Development of multiplexed biosensor for food borne bacteria using aptamer fabricated graphene oxide gold nanoparticles

Abstract

Due to the increase in the incidence of foodborne bacterial infections causing diseases such as fever, diarrhea, vomiting, and in severe cases, death, it has become important to detect the causative agent on time. Although there are multiple conventional techniques for detection such as culturing, biochemical tests, ELISA, and PCR but these techniques are time taking, laborious, costly, and need a technician to perform these tests. Therefore, there is an urgent need for detection that is simple to use, portable, cost-effective, fast, and can also detect multiple bacteria in a single experiment. Hence, detection assays using ssDNA aptamers in the presence of gold nanoparticles and graphene oxide have been developed. E. coli and S. typhimurium bacteria were detected using colorimetric and fluorometric techniques. For E. coli, E8 aptamer conjugated gold nanoparticles-based assay was developed where in the presence of bacteria, a visible color change of gold nanoparticles from red to blue was observed. S. typhimurium bacteria was detected using FAM fluorophore-labeled Sal5 aptamer in presence of Graphene oxide. Aptamer adsorbs on the graphene oxide sheets by and#960;- and#960; interaction. Graphene oxide is an excellent quencher, quenches the fluorophore of the aptamer in the absence of bacteria that get restored in the presence of target bacteria. A similar phenomenon was utilized for developing a multiplexed bacteria detection system where three different aptamers were used for detecting different bacteria simultaneously. Microfluidic chips were fabricated for developing a smartphone-based multiplexed bacterial detection device that is a point of care, cost-effective and sensitive. newline