Biofilm prevention and quorum sensing interference via surface-bound peptoid

The emergence of antibiotic resistance has ushered in a post-antibiotic era, highlighting the urgent need for alternative, cytocompatible antimicrobial strategies. Among these, antimicrobial peptides (AMPs) are promising to overcome antibacterial resistance being at the same time cytocompatible, but they are limited by fast enzymatic degradation. Peptoids are synthetic and bio-mimetic biomolecules that overcome the limitations of AMPs with resistance to proteolytic degradation. This study examined the antibacterial and cytocompatible peptoid GN2-Npm9 to reduce the risk of infection in titanium implants. Ti6Al4V samples were chemically pre-treated (CT) to favour osteointegration and functionalization. The zeta potential titration curves evidenced a mechanism of electrostatic attraction between the peptoid and CT substrate on the functionalized samples (CT_GN2-Npm9). XPS analysis and fluorescence microscopy confirmed the presence of the peptoid on CT_GN2-Npm9 and evidenced a uniform distribution. The peptoid was released in water with slow kinetics for at least 9 days (HPLC analyses). CT and CT_GN2-Npm9 specimens were subjected to biological assays against oral plaque collected from patients affected by periodontitis, showing a direct biofilm reduction of 60 % in comparison to CT and a specific effect towards pathogens as evidenced by proteomics studies. For investigating the mechanism of biofilm prevention, a culture of Pseudomonas aeruginosa was performed by conditioning the culture medium with the supernatant from the plaque test. It was observed that the biofilm of P. aeruginosa was significantly reduced due to a peptoid's indirect effect demonstrated by the expression of genes involved in the quorum sensing network and elastase gene (lasB) that resulted in down-regulation only by the supernatants from CT-GN2-Npm9 specimens.