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Alpha-fetoprotein (AFP) is inextricably linked to various diseases, including liver cancer. Thus, detecting the content of AFP in biology has great significance in diagnosis, treatment, and intervention. Motivated by the urgent need for affordable and convenient electronic sensors in the analysis and detection of aqueous biological samples, we combined the solution-gated graphene transistor (SGGT) with the catalytic reaction of enzyme nanoprobes (HRP-AuNPs-Ab2) to accurately sense AFP. The SGGT immunosensor demonstrated high specificity and stability, excellent selectivity, and excessive linearity over a range of 4 ng/mL to 500 ng/mL, with the lower detection limit down to 1.03 ng/mL. Finally, clinical samples were successfully detected by the SGGT immunosensor, and the results were consistent with chemiluminescence methods that are popular in hospitals for detecting AFP. Notably, the SGGT immunosensor is also recyclable, so it has excellent potential for use in high-throughput detection. [ABSTRACT FROM AUTHOR]

N-doped carbon Co/CoOx with laccase-like activity was directionally designed by pyrolyzing Co-coordination polymer and applied to detect epinephrine, which revealed a new preparation strategy for laccase mimics. The formation mechanism of the N-doped carbon Co/CoOx nanozyme was reconnoitered by a thermogravimetric-mass spectrometry system (TG-MS). N-doped carbon Co/CoOx exhibited outstanding laccase-like activity, and the Michaelis–Menten constant and maximum initial velocity were calculated to be 0.087 mM and 0.0089 μM s–1, respectively. Based on this principle, a simple colorimetric sensing platform was developed for the quantitative detection of epinephrine, which can be used to diagnose pheochromocytoma. In addition, the visual platform for detecting epinephrine exhibited a linear range of 3 to 20 μg mL−1 and a calculated detection limit of 0.42 μg mL−1. Therefore, the proposed colorimetric sensing platform is a promising candidate to be applied in precise early pheochromocytoma diagnosis. [ABSTRACT FROM AUTHOR]

Nanozymes are a kind of nanomaterial with enzymatic activity, and have attracted wide attention in signal probe fields owing to their good catalytic activity and stability. Herein, we designed gold@platinum nanorods (Au@Pt) with enhanced oxidase-like activity as signal probes to construct lateral flow biosensors (LFBs) for the detection of hepatitis B virus DNA (HBV-DNA). The enhanced oxidase-like activity of Au@Pt nanorods can effectively catalyze the oxidation of 3,3′,5,5′-tetramethylenebenzidine (TMB) to a blue substrate in the absence of hydrogen peroxide (H2O2). Based on this principle, LFBs using Au@Pt nanorods as signal probes can provide an effective signal amplification strategy and prevent biomolecules from being affected by H2O2. Under optimal conditions, LFBs have a good linear relationship between 0.1 nM and 50 nM, and the calculated detection limit was 8.5 pM. The technological strategy in the detection and quantification of HBV-DNA in this work may be helpful to achieve a rapid and accurate diagnosis of early HBV-DNA and provide new ideas for the development of point-of-care testing. [ABSTRACT FROM AUTHOR]

Using a simple fluorogenic reaction and the inner filter effect, a label-free ratiometric method for biothiol detection is developed. The reaction between dopamine and resorcinol can generate azamonardine with strong fluorescence. Since the absorption spectrum of azamonardine overlaps with the excitation spectrum of the mercaptopropionic acid-stabilized CdTe quantum dots (MPA-CdTe QDs), the emission of QDs can be quenched via the inner filter effect in the presence of azamonardine. Biothiols can inhibit the above fluorogenic reaction, resulting in the weakening of the fluorescence of azamonardine and the recovery of the emission of MPA-CdTe QDs. The fluorescence intensity ratio of azamonardine to MPA-CdTe QDs can be used to detect biothiols. This approach exhibited a linear trend to the biothiol concentrations in the range of 2 μM to 12 μM, with a limit of detection of 0.6 μM (S/N = 3). This ratiometric analysis strategy was further applied to detect biothiols in human serum samples, showing their great application potentials in real biological samples. The constructed method is simple, easy to prepare, and low-cost. [ABSTRACT FROM AUTHOR]

