Hydrogel patches sample skin microbes and immune cells in humans and mice

Scientists tested a hydrogel-coated microneedle patch designed to sample skin microbes and immune cells. This pilot study included human participants and mice models colonized with specific bacteria. The patches were well tolerated in humans with no reported adverse events. In mice, the device successfully preserved individual microbial signatures and tracked immune responses during different bacterial exposures. Researchers observed distinct immune patterns when mice were exposed to harmless bacteria, harmful pathogens, or both together. The study found that harmless bacteria can induce controlled immune activation that stabilizes over time, while harmful bacteria drive progressive inflammation. Additionally, harmless bacteria reshaped immune responses to harmful pathogens, leading to a temporary activation followed by reduced inflammation. This work establishes microneedle sampling as a strategy to study immune-microbiome dynamics in barrier tissues. It provides a framework for future mechanistic studies of host-microbe interactions in health and disease.