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An efficient quenching electrochemiluminescence (ECL) immunosensor based on ECL resonance energy transfer (ECL-RET) was studied for sensitive analysis of prostate specific antigen (PSA). In this protocol, nitrogen-doped graphene quantum dots (NGQDs) which could produce excellent ECL emission, were loaded onto Ni(OH) 2 with the three-dimensional (3D) hierarchical and stacked lamellar structure. Taking advantages of high conductivity and large specific surface area of Ni(OH) 2 , the better electrochemical and ECL behavior of Ni(OH) 2 /NGQDs were presented. As another part of immunosensor, the Fe 3 O 4 @MnO 2 composites with wider ultraviolet absorption range were successfully assembled. The absorption spectra of Fe 3 O 4 @MnO 2 precisely overlapped with the ECL spectra of NGQDs, leading to the significant decrement of ECL signal. Herein, the sandwich-type immunosensor was developed based on the quenching mechanism between NGQDs (ECL donor) and Fe 3 O 4 @MnO 2 (ECL acceptor). The system was optimized to realize reliable determination of PSA concentration within the linear range of 10 −5 –10 ng/mL and a detection limit of 5 fg/mL (S/N = 3). Eminently, the developed method was successfully applied in real serum samples with good recoveries in a range from 94.0% to 102%, indicating the good accuracy of the proposed method for PSA detection. [ABSTRACT FROM AUTHOR]

An ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of alpha fetoprotein (AFP). The β-cyclodextrins functionalized graphene sheets (CD-GS) were used as the sensing matrix for immobilizing adamantine-1-carboxylic acid functionalized primary anti-AFP (ADA–Ab 1 ) and enhanced the electron transfer. PdNi alloy nanoparticles decorated N-doped graphene nanoribbons (PdNi/N-GNRs) were used as labels of secondary anti-AFP (Ab 2 ), and PdNi alloy nanoparticles (PdNi NPs) exhibited high catalytic performance towards the reduction of H 2 O 2 . Meanwhile, with good dispersion, large specific surface area and good catalytic performance, N-doped graphene nanoribbons (N-GNRs) significantly amplified the electrochemical signal. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.0001–16 ng/mL with a low detection limit of 0.03 pg/mL. Additionally, the proposed immunosensor showed high specificity, good reproducibility and long-term stability, which have promising application in bioassay analysis. [ABSTRACT FROM AUTHOR]

A novel and sensitive electrochemical immunosensor for ultrasensitive detection of pancreatic cancer biomarker carbohydrate antigen 199 (CA199) was proposed by using Au@Cu x OS yolk–shell nanostructures with porous shells as labels for signal amplification. Au@Cu x OS yolk–shell nanostructures exhibit high electrocatalytic activity toward the reduction of hydrogen peroxide (H 2 O 2 ) as analytical signal. Moreover, secondary antibody (Ab 2 ) can adsorb on the surface of Au@Cu x OS with porous shells which has large surface area and could greatly increase the probability of Ab 2 –antigen interactions thereby leading to higher sensitivity. Reduced graphene oxide–tetraethylene pentamine (rGO–TEPA), containing abundant amine groups, was supported Au nanoparticles as a support platform to immobilize the primary antibody (Ab 1 ). The resulting sensing interface of rGO–TEPA/AuNPs could provide a large electroconductive surface area, allowing high loadings of the biological recognition elements as well as the occurrence of electrocatalytic and electron-transfer processes. Under optimal conditions, the immunosensor exhibited a wide linear response to CA199 ranging from 0.001 to 12 U/mL with a low detection limit of 0.0005 U/mL. The designed immunosensor displayed good precision, high sensitivity, acceptable stability and reproducibility, and has been applied to the analysis of serum with satisfactory results. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrogenerated chemiluminescence (ECL) biosensor based on the construction of triplex DNA for the detection of adenosine was designed. The ECL biosensor employs an aptamer as a molecular recognition element, and quenches ECL of tris(2,2′-bipyridine) ruthenium (Ru(bpy)3 2+) by ferrocenemonocarboxylic acid (FcA). Through self-assembly technology, the ECL probe of thiolated hairpin adenosine aptamer tagged was self-assembled onto the surface of a gold electrode with an ECL signal producer Ru(bpy)3 2+ derivative (Ru-DNA-1). The adenosine aptamer, including a section of triplex characteristic chain, formatted triplex DNA with two other DNAs (DNA-2, Fc-DNA-3) in the presence of triplex DNA binder coralyne chloride (CORA). Fc-DNA-3 was tagged with an ECL quencher ferrocenemonocarboxylic acid (FcA), a quenching probe. In the presence of adenosine, the aptamer sequence (Ru-DNA-1) prefers to form the aptamer–adenosine complex with hairpin configuration and the switch of the DNA-1 occurs in conjunction with the generation of a strong ECL signal owing to the dissociation of a quenching probe. Meanwhile, a control experiment was performed; the ECL-duplex biosensor was designed to detect adenosine. The detection limits were 2.7×10−10 molL−1 and 2.3×10−9 molL−1 for the ECL-triplex DNA biosensor and ECL-duplex DNA biosensor, respectively, which demonstrated that the ECL-triplex DNA biosensor improved the sensitivity and specificity greatly. [ABSTRACT FROM AUTHOR]

