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Mercury ion (Hg2+) poses a serious threat to human health due to its high toxicity. In this study, a smartphone-based photoelectrochemical sensor based on oxygen vacancies (OVs) driven signal enhancement for mercury ion detection was designed. BiVO 4-x /Bi 2 S 3 /AuNPs were combined with T−Hg2+−T recognition mode to construct a multi-sandwich photoelectrochemical sensor. On the one hand, the OVs can increase the adsorption of light by the materials and enhance the photocurrent response as well as the superconductivity of Au NPs to accelerate the charge transfer at the electrode interface. On the other hand, the multi-sandwich structure was exploited to increase the binding site of Hg2+, as well as the T−Hg2+−T structure for sensitive recognition of Hg2+ and signal amplification. The sensor showed good linearity for Hg2+ concentration in the range of 0.1 nM–1.0 μM with a detection limit of 4.8 pM (S/N = 3). Eventually the smartphone-based real-time detection sensor is expected to contribute to the future analysis of heavy metal ions. [Display omitted] • Vacancy-rich BiVO 4-x /Bi 2 S 3 as substrate material provides excellent performance. • Multi-sandwich chain structure increases Hg2+ recognition sites. • Sensitive recognition of Hg2+ using the T−Hg2+−T structure. • PEC sensor exhibited a low detection limit of 4.8 pM for Hg2+. [ABSTRACT FROM AUTHOR]

The incidence of esophageal cancer is positively associated with fumonisin contamination. It is necessary to develop methods for the rapid detection of fumonisins. In this work, a self-powered photoelectrochemical aptamer sensor based on ZnIn 2 S 4 /WO 3 photoanode and Au@W–Co 3 O 4 photocathode is proposed for the sensitive detection of fumonisin B1 (FB1). Among them, under visible light irradiation, the Z-type heterostructure of ZnIn 2 S 4 /WO 3 acts as a photoanode to improve the electron transfer rate, which contributes to the enhancement of the photocathode signal and lays the foundation for a wider detection range. The Au@W–Co 3 O 4 photocathode as a sensing interface reduces the probability of false positives (comparison of anode sensing platforms). The PEC sensor has a good working performance in the detection range (10 pg/mL-1000 ng/mL) with a detection limit of 2.7 pg/mL (S/N = 3). In addition, the sensor offers good selectivity, stability and excellent recoveries in real sample analysis. This work is expected to play a role in the field of analyzing environmental toxins. [ABSTRACT FROM AUTHOR]

Advanced bioelectronic detection based on the integration of modern optical electronics and biological systems has a broad prospect. The strategy of cathode signal amplification in self-powered photoelectrochemical (PEC) immunosensors with excellent performance is rarely reported in the field of immune analysis. Herein, the work demonstrates a self-powered PEC biosensor formed with BiOI photocathode and WO 3 /SnS 2 /ZnS photoanode, and CsPbBr 3 @COF–V was used as the photocathode signal quenching source for the quantitative monitoring of heart fatty acid binding protein (H-FABP). The high efficiency and stable self-powered biosensor formed not only provides continuous and powerful photocurrent response for bioanalysis through reasonable stepped band structure, but also effectively eliminates the interference of reducing substances. The quenching source CsPbBr 3 @COF–V greatly affects the photocurrent response due to steric hindrance, weak conductivity, competition with the substrate for dissolved oxygen and excitation light source. And the intervention of this key factor achieves multiple signal amplification effect and opens up an innovative vision for self-powered PEC immunosensor. Taking H-FABP as a representative analyte, the proposed signal amplification self-powered photoelectrochemical presents a broad linear range from 0.0005 to 150 ng/mL with the detection limit of 0.19 pg/mL. [ABSTRACT FROM AUTHOR]

Exploring facile strategy for developing highly efficient emitters using water-insoluble luminophores has become a vital topic in electrochemiluminescence (ECL) immunoassay. In this work, an ECL-active and water-dispersive iridium(III) complex-based polymer dots (IrPdots) was fabricated by encapsulating water-insoluble tris[1-phenylisoquinolinato-C2, N] iridium(III) complexes [Ir(piq) 3 ] into poly-(styrene-co-maleic anhydride) (PSMA) matrix by a controllable nanoprecipitation process. The obtained IrPdots generated strong ECL signals in the presence of tri- n -propylamine (TPrA) and were used to label detection antibody (Ab 2) to act as ECL probes to indicate the signal changes when analyzing target antigen. To construct a sandwich immunosensor, Pd nanoparticles (NPs) decorated MoS 2 /Ti 3 C 2 T x MXene nanocomposites (MoS 2 /Ti 3 C 2 T x MXene/Pd) were fabricated as substrates to bind capture antibody (Ab 1), which could further amplify ECL signals via a coreaction-accelerating pathway to improve the detection sensitivity. When the cytokeratin 19 fragment 21-1 (CYFRA 21-1) was chosen as model analyte, the developed immunosensor displayed a good linear relationship ranging from 0.1 pg/mL to 50 ng/mL with a low detection limit of 95 fg/mL (S / N = 3) was achieved as well. This research proposed a facile and effective method of fabricating IrPdots as ECL probes for immunoassay using water-insoluble iridium complexes, which expanded the application scope of those water-insoluble luminophores for aqueous bioanalysis. [Display omitted] • An ECL-active Ir(piq) 3 -based polymer dots (IrPdots) was fabricated through a controllable nanoprecipitation method. • The biocompatible IrPdots as ECL probe were used to construct a sandwich immunoassay. • Pd nanoparticles (NPs) decorated MoS 2 /Ti 3 C 2 T x MXene was fabricated to amplify ECL emission. • The IrPdots-based immunosensor performed high sensitivity and accuracy for CYFRA 21-1 detection. [ABSTRACT FROM AUTHOR]