In this paper, we constructed a label-free ratiometric fluorescence nanoprobe for ascorbic acid (AA) on the basis of the change in dual-emission signals by the specific reaction between cobalt oxyhydroxide (CoOOH) and AA. CoOOH nanoflakes were used as the recognition unit while polymer dots (PFO dots) and gold nanoclusters (AuNCs) served as luminescent units of the nanoprobe. After electrostatic assembly of PFO dots and AuNCs on the surface of CoOOH nanoflakes, the energy transfer between the PFO dots and CoOOH could occur and thereby quench the fluorescence of the PFO dots. When AA was present, CoOOH nanoflakes were reduced to Co2+, resulting in a recovery of the fluorescence of the PFO dots. In the meantime, the generated Co2+ could combine with the surface ligands of AuNCs, accompanied by a reduction in the luminescence intensity of the AuNCs. Therefore, the fluorescence intensity ratio of PFO dots to AuNCs would be related to the concentration of AA. The nanoprobe enabled highly sensitive analysis of AA with a detection limit of 1.9 μM and showed great performance in human serum samples and living cells. This report may not only endow a CoOOH-based nanoprobe with improved ability but also offer a novel strategy for the construction of ratiometric nanoprobes for AA and have potential applications in research into and clinical diagnosis of AA-related diseases. [ABSTRACT FROM AUTHOR]

Gold nanoclusters (Au NCs) are a type of emerging ECL emitter with molecule-like properties and low toxicity that hold great potential for sensing application. However, the application of Au NCs in ECL sensing is still limited due to their low ECL efficiency. In this work, we provided an effective way to enhance the ECL efficiency of Au NCs. By doping Ag on GSH-protected Au NCs to form bimetallic clusters (GSH-Ag/Au NCs), the ECL efficiency of Au NCs was greatly improved. Based on the enhanced ECL signal of Au NCs, an ultrasensitive ECL sensor was constructed for the detection of dopamine (DA). DA exhibited a prominent ECL quenching effect towards the formed bimetallic GSH-Ag/Au NCs which can be used for DA detection. The proposed ECL sensor exhibited excellent sensitivity, selectivity and stability and had a wide linear range from 10 nM to 1 mM with a low detection limit of 2.3 nM (S/N = 3). More importantly, this work provided a potential method to improve the ECL properties of Au NCs and widen their analytical application. [ABSTRACT FROM AUTHOR]

Water-soluble cadmium telluride quantum dots capped with 3-mercaptopropionic acid were synthesized and further modified with 3-aminophenylboronic acid to form boronic acid-functionalized quantum dots (QDs). Under excitation at 350 nm, the modified QDs display yellow fluorescence with a peak at 566 nm. On exposure to copper(II), the fluorescence of the QDs is quenched. Under optimal conditions, fluorescence drops linearly in the 0.01 to 20 μM Cu(II) concentration range, and the detection limit is 7.6 nM. This fluorescent probe was applied to the determination of Cu(II) in spiked human serum and water samples and gave satisfactory results. [ABSTRACT FROM AUTHOR]

In this work, a novel ratiometric fluorescence nanoprobe based on Au 3+ -triggered aggregation-induced emission (AIE) behavior of silver nanoclusters (Ag NCs) was designed for the label-free detection of biothiols. The probe was constructed by loading of Au 3+ on g-C 3 N 4 nanosheets surface and subsequently aggregating Ag NCs via ion binding. As Au 3+ could conversely regulate the emission of g-C 3 N 4 nanosheets and Ag NCs, the remove of Au 3+ from nanoprobe by coordination with biothiols would change the emission ratio of nanoprobe that could be used for biothiols detection. The probe provided high sensitivity for glutathione (GSH) determination with the limit of detection as low as 0.8 μM and showed satisfying performance in human serum samples. This report may offer a new sight for the construction of ratiometric probe based on the AIE behavior of Ag NCs and broaden its applications in biosensing. [ABSTRACT FROM AUTHOR]

