Towards point-of-care detection of polymicrobial infections: Rapid colorimetric response using a portable spectrophotometer

• “Chemical nose” can detect polymicrobial mixtures of bacteria.
• Kinetic colorimetric response of each bacterial mixture is unique.
• A portable spectrophotometer provides sufficient information within 2 min.

Infectious diseases spread rapidly because current diagnostic methods are slow, expensive, and require technical expertise. Biosensors have recently been used as devices that can be deployed at the point-of-care for rapid and accurate diagnosis. Here, we show that a “chemical nose” biosensor based on gold nanoparticles can be coupled with a portable spectrophotometer to detect monomicrobial and polymicrobial solutions of pathogenic bacteria within 2 min of data collection. The design presented here exploits the rapid kinetics of gold nanoparticle aggregation around bacteria, which leads to a dramatic color change. The “chemical nose” produces unique signals based on the surface characteristics of the bacteria—such as the presence of extracellular polymeric substances, distribution of charged lipids, and localization of proteins—and hence provides a versatile platform for detection. We present a biosensor design that can easily be translated to the point-of-care because of its rapid response and simple output.