Surficial N⁺ Charge Density as Key Factor for Inhibition of Pseudomonas Biofilm Formation in Non-Leaching Quaternary...

Marine biofouling represents significant environmental and economic concerns, highlighting the need for sustainable and non-leaching antifouling materials. In this work, we developed cross-linked polydimethylsiloxane (PDMS) coatings functionalized with methyldimethoxysilanes bearing quaternary ammonium groups and alkyl side chains of two different lengths (C8 and C12). ²⁹Si and ¹³C solid-state nuclear magnetic resonance (CP-MAS NMR) and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful incorporation of silanes into the polymer matrix. Surface analysis was carried out by fluorescein assay, surface roughness, and contact angle measurements. Antifouling assays against Pseudomonas delhiensis PS27, a robust Gram-negative strain exhibiting strong resilience to environmental stresses, demonstrated notable biofilm inhibition in coatings with higher charge surface density without affecting the physiological fitness of planktonic cells. An observed minimum effective value of surface charge density (6.23 ± 0.76)·10¹⁶ N⁺/cm² for biofilm inhibition was observed. These findings suggest a link between surficial N⁺ charge density and antifouling efficacy. The developed coatings represent a promising and durable strategy for environmentally friendly fouling prevention in marine and aquatic environments.