Carbonized Cellulase-Derived Carbon Dots for disruption of Pseudomonas aeruginosa Biofilms through Charge-Dependent Electrostatic Interaction

Chronic wound infections caused by bacterial biofilms are difficult to treat because biofilms EPS protect bacteria from antibiotics. To overcome this problem, we developed carbonized carbon dots (CDs) made from cellulase, a natural and biocompatible material, to study their antibacterial and antibiofilm properties against Pseudomonas aeruginosa. The CDs were prepared using a controlled microwave process(5-120min), which allowed adjustment of their carbonization level, particle size, and surface charge. We found that CDs with a balanced level of carbonization and a positive surface charge were most effective in reducing 24hr biofilm formation and damaging bacterial cell membranes. Microscopy showed extensive permeabilization of the cell membrane and cell death, whereas micro rheology showed large softening of the EPS matrix, changing the rheological properties of biofilms from elastic to viscous regimes.

Over-carbonized CDs, however, showed lower activity due to surface changes and particle aggregation, with greatly reduced antibiofilm action. These findings provide a mechanistic model correlating the charge dependence on the method of preparation of CDs with the nanoscale physical disruption of biofilms. It provides a rational design model for carbon-related nanomaterials having large antibiofilm, antibacterial properties, thereby providing for the preparation of adaptive physicochemical charge-engineered materials able to combat chronic biofilm-associated infections