Detection of bacterial contaminants via frequency manipulation of amino-groups functionalized Fe3O4 nanoparticles based resonant sensor

Bacterial infections have a large impact on public health. Through this study, we report on the development of complementary split-ring resonators (CSRR) supplemented by functionalized nanoparticles to detect bacteria in the aqueous medium. Iron oxide (Fe3O4) nanoparticles were functionalized with amino groups using (3-aminopropyl) triethoxysilane (APTES) to form (APTES@Fe3O4) nanoparticles, which have a specific affinity towards the bacterial species. This affinity was evaluated using the Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacterial species. The resonant sensor was tuned at 430 MHz and the CSRR sensor bed was further activated using APTES@Fe3O4 nanoparticles. Bacterial detection was studied over a range of concentrations from 2.66 x 10(9) cells to 2.66 x 10(8) cells. The sensor actively responded to small changes in bacterial concentration, showing an overall shift in resonance frequency of similar to 44 MHz (similar to 40 MHz/cell count) for E. coli and similar to 55 MHz (50.43 MHz/cell count) for S. aureus. Dextran sulphate and Chitosan were used as the references. The magnetic character of the conjugated system exhibited strong interaction of the bacterial species with APTES@Fe3O4, justifying the high selectivity towards these species. This demonstrates the feasibility of a sensitive, fast, portable device, against the traditionally used time-consuming bio-assays.