ultrasensitive aptamer fluorometric detection of gamma-interferon by dual ATRP amplification. • A new aptamer fluorometric protein sensor was fabricated by dual ATRP amplification. • This supersandwich fluorescence method has great potential in realize ultrasensitive protein (IFN-γ) detection in human serum. • This novel preparation is simple, gentle and convenient. Exploiting biological detection methods with high selectivity and sensitivity has been an urgent demand for low abundance biomolecules. Herein, an ultrasensitive aptamer fluorometric method of protein detection was fabricated via a sequential dual atom transfer radical polymerization (ATRP). For the first time, surface-initiated dual ATRP was utilized to make the fluorometric signal amplification for gamma-interferon (IFN- γ) protein assay. Two aptamers are used as protein probes, which can form a high stable and selective "aptamer/ protein/aptamer" sandwich structure. One aptamer probe is attached on superparamagnetic nanoparticle via surface self-assembled, the other one is linked with initiators of dual ATRP amplification by click chemistry formed triazole group. With large numbers of fluorescein-o-acrylate grown directly on a nanoparticle surface, a convenient "aptamer/protein/aptamer-polymer" supersandwich sensor was fabricated. Under optimal conditions, IFN- γ can be assayed with detection limit down to 0.178 fM in PBS buffer (equals to 1.072 ˣ103 IFN-γ molecules). Even in complex human serum, IFN-γ can also be detected with the limit of 1.54 fM, equals to 9.275 ˣ103 IFN-γ molecules. Results show a great potential in real ultrasensitive protein detection for its high selectivity, efficiency and stability. Besides, this proposed sensing method, which combines the advantages of superparamagnetic nanomaterial and chemically catalyzed surface-initiated dual ATRP polymerization, compared to the traditional signal amplify methods, is novel, more convenient, simpler and enzyme-free cascade amplification. [ABSTRACT FROM AUTHOR]

Abstract A novel, simple, and label-free amplification electrochemical impedance method for quantitative detection of Human T-lymphotropic virus types II(HTLV-II) via click chemistry-mediated of hairpin DNA probes (hairpins) with polymers was developed. The hairpins were firstly attached to the gold electrode surface by an S-Au bond, the azido terminals of hairpins were close to the electrode surface, which make it difficult to be approached. After hybridizing with HTLV-II, the hairpins were unfolded and experienced a big configuration change, which made the azido terminals of the hairpins available to conjugate with alkynyl-containing polymer, called P(DEB-DSDA), formed by 1,4-diacetylenebenzene (DEB) and 4,4′-Diazido-2,2′-stilbenedisulfonic acid disodium salt tetrahydrate (DSDA) via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). With amount of P(DEB-DSDA) conjugated with the hairpin probes via click polymerization, its electrochemical signal can have a great amplification. Under optimized experimental conditions, this new probe showed a low detection limit of 0.171 pM with a good liner in the range of 1 pM-1 nM. Meanwhile, the biosensor also exhibited good selectivity and reliability in detection of real serum samples, indicating that it has great application potential in clinical DNA diagnosis and detection. Graphical abstract A novel, simple, and label-free amplification electrochemical impedance method for quantitative detection of Human T-lymphotropic virus types II via click chemistry-mediated of hairpin DNA probes (hairpins) with polymers was developed. Image 1 Highlights • In absence of enzymes and nanomaterials, a novel and label-free amplification electrochemical impedance technique for the detection of HTLV-II was developed. • The DNA detection based on click-chemistry EIS amplification has considerable simplicity, label-free, cheap "green" process, highly selective and flexibility with respect to reporter design. [ABSTRACT FROM AUTHOR]

Abstract Here we report a highly selective and ultrasensitive DNA biosensor based on electrochemical atom transfer radical polymerization (ATRP) signal amplification and "Click Chemistry". The DNA biosensor was prepared by immobilizing thiol and azide modified hairpin DNAs on gold electrode surface. In the presence of target DNAs (T-DNA), hairpin probes hybridized with T-DNAs to form a duplex DNA, and the ring of hairpin DNA was opened to make azide groups accessible at 3′ ends. "Click reactions" proceeded between the azide and propargyl-2-bromoisobutyrate (PBIB) to initiate the ATRP reaction which brought a large number of ferrocenylmethyl methacrylate (FMMA) on the electrode surface. The amount of FMMA was proportional to the concentration of T-DNA and quantified by square wave voltammetry. Combining ATRP signal amplification with "Click Chemistry", the optimized DNA biosensor was capable of detecting 0.2 aM. T-DNA. The preliminary application of the developed DNA biosensor was demonstrated by detecting target DNA in spiked serum samples. The developed DNA biosensor shows great promise for the detection of gene biomarkers. Highlights • A highly selective and ultrasensitive DNA detection method was developed by utilizing electrochemical atom transfer radical polymerization (ATRP) signal amplification and click chemistry. • The optimized biosensor was capable of detecting 0.2 aM target DNA. • This signal amplification strategy can be applied for the detection of protein and other biological molecular. [ABSTRACT FROM AUTHOR]

A new Schiff base fluorescent probe, (E)-2-(2-hydroxybenzylidene) hydrazine-1-carboxamid (L), was synthesized and it exhibited solvent-directed high selectivity and sensitivity for Cu2+ and Mg2+ detections. Further, the interactions of L with Cu2+ and Mg2+ were investigated by Job's plot analysis, NMR, IR and XPS. [Display omitted] • A solvent-directed Schiff base fluorescent probe was synthesized. • The probe displayed excellent selectivity and sensitivity for Cu2+ in PBS buffer. • The probe displayed excellent selectivity and sensitivity for Mg2+ in acetonitrile. • The interactions of probe with Cu2+ and Mg2+ were characterized by NMR, IR and XPS. A solvent-directed, new Schiff base multiple correspondence fluorescent probe, (E)-2-(2-hydroxybenzylidene) hydrazine-1-carboxamid (L), was synthesized for selective sensing of Cu2+ and Mg2+ ions. L showed excellent selectivity and high sensitivity toward Cu2+ in "turn off" mode with a detection limit of 40.5 nM in 10 mM, pH = 7.0 PBS buffer. Contrary to that, when acetonitrile was used as the solvent, L exhibited highly selective and sensitive fluorescence sensing ability for Mg2+ in "turn on" mode with a detection limit of 9.5 nM. L can coordinate to Cu2+ and Mg2+ in a 1:1 molar ratio, respectively, evidenced by Job's plot analysis. Their binding modes were investigated by NMR, IR and XPS spectroscopies. Moreover, the satisfied results were obtained when L was used to detect Cu2+ and Mg2+ in real water samples. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new fluorescent DNA click reactant was fabricated by the combination of two commercial modified DNA fragments. • This supersandwich fluorescence method can realize ultrasensitive protein detection via DNA based click polymerization. • This novel preparation is simple, gentle and convenient. Abstract With the demanding of low abundance biomolecule detection increase, to develop novel signal amplification strategies and simple, convenient, sensitive sensors are necessary for ultrasensitive bioassays in disease diagnosis, drug therapy and environmental monitoring. Herein, for the first time, a new “aptamer/protein / aptamer-polymer” supersandwich fluorescence sensor for the ultrasensitive protein detection via DNA based click polymerization was fabricated. During the fabrication process, a new fluorescent DNA click reactant was prepared through a quick, gentle and spontaneous combination of two DNA fragments. Functionalized Fe 3 O 4 magnetic nanoparticles provide abundant sites due to their large surface area, and enable the sensor prepared easily, without the need for complicated synthesis and purification steps. Under optimal conditions, this proposed supersandwich strategy could detect IFN-γ protein down to 0.175 fM with a broad concentration range from 0.01 pM to 10 nM. Meanwhile, good detection limit of 1.63 fM in fetal bovine serum indicates that this convenient, sensitive and high selective sensor shows a great potential in clinical ultrasensitive protein detection. [ABSTRACT FROM AUTHOR]

