Smartphone-integrated ratiometric colorimetric aptasensor for visual detection of ampicillin residue in animal-derived food samples.

The antibiotic residue in food accelerates bacteria's resistance process that is responsible for serious health issues. A smartphone-integrated ratiometric colorimetric aptasensor has been developed for ampicillin (AMP) detection in milk and egg samples. The sensing phenomenon utilizes the optical and color-changing properties of gold nanoparticles (AuNPs) and specific aptamer with higher affinity towards AMP for its selective detection. The aptasensor shows linear response with AMP concentration 0.06-9.9 μM with a lower detection limit (LOD) of 45.0 nM. The smartphone-integrated color analyzer application was used to identify the solution's red, green, and blue (RGB) color intensity and calculate the G/R ratio of color intensities in the presence of AMP. Aptasensor show linear response with AMP concentration (0-6.6 μM), with a LOD of 53.0 nM. The sensor's results were further validated with liquid chromatography and mass spectroscopy techniques (LC-MS), showing that the developed sensor is suitable for food monitoring and safety applications.