4 - Detection of food contaminants by gold and silver nanoparticles

Abstract

Detection of foodborne contaminants is essential before they are released into the market. We have developed simple colorimetric detection methods for contaminants like melamine, malathion, and foodborne pathogens, like Escherichia coli O157:H7 in food items using silver and gold-based nanoparticles. The detection of these contaminants is principally based on the aggregation and disaggregation of metal nanoparticles in the presence of analyte. A comparative study was taken up for melamine detection using differently sized citrate-capped gold nanoparticles (AuNPs) based on the differential aggregation of nanoparticles. The lowest limit of detection for melamine was found to be 2.37 × 10−8 M. Another biosensor was developed based on the enzymatic inhibition of acetylcholinesterase (AChE) by pesticides like malathion in food items relying on the spectral changes in unmodified silver nanoparticles (AgNPs). The detection limit was noted to be as low as 0.1317 × 10−13 M. Finally, gold nanorods (AuNRs) were used to detect E. coli endotoxin in food items having sensitivity as low as 3 ng/mL. The metal nanoparticle-based sensors were successfully employed for the detection of contaminants in vegetable, fruit, milk, and water samples.