In this work, a biosensor for ultrasensitive detection of glucose via electrochemically mediated atom transfer radical polymerization (eATRP) was firstly reported in the field of biosensing analysis. Firstly, 4-mercaptophenylboronic acid was immobilized onto Au electrode surface via Au S bond to recognize glucose by producing 5-membered cyclic boronic ester. Then initiators of atom transfer radical polymerization were introduced to the electrode surface by the reaction between 2-bromoisobutyryl bromide and the remaining hydroxyl groups of glucose to produce the alkyl halide initiation site. The monomer began to graft onto the electrode surface, and an electrochemical potential was applied to activate the copper catalyst for the formation of polymeric chains which were labeled numerous electroactive probes ferrocene. The square wave voltammetry was applied to monitor electrochemical signal of quantitatively labeled ferrocene. Under optimal conditions, this strategy for ultrasensitive detection of glucose presented a good linear relationship between oxidation current of ferrocene and logarithm of glucose concentrations in the range from 1.0 nM to 10 μM with an extremely low limit of detection of 0.32 nM (R 2  = 0.996). In addition, this strategy showed good specificity for glucose detection in physiological conditions and also showed high reliability in human serum. [ABSTRACT FROM AUTHOR]

Protein kinases play a pivotal role in cellular regulation and signal transduction, the detection of protein kinase activity and inhibition is therefore of great importance to clinical diagnosis and drug discovery. In this work, a novel electrochemical platform using the electrochemically mediated polymerization as an efficient and cost-effective signal amplification strategy is described for the highly sensitive detection of protein kinase activity. This platform involves 1) the phosphorylation of substrate peptide by protein kinase, 2) the attachment of alkyl halide to the phosphorylated sites via the carboxylate-Zr 4+ -phosphate chemistry, and 3) the in situ grafting of electroactive polymers from the phosphorylated sites through the electrochemically mediated atom transfer radical polymerization (eATRP) at a negative potential, in the presence of the surface-attached alkyl halide as the initiator and the electroactive tag-conjugated acrylate as the monomer, respectively. Due to the electrochemically mediated polymerization, a large number of electroactive tags can be linked to each phosphorylated site, thereby greatly improving the detection sensitivity. This platform has been successfully applied to detect the activity of cAMP-dependent protein kinase (PKA) with a detection limit down to 1.63 mU mL −1 . Results also demonstrate that it is highly selective and can be used for the screening of protein kinase inhibitors. The potential application of our platform for protein kinase activity detection in complex biological samples has been further verified using normal human serum and HepG2 cell lysate. Moreover, our platform is operationally simple, highly efficient and cost-effective, thus holding great potential in protein kinase detection and inhibitor screening. [ABSTRACT FROM AUTHOR]

A novel nanocomposite of nanoporous gold nanoparticles (np-AuNPs) functionalized with 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO) was prepared; assembled carboxyl groups on gold nanoporous nanoparticles surface were combined with TEMPO by the “bridge” of carboxylate-zirconium-carboxylate chemistry. SEM images and UV-Vis spectroscopies of np-AuNPs indicated that a safe, sustainable, and simplified one-step dealloying synthesis approach is successful. The TEMPO-np-AuNPs exhibited a good performance for the electrochemical detection of H2O2 due to its higher number of electrochemical activity sites and surface area of 7.49 m2g-1 for load bigger amount of TEMPO radicals. The TEMPO-functionalized np-AuNPs have a broad pH range and shorter response time for H2O2 catalysis verified by the response of amperometric signal under different pH and time interval. A wide linear range with a detection limit of 7.8 × 10-7 M and a higher sensitivity of 110.403 μA mM-1cm-2 were obtained for detecting H2O2 at optimal conditions. [ABSTRACT FROM AUTHOR]

Mn porphyrin provides a possibility to constitute the novel mimic catalyst with peroxidase-like activity. A simple method for preparing a novel catalyst PEI–AuNPs–Mn III PPIX, used in aqueous media, was presented in this paper. The covalent anchoring of Mn III PPIX and PEI were verified, meanwhile gold nanoparticles with the diameter less than 10 nm were dispersed uniformly and stably. The remarkable peroxidase-like catalytic activity of PEI–AuNPs–Mn III PPIX was displayed in the oxidative degradation of azo dye acid orange 7 (AO7) as the model reaction in the presence of trace of H 2 O 2 . The synergistic effects of PEI–AuNPs and Mn III PPIX on the enhancement of catalytic activity were observed at pH 2.0. Possible pathways involving in the formation of active radicals are proposed. The construction of PEI–AuNPs–Mn III PPIX nanocomposite offers a new insight into the application of Mn porphyrin upon activation of H 2 O 2 , which have potential applications in many fields. [ABSTRACT FROM AUTHOR]

The development of a convenient and efficient assay using miRNA-21 as a lung cancer marker is of great importance for the early prevention of cancer. Herein, an electrochemical biosensor for the detection of miRNA-21 was successfully fabricated under blue light excitation using click chemistry and photocatalytic atom transfer radical polymerization (photo-ATRP). By using hairpin DNA as a recognition probe, the electrochemical sensor deposits numerous electroactive monomers (ferrocenylmethyl methacrylate) on the electrode surface under the reaction of photocatalyst (fluorescein) and pentamethyldiethylenetriamine, thereby achieving signal amplification. This biosensor is sensitive, precise and selective for miRNA-21, and is highly specific for RNAs with different base mismatches. Under optimal conditions, the biosensor showed a linear relationship in the range of 10 fM ∼1 nM (R2 = 0.995), with a detection limit of 1.35 fM. Furthermore, the biosensor exhibits anti-interference performance when analyzing RNAs in serum samples. The biosensor is based on green chemistry and has the advantages of low cost, specificity and anti-interference ability, providing economic benefits while achieving detection objectives, which makes it highly promising for the analysis of complex samples. [Display omitted] • A miRNA-21 sensor based on atom transfer radical polymerization was designed. • Photo-ATRP based on catalyst fluorescein was first applied in biosensor. • The biosensor has highly sensitive to miRNA-21 with a detection limit of 1.35 fM. • The biosensor has good anti-interference ability in normal human serum. [ABSTRACT FROM AUTHOR]

[Display omitted] • RAFT fluorescent sensor for amplified detection of thrombin was first reported. • The magnetic enrichment analysis has good experimental stability. • This supersandwich method enables the detection of thrombin by RAFT polymerization. • This novel preparation method is gentle and easy to handle. Ultrasensitive protein detection has considerable potential for early diagnosis and screening of diseases. Here, based on Hemin-catalyzed surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization, this work developed an assay for ultrasensitive fluorescent biosensing of proteins and established a thrombin fluorescent sensor. First, the amino-modified aptamer 1 was immobilized on Fe 3 O 4 magnetic beads, and then thrombin was added to form the aptamer 1-thrombin bioaffinity complex. Another thiol-modified aptamer 2 binds to bound thrombin to form a sandwich structure. Fluorescein O-methacrylate was used as the monomer, acetylacetone (ACAC) as the initiator, and Hemin as the catalyst. Through Hemin-catalyzed SI-RAFT polymerization, a large number of thrombin molecules are labeled with fluorescein O-methacrylate, resulting in severalfold amplification of the fluorescent signal. By detecting the fluorescent signal in thrombin from 1.0 fM to 0.1 nM, the proposed super sandwich strategy can detect thrombin at 0.98 fM, which is lower than the detection limit of most other methods. [ABSTRACT FROM AUTHOR]