Self-supported Fe3N-Co2N nanoarray with high electric conductivity and large surface area was prepared for growth of MIPs and further constructing a sensitive and stable electrochemical sensor. For the evaluation of its performance, Fe3N-Co2N is used as sensing electrode material, and AMP is used as template molecule to construct the MIP electrochemical sensor. Under the optimized conditions, the developed MIPs electrochemical sensor detects AMP with a low detection limit of 3.65 × 10−10 mol L−1 and shows outstanding reproducibility and stability. When the MIPs electrochemical sensor was applied to detect AMP in milk samples via standard addition method, the recovery within 97.06–102.43% with RSD of 1.05–2.11% was obtained. The fabrication of MIPs electrochemical sensor is highly promising for sensitive and selective electrochemical measurement and food safety testing. This work can provide theoretical guidance for truly challenging problems. [ABSTRACT FROM AUTHOR]

Development of new strategies in photoelectrochemical (PEC) sensors is an important way to realize sensitive detection of biomolecule. In this study, mesoporous silica nanospheres (MSNs)-assisted split-type PEC aptasensor with in situ generation of Bi 2 S 3 was proposed to achieve reliable detection of prostate-specific antigen (PSA). To be more specific, this bioresponsive release system will release large amounts of Na 2 S by the reaction between PSA and aptamer that capped Na 2 S-loading MSNs. Next, the Na 2 S reacts with Bi to yield BiOI/BiOBr/Bi 2 S 3 composite, which leads to an alteration in the electron-hole transfer pathway of the photoelectric material and a decrease in the response. As the PSA concentration increases, more Na 2 S can be released and lower photocurrent is obtained. The linear range under the optimal experimental conditions is 10 pg·mL−1-1 μg⋅mL−1, and the detection limit is 1.23 pg⋅mL−1, which has satisfactory stability and anti-interference. [Display omitted] • MSNs-assisted PEC aptasensor is constructed to detection of PSA. • BiOI/BiOBr destruction by in situ formation of Bi 2 S 3 causes signal quencher. • The controlled-release strategy effectively ensures biological activity. [ABSTRACT FROM AUTHOR]

One competitive aptasensor based on novel intramolecular ECL emission system was investigated for ultrasensitive detection of E 2. It should be noted that the Ru(II) derivative for the mechanism of intramolecular ECL could improve electron transfer efficiency and reduce energy consumption. The Ru(II) derivatives were prepared by optimizing distribution ratio of Ru(dcbpy) 3 2+ and carbohydrazide for acquiring the ECL signal maximum. Stimulated by In3+/In+ redox reversible electron pair in the InVO 4 /β-AgVO 3 heterostructures, the InVO 4 /β-AgVO 3 heterostructures were designed as co-reaction accelerator to expedite ECL emission reaction between CON 4 H 6 • and Ru(dcbpy) 3 3+. Taking advantage of associative competition between cDNA and E 2 with aptamer, the ECL signal realized further amplification. The specific binding of the aptamer to E 2 , was stronger than that to the cDNA by hybridization. A mass of Ru(II) derivatives could adsorb and embed into the hybridized double-stranded DNA to immobilize on the electrode surface and generate satisfactory ECL signal. The specific binding of the aptamer to E 2 decreased the cDNA content on electrode surface, which contributed to lessen the adsorption amount of Ru(dcbpy) 3 2+ and distinctly affected the ECL signal. Under optimal conditions, the proposed biosensor provided an admirable linearity to the level of E 2 between 0.001 nmol/L and 100 nmol/L with a low detection limit of 0.27 pmol/L. The proposed aptasensor not only stimulates more interest in the mechanism of intramolecular ECL but also has towardly development potential for constructing competitive strategies. • This mode involved the Ru(II) derivative for the mechanism of intramolecular ECL, which could be obtained through an amide reaction between Ru(dcbpy) 3 2+ and carbohydrazide. • Stimulated by In3+/In+ redox reversible electron pair in the InVO 4 /β-AgVO 3 heterostructures, the InVO 4 /β-AgVO 3 heterostructures were designed as co-reaction accelerator to expedite ECL emission reaction between CON 4 H 6 • and Ru(dcbpy) 3 3+. • The competition between cDNA and E 2 could determine the amount of adsorption of the Ru(II) derivative to further improve the sensitivity of the aptasensor. • The proposed biosensor provided an admirable linearity to the level of E 2 between 0.001 nmol/L and 100 nmol/L with a low detection limit of 0.27 pmol/L. [ABSTRACT FROM AUTHOR]

