Anti-biofilm efficacy of novel silica-based nanoparticles functionalized with natural derivatives for surface coating

Biofilms colonize both biotic and abiotic surfaces, including living tissues, medical devices, water supply systems, and food processing equipment, posing health risks and financial burdens. In the present study, inorganic nanoparticles were functionalized with p-aminosalicylic acid or p-aminocinnamic acid, both established antibiofilm agents at non-lethal concentrations. The final aim was to obtain new nanosystems for surface covering, mitigating the drawbacks associated with current antifouling coatings and tackling the pressing issue of antimicrobial resistance. Two series of silica nanoparticles were synthesized and characterized; the one with the highest degree of functionalization was selected for coating glass coverslips. The anti-biofilm properties of the resulting surfaces were tested against Pseudomonas aeruginosa biofilm. All coated surfaces showed a significant reduction in biofilm formation compared to the untreated controls, with a decrease ranging from -59.2 +/- 2.2 to -83.7 +/- 3.4. Importantly, the anti-biofilm coating did not affect the bacterial viability of both planktonic and sessile cells. Interestingly, the interaction between bacteria and the new surfaces led to an increase in bacterial metabolic activity, total protein amount, and oxidative stress levels. These findings indicate that the coatings affect biofilm formation by influencing bacterial physiology rather than simply killing the bacteria outright.