A novel dansyl-modified peptide fluorescence sensor (Dansyl-Glu-Glu-Pro-Glu-Trp-COOH) was synthesized and it exhibited a high selectivity and sensitivity for UO 2 2+ detection. Further, the interaction of the sensor with UO 2 2+ was characterized by ESI-MS, IR, XPS, Time-resolved fluorescence spectroscopy and ITC measurement [Display omitted] • A novel dansyl-modified peptide fluorescence sensor was synthesized via Fmoc solid phase peptide synthesis. • The sensor displayed an excellent selectivity and high sensitivity for UO 2 2+ detection by turn off fluorescence response. • The interaction of the sensor with UO 2 2+ was characterized by ESI-MS, IR, XPS and Time-resolved fluorescence spectroscopy and ITC measurement. • The sensor showed good practicality for UO 2 2+ detection in lake water sample. It is of great significance to sensitively and selectively detect uranyl ion (UO 2 2+) in environmental and biological samples due to the high risks of UO 2 2+ to human health. However, such suitable sensors are still scarce. A novel fluorescence sensor based on a dansyl-modified peptide, Dansyl-Glu-Glu-Pro-Glu-Trp-COOH (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. As the first linear peptide-based fluorescence sensor for UO 2 2+, D-P5 exhibited high selectivity and sensitivity to UO 2 2+ over 27 metal ions (UO 2 2+, Cr3+, Cu2+, Ba2+, Hg2+, Pb2+, Co2+, Ag+, Fe3+, Ca2+, K+, Mg2+, Mn2+, Na+, Ni2+, Cd2+, Zn2+, Al3+, Dy3+, Er3+, Gd2+, Ho3+, La3+, Lu3+, Pr3+, Sm3+, Tm3+) by a turn-off fluorescence response in 10 mM HEPES buffer (pH 6.3). The effects of anions such as S2−, NO 3 –, SO 4 2− CO 3 2–, HCOO–, antioxidant ascorbic acid and 4-nitrophenyl acetate on the selectivity for UO 2 2+ detection were also studies. D-P5 sensor could be used for detecting UO 2 2+ in a good linear relationship with concentration in the range of 0–8.0 μM with a low limit of detection of 83.2 nM. Furthermore, the interaction of the sensor with UO 2 2+ was characterized by ESI-MS, IR, XPS and ITC measurements. The 1:1 binding stoichiometry between the sensor and UO 2 2+ was measured by the job's plot and further verified by ESI-MS. The binding constant of the sensor with UO 2 2+ was calculated to be 9.8 × 104 M−1 by modified Benesi-Hildebrand equation. ITC results showed that the ΔHθ and ΔSθ for the interaction of D-P5 with UO 2 2+ were −(7.167 ± 1.25) kJ·mol−1 and 66.5 J·mol−1·K−1, respectively. Time-resolved fluorescence spectroscopy indicated that the mechanism of fluorescence quenching of D-P5 by UO 2 2+ ion was static quenching process. In addition, this sensor displayed a good practicality for UO 2 2+ detection in lake water sample without tedious sample pretreatment. [ABSTRACT FROM AUTHOR]

Convenient and sensitive detection of biomolecules is of utmost importance in the field of early disease screening. In this study, a Rose Bengal-Mediated photoinduced atom transfer radical polymerization (photoATRP) method was used to achieve highly sensitive detection of target DNA (tDNA). The tDNA was specifically recognized using PNA with terminal modified sulfhydryl groups, and the initiator α-bromophenylacetic acid (BPAA) was attached to the electrode surface via a phosphate-Zr4+-carboxylate acid structure. Under the excitation of blue light, rose bengal (RB) acts as a photocatalyst, β-nicotinamide adenine dinucleotide (NADH) as an electron donor, and ferrocenylmethyl methacrylate (FMMA) as a monomer to activate the photoATRP reaction and generate a large number of electroactive polymer chains on the electrode surface. Under optimal conditions, the method can be used for the quantitative analysis of tDNA in the concentration range of 1–105 fM (R2 = 0.994) with a limit of detection (LOD) of 0.115 fM. This metal-free mediated photoATRP biosensor, with low cost and environmental friendliness, has great potential in the field of highly sensitive biomolecule detection. [Display omitted] • Rose bengal as a novel organic photocatalyst in an electrochemical sensor for high sensitivity detection of DNA. • The method has good linearity in the range of 1-105 fM in 5 μL of sample with detection limits as low as 0.115 fM. • This Metal-free photoATRP method has great potential in the analysis of biological samples due to its non-pollution, low cost, high specificity and high anti-interference ability. [ABSTRACT FROM AUTHOR]

Exosomes, as a kind of tumor biomarker, are often found at elevated levels above normal in the blood of cancer patients, making highly sensitive exosome testing important for monitoring the development and progression of cancer. In this work, an ultra-sensitive and specific fluorescence method for exosome assays was constructed on the basis of atom transfer radical polymerization (ATRP) technique. Firstly, two recognition units, the CD63 aptamer and the EGFR antibody, can specifically bind to exosomes to form a sandwich structure, which endows the proposed sensor with excellent selectivity through two specific recognitions. Secondly, activator regenerated by electron transfer ATRP (ARGET ATRP) polymerization amplification method can introduce a huge amount of the fluorescent monomers into the sensing system, leading to a marked rise in sensitivity. Under optimal experimental conditions, a clear linear relationship between the logarithm of the fluorescence intensity and the concentration of exosomes in the range of 5 × 104 exosomes/mL to 5 × 109 exosomes/mL was obtained. The limit of detection (LOD) was as low as 11,610 exosomes/mL. Furthermore, this sensor exhibited good selectivity and stability, and excellent immunity to interference, providing a new method for the detection of exosomes. The exosome detection strategy used in this system provides a new idea for effective detection of lung cancer at an early stage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • TEMPO/Cu(acac) 2 /TMB system was used for the first time to determine GSH. • TEMPO was catalyzed to produce TEMPO+ and replaced the role of highly toxic H 2 O 2. • The mechanism of TEMPO+ oxidation of TMB was studied. • The TEMPO − based method developed improves sensitivity in a well-specific manner. • The applicability of this method was confirmed by detecting GSH added to human serum. In this work, a new colorimetric method for the determination of Glutathione (GSH) on the basis of stable free radical 2,2,6,6 − tetramethylpiperidine − 1 − oxyl (TEMPO) oxidation of 3,3′,5,5′−tetramethylbenzizine (TMB) via copper(II) acetylacetonate (Cu(acac) 2) catalysis was proposed. TEMPO was catalyzed by Cu(acac) 2 to produce TEMPO+, then TEMPO+ oxidized TMB to produce oxidized TMB (ox − TMB). The resulting ox − TMB showed blue and possessed a distinct absorption peak about 650 nm. Whereas, GSH prohibited the generation of ox − TMB through inhibiting TMB oxidation. As compared to the case that GSH was absent, significantly enhanced absorption was determined, and was proportional to GSH amount. On this basis, a qualitative and quantitative detection method of GSH with the naked eye and the microplate reader was achieved. The developed TEMPO − based method achieved GSH biosensing with improved sensitivity in a good specificity − manner. The limit of detection (LOD) was 90 μM via naked eye, and the microplate reader was 4.71 μM. And the stable free radical TEMPO possessed higher stability and lower toxicity than traditional oxidant of H 2 O 2. Moreover, this TEMPO − based method achieved good results in the detection of GSH in human serums. [ABSTRACT FROM AUTHOR]

