Detection of Listeria Monocytogenes, Salmonella Typhimurium and Staphylococcus Aureus Contamination in Culture ‎Medium by Colorimetric Nanosensor Made from Aminated Graphene Oxide Nanosheets - Bromophenol Blue ‎Indicator

Today, the use of intelligent packaging in various packaging industries has received more attention than ever before. Intelligent packages can contain an indicator or nanosensor that reports the process of quality changing of the packaged product to the consumer in various ways such as color change, voltage change, etc. In this regard, the use of nanoparticles due to their unique and useful properties has improved the performance of nanosensors. For this reason, in the present study, growth of food pathogens, Listeria monocytogenes, Salmonella typhimurium and Staphylococcus aureus, in culture medium was studied using a colorimetric nanosensor made by aminated graphene oxide nanosheet and bromophenol blue indicator based on Whatman paper. The results showed that at the beginning of experiment no colony was observed for L. monocytogenes however, it reached to 189 ± 0.81 colonies after 24 hours (p <0.05).  Growth of S. aureus showed an increasing trend and it reached to 196 ± 4.54 colonies at the end of the incubation period (p <0.05). The number of S. typhimurium coloniesin the culture medium also increased from 0 to 203 ± 5.17 colonies (p <0.05). The results also showed that the color of prepared nanosensors was changed with increasing the number of bacterial colonies, and in this regard the color of the nanosensors was changed from green to blue in all plates. However, the intensity of color difference (ΔE) was different in the presence of different bacteria and the highest ΔE (61.01) was observed in the medium inoculated with S. typhimurium. Correlation between ΔE and increasing the number of L. monocytogenes, S. typhimurium and S. aureus was positive 0.9, positive 0.95 and positive 0.94, respectively.