Target-activated DNA hydrogel-encapsulated trimetallic nanozyme platform for surface-enhanced Raman scattering detection of botulinum neurotoxin type A

Conventional meat products are susceptible to bacterial toxin contamination, posing serious risks to food safety. This study presents a portable surface-enhanced Raman scattering (SERS) platform integrated with stimuli-responsive DNA hydrogels and trimetallic nanozymes for the detection of botulinum neurotoxin type A (BoNT/A). The system employs Cu/Au/Pt trimetallic nanozymes immobilized on a steel mesh alongside DNA anchor strands that initiate hydrogel film formation. Through sequential assembly of BoNT/A aptamers and crosslinked DNA strands, a stimuli-responsive hydrogel encapsulating the nanozymes is constructed. In the presence of BoNT/A, the aptamer triggers hydrogel cleavage facilitated by exonuclease I, releasing the nanozymes to catalyze the oxidation of TMB. This reaction generates a visible colorimetric change for rapid visual screening, while the concurrently enhanced SERS signals provide the basis for highly sensitive and quantitative detection. The platform achieves an exceptionally low detection limit of 1   ng/L for BoNT/A within 45   minutes, with a linear SERS response between 5.0 and 400.0   ng/L. Successful application in real meat samples confirms its practicality as a robust, on-site tool for food safety monitoring.