In many cases of in-situ or point-of-care testing (POCT), the single pursuit of good detection performance cannot meet the testing requirements, and thus no-wash testing has become one of the most effective methods to develop sustainable biosensing assay, providing more convenient operation procedures and shorting the detection time. Herein, a disposable POC biosensing assay was prepared based on the RGB color detector software on the smartphone and the peroxide-like activity of gold nanoparticles (Au NPs) for aflatoxin B1 (AFB1) sensitive detection. Using syringe filters for a simple physical separation procedure can easily realize washing free detection, which is superior to most biosensing assays with cumbersome detection procedures. The syringe filters with 200 nm pore diameter could only pass through small Au NPs (30 nm) while the large-sized SiO 2 nanoparticles (300 nm) was blocked on the membrane. In this work, Au NPs utilized their inherent peroxidase-like activity to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H 2 O 2 to ox-TMB under acidic conditions, which results in blue color in aqueous solution. The color change due to different antigen concentrations was quantitatively determined by measuring the color intensity with a smartphone and the RGB color detector. By measuring the color intensity, it was known that the linear concentration range of the biosensing assay was 100 fg mL−1 to 50 ng mL−1, and the detection limit of AFB1 was 33 fg mL−1 (S/N = 3). Additionally, the designed biosensing assay exhibited excellent selectivity, storage stability and reproducibility. More importantly, the innovation of detecting and analyzing technology is the outstanding advantage of the biosensing assay, providing a more flexible and convenient strategy for some other small molecule analysis. [Display omitted] • A no-washing point-of-care biosensor for the determination of AFB1 was designed. • The introduction of disposable syringes simplified the detection procedure and shortened the testing time. • The colorimetric biosensor exhibited a low detection limit of 33 fg mL−1. [ABSTRACT FROM AUTHOR]

Nanostructured materials with elegant properties have promising potentials in chemiluminescence (CL) immunoassay. However, the robust preparation of such nanomaterials is still challenging. In this work, biocompatible and easily prepared gelatin/horseradish peroxidase (Gel/HRP) nanogels were exploited as signal labels for chemiluminescence immunoassays. The catalytic property of HRP was well retained and the stability was improved after the incorporation into nanogels. The prepared protein nanogels show enhanced and glow-type luminescence behaviors in luminol-H 2 O 2 CL system. Persistent and sensitive CL immunoassay for CEA were constructed using Gel/HRP nanogels as signal labels. A wide linear response range from 0.01 to 100 ng/mL was obtained with the limit of detection was 3.39 pg/mL (S/N = 3). [Display omitted] • Long-lasting chemiluminescence through nanogels with internal 3D network structure. • Green and simple to synthesize labeled probes with excellent biocompatibility. • High activity of horseradish peroxidase is retained • Immunoassay for accurate detection in an interference environment. [ABSTRACT FROM AUTHOR]

• ZIFs-derived Zn x Co 3-x O 4 dodecahedron was adopted to construct PEC aptasensor for the first time. • The hollow Zn x Co 3-x O 4 /N-GQDs/AgBiS 2 composite exhibited remarkable photoactivity using as matrix for PEC aptasensing. • The designed PEC aptasensor showed superior performances for ampicillin detecting. A sensitive photoelectrochemical (PEC) aptasensing platform based on Nitrogen-doped graphene quantum dots (N-GQDs) and AgBiS 2 dual-sensitized Zn/Co bimetallic oxide (Zn x Co 3-x O 4) dodecahedron as a matrix was constructed for the ultrasensitive detection of ampicillin (AMP). Concretely, the Zn x Co 3-x O 4 dodecahedron derived from ZnCo-ZIFs retained the unique hollow porous structure, which provided large specific surface and efficacious active sites, and thereby significantly enhancing the light utilization and shortening the photoelectrons transmission path. Both N-GQDs with the up-conversion effect and eco-friendly AgBiS 2 with optimal band gap for solar absorption were utilized to dual-sensitize Zn x Co 3-x O 4 dodecahedron to further strengthen the PEC performance. Subsequently, the aptamer recognition technology was integrated with the modified photoelectrode, adopting AMP-aptamer to catch the target AMP, accompanied the hole oxidation of bind AMP causing the remarkable increase of photocurrent signal, the AMP could be specific and sensitive detect. Under optimized conditions, the photocurrent of developed aptasensor increased linearly displayed large liner response of 0.5 pmol/L – 10 nmol/L with a detection limit of 0.25 pmol/L (S/N = 3). Besides, the novel PEC AMP-sensoring exhibited excellent reproducibility, perfect stability and selectivity, which could open a potential avenue for antibiotic residues detection in environmental media. [ABSTRACT FROM AUTHOR]

