Dopamine-Loaded Liposomes for in-Situ Amplified Photoelectrochemical Immunoassay of AFB to Enhance Photocurrent of Mn-Doped Zn(OH)VO 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 B (AFB) in foodstuff, using Mn-doped Zn(OH)VO·2HO nanobelts. The signal was amplified by high-loaded capacity of liposome and the highly efficient dopamine molecule to enhance photocurrent of Mn-doped Zn(OH)VO·2HO 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 AFB-bovine serum albumin (AFB-BSA) conjugate was covalently bound with the multifunctional liposome via the cross-linkage glutaraldehyde, whereas monoclonal anti-AFB antibody was labeled onto a magnetic bead by typical carbodiimide coupling. Upon addition of target AFB, a competitive immunoreaction was carried out between the analyte and the AFB-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 Mn-doped Zn(OH)VO·2HO nanobelts. The photocurrent depended on the as-released amount of the dopamine. The change in the photocurrent enhanced with the increasing AFB concentration. Under the optimal conditions, Mn-doped Zn(OH)VO·2HO nanobelts exhibited good photoelectrochemical responses for the detection of AFB and allowed the detection of AFB at a concentration as low as 0.3 pg mL within a linear range from 0.5 pg mL to 10 ng mL. Importantly, this system provided an ideal PEC immune sensing platform based on Mn-doped Zn(OH)VO·2HO nanobelts and the high-loaded liposome for the detection of small molecules.