Molecular detection of nucleic acid plays an important role in early diagnosis and therapy of disease. Herein, a novel and enhanced electrochemical biosensor was exploited based on target-activated CRISPR/Cas12a system coupling with nanoparticle-labeled covalent organic frameworks (COFs) as signal reporters. Hollow spherical COFs (HCOFs) not only served as the nanocarriers of silver nanoparticles (AgNPs)-DNA conjugates for enhanced signal output but also acted as three-dimensional tracks of CRISPR/Cas12a system to improve the cleavage accessibility and efficiency. The presence of target DNA triggered the trans-cleavage activity of the CRISPR/Cas12a system, which rapidly cleaved the AgNPs-DNA conjugates on HCOFs, resulting in a remarkable decrease of the electrochemical signal. As a proof of concept, the fabricated biosensing platform realized highly sensitive and selective detection of human papillomavirus type 16 (HPV-16) DNA ranging from 100 fM to 1 nM with the detection limit of 57.2 fM. Furthermore, the proposed strategy provided a versatile and high-performance biosensor for the detection of different targets by simple modification of the crRNA protospacer, holding promising applications in disease diagnosis. [ABSTRACT FROM AUTHOR]

Owing to its rapid response and ultra-high sensitivity at single-entity level, single-particle collision electrochemistry (SPCE) shows great application prospects in sensitive detection of biomolecules. However, its widespread use in actual samples is constrained by the poor signal conversion efficiency and heavy interference from complicated samples. Here, a new SPCE biosensor for clinical analysis of cardiac troponin I (cTnI) was developed based on the effective signal amplification of CRISPR/Cas12a as well as the good separation and enrichment capabilities of magnetic nanobeads (MBs). The trans-cleavage capability of CRISPR/Cas12a can only be triggered in the presence of target cTnI to effectively cleave ssDNA 2 on the surface of Au@Pt nanoparticles (Au@Pt NPs) within 30 min. Each cTnI molecule could cause the release of 4.68×104 Au@Pt NPs by utilizing the superior cleaving activity of CRISPR/Cas12a, significantly amplifying the signal and improving the sensitivity of analysis. The developed SPCE biosensor for cTnI had a detection limit as low as 0.35 fg/mL, which was 2–6 orders in magnitude less than existing cTnI detection techniques. Additionally, MBs allow the biosensor to detect cTnI in patient samples with excellent sensitivity and specificity by directly sampling from the complex matrix. [Display omitted] • Using collision frequency instead of current intensity can solve the problem of current fluctuation. • CRISPR/Cas12a-assisted SPCE biosensor realized ultrasensitive detection of cTnI with a low detection limit of 0.35 fg/mL. • MBs allow the biosensor to detect cTnI in patient samples with excellent sensitivity and specificity. [ABSTRACT FROM AUTHOR]

The development of some sensitive methods for MUC1 is critical for preclinical diagnosis of tumors. In this experiment, we built a triple-amplified electrochemical aptasensor to achieve sensitive detection of MUC1, which was based on exonuclease III (Exo III)-assisted with strand displacement reaction and enzyme catalytic strategy. Firstly, with the help of Exo III, MUC1 and aptamer could be recycled during the cycle I, the single stranded DNA-1 (S-1) was produced during the process and was introduced to the hybride reaction on the electrode. Secondly, during the cycle II, strand displacement reaction was triggered on the electrode with the adding of hairpin DNA-2 (H-2). Thirdly, after the gold nanoparticles (AuNPs)-DNA-enzyme conjugates hybrided with the H-2 on the electrode, the AuNPs-DNA-enzyme conjugates could act as signal probe to produce electrochemical catalytic signal. We used the fabricated triple-amplified electrochemical aptasensor that could detect MUC1 from 0.1 pg mL−1 to 10 ng mL−1 with the detection limit of 0.04 pg mL−1 under the optimized experimental conditions. The constructed triple-amplified electrochemical aptasensor could be applied in real samples determination. Besides, the strategy can be applied to detect other proteins for health monitoring. Image 1 • The proposed electrochemical aptasensor achieved sensitive detection of MUC1. • The Exo III-assisted cycling and strand displacement reaction improved the sensitivity of MUC1 detection. • The AuNPs-DNA-enzyme conjugates could act as signal probe resulted in significant signal output. • The aptasensor could be applied in real samples determination and hold great potential for the detection of other proteins. [ABSTRACT FROM AUTHOR]