Exosome is an emerging tumor marker, whose concentration level can reflect the occurrence and development of tumors. The development of rapid and sensitive exosome detection platform is of great significance for early warning of cancer occurrence. Here, a strategy for electrochemical detection of A549-cell-derived exosomes was established based on DNA/ferrocene-modified single-walled carbon nanotube complex (DNA/SWCNT-Fc). DNA/SWCNT-Fc complexes function as a signal amplification platform to promote electron transfer between electrochemical signal molecules and electrodes, thereby improving sensitivity. At the same time, the exosomes can be attached to DNA/SWCNT-Fc nanocomposites via the established PO 4 3--Ti4+-PO 4 3- method. Moreover, the application of EGFR antibody, which can specifically capture A549 exosomes, could improve the accuracy of this sensing system. Under optimal experimental conditions, the biosensor showed good linear relationship between the peak current and the logarithm of exosomes concentration from 4.66 × 106 to 9.32 × 109 exosomes/mL with a detection limit of 9.38 × 104 exosomes/mL. Furthermore, this strategy provides high selectivity for exosomes of different cancer cells, which can be applied to the detection of exosomes in serum samples. Thus, owing to its advantages of high sensitivity and good selectivity, this method provides a diversified platform for exosomes identification and has great potential in early diagnosis and biomedical applications. Electrochemical modification process and electrochemical exosome detection principle based on DNA/SWCNT-Fc nanoamplification. [Display omitted] • A novel method for exosome detection based on DNA/ferrocene-modified single-walled carbon nanotube complex. • The limit of detection of this sensor is as low as 9.38 × 104 exosomes/mL. • The proposed sensor has the advantages of high sensitivity, high selectivity, simplicity and low cost. • This strategy may have great potential for biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The use of hemoglobin (Hb) to drive atom transfer radical polymerization (ATRP) process (Hb-ATRP) for detection of lung cancer related nucleic acid is firstly reported. Hb does not need to be treated prior to using indicating the potential for synthetic engineering in complex biological microenvironments without the need for in vitro techniques. Here, we report a new signal amplification strategy using Hb-mediated graft of nitronyl niroxide monoradical polymers as a signal-on electrochemical biosensor for ultralow level DNA highly selective detection. Building DNA biosensors includes: (i) the fixation of peptide nucleic acid (PNA) probe (no phosphate group) via the 5′ terminus-SH; (ii) the modification of transition metal; (iii) Site-specific markers of Hb-ATRP promoter, and (iv) the grafting of polymers with electrochemical signal by Hb-ATRP process. Through the Hb-ATRP process of nitronyl nitroxide monoradical (TEMPO), the presence of a small amount of DNA can eventually result in calling a certain number of TEMPO redox tags. Obviously, the Hb-ATRP is a method of easy source of raw materials, simple operation and no need for complex equipment. The constructed biosensor, as expected, is highly selective and sensitive to target DNA. The detection limit can be calculated as 15.96 fM under optimal conditions. The excellent performance also shows that the constructed DNA biosensor is suitable for DNA screening and DNA concentration determination in complex sample matrix. [ABSTRACT FROM AUTHOR]

[Display omitted] • RAFT sensor for the amplified detection of cocaine was firstly reported. • Combining RAFT with host–guest interaction for the first time. • This biosensor was successfully achieved in biological samples. In this study, we reported a novel amplification method based on thermally mediated surface − initiated reversible addition − fragmentation chain transfer (SI–RAFT) and host–guest chemistry for electrochemical analysis of cocaine. Firstly, the NH 2 –DNA probes were fixed on the surface of the indium tin oxide (ITO) electrode by addition reaction with 1,4–phenylenediisothiocyanate (PDITC). Then the NH 2 –DNA could specifically recognize target cocaine, and the Ferrocene–DNA (Fc–DNA) probes was connected to the ITO electrode also by specifically binding with cocaine. Next, β–CD–Br 15 was fixed on the surface of the ITO by host–guest interaction between Fc and β–cyclodextrin (β–CD). Finally, ferrocenylmethyl methacrylates (FcMMA) were grown on the surface of ITO via SI–RAFT to form polymer, and then the obtained electrode was measured by square wave voltammetry (SWV). The intensity of signal and the logarithm of cocaine concentration has a good linear relationship in the range of 0.01 ng/mL to 1 µg/mL (R2 = 0.9963), and the detection limit can go down to 0.003 ng/mL (S/N = 3). Moreover, this strategy is appropriate for illegal drugs detection and possess good anti–interference ability for the detection of cocaine in serum samples. [ABSTRACT FROM AUTHOR]

In this work, it came up a hydrophilic and stable nitronyl nitroxide monoradical 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl freeradical (MATMP) as new monomer of polymerization for DNA detection. The detection limit was over 1,000,000 times lower than 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivatives as electrochemical labels alone. Within this approach, a single biomolecule can be converted into the strong electrochemical signal, therefore lung cancer DNA can be detected at low concentration. For the first step, the HS-PNA probe was fixed on the surface of the Au electrode. After the target DNA was captured by complementary base pairing, 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPAD), chain transfer agent of RAFT polymerization, was bonded to target DNA as reaction via coordination bond of Zr4+. Electroactive polymers had grown by means of surface initiated thermally RAFT polymerization with MATMP as monomer. MATMP polymer significantly improves the electrochemical signal. This method can detect DNA from 0.01 fM to 10 pM, and detection limit is 1.51 aM. The sensitivity of this method is greater than that in most other reported signal amplification strategies of DNA biosensor, which indicates that it is appropriate for single nucleotide polymorphism analysis and will broaden prospects for biological molecules detection application. Schematic diagram illustrating lung cancer relevant sample that can be monitored using thermally initiated RAFT polymerization DNA biosensor analysis techniques. [Display omitted] • Stable nitronyl nitroxide monoradical MATMP polymer is firstly applied for DNA detection. • The biosensor detection limit is more than 1,000,000 times lower than TEMPO derivatives as electrochemical labels alone. • The proposed method can detect DNA from 0.01 fM to 10 pM, and detection limit is 1.51 aM. [ABSTRACT FROM AUTHOR]

Herein we designed a highly sensitive and selective biosensor for methamphetamine (METH) detection based on aptamer recognition probe and atom transfer radical polymerization (ATRP) signal amplification strategy. In this experiment, METH aptamer and its complementary DNA strand were first attached to the electrode surface. In the presence of METH, the prioritized conjugation between METH and the aptamer will take one strand of DNA from the double-stranded DNA, so that the third segment of azide-modified DNA could be successfully modified onto the electrode surface. Through click chemistry and ATRP polymerization, the monomers with ferrocene were polymerized into a long chain, and the signal was amplified, then high-sensitivity detection of METH can be carried out. The result showed that the sensor could detect METH as low as 17 fM, which is about two orders of magnitude lower than that by traditional METH detection methods. Moreover, when different concentrations of METH were added to serum and urine, the recovery rate of the biosensor was as high as 93%. Therefore, using nucleic acid aptamer as capture probe and ATRP as signal amplification strategy can provide a promising application platform for sensitive detection of low concentration toxicants. [Display omitted] • A highly sensitive and selective electrochemical METH biosensor has been described. • The eATRP polymerization combined with click chemistry has been exploited for detecting METH in serum and urine. • The optimized biosensor was capable of detecting 17 fM METH. [ABSTRACT FROM AUTHOR]

Ultrasensitive detection of biomarkers at an early stage is generally limited by external influence factors such as high reaction temperature, complex operations, and sophisticated instruments. Here, we circumvent these problems by using nicotinamide adenine dinucleotide (NAD+) to control electroinitiated reversible addition fragmentation chain transfer (electro−RAFT) polymerization for biosensing that enables the detection of a few molecules of target DNA. In this coenzyme−catalyzed electro−RAFT polymerization, numerous ferrocenylmethyl methacrylate (FCMMA) as monomer with electrochemistry signal were linked to the biomarker on Au electrode. Afterwards, a strong oxidation peak appears at the potential of about 0.3 V that represents a typical oxidation potential of FCMMA. The sensitivity of this methodology was presented by detecting DNA from 10−1 to 104 fM concentration and detection limit (LOD) being down to 4.39 aM in 10 μL samples. This is lower by factors than detection limits of most other ultra−sensitive electrochemical DNA assays. [Display omitted] • The nicotinamide adenine dinucleotide (NAD+) is novel to apply in electrochemical biosensing for the detection of DNA. • We detect DNA from 10−1 to 104 fM concentration and the detection limit is as low as 4.39 aM in 10 μL samples. • This platform has the advantages of low background signals, high selectivity, simple preparation and cost effectiveness. [ABSTRACT FROM AUTHOR]