Abstract: A novel and sensitive sandwich electrochemical biosensor based on the amplification of magnetic microbeads and Au nanoparticles (NPs) modified with bio bar code and PbS nanoparticles was constructed in the present work. In this method, the magnetic microspheres were coated with 4 layers polyelectrolytes in order to increase carboxyl groups on the surface of the magnetic microbeads, which enhanced the amount of the capture DNA. The amino-functionalized capture DNA on the surface of magnetic microbeads hybridized with one end of target DNA, the other end of which was hybridized with signal DNA probe labelled with Au NPs on the terminus. The Au NPs were modified with bio bar code and the PbS NPs were used as a marker for identifying the target oligoncleotide. The modification of magnetic microbeads could immobilize more amino-group terminal capture DNA, and the bio bar code could increase the amount of Au NPs that combined with the target DNA. The detection of lead ions performed by anodic stripping voltammetry (ASV) technology further improved the sensitivity of the biosensor. As a result, the present DNA biosensor showed good selectivity and sensitivity by the combined amplification. Under the optimum conditions, the linear relationship with the concentration of the target DNA was ranging from 2.0×10−14 M to 1.0×10−12 M and a detection limit as low as 5.0×10−15 M was obtained. [Copyright &y& Elsevier]

The ECL emission of simple and stable zirconium dioxide nanomaterials has always been a blank slate in the ECL sensors field. In this work, zirconium dioxide (ZrO 2)-titanium dioxide (TiO 2)-gold nanoparticle (AuNPs) composite (ZT-Au), a novel self-enhanced ECL emitter, was introduced the system of dual-quenching ECL immunosensor. The anodic luminescence of ZrO 2 in the system of tripropylamine (TPrA) as a co-reagent was first reported and explored. Meanwhile, TiO 2 was designed into the ECL scheme as a co-reaction accelerator to form the ZrO 2 /TPrA/TiO 2 ternary system, which can efficiently amplify the ECL signal of the emitter. In addition, cuprous oxide-triaminophenol (Cu 2 O-APF) as the quencher was devoted to the dual-quenching sensing strategy. The dual-quenching mechanism that effectively boosted the immunosensor sensitivity was adequately investigated and conjectured in this paper. The sensing model based on the luminophor ZT-Au and the quencher Cu 2 O-APF was utilized for the detection of D-dimer, a reliable marker for the diagnosis and evaluation of thrombotic diseases. The short peptide ligands NARKFYKGC (NFC) with efficient biological affinity were used to site-directionally capture antibodies for adequately protecting the activity of antigen binding sites during the construction of the immunosensor. The implemented immunosensor was equipped with a broad linear range of 0.01–500 ng/mL and a low detection limit of 3.6 pg/mL. The original methodology opens up the field of vision for the detection of additional biomarkers. [ABSTRACT FROM AUTHOR]

