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An enzyme-catalyzed high-performing reaction with in-situ amplified photocurrent was innovatively designed for the quantitative screening of carcinoembryonic antigen (CEA) in biological fluids by coupling with carbon-functionalized inorganic photoanode. A split-type photoelectrochemical (PEC) immunoassay was initially executed with horseradish peroxidase (HRP)-labeled secondary antibody on the capture antibody-coated microtiter. Then, the photocurrent of carbon-functionalized inorganic photoanode were improved through enzymatic insoluble product. Experimental results revealed that introduction of the outer carbon layer on the inorganic photoactive materials caused the amplifying photocurrent because of the improving light harvesting and separation of photo-generated e - /h + pairs. Under optimum conditions, the split-type photoelectrochemical immunosensing platform displayed good photocurrent responses within the dynamic range of 0.01 - 80 ng mL -1 CEA, and allowed the detection of CEA as low as a concentration of 3.6 pg mL -1 at the 3S blank level. The strong attachment of antibodies onto nano label and high-performing photoanode resulted in a good repeatability and intermediate precision down to 9.83%. No significant differences at the 0.05 significance level were encountered in the analysis of six human serum specimens between the developed PEC immunoassay and the commercially available CEA ELISA kits., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Designing a universal route for rational synthesis of a family of hollow multinary chalcogenide semiconductors for photoelectrochemical biosensors is still facing to the enormous challenges ahead. Herein a template-assisted Cu 2 O surface vulcanization and etching through a Pearson's hard and soft acid-base (HSAB) principle was utilized to synthesize hollow Cu 2-x S photoactive materials for photocurrent detection of prostate-specific antigen (PSA). We initially synthesized cubic Cu 2 O and further surface sulfidation and HCl etching to obtain cubic Cu 2-x S. Inspiringly, stirring of CuS, phosphine (TBP: tributylphosphine) and other metal salts could replace Cu + ions to obtain new metal sulfides without changing the framework, size and thickness of the original material. This interesting phenomenon could be explained by HSAB theory, which soft base was favorable for combining soft acid (Cu + ) to drive Cu + out of the framework. Based on the results, HSAB-based reaction system was applied to develop novel photoelectrochemical PSA immunoassay. Polymetallic-doped sulfides (Zn x Cd 1-x S) had better photocurrent response than pure binary sulfides. A copper oxide (CuO)-labeled detection antibody is captured in a microplate along with a sandwich immunoassay in the presence of target PSA. Subsequently, the CuO nanoparticles were dissociated by hydrochloric acid, releasing a large amount of copper ions to participate in the cation exchange reaction with Zn x Cd 1-x S. Such excellent photoelectric conversion materials could sensitively detect target PSA with a wide linear range from 1.0 pg/mL to 10 ng/mL at a limit of detection down to 0.32 pg/mL. Additionally, favorable stability, great anti-interference ability, easy-fabrication, low-cost, and satisfactory accuracy for the analysis of actual samples were acquired. Importantly, the concept of cation exchange reaction can be widely used to synthesize advanced nanomaterials for fabrication of high-efficiency biosensing systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Photoelectrochemical immunoassays/immunosensors have been employed for biomarker detection, but most are lack of high-efficiency photo-electron transfer nanomaterials for widespread utilization. Herein we synthesized single-atom platinum-anchored Zn 0.5 Cd 0.5 S nanostructures to construct an innovative photoelectrochemical (PEC) immunosensor for photocurrent determination of prostate-specific antigen (PSA). Improvement of the photocurrent on the sensing interface derived from the ion-exchange reaction between cupric oxide nanoparticle (CuO NP)-labeled secondary antibody and single-atom platinum-anchored Zn 0.5 Cd 0.5 S. The experimental results showed that the doping of zinc ions and atomically dispersed platinum into CdS could significantly enhance the photocurrent, which further improved the sensitivity of immunoassay. Specifically, upon sensing the target PSA, a CuO-labeled detection antibody was introduced by sandwich immunoreaction and numerous copper ions (Cu 2+ ) were released from CuO by acid to participate in the ion-exchange reaction. Thereafter, the ion-exchange reaction between Cu 2+ ions and single-atom platinum-anchored Zn 0.5 Cd 0.5 S resulted in the quenching of the photocurrent from single-atom platinum-anchored Zn 0.5 Cd 0.5 S owing to weak photoactive material Cu x S formation. Under optimized conditions, single-atom platinum-anchored Zn 0.5 Cd 0.5 S-based photoelectrochemical immunoassay gave good PEC signals toward PSA from 1.0 to 10000 pg/mL with a limit of detection of 0.22 pg/mL. Additionally, good repeatability, intermediate precision, strong anti-interference and high accuracy (relative to commercialized ELISA kit) for the measurement of human serum specimens were acquired. Importantly, use of single-atom platinum-anchored Zn 0.5 Cd 0.5 S can provide an important idea for early tumor screening and diagnosis., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A simple and feasible electrochemical immunosensing protocol with glucometer readout was designed for the detection of low-abundance disease-related biomarker (alpha-fetoprotein; AFP) on the basis of backfilling rolling cycle amplification (RCA) with invertase-DNA 2 conjugates on the detection antibody. The assay consisted of the immunoreaction, RCA reaction, DNA 2 -invertase hybridization and glucose measurement. Initially, a sandwiched immunoreaction was carried out between anti-AFP capture antibody-coated microplate between nanogold-labeled pAb 2 detection antibody conjugated with DNA 1 primer (DNA 1 -AuNP-pAb 2 ) in the presence of target ATP. Thereafter, the carried primers triggered the RCA reaction in the presence of circular DNA template, polymerase and dNTP, to produce numerous repeated oligonucleotide sequences for hybridization with many invertase-DNA 2 conjugates. The carried invertase molecules accompanying the hybridization reaction hydrolyzed sucrose into glucose, thereby resulting in the amplification of the detectable signal on a handheld personal glucometer (PGM). Under optimum conditions, the developed immunoassay exhibited high sensitivity for the quantitative screening of AFP within a dynamic range of 0.1-100 ng mL -1 at a low detection limit of 0.087 ng mL -1 . Other biomarkers and proteins did not interfere the signals of this system. In addition, this method was utilized to determine human serum samples containing target AFP, and received well-matched results with the referenced enzyme-linked immunosorbent assay (ELISA) method., (Copyright © 2019 Elsevier B.V. All rights reserved.)