"Biofilms are a dense matrix of bacterial cells and proteins. While sterilizing agents can kill bacteria, the matrix protects them, making it much harder to treat or clean with chemicals. For example, hydrogen peroxide has been used for centuries but only cleanses the surface and does not penetrate the film," said Illinois chemical and biomolecular engineering professor Hyunjoon Kong, the research team's leader. "We take a mechanical approach: Our particles infiltrate the biofilm first and then generate bubbles inside the matrix, disrupting it."

Bubble-powered particles break through

Kong's group developed tiny cylinders made of biosilica coated in manganese dioxide, a catalyst that releases tiny oxygen bubbles when exposed to a hydrogen peroxide solution. The bubbles accumulate within the hollow cylinder, then are released, propelling the microparticles even deeper into the matrix where they continue to produce bubbles, said graduate student Joo Hun Lee, the first author of the first paper, published in ACS Applied Materials and Interfaces.

The researchers watched the bubbles form and rupture, the particles move, and biofilm disperse using high-speed cameras and Optical Coherence Tomography in collaboration with Stephen Boppart, a University of Illinois professor of bioengineering and professor of biomedical and translational sciences in the Carle Illinois College of Medicine.