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Abstract A sandwich-type photoelectrochemical (PEC) immunosensing platform was designed for detection of amino-terminal pro-B-type natriuretic peptide (NT-pro BNP). Thereinto, flower-like Bi 2 WO 6 /Ag 2 S nanoparticles (F-Bi 2 WO 6 /Ag 2 S) were employed as photoelectrochemical matrix, and graphene oxide and polydopamine composite (GO/PDA) were prepared as signal labels. In this proposal, Ag 2 S was in-situ growth on the surface of F-Bi 2 WO 6 modified with thioglycolic acid (TGA). Specially, a cascade-like band-edge level between F-Bi 2 WO 6 and Ag 2 S effectively improved the photocurrent conversion efficiency and enhanced the photocurrent response. Then, the conjugated GO/PDA aimed to further amplify signal because PDA as electron donor could sweep the holes and inhibit the recombination of photogenerated electron-hole pairs, while GO owned brilliant conductivity speeding up the electrons transfer. The photocurrent increased with the amount of GO/PDA conjugates which had positive correlation with the NT-pro BNP. Under optimal experimental conditions, the proposed sandwich-type PEC immunosensor presented a desirable linear relationship ranged from 0.1 pg/mL to 100 ng/mL for NT-pro BNP with the detection limit of 0.03 pg/mL (S/N = 3). The prepared PEC immunosensor exhibited high stability and selectivity, which offered an innovative idea for the detection of other biomolecules. Highlights • A sandwich-type PEC immunosensor was fabricated for NT-pro BNP detection. • F-Bi 2 WO 6 loaded with Ag 2 S was used as photoactive matrix. • GO/PDA was first utilized as label for signal amplification. • The PEC immunosensor exhibited a low detection limit of 0.03 pg/mL. [ABSTRACT FROM AUTHOR]

A new, photoelectrochemical immunosensor was proposed on the basis of the La-CdS/3D ZnIn 2 S 4 /Au@ZnO sensitization structure for detection of aminoterminal pro-brain natriuretic peptides (NT-proBNP). The Au@ZnO-modified electrode was first assembled with 3D ZnIn 2 S 4 , and then further deposited with lanthanum doped cadmium sulfide (La-CdS) via successive ionic layer adsorption and reaction strategy. The Au@ZnO has excellent photoelectric activity and electrical conductivity. The ZnIn 2 S 4 with 3D architectures not only exhibit high photocurrent intensity under visible-light irradiation but also have large surface for the La-CdS deposition. Meanwhile, the La-CdS doped structure could depress the charge recombination, which effectively promotes separation of the generated electron-hole (e - /h + ) pairs and consequently enhances the photocurrent conversion efficiency. The polydopamine (PDA) was used not only as a cross-linker reagent for the immobilization of the anti-NT-proBNP but also as an electron donor for promoting the photo-generated e - /h + separation of the semiconductors. Under optimal conditions, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 0.32 pg mL −1 and a wide linear range from 0.8 pg mL −1 to 45 ng mL −1 for target NT-proBNP detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising strategy for the detection of other important tumor markers. [ABSTRACT FROM AUTHOR]

A label-free photoelectrochemical (PEC) platform with high visible-light activity for quantitative detection of the ochratoxin A (OTA) was developed by assembly of Ag 2 S nanoparticles (NPs) sensitized on titanium dioxide/red blood cell-like shape bismuth vanadate (TiO 2 /S-BiVO 4 ) electrode via layer-by-layer (LBL) strategy. In this protocol, ascorbic acid was used as an efficient electron donor for scavenging photo-generated holes and inhibiting light driven electron-hole pair recombination. TiO 2 has good photoelectric activity and large surface area. The S-BiVO 4 with porous structure surfaces can contribute to the high photocurrent intensity under visible-light irradiation. Moreover, the Ag 2 S NPs were in-situ growth on surfaces of thioglycolic acid modified S-BiVO 4 , which enhanced photocurrent response and further improved the photocurrent conversion efficiency. Under optimal conditions, the PEC immunosensor exhibited a wide linear concentration range from 5 pg mL −1 to 750 ng mL −1 , with a low detection limit of 1.7 pg mL −1 (S/N = 3) for OTA. Additionally, the designed immunosensor was performed with good stability, reproducibility and selectivity, thus opening up a new promising PEC platform for some other small molecules analysis. [ABSTRACT FROM AUTHOR]