This work for the first time proposed a photoelectrochemical (PEC) sensor based on the in situ generation of BiOBr/Bi 2 S 3 by Cs 3 Bi 2 Br 9 to detect trenbolone (TB). To be specific, Cs 3 Bi 2 Br 9 /BiOBr/Bi 2 S 3 heterojunction, the chosen photoelectric material, that could produce stable and large photocurrent was obtained through two steps in situ growth method on the basic of Cs 3 Bi 2 Br 9 perovskite. CdS and Au nanoparticles with outstanding light absorption characteristics were selected as TB antigen (Ag) marker. Under the aid of Au/CdS, the association between TB concentration and output current will be revealed by the competitive combining of TB antibodies (Ab) with TB or Ag-Au/CdS. If the concentration of TB was lower, the more Ag-Au/CdS was connected to the Ab, and the higher photocurrent signal was obtained. Hence, the competitive PEC sensor could realize reliable detection of TB with a lower detection limit of 29.7 fg mL-1. • We for the first time constructed a PEC sensor to detect trenbolone. • Cs 3 Bi 2 Br 9 /BiOBr/Bi 2 S 3 was prepared by two steps in situ growth method. • Au/CdS was selected as a signal enhancer to improve the sensitivity of sensor. • The detection limit was 29.7 fg mL−1. [ABSTRACT FROM AUTHOR]

In the realm of photoelectrochemical (PEC) analysis, it is customary to employ a lone photoanode or photocathode system for analyte detection. Nonetheless, such a single detection scheme inherently carries some deficiencies. While photoanode-based PEC immunoassay methods do exhibit conspicuous photocurrent responses and heightened sensitivity, they do suffer from inadequate resistance to interference when detecting in real sample detection. Photocathode-based analysis methods are capable of effectively surmounting the limitations of photoanode-based analysis methods, but their stability is poor. Based on the above reasons, this paper reports a novel immunosensing system combining ITO/WO 3 /Bi 2 S 3 photoanode and ITO/CuInS 2 photocathode. The system that incorporates both photoanode and photocathode exhibits a steady and discernible photocurrent, possesses robust resistance to external interference, and has effectively accomplished the quantification of NSE in the linear range from 5 pg/mL to 30 ng/mL. Remarkably, the detection limit has been determined to be 1.59 pg/mL. Besides the notable advantages of satisfactory stability, exceptional specificity, and outstanding reproducibility, the sensing system also introduces an innovative approach to fabricate PEC immunosensors. [Display omitted] • A photoelectrochemical sensing platform integrating photoanode and photocathode is constructed. • The WO 3 /Bi 2 S 3 nanomaterial electrode replaces the Pt electrode as the counter electrode. • Overcome the inherent shortcomings of single-photoanode mode and single-photocathode mode. • Satisfactory detection of NSE. [ABSTRACT FROM AUTHOR]

Abstract A sandwich-type electrochemical immunosensor for prostate-specific antigen (PSA) detection was constructed. In this sensing platform, palladium nanoparticles (Pd NPs) loaded electroactive amino-zeolitic imidazolate framework-67 (Pd/NH 2 -ZIF-67) nanocomposite is utilized as a novel redox mediator. Pd NPs, as the labeling signal molecule, owns good biocompatibility and excellent catalytic performance. Meanwhile, the electroactive ZIF-67 with lamellar structures serves not only as a carrier of Pd NPs but also as a synergistic catalyst of palladium to decompose H 2 O 2. Amperometric method is used to determine the current signal generated on the electrode surface, which is conducive to achieve the quantitative determination of PSA. Under optimum conditions, the proposed immunosensor shows a wide detection range from 100 fg mL–1 to 50 ng mL–1 with a low detection limit of 0.03 pg mL–1, featuring favorable selectivity, repeatability and stability. This proposed immunosensor is expected to be a powerful tool for realizing quantitative detection of PSA and other biomarkers in actural sample analysis. Highlights • Electrochemical immunoassay is proposed for detection of PSA based on Pd/NH 2 -ZIF-67. • The response signal is amplified by the synergetic effect between Pd and Co2+/3+. • The immunosensor exhibits a low detection limit of 0.03 pg mL-1 for PSA detection. [ABSTRACT FROM AUTHOR]

