Towards targeted Escherichia coli fluorescence biosensor using quantum dots decorated geothermal silica nanoparticles

Abstract

The quality of water is assessed not solely by its physical and chemical characteristics but also by its biological parameters, such as the presence of Escherichia coli (E. coli) bacteria, a significant pathogen in waterborne diseases. In this study, we developed a highly sensitive fluorescent biosensor platform using quantum dot-modified geothermal silica-based nanoparticles (SiNP@QD). Amine-CdSe quantum dots (QDs) were integrated on the surface as optical transducers and then immobilized with E. coli antibodies for enhanced selectivity (SiNP@QD-Ab). The Brunauer-Emmett-Teller (BET) method determined the surface area of the silica nanoparticles to be 137.75 m²/g, with a particle size ranging from 40 to 70 nm revealed from field emission-scanning electron microscope (FESEM) analysis. X-ray diffraction (XRD) analysis confirmed that the nanoparticles were in their amorphous phase. Detection of the bacteria using SiNP@QD-Ab as a biosensor was observed using a fluorescence spectrophotometer with an excitation wavelength of 360 nm, and emission was observed in the range of 400-800 nm. The analytical performance of the biosensor was observed by varying the incubation times and E. coli concentrations, with the optimal incubation time being 15 minutes. The limit of detection (LOD) for SiNP@QD-Ab, at the maximum emission peak of 435 nm, was determined to be 1.6 CFU/mL. The SiNP@QD-Ab biosensor offers a swift and accurate method for detecting E. coli, promising significant advancements in public health safety and environmental monitoring.