In this work, a sensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of prostate-specific antigen (PSA) by amperometric i-t . The Au loaded on thionine functionalized graphene oxide (Au@Th/GO) was used as a platform to immobilize primary antibodies (Ab 1 ) and accelerate the electron transfer on the electrode interface. PtCu bimetallic hybrid were loaded on 2D/2D reduced graphene oxide/graphitic carbon nitride (PtCu@rGO/g-C 3 N 4 ) with large surface area and biocompatibility, which were employed as labels for combining secondary antibodies (Ab 2 ) and amplifying signals to improve the sensitivity of the designed immunosensor which attributes to its good activity for the reduction of hydrogen peroxide (H 2 O 2 ). Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 50 fg/mL to 40 ng/mL, with a low detection limit of 16.6 fg/mL (S/N=3) for PSA. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyze human serum samples indicated potential application promising in clinical monitoring of tumor markers. [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]

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). To this end, the amino functionalized cuprous oxide @ ceric dioxide (Cu 2 O@CeO 2 - NH 2 ) core-shell nanocomposites were prepared to bond gold nanoparticles (Au NPs) by constructing stable Au - N bond between Au NPs and -NH 2 . Because the synergetic effect presents in Cu 2 O@CeO 2 core-shell loaded with Au NPs (Cu 2 O@CeO 2 -Au), it shows better electrocatalytic activity towards the reduction of hydrogen peroxide (H 2 O 2 ) than single Cu 2 O, Au NPs and Cu 2 O@CeO 2 . Featured by large specific surface area, good biocompatibility and good electrochemical properties which can greatly improve the electronic transmission rate, Cu 2 O@CeO 2 -Au was used as transducing materials to achieve efficiently capture antibodies and triple signal amplification of the proposed immunosensor. Under the optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.1 pg/mL to 100 ng/mL with a low detection limit of 0.03 pg/mL (S/N=3). Furthermore, the proposed label-free immunosensor has been used to determine PSA in human serum with satisfactory results. Meanwhile, it displayed good reproducibility, acceptable selectivity, and long-term stability, which had promising application in bioassay analysis. [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]

Abstract A novel and sensitive sandwich-type photoelectrochemical (PEC) immunosensor was developed for the quantitative detection of β-amyloid protein (Aβ). A ITO electrode was sequentially coated with hierarchical porous zinc oxide (ZnO) microspheres with a large specific area, sensitized with tris(bipyridine)ruthenium(II) ion (Ru(bpy) 3 2+) to achieve high visible light absorption, and modified with cerium-doped cadmium sulfide (Ce-CdS) nanoparticles to enhance the PEC response. Under the stimulation of visible light and ascorbic acid as an efficient electron donor, the photoelectric signal of ZnO/Ru(bpy) 3 2+/Ce-CdS was 70 times that of pure ZnO. The amino-functionalized polystyrene (PS) microspheres coated with copper sulfide (CuS) was linked with a secondary antibody (Ab 2) for the first time for the Aβ detection by the immunosensor. The good insulation and steric resistance of the as-prepared polystyrene@CuS-Ab 2 (PS@CuS-Ab 2) composite significantly weakened the photocurrent response of the immunosensor in the specific immune recognition. Under the optimal conditions, the quantitative detection of Aβ was achieved within the range of 0.001–100 ng/mL with the detection limit of 0.37 pg/mL. In addition, the PEC immunosensor is easy to make, stable and selective, which has provided a good experimental platform for the detection of disease biomarkers. Highlights • A unique hierarchical porous ZnO microspheres was used for the PEC sensor. • Sensitization of Ru(bpy) 3 2+ enhanced the absorption of ZnO to visible light. • Ce-CdS nanoparticles modified ZnO/Ru(bpy) 3 2+ showed remarkable PEC activity. • The polystyrene@CuS was combined with Ab 2 for the first time as signal dual inhibition labels. • The facile PEC sensor realized the ultrasensitive detection of Aβ. [ABSTRACT FROM AUTHOR]

