Naked eye colorimetric detection of Escherichia coli using aptamer conjugated graphene oxide enclosed Gold nanoparticles

Abstract

E. coli is the most common foodborne bacteria causing illnesses including diarrhea, fever, and death if left undiagnosed and untreated, which makes its detection most important. Traditional detection methods such as culture methods, PCR, or ELISA are time-consuming and require skilled manpower. To overcome the disadvantages of traditional detection methods, a fast, easy, and cost-effective platform is required. ssDNA aptamer is a stable, sensitive, and selective biomolecule used extensively for detection. To provide naked eye visible detection, gold nanoparticles (AuNPs) were used, and to increase the aptamer conjugation, AuNPs were covered with Graphene Oxide. Thus, the overall sensitivity of the designed nanoprobe was also augmented. Therefore, exploiting the properties of gold nanoparticles and graphene oxide, a detection platform with aptamer conjugation has been developed in this study. In the manifestation of E. coli cells, the visible color change was observed from red to blue within an hour incubation. The limit of detection observed visually was 102 cells/mL with GO coating and 103 cells/mL without GO. The detection limit in real time coconut water samples was also 102 cells/mL. This platform was found to be applicable in glass capillary which provides opportunities for making a point of care detection device.