Title : Harnessing gold nanoparticle colour transitions for rapid microbial detection in fuels
Abstract:
Microbial contamination in fuels degrades fuel quality and induces microbiologically influenced corrosion, posing significant risks to fuel system integrity. Conventional monitoring relies on culture-based techniques that require several days for detectable outcomes, highlighting the need for rapid, reliable alternatives. We developed a nanoplasmonic biosensor leveraging the localised surface plasmon resonance (LSPR) properties of gold nanoparticles (AuNPs) for colorimetric detection of Sphingomonas paucimobilis, a hydrocarbon-degrading bacterium prevalent in contaminated fuels. Using Cell-SELEX, we identified a high-affinity DNA aptamer specific to S. paucimobilis, marking the first aptamer developed for this microbe. The biosensor exploits the LSPR-mediated colour transition of AuNPs, where aptamer-induced stabilisation of the AuNPs enables the solution to shift from red to purple colour upon bacterial presence. By systematically optimising aptamer length and functional group modifications, we fine-tuned the colloidal stability of the nanoparticles, enhancing sensitivity for robust biosensing. The optimised aptamer-AuNP system enables detection across a broad dynamic range (10²–10? CFU/mL), facilitating early microbial identification in complex fuel matrices. To enhance field applicability, we developed a smartphone-based application that quantifies nanoparticle aggregation via RGB colour analysis, achieving a 95% correlation with ultraviolet-visible (UV-Vis) spectrophotometry. The biosensor was validated in fuel samples, demonstrating reliable performance in non-aqueous environments. At a minimal assay cost of €0.23, our technology provides an accessible and scalable platform for rapid, on-site microbial diagnostics, with potential adaptability to diverse biosensing applications in environmental, biomedical, and industrial settings. By integrating LSPR nanotechnology with aptamer-based molecular recognition, this work advances the frontier of nanobiotechnology for microbial detection in real-world applications.
