Development of magnetic nanoparticle assisted aptamer-quantum dot based biosensor for the detection of Escherichia coli in water samples

The contamination of food and potable water with microorganisms may cause food-borne and water-borne diseases. The common contaminants include Escherichia coli (E. coli), Salmonella sp. etc. The conventional methods for monitoring the water quality for the presence of bacterial contaminants are time-consuming, expensive, and not suitable for rapid on-spot detection in field conditions. In the current study, super paramagnetic iron oxide nanoparticles (SPIONs) were synthesized and conjugated with E. coli specific Aptamer I to detect E. coli cells qualitatively as well as quantitatively. The sludge consisting of E. coli- SPION complex was separated via magnetic separation. The presence of E. coli cells was confirmed with the help of standard techniques and confocal laser scanning microscopy (CLSM) employing Aptamer II conjugated CdTe-MPA quantum dots (QDs). Finally, an ATmega 328P prototype biosensor based on Aptamer II conjugated CdTe MPA QDs exhibited quantitative and qualitative abilities to detect E.coli. This prototype biosensor can even detect low bacterial counts (up to 1 × 102 cfu) with the help of a photodiode and plano-convex lens. Further, the prototype biosensor made up of ultraviolet light-emitting diode (UV LED), liquid crystal display (LCD) and ATmega328Pmicrocontroller offers on-spot detection of E.coli in water samples with high resolution and sensitivity. Similarly, this in-house developed prototype biosensor can also be utilized to detect bacterial contamination in food samples. [Display omitted] •A biosensor for on-spot detection of E. coli in water samples using specific aptamer has been developed.•Quantitative and qualitative ability for precise estimation of E. coli.•Arduino 328P microcontroller used for cost effective and sensitive detection of the pathogen.•The biosensor is capable of detection of lowest limit of 1 × 102 bacterial cells.•This technology can be utilized for bacterial detection in various samples.