Bimetallic nanozymes laden DNA hydrogel for ultrasensitive optical detection of ractopamine

Ractopamine (RAC) is a synthetic β-adrenergic agonist, used for the reduction of fat deposition and increasing muscle conversion. Despite its wide application as a feed additive, it has some serious side effects. Therefore, RAC exists at low concentrations in meat products and is difficult to detect, hence its ultrasensitive detection is significant in protecting human health. Herein, a novel nanozymes-laden bioactive hydrogel based on the Au@Pd and DNA hydrogel is developed for ultrasensitive optical detection of RAC. The RAC aptamer acts as a crosslinker and Au@Pd is evenly embedded in the DNA hydrogel. The formed hydrogel collapses when the RAC binds to the aptamer, releasing the embedded Au@Pd. This catalyst is then used in the reaction of hydrogen peroxide (H2O2) with tetramethyl benzidine (TMB) to produce color changes that deepen with increasing RAC concentration. The proposed nanozymes-laden bioactive hydrogel has a low detection limit (7.39 ng L−1) and a wide detection range (0.01–1000 μg L−1) and is of great potential for future practical applications in the ultrasensitive detection of food additives.