Abstract A sensitive dual mode competitive electrochemical immunosensor for the detection of B-type natriuretic peptide (BNP) was successfully fabricated, which based on differential pulse voltammetry (DPV) and amperometric i-t curve response modes. Polyaniline (PAN) and tin dioxide (SnO 2) were loaded on graphene sheets (GS), which could effectively promote the electron transfer process, thereby amplifying the current signal and increasing the sensitivity of the immunosensor. To promote biocompatibility, gold nanoparticles (Au) were incorporated on GS/SnO 2 /PAN (GS/SnO 2 /PAN-Au). GS/SnO 2 /PAN-Au complex was gotten to act as the platform which could provide a clearly DPV signals. N-doped carbon nanotubes (N-CNTs) embellished by ZnCo 2 O 4 quantum dots (ZnCo 2 O 4 /N-CNTs) with excellent catalytic properties for the reduction of H 2 O 2 was gotten to act as the label of the antibody-BNP (Ab), providing an obviously current signal through amperometric i-t curve method. A large quantity of BNP could be stable loaded in the modified electrode via GS/SnO 2 /PAN-Au with excellent electrical conductivity and good biocompatibility, which could compete with target-BNP to combine Ab that labelled by ZnCo 2 O 4 /N-CNTs. Under the optimum conditions, the immunosensor exhibited remarkable analytical performance of a linear range from 0.01 pg/mL to 1 ng/mL with a detection limit of 3.4 fg/mL for quantitative detection of BNP (S/N = 3). This method was able to become a universal strategy for other biological detection. Highlights • A dual mode competitive electrochemical immunosensor was fabricated. • GS/SnO 2 /PAN-Au possessed excellent electrical conductivity and good bioactivity. • ZnCo 2 O 4 /N-CNTs owned excellent catalytic properties for reduction of H 2 O 2. • The electrochemical immunosensor employed DPV and amperometric i-t curve methods. • The designed immunosensor exhibited low detection limit of 3.34 fg mL−1 for BNP. [ABSTRACT FROM AUTHOR]

Abstract A high sensitivity photoelectrochemical (PEC) immunosensor for amyloid beta (Aβ) detection, which has great neurotoxic effect on the progression of Alzheimer's disease (AD), was presented based on the sensitization of Mn2+ doped CdSe (Mn:CdSe) to Bi 2 WO 6 /CdS electrode. Bi 2 WO 6 was synthesized successfully with a unique flower-like amorphous structure, providing a merit to load functional CdS for obtaining an expected PEC response. Mn:CdSe was used to label Aβ for acquiring Mn:CdSe-Aβ bioconjugate and enhancing the detection sensitivity via the competitive immunoreaction of Mn:CdSe-Aβ and Aβ with antibody immobilized on Bi 2 WO 6 /CdS electrode. The doped of Mn2+ in CdSe nanoparticles could induce energy defect that impeded the recombination of photo-generated charges, and greatly enhanced PEC response for ultrasensitive detection of Aβ. The proposed immunosensor for Aβ showed a linear range of 0.2 pg mL−1–50 ng mL−1 with a detection limit of 0.068 pg mL−1, also with good stability, high selectivity, and acceptable reproducibility. The sensitization of Mn:CdSe provided a new way for preparation of highly sensitive protein biosensors. Highlights • A novel PEC immunosensor for ultrasensitive detection of Aβ was proposed at Bi 2 WO 6 /CdS modified electrode. • Aβ was labeled with Mn2+ doped CdSe for signal amplification. • The sensitization of Mn:CdSe to Bi 2 WO 6 /CdS remarkably enhanced the PEC intensity. • The biosensor for Aβ exhibited the detection limit of 0.068 pg mL−1. [ABSTRACT FROM AUTHOR]

Abstract An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag 2 S sensitized SnO 2 /SnS 2 nanocomposites. Specifically, SnO 2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS 2 , which brought about the sensitization of SnO 2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag 2 S was in-situ growth on the surface of SnO 2 /SnS 2 , which further enhanced the photocurrent response significantly. Therefore, SnO 2 /SnS 2 /Ag 2 S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5 pg mL−1 to 100 ng mL−1, with low limit of detection (0.17 pg mL−1) and limit of quantification (0.56 pg mL−1). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields. Highlights • A label-free PEC immunosensor was developed based on SnO 2 /SnS 2 /Ag 2 S nanocomposites. • SnO 2 /SnS 2 /Ag 2 S nanocomposites exhibited excellent photoelectrochemical performance. • The PEC immunosensor displayed highly sensitive detection toward amyloid β-protein. [ABSTRACT FROM AUTHOR]