The detection of trace tumor-related serum miRNA biomarkers is in great demand for the early diagnosis of cancer. Herein, for the first time, an electrochemical sensing platform based on atom transfer radical polymerization (ATRP) signal amplification strategy for ultrasensitive determination of the breast and prostate cancer marker miRNA-141 has been developed. The hairpin DNAs were immobilized on the benzoic acid modified electrode to capture the target miRNA-141, the recognition of miRNA-141 released thiol groups on the end of probes, followed by the association of ATRP initiators modified gold nanoparticles with thiol groups, and then triggered the polymerization on electrode surface, causing a great number of ferrocene (Fc) signal molecules grafted on the sensor interface. As a result, the electrochemical signal intensity of signal molecule has been greatly increased. The proposed biosensor has a linear range from 10 pM to 10 aM with a detection limit of 3.23 aM for miRNA-141, opening a new and promising path for ultrasensitive analysis of tumor-related miRNAs. [Display omitted] • The AGET ATRP signal amplification strategy was introduced for miRNA-141 detection for the first time. • The proposed signal amplification strategy provides a new way for the analysis of other tumor-related miRNA biomarkers. • Compared with other methods, our signal amplification strategy has higher sensitivity. [ABSTRACT FROM AUTHOR]

As an important hydrolytic enzyme, abnormal activity of alkaline phosphatase (ALP) is closely associated with a variety of diseases. It has been identified as an important diagnostic indicator for clinical hepatobiliary and bone diseases. Herein, a novel electrochemical sensor based on signal amplification strategy through ring-opening polymerization (ROP) has been developed to assay of ALP activity. First of all, 3-mercaptopropanoic acid (MPA) was employed as a cross-linking agent to attach O -phosphoethanolamine to the electrode surface via amide bond. Then, ALP catalyzed the hydrolysis of phosphate monoester structures to hydroxyl groups, which could initiate ROP reaction. The polymer grafted on the electrode surface contains a large number of ferrocene electroactive molecules, which effectively increased the signal output of the electrochemical sensor and improved the sensitivity of ALP activity detection. Under optimum conditions, this electrochemical sensor rendered a satisfactory linear dependence over the range from 20 to 120 mU mL−1, with a low detection limit of 0.66 mU mL−1. Furthermore, this strategy presented satisfactory selectivity and interference resistance in human serum sample, and compared with clinical data, the relative error of the results obtained by this method was less than 5%. Thus, this method showed considerable potential for the detection of ALP activity in clinical application. A novel electrochemical sensor for alkaline phosphatase activity detection based on ring-opening polymerization signal amplification strategy. [Display omitted] • We presented a novel biosensor for alkaline phosphatase activity detection. • The first use of ROP signal amplification technique for ALP activity detection. • It was highly specific and showed acceptable analytical reliability in serum samples. [ABSTRACT FROM AUTHOR]

Schematic illustration of electrochemical detection biosensor of exosomes based on C 60 -Au-Tb as signal marker. [Display omitted] • A novel approach based on C 60 -Au-Tb for exosome detection is developed for the first time. • The limit of detection of this sensor is as low as 2.67 × 104 exosomes/mL. • The proposed sensor has the advantages of high sensitivity, high selectivity, simplicity and low cost. • This strategy may hold great potential in biomedical research and clinical diagnosis. As a new serum biomarker, the sensitive detection of exosomes is significant for the early diagnosis of diseases. In this paper, a novel electrochemical biosensor for the sensitive detection of exosomes was constructed utilizing a novel C 60 hybrid as a tracer. Firstly, the epidermal growth factor receptor (EGFR) antibody was immobilized on the electrode surface via Au-NH 2 bonding with Nafion AuNPs substrate. After specific capture of exosomes, C 60 -Au-Tb was grafted onto the surface of exosomes through "carboxyl-Zr4+-phosphate" chemistry, causing a change in the current signal. Under the optimal conditions, there was a linear relationship between the SWV signal and the logarithm of exosomes concentration from 5 × 104 exosomes/mL to 5 × 109 exosomes/mL, and the detection limit was 2.67 × 104 exosomes/mL. In addition, the biosensor had the advantages of high specificity, strong anti-interference ability, good repeatability, and stability. In conclusion, this method had great potential in diagnosing early cancers associated with exosomes. [ABSTRACT FROM AUTHOR]

Cocaine (Coc) is one of the illegal drugs and is harmful to digestive, immune, cardiovascular and urogenital systems. To achieve drug abuse control and legal action, it is essential to develop an effective method for cocaine analysis. In this work, an aptasensor has been developed using atom transfer radical polymerization (ATRP) based on host−guest chemistry for electrochemical analysis of cocaine. The NH 2 −DNA (Apt1) was immobilized on the indium tin oxide (ITO) electrode via addition reaction, and Fc−DNA (Apt2) was introduced to ITO relying on the specific recognition of cocaine. The Apt2 can initiate host−guest chemistry between Apt2 and ATRP initiators (β−CD−Br 15), then the β−CD−Br 15 further triggers ATRP. Moreover, ATRP avoids the sluggish kinetics and poor coupling capability sustained. The result shows a sensitive and selective analysis of cocaine within a linear range from 0.1 ng/mL to 10 μg/mL (R2 = 0.9985), with the detection limit down to 0.0335 ng/mL. Thus, this strategy provides a universal method for the analysis of illegal drugs. [Display omitted] • Firstly, it was reported for cocaine detection based on host−guest chemistry and atom transfer radical polymerization (ATRP). • Ultra-high efficiency was discovered in the synthesized macroinitiator β−CD−Br 15. • This biosensor was successfully achieved in biological samples. [ABSTRACT FROM AUTHOR]

Exosomes, as a biomarker with enhancing tumor invasion and spread, play an essential role for lung cancer diagnosis, therapy, and prognosis. In this work, a novel electrochemical sensor was fabricated for detecting exosomes secreted by lung cancer cells based on polysaccharide-initiated ring-opening polymerization (ROP) and click polymerization. First, MPA formed a self-assembled monolayer on the gold electrode surface, and then anti-EGFR was immobilized on the electrode surface by amide bond. Subsequently, a lot of phosphate groups were introduced by the specific recognition between anti-EGFR and exosomes, then sodium alginate grafted Glycidyl propargyl ether (SA- g -GPE) prepared via ROP was attached to the exosomes through PO 4 3-Zr4+-COOH coordination bond. After that, click polymerization was initiated by alkyne groups on the SA- g -GPE polymerization chain to realize highly sensitive detection of A549 exosomes. Under the optimum conditions, the fabricated sensor showed a good linear relationship between the logarithm of exosomes concentration and peak current in the range of 5 × 103 - 5 × 109 particles/mL, and the limit of detection (LOD) was as low as 1.49 × 102 particles/mL. In addition, this method had the advantages of high specificity, anti-interference, high sensitivity, simplicity, rapidity and green economy, which proposed a novel avenue for the detection of exosomes, and also had potential applications in early cancer diagnosis and biomedicine. [Display omitted] • A novel electrochemical sensor is developed for the detection of lung cancer exosomes. • A limit of detection of 1.49 × 102 particles/mL is achieved based on polysaccharide-initiated ROP and click polymerization. • The proposed sensor shows high sensitivity, selectivity, simple , green and economical. • This sensor holds great potential in early diagnosis of lung cancer and biomedical research. [ABSTRACT FROM AUTHOR]

