A sensitive colorimetric aptasensor for chloramphenicol detection in fish and pork based on the amplification of a nano-peroxidase-polymer

A novel colorimetric aptasensor was developed for sensitive and selective determination of chloramphenicol (CAP) based on gold nanoparticles (AuNPs) labeled with Power Vision (PV) and magnetic separation. PV, with a high enzyme-to-antibody ratio, is composed of a compact enzyme-linker antibody conjunction. In this assay, an aptamer of CAP was immobilized on Fe3O4@Au magnetic nanoparticles as a capture probe (AuMNPs-Apt) to concentrate target CAP. The complementary DNA (cDNA) and PV were both labeled on AuNPs to form a nano-peroxidase polymer as a signal tag (cDNA-AuNPs-PV). And the special tags could hybridize with the aptamer and cDNA to form AuMNP-Apt/cDNA-AuNP-PV conjugates. In the presence of CAP, the aptamer preferentially bound to CAP and caused the dissociation of some cDNA-AuNPs-PV on the conjugates with magnetic separation. PV, carried on signal tags, could greatly catalyze 3,3',5,5'-tetramethylbenzidine (TMB) leading to color development, which could be quantified by Ultraviolet-visible (UV-vis) spectroscopy. A linear response to CAP concentration in the range of 0.05-200 ng mL(-1) was obtained by this proposed method, with a low detection limit down to 0.02 ng mL(-1). Besides, this assay was successfully employed to analyze CAP in fish and pork samples, whose results were consistent with those of the conventional enzyme-linked immunosorbent assay (ELISA) method.