Label-free selective and sensitive colorimetric detection of ampicillin in milk and water using silver nanoparticles

Overuse of antibiotics like ampicillin in various developing and industrializing countries leads to the evolution of drug-resistant bacteria and different adverse effects on an individual's health. Though creating a facile, sensitive, and selective method for ampicillin detection is critical, this remains a strategic task. The poly(vinyl alcohol) (PVA)-capped silver nanoparticles (AgNPs) were used to develop a colorimetric assay for the detection of ampicillin. UV-Vis spectroscopy shows a strong peak at 402 nm due to the excitation of surface plasmon resonance (SPR). The X-ray diffraction (XRD) pattern of AgNPs shows lattice planes (111) and (200) correspond to 2θ values of 38.4° and 44.67°, respectively. Transmission electron microscopy (TEM) histogram shows the large number of particles synthesized in the range of 9–13 nm. As-synthesized AgNPs were used to evaluate the selectivity of the assay against various competitive antibiotics. The colour change of the assay mixture from yellow to orange was found in the presence of ampicillin due to target-specific aggregation and localized surface plasmon resonance changed from 402 nm to 550 nm. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 6.2 μM and 18.8 μM (linear range 0.5–10 μM) respectively. The colorimetric assay was used to detect the ampicillin-spiked actual samples (tap water, Yamuna River water, and milk). The developed colorimetric assay provides a real-time, rapid, and easy-to-use platform for detecting ampicillin for real sample analysis.