Mesoporous silica supported Au-Cu bimetallic nanoparticles-based electrochemical aptasensor for estimation of...

The presence of antibiotic residues, such as ampicillin (AMP), in milk poses significant public health concerns, necessitates rapid, sensitive, and reliable detection methods for food safety monitoring. Here, we report a highly sensitive impedimetric aptasensor for the detection and estimation of AMP residues in raw milk. Au-Cu bimetallic nanoparticles were electrodeposited in a single step onto a mesoporous silica-supported FTO electrode, enhancing both the conductivity and surface area. An AMP-specific aptamer was immobilized using (3-glycidyloxypropyl)trimethoxysilane (GOPS) via covalent bonding through epoxide ring opening for selective target recognition. The binding of AMP led to an increase in charge transfer resistance (R_ct), forming the basis of detection. The optimized sensor demonstrated a linear response across 0.1 ng mL^-1-1000 ng mL^-1, with a sensitivity of 1.84 mΩ (ng mL^-1)^-1 cm^-2, a limit of detection of 0.15 ng mL^-1, and a quantification limit of 0.5 ng mL^-1. Detection of AMP was achieved within 20 min. The performance of the fabricated sensor in real milk samples was validated with the standard LC-MS technique. In conclusion, the sensor showed excellent accuracy, sensitivity, and stability. The proposed aptasensor offers a strong, low-cost platform for rapid monitoring of AMP residues in milk.