We reported an electrochemical biosensor via CuFe 2 O 4 -enhanced photoinitiated chain-growth polymerization for ultrasensitive detection of lung cancer-related gene. In this work, photoinitiated atom transfer radical polymerization (ATRP) was applied to amplify the electrochemical signal corresponding to lung cancer-related gene, and polymerization was triggered off under the illumination of blue light which was involved in copper-mediated reductive quenching cycle. At the same time, CuFe 2 O 4 –H 2 O 2 system was also activated to enhance polymerization based on the photocatalysis of CuFe 2 O 4 , which was based on the reaction between •OH and methacrylic monomers to generate carbon-based radicals. Numerous ferrocene-based polymer was graft onto electrode surface through this amplification stages. The limit of detection was low to 1.98 aM (in 10 μL, ∼11.9 molecules) (R2 = 0.998) with a wide linear range from 0.1 fM to 10 pM. This strategy made a good trade-off between cost-effectiveness and sensitivity, and it also presented a high selectivity and anti-interference. In addition, the operation was greatly simplified and detection time was also shortened, which endowed this electrochemical DNA biosensor great application potential. [Display omitted] • A copper ferrite-enhanced electrochemical biosensor was constructed for lung cancer-related gene detection. • Photoinitiated chain-growth polymerization via photocatalysis of copper ferrite was first designed to detect biomolecules. • This biosensor has great potential for portable detection equipment. [ABSTRACT FROM AUTHOR]

• The immunoassay based on the PCL-PEO block copolymer has been firstly used to detect CYFRA. • The method possesses real time monitor, simple operation, high sensitivity and selectivity. • The strategy provides a new approach for early clinical diagnosis. As importance of early diagnosis, prognosis, and clinical monitoring in improving survival rate of lung cancer is increasing, the advance of effective diagnostic method for tumor marker is crucial. Herein, linear poly(ε -caprolactone)- b -poly(ethylene oxide) (PCL-PEO) copolymer with hydrophilic property is applied to detect CYFRA 21-1 in label-free electrochemical immunoassay. 4-(2-trimethylsilylethynyl)benzoic acid (TEB) as "bridge" bond first connects initial antibody to the surface of gold electrode. Then one side of CYFRA 21-1 antigen can recognize with initial antibody of electrode interface, and the other side hybridize specifically secondary antibody grafted PCL-PEO copolymer. So far we have constructed a complete immunoassay for CYFRA 21-1 detection using electrochemical impedance spectroscopy. The sensitivity and selectivity of analytical method depend on "Au–C" bonding, specific recognition of "antibody-antigen–antibody sandwich", and PCL-PEO copolymer. Under optimal conditions, the analytical method for quantitative detection of CYFRA 21-1 manifests a broad linear range (1 pg/mL–10 ng/mL) and a low detection limit (0.125 pg/mL, about 3.47 × 10-15 M). Furthermore, according to the analysis results in clinical samples, the constructed strategy also shows satisfactory sensitivity and anti-interference. It indicates that the immunoassay has broad promising applications for expecting to be applied in practical clinical prevention and monitoring. [ABSTRACT FROM AUTHOR]

• The eATRP signal amplification strategy was used to detect MMP-2 for the first time. • The eATRP signal amplification method provides a new idea for other MMPs analysis. • The detection limit of MMP-2 was as low as 0.53 fM. In this paper, a peptide-based biosensor was developed for sensitive and selective analysis of matrix metalloproteinase 2 (MMP-2) through a signal amplification strategy of electrochemically mediated atom transfer radical polymerization (eATRP). Briefly, α-bromophenylacetic acid (BPAA) initiators were connected to the end of the MMP-2 specific peptide, and then ATRP reaction was carried out with ferrocenylmethyl methacrylates (FMMA) monomers under the action of copper activators to obtain the polymers of Fc. The presence of target MMP-2 caused the part of peptides were specifically cleaved, and the electrochemical signal decreased of Fc. As a result, there was a linear relationship between Fc signal change value and MMP-2 concentration at 8 fM to 80 pM range. The MMP-2 detection limit was calculated as low as 0.53 fM, which was much lower than that in the reported literatures. The proposed peptide-based biosensor showed a good performance for the determination of MMP-2 in human serum samples. This highly efficient and simple method would have great potential in the clinical analysis of matrix metalloproteinase. [ABSTRACT FROM AUTHOR]

Cytokeratin fragment antigen 21-1 (CYFRA 21-1) DNA is perceived as sensitive tumor marker for the diagnosis of non-small cell lung cancer and other tumor. Herein, linear chain poly(ε-caprolactone) (PCL) synthesized by ring-opening polymerization is applied to ultrasensitive label-free electrochemical impedance detection system for CYFRA 21-1 DNA. First, thiolated peptide nucleic acid (PNA) is self-assembled into the Au electrode surface through the formation of Au–S bonds, allowing the PNA to act as biomolecular probe and form PNA/DNA heteroduplex with the target DNA via specific hybridization. Then, PCL is conjugated to the immobilized DNA on the electrode via "carboxylate–Zr4+–phosphate" bridges. Finally, the electrochemical response of modified PNA/DNA/Zr4+/PCL electrode is determined by electrochemical impedance method to quantify of CYFRA 21-1 DNA. Under optimal conditions, this method exhibits highly sensitivity with a broad linear range (0.1 fM – 1 nM) (R 2 = 0.995) and the limit of detection (LOD) is as low as 10.73 aM, which is equivalent to just 64 molecules in a 10 μL sample. What's more, the high selectivity, good anti-interference, label-free operation, and real-time monitoring in complex samples of the proposed strategy demonstrate its broad application for the early diagnosis and clinical monitoring. A novel, label-free, real-time, and highly sensitive EIS detection system for quantitatively detecting CYFRA 21-1 DNA based on PCL polymer was developed. Image 1 • The combination of ROP and EIS biosensing has been firstly used in the detection of small biological molecules. • The EIS method possesses real time monitor, label-free analysis, simple operation, high sensitivity and selectivity. • The strategy provides a new approach for early clinical diagnosis of lung cancer. [ABSTRACT FROM AUTHOR]

Cytokeratin fragment antigen 21–1 (CYFRA21-1), a characteristic biomarker of non-small cell lung cancer (NSCLC), its abundance is closely related to the diagnosis and prognosis of the disease. Thus, an ultrasensitive electrochemical immunosensor for the detection of CYFRA21-1 was designed by exploiting reversible addition-fragmentation chain transfer (RAFT) polymerization signal amplification strategy. Briefly, graphene oxide (GO) was immobilized on a glassy carbon electrode (GCE) surface to bind a CYFRA21-1 primary antibody (Ab 1) via an amide bond, allowing the analyte CYFRA21-1 to be selectively anchored to Ab 1 by specific antigen-antibody interactions. Then, the chain transfer agent-conjugated a CYFRA21-1 secondary antibody was attached to the CYFRA21-1, forming a sandwich-like immunocomplex that can be linked to numerous monomers through RAFT polymerization. Accordingly, a high-density electroactive polymer chain was then grafted onto the immunocomplex, dramatically amplifying the electrochemical signal generated by the immobilized CYFRA21-1. Using the strategy, the current response increased linearly with the logarithm of the CYFRA21-1 concentration in the range of 0.5 fg mL−1 to 10 pg mL−1 (R 2 = 0.998), with a low detection limit of 0.14 fg mL−1 (S/N = 3). Furthermore, the CYFRA21-1 concentrations in clinical serum samples analyzed by our method were consistent with those obtained by magnetic particle chemiluminescence assay (MPCA) method. Thus, owing to its high sensitivity, environmental benignity, and low cost, this strategy shows great potential for clinical diagnosis and analysis. An ultrasensitive electrochemical immunosensor for the detection of lung cancer biomarker via RAFT polymerization signal amplification was developed. Unlabelled Image • The immunosensor has an ultra-low detection limit of 0.14 fg mL−1. • The electrochemical signal is dramatically amplified by RAFT polymerization. • It is applicable for CYFRA21-1 detection in complex biological samples. • The proposed strategy can be used as a universal platform for other biomarkers detection. [ABSTRACT FROM AUTHOR]