Ultrasensitive and accurate physiological monitoring is of great significance for disease diagnosis and treatment. In this project, an efficient photoelectrochemical (PEC) split-type sensor on the basis of controlled release strategy was established with great success. Heterojunction formation between g-C 3 N 4 and Zn-doped CdS improved the visible light absorption efficiency, reduced carrier complexation, improved the PEC signal, and increased the stability of the PEC platform. Compared to the traditional model of immunosensors, the process of antigen-antibody specific binding was done in a 96 microplate, and the sensor separated the immune reaction from the photoelectrochemical conversion process, eliminating mutual interference. Cu 2 O nanocubes were used to label the second antibody (Ab 2), and acid etching using HNO 3 released a large amount of divalent copper ions, which exchanged cations with Cd2+ in the substrate material, causing a sharp drop in photocurrent and improving the sensitivity of the sensor. Under the optimized experimental conditions, the PEC sensor based on the controlled release strategy for CYFRA21-1 target detection had a wide concentration linear range of 5 × 10−5 to 100 ng/mL with a low detection limit of 0.0167 pg/mL (S/N = 3). This intelligent response variation pattern could also offer the possibility of additional clinical applications for other target detection. [Display omitted] • This split-type sensor separates immune response from photoelectric conversion. • Zn-doped CdS and g-C 3 N 4 forms a heterojunction as the matrix to give basic PEC response. • The Cu2+ released by Cu 2 O achieves photocurrent bursting by cation exchange. • The biosensor for CYFRA21-1 detection exhibited a detection limit of 0.0167 pg mL−1. [ABSTRACT FROM AUTHOR]

The establishment of new mechanisms for target identification and signal amplification continues to drive innovation in electrochemiluminescence (ECL) sensing platforms. In this paper, a novel ECL insulin sensing platform was constructed by utilizing the molecular recognition properties of cucurbit[7]uril. Specifically, the macrocyclic host molecule cucurbit[7]uril was immobilized on the surface of the sensing platform as an identification probe, which could selectively capture insulin according to the inherent properties of the protein N-terminal. Introducing the rigid molecule cucurbit[7]uril into the sensing interface could reduce the influence of the environmental parameters on the sensing system, which provides a reliable guarantee for the accurate detection of insulin. Furthermore, gold nanoclusters were modified by utilizing the molecular recognition properties of cucurbit[7]uril, and used as anode signal probes for ECL sensing platform. The macrocyclic molecules cucurbit[7]uril passivated the surface of the nanoclusters, inhibited the non-radiative relaxation and improved the physical stability of the luminophore, leading to a significant increase in the sensitivity and stability of the ECL probe. The ECL sensing platforms exhibited a linear range from 50.00 fg/mL to 100.0 ng/mL, with a detection limit of 5.44 fg/mL. This study revealed the critical role of cucurbit[7]uril in target recognition and signal amplification, extending the scope of supramolecular applications in ECL. [ABSTRACT FROM AUTHOR]

Herein, a split-type photoelectrochemical (PEC) immunosensor is designed to detect neuron-specific enolase (NSE), which is a tumor marker for small cell lung cancer present in nerve and neuroendocrine tissues. In this study, a heterogeneous In 2 O 3 /BiVO 4 structure is developed with coral-like BiVO 4 films adsorbed onto In 2 O 3 based on simplified successive ionic layer adsorption and reaction (s-SILAR). Moreover, immune recognition occurs in a 96-well plate in the split-type PEC immunosensor, thus effectively avoiding interference with the recognition of biomolecules. However, the sensitivity of zeolitic imidazolate framework (ZIF)− 8 molecules to pH varies, and most of the degradation of ZIF-8 molecules can be achieved by a reaction at a pH of 5.5–6.5 for > 30 min. Therefore, SiO 2 -glucose oxidase is selected as a regulatory switch to act on ZIF-8 molecules by catalyzing the conversion of glucose to gluconic acid, whereas In 2 O 3 /BiVO 4 is selected as the photoactive substrate and ZIF-8 protective layer as the signal switch. By constructing a split-type PEC immunosensor, gluconic acid of different concentrations is released in the 96-well plate through the change of NSE concentration to regulate the degradation of the ZIF-8 protective layer and achieve the sensitive detection of NSE. The constructed PEC sensor exhibits an excellent photocurrent response between 0.1 pg mL–1 and 100 ng mL–1, with a detection limit of 0.03 pg mL–1. Simultaneously, the accuracy, specificity, stability, and reproducibility of this split-type PEC sensing platform predict its promising application in the future in the field of biomolecules. • S-SILAR In 2 O 3 /BiVO 4 exhibited excellent PEC behavior. • The ZIF-8 layer is used as a medium for regulating photosensitive signals. • Tandem reforming of ZIF-8 layer with SiO 2 -GOx markers. • A split-type PEC sensor exhibited a low detection limit of 0.03 pg/mL for NSE. [ABSTRACT FROM AUTHOR]

In this paper, a photoelectrochemical (PEC) immunosensor was constructed to detect neuron-specific enolase (NSE) with ITO/BiVO 4 /BiOI/Ag 2 S as photoanode and ITO/CuInS 2 as photocathode. Due to its excellent photocurrent response, Ag 2 S sensitized BiVO 4 /BiOI composite was selected to provide stable photocurrent in place of the traditional Pt electrode. ITO/CuInS 2 electrode was used to immobilize biomolecules, which solved the deficiency of poor anti-interference ability of single photoanode. Under the optimal experimental conditions, the PEC immunosensor had outstanding linear relationship within the range of NSE concentration from 5 pg/mL-200 ng/mL, and the detection limit was 1.2 pg/mL. The constructed PEC immunosensor had two advantages. On the one hand, the PEC immunosensor was built on the photocathode, which had better anti-interference ability because of the separation of light capture and biomolecular recognition process. On the other hand, the introduction of photoanode increased the photocurrent response and reduced the detection limit of target antigen. The PEC immunosensor had good stability, reproducibility and specificity, and provided a broad prospect for the detection of other molecules. [ABSTRACT FROM AUTHOR]

