Advances in Screening, Detection and Enumeration of Escherichia coli Using Nanotechnology-Based Methods: A Review

Amongst the various microorganisms found as contaminants in food and water samples, Escherichia coli (E. coli) is one of the most predominant bacteria observed. The presence of the various strains of E. coli, pathogenic or non-pathogenic, in either food or water samples serves as an indicator of faecal contamination and helps to determine the hygienic condition, potability and safety of a given water or food sample for consumption. Although several conventional microbial analytical methods and the more advanced biochemical and molecular biology based methods exist for detection of E. coli, these are laden with several limitations. Nanotechnology offers cheaper, more reliable, quicker and more sensitive detection platforms for screening and/or enumerating the load of E. coli in a given sample. The present review outlines in brief the conventional methods available for E. coli detection enlisting the drawbacks of the same. Against this background, nanotechnology-based sensing systems developed for detection and capturing of E. coli so far have been highlighted. The most commonly developed nanosensors employ gold or silver nanoparticles with magnetic nanobeads also being currently employed for sensor development. Further, the evolution of green nanoparticle technology and its application in E. coli sensing has been explored with various examples of carbon dots, graphitic carbon nitride, glycopolymers and rice husk ash being cited. Furthermore, the development of nanosensors for E. coli using bimetallic nanoparticles has also been reviewed. These nanobased sensors have proved to exhibit high sensitivities and low detection limits for E. coli. However, approaches to enhance the sensitivity to detection even further lower limits and provide nanosensors as multifunctionalized detection tools for multiple pathogenic strains are underway.