MXene/Gold nanoparticles heterostructure as catalase mimic for colorimetric detection of penicillin G

Penicillin G (PenG) is a common antibiotic used to fight bacterial infections in livestock. Its excessive use leads to animal products tainted with antibiotic residues. Consumption of foods contaminated with antibiotics can cause their accumulation in our bodies and pose threats to our health. We developed a colorimetric assay to detect the presence of PenG in real matrices using a hierarchical nanostructure material composed of layered titanium carbide MXene nanosheets (Ti3C2Tx) decorated with gold nanoparticles (AuNPs). The AuNPs were directly grown on the MXene nanosheets via a facile method, which significantly enhanced the catalase-like enzyme activity of MXene. The Ti3C2Tx/AuNPs nanocomposite catalyzed the enzymatic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to its oxidized form in the presence of hydrogen peroxide, and the reaction products turned the sample solution greenish blue. However, this color-change reaction does not occur when PenG is present in the solution. Our assay performed well with a limit of detection (LOD) of 7.51 nM, which is below the established maximum residue limits for raw milk. We hypothesized and experimentally verified that superoxide anions (O2•-) generated play a critical role in the catalysis of PenG. Our results may help develop a simple and inexpensive colorimetric sensor for the routine detection of PenG in food samples.