• The dual-amplified biosensor achieved ultrasensitive PPase detection and inhibitors screening. • One-pot synthesis of AuNCs-MnO 2 nanoflakes with peroxidase-like characteristics provided an effective catalytic platform. • Enzymatic hydrolysate-induced Cu2+ release from Cu2+–PPi complex opened Cu2+-DNAzymes amplification process. • Cu2+-DNAzymes and Exo III built a signal-on detection mode that inproved the sensitivity and selectivity of biosensor. A novel dual-amplified electrochemical biosensor based on Exonuclease III (Exo III) and Cu(II)-dependent DNAzymes (Cu2+-DNAzymes) was developed for ultrasensitive electrochemical evaluation of pyrophosphatase (PPase) activity with the help of one-step synthesis of BSA-directed gold nanoclusters-manganese dioxide (AuNCs-MnO 2) nanoflakes with peroxidase-like characteristics as a catalytic platform. For biosensor preparation, under the catalytic hydrolysis of the PPase, copper ion (Cu2+) was released from the Cu2+-coordinated pyrophosphate ions (Cu2+–PPi) complex which was formed by the coordination reaction of copper ion (Cu2+) and pyrophosphate ions (PPi). The released Cu2+, acting as an indispensable cofactor, could activate Cu2+-DNAzymes to turn on the amplification process and then generated the single-stranded product (S1) that hybridized to the hairpin-type capture probe (HP1). Subsequently, the addition of Exonuclease III (Exo III) enabled the reuse of S1 and produced the final cleavage fragment, which closely linked the functionalized AuNCs-MnO 2 nanoflakes to the electrode surface. The superior peroxidase-like characteristics of nanoflakes provided stable catalytic signal output and realized electrochemical monitoring of PPase activity with a detection limit of 0.0058 mU/mL. Importantly, the biosensor also had a good performance in inhibitors screening of target PPase. The use of AuNCs-MnO 2 nanoflakes instead of natural enzymes combined with DNAzymes amplification strategy offered more possibilities for the detection of various biomolecules. [ABSTRACT FROM AUTHOR]

Abstract In this work, an innovative aptasensor based on electrochemiluminescence resonance energy transfer (ECL-RET) from CdTe quantum dots (QDs) to a cyanine dye (Cy5) fluorophore for the determination of Ochratoxin A (OTA) was fabricated. A strong cathodic ECL emission was obtained by the CdTe QDs modified glassy carbon electrode (GCE). After the immobilization with the capture DNA (cDNA) and the sequential hybridization with the probe DNA-modified Cy5 (pDNA, the aptamer of OTA), the ECL signal enhanced obviously through the ECL-RET. Meanwhile, the spectrum- and distance-related ECL enhancement effect was investigated. When the target OTA was in the presence, the pDNA-Cy5 molecules were released from the electrode surface owing to the specific interaction between OTA and aptamer, resulting in an evident decrease of ECL signal. Under optimal conditions, the developed aptasensor displayed the linear response toward OTA in the wide range of 0.0005–50 ng/mL with a low detection limit of 0.17 pg/mL. With the excellent selectivity, stability and repeatability, the strategy provided an efficient and universal method for the sensitive detection of target in practical application. Graphical abstract fx1 Highlights • A simple and convenient aptasensor for OTA was prepared. • The ECL-RET aptasensor based on CdTe QDs and Cy5 has high sensitivity. • This sensor has a good specificity since the great affinity of aptamer to target. • The aptasensor could be applied to detect OTA in corn. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) have been perceived as important regulators in multifarious biological processes as well as potential biomarkers in clinical diagnosis. Exploring high-efficient sensing platforms for tracing miRNAs in complex biological samples is of great vital. Herein, an ultrasensitive and enzyme-free electrochemical biosensor was constructed based on integration of efficiently catalytic electrochemical−chemical−chemical (ECC) redox cycling with target-induced magnetic DNAzyme walker. Employing porous and easily functionalized covalent organic framework (COF) as carriers, Pt@COF nanospheres (Pt@COF NSs) were facilely prepared by in-situ reduction of platinum precursors in the nanopores-structure of COF. This not only addressed the inevitable migration of pure Pt nanoparticles, but endowed Pt@COF NSs with desirable stability and excellent catalytic activity to boost ECC redox cycling for effective signal enhancement. On this basis, a target-induced magnetic DNAzyme walker was obediently induced to recognize, separate and convert low-abundant miRNA-21 targets into plentiful output DNA chains for accumulated signal amplification. Finally, the as-prepared robust biosensor manifested highly sensitive and selective determination of miRNA-21 with a wide detection range from 100 aM to 10 pM and a low detection limit of 47.5 aM. Meanwhile, the credible detectability and anti-interference were also demonstrated in serum and cell samples, indicating its promising application toward diseases warning. [Display omitted] • Pt@COF nanocatalyst was gained by in-situ growth of Pt in porous COF carriers. • The catalytic Pt@COF-based redox cycling greatly boosted electrochemical signal. • A magnetic DNAzyme walker achieved miRNA-21 recognition, separation and conversion. • This signal amplification system was used for ultrasensitive miRNA-21 detection. [ABSTRACT FROM AUTHOR]