Abstract In this study, we propose a SnO 2 /CdCO 3 /CdS-based label-free photoelectrochemical (PEC) immunosensor for the sensitive quantification of amyloid β-protein (Aβ) which plays a critical role in the early diagnosis of Alzheimer's disease. Under specific pH conditions, SnO 2 /CdCO 3 /CdS was first designed and successfully synthesized with simple one-pot method. The synthesis of SnO 2 /CdCO 3 /CdS circumvents the trouble of traditional composite materials to be gradually compounded, saving a lot of time and energy. The synthesis mechanism of SnO 2 /CdCO 3 /CdS nanocomposite was also deeply explored. Moreover, thanks to the matched energy levels of its three components, SnO 2 /CdCO 3 /CdS nanocomposite exhibited enhanced photocurrent intensity, which is dozens of times bigger than any of its components, thus making it an excellent photoactive matrix for PEC immunosensor. Under optimal conditions, the as-constructed PEC immunosensor manifested a broad linear range (0.1 pg mL−1 to 100 ng mL−1) with a low detection limit (LOD, 0.05 pg mL−1, S/N = 3). High selectivity, coupled with good stability, allowed the developed PEC immunosensor to be applied in the clinical detection of Aβ or other biomarkers in human serum. Highlights • SnO 2 /CdCO 3 /CdS was first synthesized by a simple one-pot approach. • The mechanism of SnO 2 /CdCO 3 /CdS formation was discussed. • A label-free photoelectrochemical immunosensor was fabricated to detect Aβ. • The photoelectrochemical immunosensor reveals good stability and high sensitivity. [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]

Abstracts Rapidity and high sensitivity are the critical factors for the diagnoses of heart attacks and cardiac troponin I (cTnI) is used as a gold standard marker for its diagnosis. To realize the accurate detection of cTnI, a novel ultrasensitive photoelectrochemical (PEC) immunosensor for cTnI determination was developed upon dual inhibition effect of Ag@Cu 2 O core-shell submicron-particles(SPs) toward CdS sensitized the (001) facets of anatase titanium dioxide nanosheets (TiO 2 /CdS). In this study, the TiO 2 /CdS composite not only indicated stable and excellent photoelectric signal but also provided abundant functional group to immobilized cTnI antibodies (Ab 1 ). To obtain the high sensitivity, Ag@Cu 2 O core-shell SPs were used as labels of the secondary antibodies (Ab 2 ), owning to competitive absorption of light and consumption of electron donor, less light energy and electron donors arrived at the TiO 2 /CdS sensitization structure. Besides, the remarkable steric hindrance effect of Ag@Cu 2 O core-shell SPs labeled secondary antibodies (Ab 2 ) conjugates obstructed the transfer of electrons and diffusion of the electron donors to the photoelectrode surface, leading to further decrease of photocurrent. Therefore, the constructed immunosensor has an ultrasensitive response to cTnI in a liner range of 0.02 pg/mL to 50 ng/mL with a low detection limit of 6.7 fg/mL, and exhibits good sensitivity and admirable stability. Moreover, the strategy provided an efficient and novel approach for dual inhibition effect in PEC immunoassay development. [ABSTRACT FROM AUTHOR]

Signal amplification is crucial for obtaining low detection limits in electrochemical immunosensor. In this work, we developed a novel signal amplification strategy using Au@Ag nanoparticles loaded by polydopamine functionalized phenolic resin microporous carbon spheres (Au@Ag/PDA-PR-MCS). Phenolic resin microporous carbon spheres (PR-MCS) possesses uniform size and a large surface area (1656.8 m 2 g −1 ). Polydopamine (PDA) functionalized phenolic resin microporous carbon spheres (PDA-PR-MCS) retains the advantages of PR-MCS and possesses strong adsorption ability. With the unique structure of PDA-PR-MCS, it not only improves the loading capacity and dispersity of Au@Ag nanoparticles (Au@Ag NPs), but also enhances the stability for the combination of the Au@Ag NPs by chemical absorption between Au@Ag NPs and -NH 2 of PDA. The Au@Ag/PDA-PR-MCS exhibits extraordinary electrocatalytic activity towards reduction of hydrogen peroxide (H 2 O 2 ) to make the electrochemical response more sensitive. Furthermore, Au NPs with good biocompatibility and excellent conductivity were electrodeposited on the surface of electrode, which was used as a sensing platform to immobilize primary antibody (Ab 1 ) and accelerate the electron transfer on the electrode interface. Herein, the designed immunosensor provided a broad linear range from 20 fg/mL to 100 ng/mL for alpha fetoprotein (AFP) detection and a low detection limit of 6.7 fg/mL (signal-to-noise ratio of 3) under optimal experimental conditions. Moreover, the excellent performance in detection of human serum samples indicated that the proposed immunosensor will provide promising applications in clinical monitoring of AFP. [ABSTRACT FROM AUTHOR]

