Liposome-coated mesoporous silica nanoparticles loaded with L-cysteine for photoelectrochemical immunoassay of aflatoxin B.

The authors describe a photoelectrochemical (PEC) immunoassay for determination of aflatoxin B (AFB) in foodstuff. The competitive immunoreaction is carried out on a microplate coated with a capture antibody against AFB using AFB-bovine serum albumin (BSA)-liposome-coated mesoporous silica nanoparticles (MSN) loaded with L-cysteine as a support. The photocurrent is produced by a photoactive material consisting of cerium-doped BiMoO. Initially, L-cysteine acting as the electron donor is gated in the pores by interaction between mesoporous silica and liposome. Thereafter, AFB-BSA conjugates are covalently bound to the liposomes. Upon introduction of the analyte (AFB), the labeled AFB-BSA complex competes with the analyte for the antibody deposited on the microplate. Accompanying with the immunocomplex, the liposomes on the MSNs are lysed upon addition of Triton X-100. This results in the opening of the pores and in a release of L-cysteine. Free cysteine then induces the electron-hole scavenger of the photoactive nanosheets to increase the photocurrent. The photocurrent (relative to background signal) increases with increasing AFB concentration. Under optimum conditions, the photoactive nanosheets display good photoelectrochemical responses, and allow the detection of AFB at a concentration as low as 0.1 pg·mL within a linear response in the 0.3 pg·mL to 10 ng·mL concentration range. Accuracy was evaluated by analyzing naturally contaminated and spiked peanut samples by using a commercial AFB ELISA kit as the reference, and well-matching results were obtained. Graphical abstract Schematic presentation of a photoelectrochemical immunoassay for AFB. It is based on the use of Ce-doped BiMoO nanosheets and of liposome-coated mesoporous silica nanoparticles loaded with L-cysteine.