Rapid and sensitive virus genes detection with point-of-care testing is the key to improving the probability of survival and lowering infectious rate. Here, we proposed a sensitive and quantitative colorimetric lateral flow biosensor (CLFB) for human immunodeficiency virus-DNA (HIV-DNA) detection with a novel nanomaterial (Pt nanoparticles decorated Ti 3 C 2 T x MXene, Pt/Ti 3 C 2 T x) as signal reporters. Pt/Ti 3 C 2 T x was synthesized by a self-reduction method with Ti 3 C 2 T x as both reducing agent and supporter. Each Pt/Ti 3 C 2 T x contained hundreds of Pt nanoparticles to achieve enhanced colorimetric dual-readout, which can not only show gray color itself, but also catalyze its substrate to produce more obvious red color within 3 min. The integration of mimic enzyme property of Pt/Ti 3 C 2 T x improved the colorimetric signal brightness and decreased naked-eye detection limit of HIV-DNA to 0.1 nM relative to original 0.8 nM. Capture DNA was further modified onto the Pt/Ti 3 C 2 T x to realize specific binding with HIV-DNA, enabling the CLFB good reproducibility with an average intra-assay deviation of 4.3% and an inter-assay deviation of 4.2% respectively. Furthermore, the successful detection of HIV-DNA in serum samples demonstrated its great application potential in real samples and timely diagnosis. [Display omitted] • Pt/Ti 3 C 2 T x was prepared by one-step self-reduction method and used as signal reporters in CLFB for the first time. • Each Pt/Ti 3 C 2 T x contained hundreds of Pt NPs, enhancing colorimetric signal and exhibiting excellent mimic enzyme activity. • The colorimetric lateral flow biosensor has great potential in point-of-care testing (POCT) and early diagnosis. [ABSTRACT FROM AUTHOR]

In this work, a flexible and label-free electrochemical biosensing platform had been developed based on split aptamers and the cleavage effect of exonuclease I, which was applied for the detection of different targets in parallel. In the presence of targets, the two split aptamers could specifically recognize targets to form a ternary complex, which cannot be digested by exonuclease I, resulting in significant impedance signal output. The proposed label-free aptasensor realized sensitive and selective detection of thrombin, adenosine triphosphate and mercury ion with the detection limits of 32 fM, 1.43 pM and 1.65 pM, respectively. The designed strategy provided a simple and powerful tool for multiple targets detection, holding promising applications in disease diagnosis and environmental monitoring. [Display omitted] • A flexible label-free electrochemical impedance sensor based on split aptamers has been developed. • The split aptamers simplifies the experimental procedure and enhances the detection efficiency. • The Exo I based signal amplification strategy combined with the split aptamers improves the performance of the aptasensor. • The flexibility of the proposed aptasensor was verified by detecting thrombin, ATP and Hg2+, respectively. [ABSTRACT FROM AUTHOR]