Generally, the photoanodic photoelectrochemical (PEC) immunoassay method has an outstanding photocurrent and low detection limit, but its poor anti-interference ability in the detection of real samples restricts its performance. The photocathode immunoassay method has an excellent ability to see interference in actual sample detection, but it has its own defect in that the photocurrent is not obvious. Here, a promising new cathodic PEC immunosensing platform is reported, which integrates a photocathode and photoanode. The photoanode and photocathode are WO 3 /Mn:CdS composite modified and reduced graphene oxide (RGO) modified indium tin oxide (ITO) electrodes, respectively. In addition to an excellent PEC response, the immunosensor constructed by the integrating the photoanode and photocathode also has good anti-interference ability in actual sample analysis. The constructed immunosensor achieves accurate detection of NSE with a range from 5.0 pg/mL to 20 ng/mL, and the limit of detection (LOD) is 1.2 pg/mL. The proposed immunoassay method has good stability, selectivity and reproducibility. Moreover, it introduces new ideas for the construction of PEC immunosensors. [ABSTRACT FROM AUTHOR]

In this item, a high-efficiency signal "on-off-on" strategy photoelectrochemical (PEC) apatsensor was resoundingly developed for target ultrasensitive analysis. Primarily, the heterojunction formation between Cd: Sb 2 S 3 and La 2 Ti 2 O 7 was contributed to the first "signal-on" state to improve the stability of the PEC platform. Secondly, V 2 O 5 nanosphere act as a catalyst for H 2 O 2 was used to label on aptamer DNA to consume electron donor for achieving "signal-off" state. Then target analyte was modified on the surface of the PEC platform, and part of V 2 O 5 with aptamer DNA would be released from the aptasensor surface, thus, the "signal-on" state was realized again. In this signal "on-off-on" strategy, the PEC performance of perovskite La 2 Ti 2 O 7 was effectively perfected with Cd: Sb 2 S 3 sensitization, and broaden the application of perovskite in PEC sensor field. And the signal attenuation and recovery strategy were distinctly elevated the sensitivity of the aptasensor. In the preferred detection conditions, the proposed PEC sensor for analyte (PSA as an example) analysis revealed a wide sensing range from 1.000 × 10−5 to 500.0 ng/mL, own a low detection limit of 4.300 fg/mL. This smart response change mode also provide prospect for other target detection, and offer a reference to signal transform for other electrochemical method. • Signal "on-off-on" photoelectrochemical aptasensor was successfully fabricated for cancer marker detection. • Photoelectrochemical performance of perovskite La 2 Ti 2 O 7 was improved greatly by Sb 2 S 3. • V 2 O 5 nanosphere catalyzed electron donor weaken the PEC signal. • The aptasensor for target exhibited the low detection limit of 4.3 fg/mL. [ABSTRACT FROM AUTHOR]

A self-powered photoanode-supported photoelectrochemical (PEC) immunosensor was designed based on In 2 O 3 /In 2 S 3 /CdIn 2 S 4 as photoanode and PDA@CNTs as biocathode for the detection of CYFRA 21–1. In this proposal, In 2 O 3 /In 2 S 3 /CdIn 2 S 4 heterojunction modified indium-tin oxide (ITO) electrode was served as a substitute for platinum (Pt) counter electrode to provide an evident and stable photocurrent signal. The matched band structure of In 2 O 3 , In 2 S 3 and CdIn 2 S 4 as well as the unique hollow porous structure of In 2 O 3 /In 2 S 3 /CdIn 2 S 4 played a pivotal role in accelerating the separation and transfer of photocarrier. Meanwhile, PDA@CNTs with excellent conductivity further enhanced the photocurrent which was provided by photoanode In 2 O 3 /In 2 S 3 /CdIn 2 S 4 heterojunction. Besides, PDA could effectively capture the antibody (Ab) through Michael addition. Separating photoanode from the sensing biocathode was conducive to improve the anti-interference capability of PEC sensor because the reductive species in biologic media will change PEC properties of the photoanode interface. Under optimal conditions, the PEC immunosensor have realized the detection of CYFRA 21–1 (0.5 pg/mL - 50 ng/mL) and the detection limitation with 0.16 pg/mL. In addition, the proposed self-powered PEC sensor with acceptable selectivity, reproducibility, and stability provide a new horizon for designing PEC immunosensing platform in bioassays. • A self-powered photoanode-supported PEC sensor for CYFRA21-1 detection was designed. • In 2 O 3 /In 2 S 3 /CdIn 2 S 4 was used as photoanode matrix to provide stable photocurrent signal. • PDA@CNTs with excellent conductivity was served as biocathode for target analyte capture. • The immunosensor exhibited a low detection limit of 0.16 pg/mL. [ABSTRACT FROM AUTHOR]

