Dopamine-Loaded Liposomes for in-Situ Amplified Photoelectrochemical Immunoassay of AFB₁ to Enhance Photocurrent of Mn²⁺-Doped Zn₃(OH)₂V₂O₇ Nanobelts

A novel signal-amplified strategy based on dopamine-loaded liposome (DLL) was developed for competitive-type nonenzymatic photoelectrochemical (PEC) immunoassay of small- molecular aflatoxin B1 (AFB1) in foodstuff, using Mn2+-doped Zn3(OH)2V2O7·2H2O nanobelts. The signal was amplified by high-loaded capacity of liposome and the highly efficient dopamine molecule to enhance photocurrent of Mn2+-doped Zn3(OH)2V2O7·2H2O nanobelts. The loaded dopamine in the liposome was used as an electron donor to scavenge the hole and inhibit the charge recombination. To design such an immunoassay system, a AFB1–bovine serum albumin (AFB1–BSA) conjugate was covalently bound with the multifunctional liposome via the cross-linkage glutaraldehyde, whereas monoclonal anti-AFB1 antibody was labeled onto a magnetic bead by typical carbodiimide coupling. Upon addition of target AFB1, a competitive immunoreaction was carried out between the analyte and the AFB1–BSA–DLL for the conjugated antibody on the magnetic bead. Followed by magnetic separation, the carried DLL on the magnetic bead was lysed by using Triton X-100 to release the encapsulated dopamine. The as-produced dopamine (as an elector donor) increased the photocurrent of the Mn2+-doped Zn3(OH)2V2O7·2H2O nanobelts. The photocurrent depended on the as-released amount of the dopamine. The change in the photocurrent enhanced with the increasing AFB1 concentration. Under the optimal conditions, Mn2+-doped Zn3(OH)2V2O7·2H2O nanobelts exhibited good photoelectrochemical responses for the detection of AFB1 and allowed the detection of AFB1 at a concentration as low as 0.3 pg mL–1 within a linear range from 0.5 pg mL–1 to 10 ng mL–1. Importantly, this system provided an ideal PEC immune sensing platform based on Mn2+-doped Zn3(OH)2V2O7·2H2O nanobelts and the high-loaded liposome for the detection of small molecules.

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