A sensitive sandwich-type electrochemical immunosensor for the detection of hepatitis B e antigen (HBeAg) was successfully developed based on the gold@palladium nanoparticles (Au@Pd NPs) loaded by molybdenum disulfide functionalized multiwalled carbon nanotubes (Au@Pd/MoS 2 @MWCNTs). The resultant nanocomposites not only possessed high specific surface area and good biocompatibility, but also exhibited excellent electro-catalytical property. Au NPs functionalized porous graphene oxide (p-GO@Au) were used as sensing platforms and primary antibodies carriers, which can accelerate the electron transfer and improve the load capacity of primary antibodies (Ab 1 ), improving the sensitivity of the immunosensor. Under optimal conditions, the designed immunosensor could detect target HBeAg concentration in the range from 0.1pg/mL to 500 pg/mL, with a low detection limit of 26 fg/mL (S/N = 3) for HBeAg. Additionally, the designed immunosensor showed excellent specificity, good reproducibility and acceptable stability. The satisfactory results in analysis of human serum samples indicated that it had potential application in clinical monitoring of tumor markers. [ABSTRACT FROM AUTHOR]

An ultrasensitive sandwich-type electrochemical immunosensor was proposed for quantitative detection of hepatitis B surface antigen, which is a representative biomarker of the Hepatitis B virus. First, the porous graphene oxide/Au composites with good conductive ability were employed to accelerate the electron transfer on the electrode interface. Furthermore, the amino functionalized molybdenum disulfide @ cuprous oxide hybrid with coral morphology was prepared to combine platinum nanoparticles for achieving signal amplification strategy. The resulting nanocomposites (molybdenum disulfide @ cuprous oxide – platinum) demonstrated uniform coral morphology, which effectively improved the specific surface area available for loading the secondary antibody and the number of catalytically active sites, even also increased the electrical conductivity. Based on these advantages, this composite system yielded a superior electrocatalytic current response toward the reduction of hydrogen peroxide. In addition, porous graphene oxide/Au composites were used to modify the glassy carbon electrode, thereby presenting a large surface area and becoming biocompatible, for improving the loading capacity of the primary antibody. Under optimal conditions, we obtained a linear relationship between current signal and hepatitis B surface antigen concentration in the broad range from 0.5 pg/mL to 200 ng/mL, with a detection limit of 0.15 pg/mL (signal-to-noise ratio of 3). These values are promising towards clinical applications. [ABSTRACT FROM AUTHOR]

Recently early diagnosis of squamous cell carcinoma antigen (SCCA) as a tumor maker of various cancers has increasingly attracted a lot of attention with heightening of incidence rate of cancer. The SCCA with low concentration in human serum should be diluted before detecting. Thus, an immunoassay with high sensitivity is significant for early detecting SCCA. Therefore, a nonenzymatic sandwich-type electrochemical immunosensor herein was conducted to quantitative detection of squamous cell carcinoma antigen (SCCA). The amino functionalized cobaltosic oxide @ ceric dioxide nanocubes with core-shell morphology were prepared to combine sea-urchin like gold @ platinum nanoparticles (Co 3 O 4 @CeO 2 -Au@Pt), and used as labels to conjugate with secondary antibodies for signal amplification. Due to the synergetic effect, excellent electrochemical property and superior auxiliary catalytic activity of Co 3 O 4 @CeO 2 -Au@Pt, high electrocatalytic current responses toward the reduction of hydrogen peroxide (H 2 O 2 ) were achieved. Besides, the electrodeposited gold nanoparticles (D-Au NPs) which were modified on glassy carbon electrodes (GCE) were used as antibodies carriers and sensing platforms. With the well cooperation of Co 3 O 4 @CeO 2 -Au@Pt and D-Au NPs, a broad linear range from 100 fg/mL to 80 ng/mL with a low detection limit of 33 fg/mL for detecting SCCA was achieved. In addition, the immunosensor displayed with good reproducibility, high selectivity and stability. The results are satisfactory when the proposed method has been applied to analyze human serum samples, indicating that the potential application is promising in clinical monitoring of tumor markers. [ABSTRACT FROM AUTHOR]