In this work, a signal amplification competitive-type photoelectrochemical system comprised of bismuth sulfide/bismuth oxyiodide/zinc oxide (Bi 2 S 3 /BiOI/ZnO) nano-array as platform and Ag 2 S-modified aptamers probe DNA (p DNA@Ag 2 S) as competition content for rapid and sensitive detection of OTA in microfluidic devices. The BiOI nano-array was first growth on surfaces of ZnO by a simple electrodeposited method, which provided large specific surface area and high stability to solve distribution of sensing platform and loose of combination of sensing substrate. Then, the Bi 2 S 3 could be in-situ growth by self-sacrificial part Bi3+ of BiOI to form heterojunction without destroying the structure of the nano-array. A strong photocurrent intensity was acquired by the Bi 2 S 3 /BiOI/ZnO modified onto indium tin oxide (ITO) electrode, due to its good matching cascade band-edge levels could improve efficient separation of photo-generated e-/h+ pairs. After immobilizing with the capture DNA (c DNA) and the sequential hybridization of p DNA@Ag 2 S, the photocurrent intensity reduced obviously because part photo-generated electron transformed to Ag 2 S rather than Bi 2 S 3 /BiOI/ZnO electrode. Subsequently, the photocurrent intensity increased evident when immobilized the target OTA, owing to the OTA could bind the p DNA@Ag 2 S to form the specific-complex that were released from the electrode surface. Under optimal conditions, the prepared PEC microfluidic sensor exhibited a linear concentration of OTA from 0.01 pg/mL to 200 ng/mL with a low detection limit of 0.0035 pg/mL (S/N = 3). Furthermore, it achieved high sensitivity, good specificity, and acceptable stability and further provided an efficient method for sensitive detection of other target mycotoxins in practical application. • A competitive-type PEC immunosensor for OTA detection was designed in microfluidic devices. • The Bi 2 S 3 /BiOI/ZnO nano-array was prepared as platform. • The Ag 2 S-modified aptamers probe DNA was formed as competition content. • The PEC immunosensor exhibited a low detection limit of 0.0035 pg/mL. [ABSTRACT FROM AUTHOR]

• The signal indicator and matrix, Fe 3 S 4 -Pd, displayed excellent electrocatalytic activity for H 2 O 2 redox reaction. • Magnetic glassy carbon electrode was used to firmly immobilized the magnetic Fe 3 S 4 -Pd to achieve satisfied stability. • PBG nanomaterial played a role as the electron blocking label that realized a sensitive variation of current signal. • The signal-off sensing platform was successfully constructed, with a low detection limit of 130 fg/mL. Herein, a sandwich-type electrochemical (EC) immunosensor is proposed based on a special signal-off mode for the sensitive detection of procalcitonin (PCT) by utilizing Fe 3 S 4 loaded with Pd nanoparticles (Fe 3 S 4 -Pd) as a signal indicator and matrix and functionalized pineal mesoporous bioactive glass (PBG) as the label for signal amplification. Fe 3 S 4 -Pd not only shows excellent electrocatalytic activity for the H 2 O 2 redox reaction but is also firmly immobilized on a magnetic glassy carbon electrode due to its excellent magnetic properties; because of the above features, this immunosensor exhibits excellent sensitivity and stability, respectively. Glutaraldehyde is used as a cross-linking agent to bond the secondary antibodies (Ab 2) with PBG. It is worth mentioning that the electron transfer rate between the electrolyte and electrode is decreased significantly by PBG-Ab 2 ; thus, a sensitive variation in the current signal is observed, and a further improvement in the sensitivity of the immunosensor is realized. More importantly, the proposed signal-off sensing system has a wide linear detection range of 500 fg/mL to 50 ng/mL for PCT and a low detection limit of 130 fg/mL, which promotes it as a promising detection method for the sensitive detection of other biomarkers. [ABSTRACT FROM AUTHOR]

• Bifunctional peptides that biomineralize gold clusters and specifically recognize antibody Fc domains. • Flexible fragmented-antibody are used as sensing substrate instead of using traditional micro-nano carrier. • The sensing platform fabricated by these strategies exhibit ultralow detection limit of 1.8 fg/mL. Non-competitive immunoassay systems often are used for detecting biomarkers, and their sensitivity depends on the arrangement mode of substrate and the property of signal label. In this work, a novel electrochemiluminescence (ECL) sensing platform utilizing split antibody fragments (Fab') 2 as substrate and self-designed nonapeptide H 2 N-CCYHWRGWV-COOH (CCYTAR) biomineralized gold nanocluster (Au NCs) as label was fabricated. Fixated (Fab') 2 domains on gold-plated electrodes via Au-S bonds could form well-ordered microarray with higher immune affinity than random antibody fixation. Besides, The CCYTAR nonapeptide not only could function as reductant and capping agent for synthesizing Au NCs, but also act as specific antibody immobilizer for recognizing Fc domains specifically. Also, related experiments verified that CCY and TAR, two independent regions of bifunctional nonapeptide, acted independently. In the end, the Cyfra 21-1 is employed as target to test the feasibility of all strategies, and the results confirmed that the sensing platform could be promising candidate for ECL-based biosensor fabrication in the future. [ABSTRACT FROM AUTHOR]

