Detection of bacterial contaminants via frequency manipulation of amino-groups functionalized Fe₃O₄nanoparticles...

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 theEscherichia coli (E. coli)andStaphylococcus aureus (S. aureus)bacterial species. The resonant sensor was tuned at 430 MHz and the CSRR sensor bed was further activated using APTES@Fe₃O₄nanoparticles. Bacterial detection was studied over a range of concentrations from 2.66 × 10⁹cells to 2.66 × 10⁸cells. The sensor actively responded to small changes in bacterial concentration, showing an overall shift in resonance frequency of ∼44 MHz (∼40 MHz/cell count) forE. coliand ∼55 MHz (50.43 MHz/cell count) forS. 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.