Cardiac troponin I (cTnI) is a specific and sensitive biomarker for the early diagnosis of acute myocardial infarction and for the subsequent clinical treatments. In this work, novel electrochemical sensing platform for sensing of cTnI based on aptamer-MoS 2 nanoconjugates was proposed. For comparison, core-shell Au@SiO 2 @Au nanoparticles were also used for sensing of cTnI. The sensing schemes and electrochemical responses of the proposed sensors were investigated by electrochemical impedance spectroscopy (EIS) in 5.0 mM K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] (1:1) solution containing 0.1 M KCl, respectively. Results showed that the aptamer-Au@SiO 2 @Au based aptasensor shows a linear rage of 10 pM-10.0 μM with the detection limits of 1.23 pM For the aptamer-MoS 2 nanosheets based aptasensor, the linear range for cTnI detection was from 10 pM to 1.0 μM with a lower detection limit of 0.95 pM Meanwhile, both the sensors were successfully applied for detection of cTnI in human blood samples. The two kinds of aptsensors have been successfully used for detecting of cTnI in human blood serums. Moreover, no negligible signal changes could be observed in the presence of non-targets of CK-MB and Myo, suggesting the good potential for clinic diagnosis. [ABSTRACT FROM AUTHOR]

In this work, Ru(bpy) 3 2+ encapsulated in metal–organic frameworks (MOFs) UiO-67 (Ru(bpy) 3 2+ /UiO-67) as luminophor was easily prepared and firstly applied in constructing an electrochemiluminescence (ECL) immunosensor to efficiently estimate diethylstilbestrol (DES). The competitive method-based ECL immunosensor platform was fabricated by amino-silicon dioxide which possesses large surface area. The poriness of UiO-67 was splendid so that Ru(bpy) 3 2+ could be easily encapsulated. Ru(bpy) 3 2+ /UiO-67 with excellent ECL luminescence signal existed large specific surface area for easily labeled with antibodies. DES competed with bovine serum albumin-diethylstilbestrol (BSA-DES) for binding to antibody-specific sites in the constructed immunosensor. However DES was micromolecule, which was easier to bond to antibodies than BSA-DES. The ECL signal was gradually decreases with the increase of the concentration of DES. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 pg mL −1 to 50 ng mL −1 with a low detetion limit of 3.27 fg mL −1 (S/N = 3). The novel fabricated immunosensor with interference immunity and high stability may cause an attractive approach for the other targets determination. [ABSTRACT FROM AUTHOR]

In this study, a sensitive sandwich-type electrochemical immunosensor was fabricated for the detection of alpha fetoprotein (AFP) based on Co 3 O 4 @MnO 2 -thionine (Co 3 O 4 @MnO 2 -Th) and the screen printing technique. Meanwhile, the pseudo enzyme-linked immunosorbent assay (pseudo-ELISA) method was applied in fabricating the immunosensor. Screen-printed carbon electrode (SPCE) was applied for achieving the detection of AFP. Simultaneously, the amino functionalized Co 3 O 4 @MnO 2 -Th was employed as secondary label and could greatly improve the electrochemical response signal, which was beneficial for detecting AFP. Differential pulse voltammetry (DPV) was applied for the detection of AFP and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal conditions, the immunosensor exhibited a linear response toward AFP in the range of 0.001–100 ng/mL, with a low detection limit of 0.33 pg/mL. Simultaneously, the proposed immunosensor displayed acceptable selectivity, excellent stability and well reproducibility. Furthermore, this proposed strategy may open up new ideas and find many potential applications in the detection of other tumor markers. [ABSTRACT FROM AUTHOR]