• An enzyme-free colorimetric immunosensor was designed for detection PCT. • MgFe 2 O 4 @Cys was first used as the sacrificial probe of the immunosensor. • MgFe 2 O 4 @Cys released Fe3+ under acidic condition and reacted with [Fe(CN) 6 4− can generate soluble PB. • PCT determination was established by measuring absorbance of generated PB. • It achieved an excellent result in human serum sample analysis. An enzyme-free immunosorbent assay using MgFe 2 O 4 modified with cysteine (MgFe 2 O 4 @Cys) as sacrificial probe for the detection of procalcitonin (PCT) was developed. MgFe 2 O 4 @Cys was linked with second antibody of PCT (Ab 2) by cysteine amino group and released Fe3+ under acidic conditions. Taking advantage of Fe3+ and [Fe(CN) 6 4− generating soluble Prussian blue (PB), a novel method of PCT determination was established by measuring the absorbance of the generated PB. Different from the traditional immunosensor detection mode, the enzyme-free colorimetric immunosensor in this work can not only avoid the interference of nano-enzymes or enzymes, but also has the advantages of rapid detection, low cost, high selectivity and sensitivity. Therefore, the developed immunosensor for PCT detection exhibited a wide linear response (0.0001–50 ng/mL) and a low detection limit (44.9 fg/mL). Additionally, the immunosensor exhibits satisfactory performance in human serum testing, which indicated its good application value in clinical diagnoses. [ABSTRACT FROM AUTHOR]

In this work, a novel self-powered photoelectrochemical (PEC) aptasensor integrated photoanode and photocathode for the accurate and selective detection of 17β-estradiol (E 2) was proposed for the first time. FeOOH/In 2 S 3 heterojunction was built initially and used as a substitute for platinum (Pt) counter electrode. The matched band gap edge of FeOOH and In 2 S 3 facilitated the transfer of photo-generate electrons to photoanode, while the holes left in the valence band of photocathode (CuInS 2) can be attracted by the electrons flowed from the photoanode, which reduced the recombination of electron-hole pairs and promote the cathodic photocurrent. Under optimal conditions, the constructed cathodic aptasensor of E 2 presented linear scope in 10 fg/mL-1 μg/mL with detection limit of 3.65 fg/mL. Besides, the cathodic aptasensor exhibited admiring selectivity, stability and reproducibility. This work verified that the cathodic photocurrent response can be regulated by the corresponding photoanode which provided a new design thought for PEC aptasensor on the basis of p-type semiconductor. • A novel self-powered photoelectrochemical cathodic aptasensor for the detection of 17β-estradiol was constructed. • FeOOH/In 2 S 3 heterojunction was employed as photoanode for the first time. • The holes generated on photocathode was attracted by electrons flowed from photoanode. [ABSTRACT FROM AUTHOR]

• An ECASE-based PEC sandwich-type immunosensor for PCT detection was designed. • The porous nanoarray BiVO 4 /CuS was prepared as matrix material. • The photocurrent could be significantly enhanced by the ECASE-based PEC strategy. • PS@Ab 2 bioconjugate act as labels for enhancing the sensitivity of PEC immunosensor. • The PEC immunosensor exhibited a low detection limit of 17.3 fg mL−1. A new, porous nanoarray BiVO 4 /Cu x S (PN-BiVO 4 /Cu x S) platform as an advanced signal amplification strategy under anodic bias on the process of electrochemical catalysis assisted self-enhancing based photoelectrochemical (ECASE-based PEC) without electron donors was established for ultrasensitive procalcitonin (PCT) detection. The system operated upon that the PN-BiVO 4 /Cu x S electrode could enhance separation of e−/h+ pairs under illumination of visible-light because the energy levels between BiVO 4 and Cu x S matched well. Afterwards, the photoexcited electrons could shift to working electrode as output signal, while the photoexcited holes could oxidize water under anodic bias to produce hydrogen peroxide (H 2 O 2) that was subsequently reduced by Cu x S, which resulted in significantly enhanced photocurrent intensity by electrochemical process. To further enhance the sensitivity of PEC immunosensor, amino-modified polystyrene (PS) nanoparticles act as labels for immobilizing secondary antibodies (Ab 2) to form PS@Ab 2 conjugates for construction of sandwich-type immunosensor on the basis of ECASE-based PEC strategy. The designed PEC immunosensor exhibited a linear concentration range from 50 fg mL-1 to 100 ng mL-1, with a low detection limit of 17.3 fg/mL (S/N = 3) for PCT, and achieved good selectivity, acceptable stability, and high sensitivity. This work first conducted the ECASE-based PEC system, and we believed it will provide a new perspective for developing innovative signal amplification toward detection of other biomarker in the future. [ABSTRACT FROM AUTHOR]