Dual-Modal Split-Type Immunosensor for Sensitive Detection of Microcystin-LR: Enzyme-Induced Photoelectrochemistry and Colorimetry

Abstract

Microcystins, the lethal cyanotoxins from Microcystis aeruginosa, can inhibit the activity of protein phosphatase and promote liver tumors. Herein, a dual-modal split-type immunosensor was constructed to detect microcystin-LR (MC-LR), based on the photocurrent change of CdS/ZnO hollow nanorod arrays (HNRs) and the blue shift of the surface plasmon resonance peak from Au nanobipyramids@Ag. By using mesoporous silica nanospheres as the carrier to immobilize secondary antibody and DNA primer, a hybridization chain reaction was adopted to capture alkaline phosphatase, while its catalytic reaction product, ascorbic acid, exhibited dual functions. The detailed mechanism was investigated, showing that ascorbic acid can not only act as the electron donor to capture the holes in CdS/ZnO-HNRs, leading to the increase photocurrent, but also as the reductant to form silver shells on Au nanobipyramids, generating multiply vivid color variations and blue shifts. Compared with the traditional photoelectrochemical immunosensor or colorimetric method for MC-LR, a more accurate and reliable result can be obtained, due to different mechanisms and independent signal transduction. Therefore, this work can not only propose a new dual-modal immunosensor for MC-LR detection but also provide innovative inspiration for constructing sensitive, accurate, and visual analysis for toxins.

Direct‐Laser‐Writing of Metal Sulfide‐Graphene Nanocomposite Photoelectrode toward Sensitive Photoelectrochemical Sensing

“…In the past decade, there has been a continuous effort to construct PEC (bio‐)sensing platforms by using various metal sulfides (MS) as photoactive materials on photoelectrode, such as CdS, PbS, Bi 2 S 3 , and Ag 2 S . To boost the photo‐to‐current conversion efficiencies and, thus, the sensitivities of MS‐based PEC sensors, a variety of approaches has been proposed toward the incorporation of MS with binary metal oxide semiconductor, ternary metal oxide semiconductors, or carbon nitride . As an excellent charge transport matrix, graphene (G) has been extensively investigated for the construction of heterojunction composites with MS, especially CdS‐G, not only preventing charge carrier trapping but also retarding the electron–hole recombination in these MS.…”

Nanomaterials-Based Colorimetric Immunoassays

“…Moreover, Gao’s group proposed a signal amplification immunoassay based on the conversion of p-aminophenol phosphate into p-aminophenol by alkaline phosphatase [127]. Very recently, Liu and co-workers constructed a dual-modal split-type photoelectrochemical and colorimetric immunosensor for microcystin-LR (MC-LR) detection by using Au nanobipyramids (Au NBPs) instead of AuNRs [143].…”

Universal Nanoplatform for Formaldehyde Detection Based on the Oxidase-Mimicking Activity of MnO2 Nanosheets and the In Situ Catalysis-Produced Fluorescence Species

“…Because formaldehyde has certain reducibility and oxidation ability, it can be determined by spectrophotometry, chromatography, electrochemical methods, and so on. − However, most of these methods have problems such as bad anti-interference ability and instability, and they can only detect formaldehyde in air or in samples with a higher HCHO concentration. The lower contents of formaldehyde in food samples cannot be detected owing to the lower detection sensitivity.…”