Among one-dimensional nanostructures, copper oxide nanotubes (CuO NTs) have aroused wide attention due to their prominent performance in electronic, optical and energy conversion devices. However, the lack of suitable synthetic methods limits its large-scale production and broad application. Here, a new method for preparing well-dispersed CuO NTs with simple operation, mild conditions and low cost was established by integrating the synergy effect of H+ corrosion with the protection of CH 3 COO− and surfactant. Different surfactants were applied to regulate the synthetic process and polyvinylpyrrolidone-protected CuO NTs (PVP-CuO NTs) owned the best uniform morphology and dispersibility. The synthesis mechanism was deeply investigated to provide guidance for the synthesis of other oxide nanotube structures. As an excellent semiconductor material, CuO NTs can be excited to produce multiple electron-hole pairs under light irradiation, thus catalyzing the reduction of H 2 O 2. CuO NTs modified photocathode realized photoelectrochemical sensing of H 2 O 2 in the range of 1 μM-1 mM. Interestingly, the prepared CuO NTs exhibited wonderful mimic enzyme properties, providing the possibility of colorimetric sensing and point-of-care detection. The colorimetric sensor for H 2 O 2 detection had a linear relationship from 2 μM to 150 μM with a detection limit of 0.62 μM. The successful construction of the two sensing modes not only demonstrated the excellent performance of multifunctional CuO NTs, but also indicated its great promise in practical application. A new method for synthesizing CuO NTs and its application in photoelectrochemical and colorimetric detection of H 2 O 2. [Display omitted] • A new method for synthesis of dual-functional CuO NTs with simple operation, mild conditions and low cost was established. • The formation mechanism of CuO NTs was explored, which was attributed to the synergy effect of H+ corrosion and the protection of CH 3 COO− and surfactants. • Two sensing modes, photoelectrochemical and colorimetric, were developed for H 2 O 2 detection with a detection limit low to 0.08 μM and 0.62 μM respectively. [ABSTRACT FROM AUTHOR]

Dual-amplification strategies of co-reaction accelerators and DNA walker was adopted to construct ECL sensor for ultrasensitive detection of miRNA-141. [Display omitted] • SQDs were obtained through a PEG-stabilized and H 2 O 2 -assisted top-down method. • Pd@Au NPs were served as co-reaction accelerators to boost ECL emission of SQDs. • DNA walker greatly promoted the signal-amplification for constructed ECL sensor. • SQDs-based ECL biosensor provided a low LOD of 1.39 fM for miRNA-141 detection. Herein, a novel electrochemiluminescence (ECL) biosensor for sensitive detection of miRNA-141 was fabricated based on sulfur quantum dots (SQDs) with the strategies of co-reaction accelerators and endonuclease recycling dual-amplification. Using SQDs as an ECL signal probe, the DNA walker was immobilized on the modified electrode for dual-amplification. At first, convex hexoctahedral palladium@gold nanoparticles (Pd@Au NPs) which acted as co-reaction accelerators could catalyze the dissociation of co-reactants into active radicals and significantly promote the ECL emission of SQDs. Secondly, the Pd@Au NPs acting as the carrier for DNA walker provided an enzymatic-cycling amplification strategy for ultrasensitive and specific detection of miRNA-141. Thereinto, the restriction endonuclease Nt.BbvCI recognized the specific sequence and cleaved the ferrocene-labeled oligonucleotides (Fc-S2) from the double-stranded DNA substrate. Thus, ferrocene (Fc) was detached far away from the biosensor's surface and the exposed Pd@Au NPs acted as co-reaction accelerators to enhance ECL signal. This greatly improved the ECL emission efficiency of SQDs and the sensitivity of the biosensor. Based on the dual-amplification strategy, the ECL biosensor had a detection range from 10 fM to 300 pM with a low detection limit of 1.39 fM. The present strategy enabled highly accurate and sensitive detection of miRNA-141 in multifarious bioanalysis and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Self-powered sensing platforms have received widespread attention in areas such as portable, wearable and point-of-care devices. Here we reported visible light mediated self-powered electrochemical sensing based on target induced recombination of photogenerated carriers, which has highly sensitive to detect copper ions concentration. We utilized the recombination of photogenerated carriers mechanism to design visible light-responsive Fe 2 O 3 -CdS n-n heterojunction as photoanode material, which greatly improved the problem of output energy in photocatalytic self-powered sensors. Expectedly, our proposed visible light mediated self-powered electrochemical system has high separation efficiency of photogenerated carriers, which is 8.4 times that in presence of Cu2+. Furthermore, this self-powered electrochemical sensing platform used Cu2+ induced recombination of photogenerated carriers, showed a clear linear relationship from 1 nM to 5000 nM with an acceptable detection limit of 0.4 nM. This self-powered electrochemical sensing platform with excellent selectivity, accredited reproducibility and believable stability exhibited promising prospects in developing portable sensing devices and detection chip for real-time and rapid monitoring of Cu2+. ga1 • We designed self-powered sensor based on recombination of photogenerated carriers. • Visible light-responsive Fe 2 O 3 -CdS n-n heterojunction as photoanode were reported. • The target induces the recombination of photogenerated carriers in heterojunction. • Fe 2 O 3 -CdS n-n heterojunction have high carrier separation efficiency. • The self-powered electrochemical sensor can detect Cu2+ in water environments. [ABSTRACT FROM AUTHOR]