In this work, a highly-efficient competitive method-based electrochemiluminescence (ECL) immunosensor was proposed based on {[Ru(bpy) 3 ][Cu 2x Ni 2(1−x) (ox) 3 ]} n (Cu/Ni/Ru) as luminophor to efficiently detect aflatoxins B1 (AFB1). Cu/Ni/Ru exhibited excellent ECL behavior. While polyethyleneimine capped silicon dioxide (PEI@SiO 2 ) could decrease the ECL performance of Cu/Ni/Ru due that PEI could destroy the structure of Cu/Ni/Ru via producing the complex between PEI and metal ions (Cu(II)/Ni(II)), inducing the release of Ru(bpy) 3 2+ . Since Au nanoparticles can directly combine with antibody and antigen, the Cu/Ni/Ru and PEI@SiO 2 was functionalized by Au nanoparticles. The quantitative detection of AFB1 was based on the competitive binding between AFB1-bovine serum albumin labeled Au-PEI@SiO 2 (Au-PEI@SiO 2 -AFB1-BSA) and free AFB1 with antibody-AFB1 which immobilized on Au-Cu/Ni/Ru. The ECL signal increased with augmenting the concentrations of the free AFB1 due to less Au-PEI@SiO 2 -AFB1-BSA combining with antibodies. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01 ng mL −1 to 100 ng mL −1 with a detection limit of 0.0039 ng mL −1 (S/N = 3). The proposed immunosensor also provides a promising approach for ultrasensitive detection of other mycotoxins. [ABSTRACT FROM AUTHOR]

The construction of advanced systems that can accurately detect neuron-specific enolase (NSE) is critical to the rapid diagnosis of small cell lung cancer (SCLC). Herein, a luminol-based electrochemiluminescence (ECL) biosensor enhanced by reactive oxygen species (ROS) is proposed to perform the ultrasensitive detection of NSE. D-Fe 2 O 3 @Pt, synthesized as a signal indicator, was combined with luminol to significantly shorten its electron transfer pathway. Its peroxidase activity catalyzed the decomposition of H 2 O 2 to generate a large amount of •OH, thus considerably increasing the ECL signal of the luminol–H 2 O 2 system. CePO 4 /CeO 2 heterostructures with improved surface-active areas were then employed as sensing substrates. The platform enabled the accelerated generation of O 2 •− through enriched Ce4+/Ce3+ redox pairs, thereby amplifying the strength of the response of the foundation. Through integrated dual ROS amplification, the proposed sandwich ECL immunosensor configuration achieved sensitive detection in the detection range of 76 fg/mL – 100 ng/mL, with a detection limit of 72.4 fg/mL. Furthermore, the sensor exhibited high selectivity for the determination of NSE in human serum. Overall, this study serves as an important reference for integrating ROS and enzymatic strategies in ECL research to achieve accurate, sensitive, and highly selective detection of a target. [ABSTRACT FROM AUTHOR]

Nanoporous cobalt (NPCo) with three-dimensional network nanostructure was obtained by selectively dealloying Al from CoAl alloy in a mild alkaline solution. Co 3 O 4 grew further on the surface of NPCo and then NPCo/Co 3 O 4 was obtained. Gold nanoparticles functionalized NPCo/Co 3 O 4 (NPCo/Co 3 O 4 –Au) was used to fabricate electrochemiluminescence (ECL) modified electrodes for detecting mycotoxin deoxynivalenol (DON). In addition the introduction of AuNPs enhanced the conductivity, and NPCo/Co 3 O 4 –Au exhibited excellent catalytic properties for the luminescence of RuSi@Ru(bpy) 3 2+ . The fabricated ECL modified electrodes exhibited a high activity for DON in a wide linear range from 5 pg/mL to 100 ng/mL with a low detection limit of 1 pg/mL. The NPCo/Co 3 O 4 –Au based ECL modified electrodes displayed excellent stability and reproducibility, and successfully achieved the detection of DON in wheat flour with desirable results as well. The NPCo/Co 3 O 4 –Au possesses great application potential for ECL modified electrodes with sample detection, unique catalytic activity, and high structure stability. [ABSTRACT FROM AUTHOR]

