Highly sensitive and selective aflatoxin B1 biosensor based on Exonuclease I-catalyzed target recycling amplification and targeted response aptamer-crosslinked hydrogel using electronic balances as a readout

The biosensors based on aptamer based stimuli-responsive hydrogels have the characters of high specificity, good stability, portability. Electronic balance is one of the most accurate equipment and can be reached nearly in all labs. Aflatoxin B-1 (AFB(1)) is highly toxic and carcinogenic to humans and animals, it is necessary to develop simple and convenient detection method to apply in resource limited area. In this study, a novel strategy for quantitative detection of AFB(1) has been developed by combining the high selectivity and convenient of target-responsive hydrogel and the simple of using electronic balance as readout devices. The AFB(1) target responsive double crosslinked hydrogel has been constructed using linear hyaluronic acid grafted single-stranded DNA complex as the backbone, AFB(1) aptamer and polyethyleneimine as crosslinkers. And platinum nanoparticles (PtNPs) had been embedded in the hydrogel firstly. The present of AFB(1) can bind with the aptamer with high affinity and cause the releasing of aptamer from hydrogel. The addition of Exo I can specifically recognize and cleave the aptamer in AFB(1)-aptamer complex, resulting in the releasing of AFB(1), which can react with the hydrogel again, thereby achieving the target cycle. By this means, the hydrogel will collapse and many preembedded PtNPs can be released. The transferring of the released PtNPs to a drainage device which contains H2O2 can results in the increasing of the internal pressure since the production of oxygen through the catalytic decomposition of H2O2 by PtNPs has low solubility. Which will cause the discharging of water from the system and this can be collected and weighed by an electronic balance easily. The weight of water has a linear relationship with AFB(1) concentration. Under 30 min catalytic time, the linear range is 31.2 mu g/kg - 6.2 mg/kg with the detection limit of 9.4 mu g/kg (S/N = 3). The proposed method was successfully applied to the detection of AFB(1) in peanut samples.