Rapid Colorimetric Identification and Targeted Photothermal Lysis of Salmonella Bacteria by Using Bioconjugated Oval-Shaped Gold Nanoparticles

Salmonella bacteria are the major cause for the infection of 16 million people worldwide with typhoid fever each year. Antibiotic‐resistant Salmonella strains have been isolated from various food products. As a result, the development of ultrasensitive sensing technology for detection and new approaches for the treatment of infectious bacterial pathogens that do not rely on traditional therapeutic regimes is very urgent for public health, food safety, and the world economy. Driven by this need, we report herein a nanotechnology‐driven approach that uses antibody‐conjugated oval‐shaped gold nanoparticles to selectively target and destroy pathogenic bacteria. Our experiments have shown the use of a simple colorimetric assay, with an anti‐salmonella antibody conjugated to oval‐shaped gold nanoparticles, for the label‐free detection of S. typhimurium with an excellent detection limit (104 bacteria per mL) and high selectivity over other pathogens. When bacteria conjugated to oval‐shaped gold nanoparticles were exposed to near‐infrared radiation, a highly significant reduction in bacterial cell viability was observed due to photothermal lysis. Ideally, this nanotechnology‐based assay would have enormous potential for rapid, on‐site pathogen detection to avoid the distribution of contaminated foods. Seek and destroy: Gold nanotechnology has been used for the rapid selective detection and targeted photothermal lysis of the Salmonella typhimurium bacterium. When antibody‐coated oval‐shaped gold nanoparticles are attached to bacterial cells, the visible color of the nanoparticle colloids changes (see left‐hand image) and the localized heating that occurs during near‐infrared irradiation is able to cause irreparable cellular damage (see middle and right‐hand images).