A novel and simple photoelectrochemical (PEC) bioassay protocol for estradiol was proposed based on in situ generated CdS-enhanced TiO 2 film via competitive strategy. The CdS was generated in situ by immediately dropping S 2− onto the Cd 2+ -functionalized titanium phosphate nanoparticles (TiP@Cd 2+ ). The TiO 2 photoactive sensing film with countless active sites was obtained by calcination and further explored for estradiol (E 2 ) capture. The TiP@Cd 2+ was used as labels and immobilized through affinity-specific binding with E 2 on the surface of the electrode. Greatly enhanced sensitivity was achieved by using porous TiP nanoparticles as carriers to load a large amount of Cd 2+ and further for more CdS production through the S 2− deposition. What's more, the photocurrent of CdS generated on the electrode surface could be significantly amplified by the coupling of CdS and TiO 2 , which could enhance the excitation and photo-to-electric conversion efficiency. Through the application of a competitive binding assay, the proposed biosensor showed high sensitivity with a detection limit down to 2 pg/mL. This simple and fast PEC E 2 -sensing approach offers great promise to extend its application for the assay of small molecules of biomedical, food and environmental interest. Additionally, the strategy of employing in situ generated narrow-band gap semiconductors paves a new way for PEC sensing. [ABSTRACT FROM AUTHOR]

A novel non-enzymatic immunoassay was designed for ultrasensitive electrochemical detection of carcino-embryonic antigen (CEA) using β-cyclodextrin functionalized Cu@Ag (Cu@Ag-CD) core–shell nanoparticles as labels and β-cyclodextrin functionalized graphene nanosheet (CD-GN) as sensor platform. CD-GN has excellent conductivity which promoted the electric transmission between base solution and electrode surface and enhanced sensitivity of immunosensor. In addition, owing to supramolecular recognition of CD-GN for the guest molecule, quite a few synthesized adamantine-modified primary antibodies (ADA-Ab 1 ) were immobilized on the CD-GN by supramolecular host–guest interaction between CD and ADA. Cu@Ag-CD as a signal tag could be captured by ADA-modified secondary antibody (ADA-Ab 2 ) through a host–guest interaction, leading to a large loading of Cu@Ag nanoparticles with high electrical conductivity and catalytic activity. The fabricated immunosensor exhibits excellent analytical performance for the measurement of CEA with wide range linear (0.0001–20 ng/mL), low detection limit (20 fg/mL), good sensitivity, reproducibility and stability, which provide an enormous application prospect in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Abstract: Constructions of versatile electroactive labels are key issues in the development of electrochemical immunosensors. In this study, copper-doped titanium dioxide nanoparticle (Cu@TiO2) was synthesized and used as labels for fabrication of sandwich-type electrochemical immunosensors on glassy carbon electrode (GCE). Due to the presence of copper ions, Cu@TiO2 shows a strong response current when coupled to an electrode. The prepared nanocomposite also shows high electrocatalytic activity towards reduction of hydrogen peroxide (H2O2). The dual functionality of Cu@TiO2 enables the fabrication of immunosensor using different detection modes, that is, square wave voltammetry (SWV) or chronoamperometry (CA). While Cu@TiO2 was used as labels of secondary antibodies (Ab2), carboxyl functionalized graphene oxide (CFGO) was used as electrode materials to immobilize primary antibodies (Ab1). Using human immunoglobulin G (IgG) as a model analyte, the immunosensor shows high sensitivity, acceptable stability and good reproducibility for both detection modes. Under optimal conditions, a linear range from 0.1pg/mL to 100ng/mL with a detection limit of 0.052pg/mL was obtained for SWV analysis. For CA analysis, a wider linear range from 0.01pg/mL to 100ng/mL and a lower detection limit of 0.0043pg/mL were obtained. The proposed metal ion-based enzyme-free and noble metal-free immunosensor may have promising applications in clinical diagnoses and many other fields. [Copyright &y& Elsevier]

Abstract: A novel label-free electrogenerated chemiluminescence (ECL) DNA-based biosensing method for the determination of trace bleomycin (BLM) was developed on basis of Fe(II)·BLM-mediated DNA strand scission and Ru(phen)3 2+ as an ECL probe. A thiolated ss-DNA, as substrate for BLMs, was self-assembled onto surface of a gold electrode to form a hairpin structure. Ru(phen)3 2+ was intercalated into the hairpin DNA structure. In the presence of Fe(II)·BLM, the hairpin DNA sequence undergoes the irreversible cleavage event under the oxidative effect of BLM with Fe(II) as a cofactor and the intercalated Ru(phen)3 2+ released from the gold electrode, which can be transduced into a significant decrease in ECL intensity. The ECL intensity versus the concentration of BLMs was linear in the range from 0.1pM to 50pM. The detection limit was 0.03pM. This work demonstrates that using the sequence selectivity of DNA cleavage strategy for the fabrication of the label-free ECL biosensing method is a promising approach for the determination of antitumor drugs. [Copyright &y& Elsevier]

