Light-activated aptasensor for plug-and-play detection of Aflatoxin B1 in food samples

AFB1 contamination in food samples is a global concern, threatening food safety and human health. Numerous assays have been developed for AFB1 detection. Among them, fluorescent aptasensors are of great interest due to their simplicity of operation, easy to read signal output. Nevertheless, these aptasensors are "passive-type", means the target AFB1 bind with the aptamer directly and cause fluorescent signal response. They are "always active", may result in undesired signal generation and the process is hard to control. Generally, the "activable-type" aptasensor would avoid these defects.

Here we demonstrate a light activated aptasensor for plug-and-play detection of AFB1. The aptasensor is constructed by integrating an AFB1-specific aptamer with a complementary DNA strand (PC-strand) that incorporates a photocleavable o-nitrobenzyl group. The AFB1 aptamer is locked by PC-strand preventing it binding to target AFB1. With ultraviolet (UV) light irradiation, the o-nitrobenzyl group cleaves and releases the PC-strand to two short DNA fragments. This fragmentation reduces the hybridization stability with AFB1 aptamer, allowing target AFB1 to bind efficiently to AFB1 aptamer and accompanied by increasing in fluorescence signal. The aptasensor could be activated at desired time, provides a sensitive (0.074 ng/mL) and specific method for AFB1 detection. It has been demonstrated to be a reliable tool for the analysis of AFB1 in food samples (rice, corn, and soybean), yielding satisfactory results.

The aptasensor is insert to the target AFB1, while its activity could be restored in a time-resolved manner by cleaving the PC-strand to two short strands using UV light irradiation. This approach provides a promising platform for the rapid screening of AFB1 contamination in food samples, contributing to food safety and quality control.