• GR@ZIF-8 hybrids were used as template to anchor AuNCs. • On AuNCs-GR@ZIF-8 platform, LB-HCR was designed with assembly of four hairpins. • Target-triggered LB-HCR generated dendritic DNA nanostructures decorated with DNAzyme as amplifying labels. • The multiple-amplified biosensor achieved IFN-γ detection with a low detection limit of 0.6 fM. In this work, a novel electrochemical biosensor was constructed for ultrasensitive interferon-gamma (IFN-γ) detection based on graphene@zeolitic imidazolate framework-8 hybrids anchored gold nanoclusters (AuNCs-GR@ZIF-8) and hemin/G-quadruplex DNAzyme decorated layered-branched hybridization chain reaction (LB-HCR). The two-dimensional GR@ZIF-8 hybrids were utilized as template to anchor AuNCs through a sequential deposition method. On the AuNCs-GR@ZIF-8 platform, an improved and efficient LB-HCR pattern was designed on the strength of traditional HCR with the cascade-like assembly of four hairpins. In which, HP1 and HP2 participated in traditional HCR process to form long double-helix DNA, AD1 and AD2 assembled alternately to facilitate the layerly chain-branching growth of DNA nanostructures. The target-triggered LB-HCR resulted in the generation of dendritic DNA nanostructures integrated with numerous in-situ formed hemin/G quadruplex DNAzyme as amplifying labels, which catalyzed the reduction of H 2 O 2 with thionine acted as the electron mediator to realize amplified signal output. This multiple-amplified strategy exhibited good analytical performance towards IFN-γ with a wide linear range form 1 fM to 50 pM and a low detection limit of 0.6 fM, holding promising application in disease diagnosis and monitoring. [ABSTRACT FROM AUTHOR]

In this paper, a novel label-free electrochemical impedance aptasensor for highly sensitive detection of IFN-γ based on target-induced exonuclease inhibition was constructed. For this purpose, we designed a DNA hairpin modified on the gold electrode whose loop was the aptamer of the IFN-γ, and the stem was 5′-thiol-modified. In the absence of IFN-γ, Exonuclease III (Exo III) and Exonuclease I (Exo I) digested the double-stranded and single-stranded strands of the hairpin DNA, respectively, causing smaller impedance value on the surface of the electrode. In the presence of IFN-γ, the function of Exo III was greatly inhibited by the binding of the aptamer with the target, and it stopped after cutting three bases of the hairpin DNA. Forming a major target-bound aptamer digestion product, it could not be digested by Exo I, so there was larger impedance on the electrode surface. The calibration curve for IFN-γ was linear in the range of 1 pM–50 nM with the detection limit (LOD) of 0.7 pM. The proposed aptasensor proved good selectivity and reproducibility, and low cost. In addition, the biosensor was able to detect IFN-γ in serum samples successfully, which is expected to provide an efficient method for TB diagnosis at early stages. • The strategy target-induced exonuclease inhibition was developed for electrochemical detection of macromolecules. • A novel label-free electrochemical impedance aptasensor was constructed for highly sensitive detection of IFN-γ. • This aptasensor could achieved a low limit of detection of 0.7 pM with a wide linear range of 1 pM to 50 nM. [ABSTRACT FROM AUTHOR]