• ROP is first time used for highly sensitive detection of CEA. • A detection limit of 0.28 fg mL−1 is achieved based on Apt2-CNTs-PFcGE composites. • The proposed sensor shows high sensitivity, selectivity, low cost, simplicity, and good biocompatibility. • This strategy may hold great potential in biomedical research and clinical diagnosis. Carcinoembryonic antigen (CEA) is regarded as the most common tumor biomarker, the precise and sensitive measurement of which has great significance for the cancer diagnosis, treatment, and prognosis. Herein, for the first time, we construct a novel sandwich-type electrochemical aptasensor for CEA detection based on polymer-functionalized carbon nanotubes (CNTs) composites prepared by ring-opening polymerization (ROP). CEA-aptamer 1 (Apt 1) is self-assembled on a gold electrode surface and used as a probe for CEA capture. CNTs are used as the substrates for polymer chain growth to prepare poly(ferrocenyl glycidyl ether)-grafted CNTs (PFcGE-CNTs) composites by ROP. Due to the efficient polymerization and good biocompatibility of ROP technology, PFcGE-CNTs composites can provide a hydrophilic-biocompatible nanoplatform for CEA-aptamer 2 (Apt 2) capture and serve as a signal amplifier. Remarkably, PFcGE-CNTs composites feature the characteristics of good conductivity and abundant ferrocene derivatives, which significantly amplify the electrochemical signal. Under optimized conditions, the fabricated aptasensor shows a wide detection range of 1 × 10−15–1 × 10−8 g mL−1 and a limit of detection (LOD) down to 2.8 × 10−16 g mL−1, which are superior to those of most reported electrochemical methods. Furthermore, the proposed aptasensor exhibits excellent applicability for CEA detection in practical sample analysis, which is of promising application potential for the early diagnosis and monitoring of cancer. [ABSTRACT FROM AUTHOR]

• The operation of GO-based biosensor is easy. • Simplify the purification process of the material. • The sensitivity of this biosensor via GO enhancing signal is high. • This method is cost-effective. Atom transfer radical polymerization (ATRP) is an effective polymerization technology, and low ppm ATRP attracts unceasing interest in biological field. In this work, a fast and effective electrochemical biosensor based on graphene oxide (GO) via electrochemically mediated ATRP (eATRP) realized the ultrasensitive detection of lung cancer DNA. Peptide nucleic acid (PNA) was used as capture probes to specifically recognize target DNA, GO was connected to PNA/DNA heteroduplexes via phosphate-Zr4+-carboxylate chemistry to introduce eATRP initiators. Under a potentiostatic condition, eATRP was initiated with the help of reducibility of electrons, and numerous monomers labeled with ferrocene moieties were grafted onto GO. GO was synthesized by modified Hummer's method and was characterized by Fourier transform infra-red spectra (FT-IR) and X-ray diffraction (XRD). The analytical performance of this biosensor was evaluated by square wave voltammetry (SWV) under optimal conditions, its limit of detection (LOD) was 0.213 aM (R2 = 0.994) with a linear range from 1.0 aM to 100 fM. High selectivity of this biosensor indicated a good application potential of genotyping of single nucleotide polymorphisms (SNPs), and simple operation and highly sensitive analytical performance endowed this biosensor a superior application prospect. More importantly, a novel thinking for material application in biological detection was provided in this work. [ABSTRACT FROM AUTHOR]

• A novel electrochemical platform is developed for detection of CYFRA 21-1 DNA. • DNA metallization are achieved via SI-RAFT polymerization. • A detection limit of 0.89 aM is achieved based on SI-RAFT and DNA metallization. • This strategy does not involve the use of enzymes or complex materials. Cytokeratin fragment antigen 21-1 (CYFRA 21-1) DNA is a significant biomarker with relation to non-small cell lung cancer. Here, we described an ultrasensitive electrochemical biosensor for detection of CYFRA 21-1 DNA (target DNA, tDNA) via surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization-based DNA metallization signal amplification strategy. Specifically, 5′terminal modified thiol peptide nucleic acid (PNA) probes are immobilized on the gold electrode surface (by Au-S selfassembly) for the identification of specific tDNA sequences. After hybridization, the 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPAD) is tethered to the PNA/DNA duplexes by means of the recognized phosphate-Zr4+-carboxylate chemistry. Subsequently, in the situation of C 3 H 4 O as the monomer, SI-RAFT polymerization can bring numerous aldehyde groups sites for the subsequent silver mirror reaction. The acrolein-polymers act as reductant to reduce Ag+ into Ag0, and then the silver particles are deposited on the polymer skeleton, which significantly amplifies the electrochemical signal. Under optimal conditions, the designed sensor for tDNA detection show a wide linear range from 100 aM to 1 nM, and the detection limit is as low as 0.89 aM. Moreover, the proposed biosensor exhibits prominent applicability for analysis of tDNA in serum samples and high selectivity for different mismatched oligonucleotide fragments. Given the proposed biosensor without extra natural enzyme or bio-labels, this method has enormous potential in bioanalysis. [ABSTRACT FROM AUTHOR]

• Dual atom transfer radical polymerization is firstly reported for DNA detection. • Two types of polymerization are used for signal amplification. • The limit of detection of this strategy is greatly improved to 25 amol/L. • This method shows satisfied selectivity and stability for biomolecule detection. Atom transfer radical polymerization as a form of controlled/living radical polymerization is particularly attractive. In this work, dual atom transfer radical polymerization (ATRP) is reported for ultrasensitive DNA detection. Firstly, a peptide nucleic acid (PNA) modified with a thiol group was self-assembled on an electrode surface to capture target DNA (TDNA). The initiator of the first ATRP (ATRP-1), α-bromoisobutyric acid (BIBA), was linked to forming PNA/DNA heteroduplexes via coordination of Zr4+. The polymer chain formed by the monomer of ATRP-1 (2-(2-bromoisobutyryloxy) ethyl methacrylate, BIEM) was also one of initiators of the second ATRP (eATRP-2). The other initiator of eATRP-2 was additional BIBA. ATRP-1 involves activator regeneration by electron transfer (ARGET) ATRP, regulated via excess reducing agent. eATRP-2 is electrochemically mediated ATRP which can control the polymerization via an appropriate applied potential. Compared with one ATRP, more monomers of eATRP-2 modified with ferrocene are attached to electrode surface. Under optimal conditions, this dual ATRP strategy provides a low limit of detection (25 aM, ~150 molecules) with satisfactory selectivity and stability. Importantly, this strategy presents a useful prospect for the field of biomolecule detection. [ABSTRACT FROM AUTHOR]

