(591d) Bubble Effects of Self-Locomotive Microparticles in Biofilm Deterioration

Biofilms are bacterial communities that produce extracellular polymeric substances (EPS). Biofilms use EPS as a barrier toward antibiotics, which make them very resistant compared to planktonic bacteria. To develop an effective system to remove biofilm, we coated MnO₂ on the surface of hollow cylindrical-shaped diatom particles and mixed with antiseptic H₂O₂, which resulted in a self-locomotive cleaning system via the continuous generation of O₂ bubbles inside the channels of the particles. Using optical coherence tomography (OCT), we examined the process of biofilm getting removed through the particles’ continuous bubble generation and burst. The generated bubbles caused the MnO₂-diatom particles to self-propel towards the biofilm as well as induce cavitation effects inside the biofilm. Due to such effects, the particles could diffuse into the weakened EPS matrix and reach the bacterial cells, leading to 99.9% killing of the bacteria. While studying their mechanism of biofilm removal, we focused on the particles’ bubble dynamics. We examined two factors, reaction temperature and concentration of the particles, to see how they affect bubble dynamics, and furthermore studied how those affect biofilm removal efficacy. Increasing concentration resulted in an advanced bubble dynamic behavior that induced stronger cavitation effects. Increasing temperature resulted in a faster rate of H₂O₂ decomposition and faster O₂ bubble generation. Through the examination of temperature effects in bacterial viability, and colocalization of EPS and bacterial cells, we conclude that higher temperature causes higher mechanical energy of the particles to challenge the energy barrier of EPS, thus removing more biofilm. This study highlights the significance of bubble dynamics in MnO₂-diatoms’ biofilm removal process, leading to a step further in the optimization of the particles for expanded applications in the future, especially for clinical studies.