Highly specific and sensitive detection of bacteria by dark-field light-scattering imaging based on bacteriophage-modified magnetoplasmonic nanoparticles

Abstract

Bacterial infections pose significant global health concerns, necessitating precise and sensitive detection methods. This study introduces a multifunctional probe for bacterial detection. Bifunctional magnetoplasmonic nanoparticles (NPs) serve a dual purpose as carriers for magnetic separation (MS) and enhancers for light scattering of the target bacteria. We achieved exceptional selectivity at the bacterial species level by bioconjugating them with bacteriophages (phages). Optimal phage coverage was carefully determined to enhance the capture efficiency of the target bacterial cells. Additionally, we identified the ideal mixing ratios of the phage probe to bacteria, ensuring efficient MS and high light-scattering intensity. The use of the phage probe enabled the successful separation of captured target bacteria from other bacterial strains in the sample mixture. Bacterial detection was accomplished through dark-field light-scattering imaging, eliminating the need for additional labeling with other probes. This method showed a remarkable sensitivity, achieving a detection limit of ∼102 colony-forming units ml-1. This value is 2 orders of magnitude lower than that achieved using our previously reported technique using monofunctional plasmonic NPs. These phage probes hold promise for healthcare, biotech, and environmental monitoring owing to their adaptability to diverse bacterial species.