Abstract: A novel and ultrasensitive electrochemical approach for sequence-specific DNA detection based on signal dual-amplification with Au NPs and marker-loaded apoferritin NPs was reported. Target DNA was sandwiched between capture DNA coupled to magnetic beads and signal DNA self-assembled on Au NPs which were incorporated with marker-loaded apoferritin NPs. Subsequent electrochemical stripping analysis of the electroactive markers released from apoferritin NPs in acidic buffers provided a means to quantify the concentration of target DNA. In this means, one target signal could be transformed into multiple redox signals of the markers since a single Au NP could be loaded with dozens of apoferritin NPs, and an apoferritin NP could be loaded with thousands of markers. Under the optimum conditions, the linear range was from 2.0×10−16 to 1.0×10−14 M and the detection limit was 5.1×10−17 M by using the cadmium as a model marker. The proposed DNA biosensor not only exhibited excellent sensitivity but also had good reproducibility and selectivity against two-base mismatched DNA. [ABSTRACT FROM AUTHOR]

Neuron-specific enolase (NSE) is the preferred marker for monitoring small cell lung cancer and neuroblastoma. We devised a dual-signal ratiometric electrochemiluminescence (ECL) sensing strategy for sensitive detection of NSE. In this work, Ru (bpy) 3 2+ functionalized zinc-based metal-organic framework (Ru-MOF-5) nanoflowers (NFs) with plentiful carboxyl groups provide an excellent biocompatible sensing platform for the construction of immunosensor. Importantly, Ru-MOF-5 NFs possess stable and efficient "dual-potential" ECL emission of cathode (−1.5 V) and anode (1.5 V) in the existence of co-reactant K 2 S 2 O 8. Simultaneously, the cathode ECL emitter ZnO-AgNPs are employed as the secondary antibody marker, whose participation amplify the cathode ECL signal as well attenuate the anode ECL emission of Ru-MOF-5 NFs. By monitoring the ECL dual-signal of −1.5 V and 1.5 V and calculating their ratios, a ratiometric strategy of quantified readout proportional is implemented for the proposed immunosensor to precise analyze NSE. Based on optimization conditions, the ECL immunosensor displays the wide linear range of 0.0001 ng/mL to 200 ng/mL and the minimum detection limit is 0.041 pg/mL. The "dual-potential" ratiometric ECL immunosensor effectively reduces system error or background signal by self-calibration from both emissions and improves detection reliability. The dual-signal ratiometric strategy with satisfactory reproducibility and stability provides further development possibilities for other biomolecular detection and analysis. [Display omitted] • The single luminophore Ru-MOF-5 NFs showed "dual-potential" ECL emission. • The "dual-potential" of ECL emission was cathode (−1.5 V) and anode (1.5 V). • ZnO-AgNPs acted as both cathodic luminophore and anodic quencher. • The ratiometric immunosensor provided a novel strategy for NSE detection. [ABSTRACT FROM AUTHOR]

Procalcitonin (PCT) as a disease marker is of great significance in the early diagnosis of septicemia and pyemia. Biosensor have good prospects for analysis and detection of disease markers, but developing highly sensitive detection methods for detecting PCT remains a daunting task. In this paper, we develop a ratiometric electrochemical immunosensor with Au NPs modified SiO 2 -Fc-COOH complex as matrix and UiO-66 loaded with Toluidine blue (TB) as a marker for quantitative detection of procalcitonin (PCT). The SiO 2 modified by APTES not only has a large specific surface area but also contains abundant amino groups, which can be connected to the electrochemical probe of ferrocenecarboxylic acid (Fc-COOH). UiO-66 has the advantages of large specific surface area, high porosity and adjustable structure, which can adsorb toluidine blue electrochemical probe through electrostatic attraction. Measurement and analysis of the prepared immunosensor by Differential Pulse Voltammetry (DPV) show that the oxidation peak currents of Fc-COOH and TB appear at potentials of 0.30 V and −0.30 V respectively. As the PCT concentration increases, the oxidation peak current of TB increases and the oxidation peak current of Fc-COOH decreases. The ratios (ΔI = ΔI TB /ΔI Fc-COOH) between the double signals could show a certain linear relationship with the concentration of the PCT within a certain range. Under optimal conditions, the linear range of detection obtained by the immunosensor was 1 pg/mL-100 ng/mL and the detection limit was 0.3 pg/mL. In this work, the developed ratiometric electrochemical immunosensor not only provides a simple, reliable and sensitive strategy for quantitative detection of PCT but also provides a useful method for clinical detection of other disease markers. • A ratiometric electrochemical immunosensor was fabricated. • The electrochemical immunosensor utilized DPV. • SiO 2 -Fc–COOH–Au and UiO-66-TB were used as electrochemical signal probes. • The designed immunosensor exhibited low detection limit of 0.3 pg/mL for PCT. [ABSTRACT FROM AUTHOR]

