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The quantitative detection of cancer cells and the evaluation of folate receptor (FR) expression on cell membranes are of great significance for tumor‐related research. In this work, a photoelectrochemical (PEC) biosensing interface is proposed for detection of cancer cells based on the construction of nanostructured platforms coupled with surface engineering. A "sphere‐on‐tube" hierarchical nanostructure is fabricated by depositing biomimetic polydopamine nanospheres on TiO2 nanotube arrays. Enhanced PEC responses are achieved with the formation of polyethylene glycol antifouling layers and the immobilization of folic acid as a recognition ligand. Based on the ligand–receptor interaction, the antifouling PEC biosensor exhibits a wide linear range for the detection of the breast cancer cell line MDA‐MB‐231 from 20 to 2.0 × 106 cells mL−1 with a low detection limit of 15 cells mL−1 (S/N = 3). The expressing differentiation of FR on several cancer cells is well discriminated. The proposed PEC cytosensing method shows great potential in detection of cancer cells expressing folate receptors. [ABSTRACT FROM AUTHOR]

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]

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]

Based on the necessity and urgency of detecting infectious disease marker procalcitonin (PCT), a novel unlabeled photoelectrochemical (PEC) immunosensor was prepared for the rapid and sensitive detection of PCT. Firstly, SnO2 porous nanoflowers with good photocatalytic performance were prepared by combining hydrothermal synthesis and calcining. BiOI nanoflowers were synthesized by facile ultrasonic mixed reaction. Ag2S quantum dots were deposited on SnO2/BiOI composites by in situ growth method. The SnO2/BiOI/Ag2S composites with excellent photoelectric properties were employed as substrate material, which could provide significantly enhanced and stable signal because of the energy level matching of SnO2, BiOI and Ag2S and the good light absorption performance. Accordingly, a PEC immunosensor based on SnO2/BiOI/Ag2S was constructed by using the layered modification method to achieve high sensitivity analysis of PCT. The linear dynamic range of the detection method was 0.50 pg·mL−1~100 ng·mL−1, and the detection limit was 0.14 pg·mL−1. In addition, the designed PEC immunosensor exhibited satisfactory sensitivity, selectivity, stability and repeatability, which opened up a new avenue for the analyzation of PCT and further provided guidance for antibiotic therapy. [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]

• 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]

• A PEC aptamer sensor for 17β-estradiol detection was introduced. • The Mo doped porous BiVO 4 nanoarray/Bi 2 S 3 as sensing platform for immobilization of aptamer. • The Mo-p BiVO 4 /Bi 2 S 3 presented a high PEC signal by supplying additional free electrons. • The nanoarray structure provided large specific surface area and large number of binding sites. • The PEC aptamer sensor exhibited a low detection limit of 3.2 × 10−4 pM. A new porous nanoarray is constructed as sensing platform of photoelectrochemical (PEC) biosensor for detection of 17β-estradiol (E2) by using aptamer. The molybdenum (Mo) ions doped into porous bismuth vanadate (Mo-p BiVO 4) nanoarray by electrodeposition of BiOI nanoarray. Then, the bismuth sulfide (Bi 2 S 3) nanoparticles are grown in-situ on the surface of Mo-p BiVO 4 by the self-sacrificial synthesis method to form novel Mo-p BiVO 4 /Bi 2 S 3 heterojunction. Herein, the Mo-p BiVO 4 /Bi 2 S 3 heterojunction presents a high PEC signal because of Mo-p BiVO 4 could increase electron-hole separation yield by supplying additional free electrons, furthermore the heterojunction of Mo-p BiVO 4 /Bi 2 S 3 could promote ultrafast transfer of charge and inhibit the recombination of e−/h+ pairs by presenting cascade band-edge levels under irradiation of the visible light. Moreover, the nanoarray structure has large specific surface area, which could accelerate electron transfer and provide large number of binding sites to immobilize aptamer. This PEC aptamer sensor exhibits high sensitivity with a detection limit 3.2 × 10-4 pM and a good photocurrent response toward target E2 in the range of 1 × 10-3 - 5 × 102 pM. Good specificity and stability are acquired for analysis of E2 in human urine. Importantly, this designed sensor platform of Mo-p BiVO 4 /Bi 2 S 3 heterojunction provides a new promising application for other environmental estrogen analysis. [ABSTRACT FROM AUTHOR]

• A sandwich-type signal off PEC sensor was constructed for PCT detection. • The photoactive matrix was Au NPs/BiOI NSs/B-TiO 2 NPs. • PbS/Co 3 O 4 was as a quenching signal label for signal amplification. • The PEC sensor exhibited a low detection limit of 0.02 pg/mL. A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO 2 nanoparticles (Au NPs/BiOI NSs/B-TiO 2 NPs) as photoactive matrix and PbS quantum dots/Co 3 O 4 polyhedron (PbS/Co 3 O 4) as a quenching signal label for signal amplification. Concretely, BiOI NSs was fabricated by successive ionic layer absorption and reaction (SILAR) and formed the interlaced flake-like structure. Then Au NPs dropped on the BiOI NSs/B-TiO 2 NPs electrode forming Au NPs/BiOI NSs/B-TiO 2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co 3 O 4 , an effective dual suppression signal quencher, was proposed for signal-off PEC immunosensor to weaken the photocurrent response because of the steric impedance, competitive absorption of light and competing consumption of electron donor. In this proposal, PCT was chosen to measure the performance of the suggested PEC immunosensor. Consequently, the fabricated PEC immunosensor showed a widely detection ranged from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.02 pg/mL (S/N = 3). What is more, the proposed PEC immunosensor possessed satisfactory selectivity, stability and reproducibility. [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]