Cytokeratin fragment antigen 21–1 (CYFRA 21–1) DNA is a crucial biomarker closely associated with non-small cell lung cancer. Here, we fabricated a novel electrochemical biosensor for ultrasensitive detection of CYFRA 21–1 DNA via polysaccharide and electrochemically mediated atom transfer radical polymerization (eATRP) dual signal amplification. Specifically, thiolated peptide nucleic acid (PNA) probes at 5′-terminals are immobilized on the gold electrode surface for specific recognition of CYFRA 21–1 DNA (tDNA). After hybridization, hyaluronic acid (HA) is linked to the hybridized PNA/DNA duplexes via the recognized carboxylate-Zr4+-phosphate chemistry. Then multiple initiators of the polymerization reaction are introduced via esterification reaction. Lastly, large numbers of electro-active monomers are successfully grafted from the initiation sites of functionalized HA by eATRP reaction, significantly amplifying the electrochemical signal. Under optimal conditions, the constructed sensor can detect as low as 9.04 aM tDNA. Further, this proposed biosensor can also be applied to the direct detection of double-stranded DNA (dsDNA), obtaining 0.12 fM as the detection limit. Besides, this strategy shows high selectivity for mismatched bases and excellent applicability for CYFRA 21–1 DNA detection in the serum samples. Given its high sensitivity, selectivity, ease of operation, low cost and environmental friendliness, this biosensor has considerable potential in early diagnosis and biomedical application. • A novel electrochemical biosensor is developed for ultrasensitive detection of CYFRA 21–1 DNA. • A detection limit of 9.04 aM is achieved based on polysaccharide and eATRP dual amplification. • The proposed sensor shows high sensitivity, selectivity, low cost and friendly environment. • This strategy may hold great potential in biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

A new dansyl-peptide dual-functional fluorescent chemosensor (D-ECEW-NH 2 , D-P4) was developed via Fmoc solid phase peptide synthesis (SPPS), which displayed an excellent selectivity and high sensitivity for Hg2+ by turn on response in 10 mM 2-[4-(2-Hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) solution (pH 7.1). The sensing mechanism for Hg2+ is by two pathways, one is fluorescence resonance energy transfer (FRET) effect between tryptophan (donor) and dansyl (acceptor) fluorophores due to the interaction of Hg2+ ion with D-P4 evidenced by fluorescence excitation spectra at 290 nm, while the other is the chelation enhanced fluorescence (CHEF) effect evidenced by fluorescence excitation spectra at 330 nm. D-P4 sensor was used to detect Hg2+ with low detection limit of 23.0 nM. Furthermore, the binding stoichiometry and binding constant, as well as pH influence of D-P4 for Hg2+ were investigated. Surprising but interestingly, D-P4-Hg system has been found a significant fluorescence enhancement response toward biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), which can be used for the detection of biothiols. Its detection limit for Cys was 52.0 nM. A simple peptidyl dual-functional fluorescent chemosensor (Dansyl-Glu-Cys-Glu-Trp-NH 2 , D-P4) has been developed for highly selective and sensitive detection of Hg2+ over other common metal ions by fluorescence resonance energy transfer (FRET) effect and chelation enhanced fluorescence (CHEF) effect, and D-P4-Hg2+ complex was used as an excellent fluorescent sensor for biothiols (−SH) detection. Image 1 • A new dansyl-peptide dual-functional fluorescent chemosensor was synthesized and characterized. • The sensor displayed an excellent selectivity and high sensitivity for Hg2+. • The sensing mechanism for Hg2+ is via FRET effect and CHEF effect. • The complex of sensor with Hg(II) can be developed a sensitive sensor for the detection of biothiols. [ABSTRACT FROM AUTHOR]

Human T-lymphotropic virus type II (HTLV-II) is a crucial retrovirus that is closely associated with a variety of human diseases. Herein, an ultrasensitive fluorescent HTLV-II DNA detection strategy was developed for the first time based on magnetic nanoparticles (MNPs) and atom transfer radical polymerization (ATRP) amplification. In this approach, hairpin DNA probes (pDNA) labelled with 5′ thiol and 3′ azide group terminally were immobilized on amino group modified MNPs surface through sulfo-N-succinimidyl-4-maleimidobutyrate sodium salt (sulfo-GMBS) cross-linkers. In the presence of target DNAs (tDNA), pDNA hybridized with tDNA to form double-stranded DNA, and therefore its azide group was away from the MNPs surface. Subsequently, to initiate ATRP reaction, initiators were introduced into the pDNA by a Cu (I)-catalyzed alkyne-azide cycloaddition (CuAAC). Then, large numbers of 9-anthracenylmethyl methacrylate polymer (pAMMA) were successfully labelled on the MNPs surface, resulting in significant amplification of the fluorescence signal. Under optimized conditions, the fluorescence signal was proportional to the logarithm of the concentration of tDNA over the range from 1 fM to 1 nM, with a detection limit of 0.22 fM. Moreover, this strategy was capable of discriminating mismatched bases and detecting HTLV-II DNA in human serum samples. By virtue of the high sensitivity, selectivity, simplicity and economy, this ultrasensitive biosensor demonstrates great potential for biomedical research and early clinical diagnosis. An ultrasensitive fluorescent detection strategy of HTLV-II DNA was developed based on magnetic nanoparticles and atom transfer radical polymerization. Image 1 • An ultrasensitive fluorescent HTLV-II DNA sensor is developed for the first time based on ATRP amplification. • The detection limit for HTLV-II DNA is as low as 0.22 fM. • Magnetic nanoparticles and hairpin DNA probes greatly improve the sensitivity and selectivity of this sensor. • This developed method is believed to hold great potential in biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Psychological stress is a major contributor to individual health disparities. Accurate and quantitative detection of stress markers is crucial preventing mental health related problems. Supramolecular chemistry is widely used in drug delivery, catalysis, sensors and other applications. However, due to the difficulty of host functionalization such as cyclodextrins and solid-state pillar[n], it is still a challenge to directly realize the detection of guests through host-guest recognition behavior. Here, we reported an atom transfer radical polymerization (ATRP) fluorescent biosensor for direct and selective detection of guest molecule stress marker cortisol, translating molecular recognition behavior into quantifiable detection signals. Realizes quantitative chemical detection and builds a portable and affordable sensing platform for quantitative detection of target molecules without complex cross-linking steps. Overcomes the disadvantages of traditional methods that require the use of antibodies or are difficult to functionalize during the host-guest recognition process. This ATRP fluorescent biosensor was fabricated by employing zinc phthalocyanine (ZnPc) as a photocatalyst under 630 nm wavelength radiation, β-CD-Br 15 as a macromolecular initiator, and fluorescein O-methacrylate (FMA-O) as a monomer for polymerization. The system provides ultra-high sensitivity for the detection of cortisol (limit of detection 0.47 ng/mL) and specificity for the detection of cortisol in the presence of interfering substances such as progesterone and urea. Selective and real sample experiments confirm the specificity and scalability of this mechanism can also be customized by the rational design of the host-guest complex to quantitatively detect various molecules. This study confirms the feasibility of using a cyclodextrin-centered macromolecular initiator as a capture and label-free fluorescent biosensor for cortisol, a stress biomarker., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The detection of trypsin and its inhibitors is important for both clinical diagnosis and disease treatment. Abnormal trypsin activity affects pancreatic function and leads to corresponding pathological changes in the body. Therefore, the study presented a riboflavin-induced photo-ATRP electrochemical assay of trypsin activity and its inhibitor, including detection of trypsin activity in real urine samples. Experiments were performed on indium tin oxide (ITO) electrodes modified with sulfhydryl groups of 3-mercaptopropionic acid, and target trypsin-specific cleavage of BSA-Au nanocluster (BSA-Au NCs) was followed by the modification of Au NCs to the electrodes using Au-S. The Au NCs immobilized monodeoxy-monomercapto-β-cyclodextrin@adamantan-2-amine (SH-β-CD@2-NH 2 -Ada) host-guest inclusion complexes to the electrode surfaces via Au-S. In a two-component photo-initiator system consisting of riboflavin as an initiator and ascorbic acid (AA) as a mild reducing agent under mild blue light radiation, a large number of electroactive substances were grafted onto the electrode surface to generate electrochemical signals. In addition, we have successfully realized the detection of clinical drug inhibitors of trypsin. The detection limit of the system is as low as 0.0024 ng/mL, which much littler than the average standard of trypsin in the patient's urine or serum. It's worth noting that this work will provide researchers with a different route to design electrochemical sensors based on non-covalent recognition strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)