Real-Time Evaluation of Bacterial Viability Using Gold Nanoparticles

Real-time evaluation of bacterial viability is important for various purposes such as hygiene management, development of antibacterial agents, and effective utilization of bacterial resources. Here, we demonstrate a simple procedure for evaluating bacterial viability using gold nanoparticles (Au NPs). The color of bacterial suspensions containing Au NPs strongly depended on the bacterial viability. We found that the dispersion state of Au NPs affected the color of the suspension, based on the interaction of Au NPs with substances secreted by the bacteria. This color change was easily recognized with the naked eye, and viability was accurately determined by measuring the absorbance at a specific wavelength. This method was applicable to various bacterial species, regardless of whether they were Gram-positive or Gram-negative.