An electrochemiluminescence (ECL) analytical platform was proposed for ultrasensitive detection of amyloid-β proteins (Aβ) based on the ECL resonance energy transfer (ECL-RET). In this work, gold nanoparticles-functionalized graphitic carbon nitride nanosheets (g-C 3 N 4 @Au NPs) and palladium nanoparticles-coated Metal organic framework (Pd NPs@NH 2 -MIL-53) were synthesized, which were as ECL donor and ECL acceptor respectively. A strong cathode ECL emission was obtained from the g-C 3 N 4 @Au NPs when used K 2 S 2 O 8 as its co-reactant. Here, Au NPs not only was used as an accelerator to enhance and stabilize the ECL signal, but also a connector for attaching Aβ antibody. In addition, NH 2 -MIL-53(Al) was selected as a label material for supporting Pd NPs to synergistically increase the intensity and range of UV-visible absorption. The ECL signal of g-C 3 N 4 @Au NPs was intensely decreased when the ECL acceptor probe Pd NPs@NH 2 -MIL-53 was incubated onto the modified GCE by way of the specific recognition. Under the optimal condition, a wide detection range from 10 fg/mL to 50 ng/mL and a low detection limit of 3.4 fg/mL (S/N = 3) were obtained. In consideration of favorable specificity, stability and reproducibility, the proposed method was successfully applied for Aβ detection in actual human serum samples and could be a potential analytical tool for sensitive molecular trace detection in clinical analysis. • A new ECL-RET donor-receptor was proposed and fabricated for ultrasensitive detection of Aβ. • Au NPs conjugated with g-C 3 N 4 to increase its biocompatibility and emission performance. • Pd NPs coated NH 2 -MIL-53(Al) was used as the ECL quencher probe for the first time. • The designed immunosensor exhibited low detection limit of 3.4 fg mL-1 for Aβ. [ABSTRACT FROM AUTHOR]

Development of a simple, cost-effective and sensitive biosensing strategy is highly desirable to advance the applications in Alzheimer's disease diagnosis. In this paper, we present a simple, label-free and signal-on electrochemiluminescence (ECL) aptasensor for the detection of amyloid-beta (Aβ) peptide using luminol as ECL emitter and in-situ generated reactive oxygen species (ROS) as coreactant via catalytic reaction between Cu2+-Aβ and the dissolved O 2 in the presence of ascorbic acid (AA). Aβ 16 , the binding site of Cu2+ in the monomeric full-length Aβ, was used as a model in present study. As a result, this signal-on ECL aptasensor has exhibited favorable analytical performance for Aβ 16 monomer with a linear range of 1.0 × 10-13 mol/L-1.0 × 10-8 mol/L and a limit of detection of 3.5 × 10-14 mol/L (S/N=3). Furthermore, the proposed biosensor was also able to detect the full length Aβ 40 not only in the phosphate buffer saline (PBS) solution but also in human serum. The presented biosensor represents a promising, simple, turn-on and label-free diagnostic tool for blood analysis. • A simple, label-free and signal-on ECL aptasensor for the detection of Aβ peptide was development. • The aptasensor can monitor the aggregation process of Aβ 16 monomer accelerated by Cu2+. • The proposed biosensor was able to detect the full length Aβ 40 not only in the PBS solution but also in human serum. [ABSTRACT FROM AUTHOR]