SNAPP-star antimicrobial peptide-polymers are effective against bacterial biofilms and Porphyromonas gingivalis.

Introduction:
Peri-implantitis and periodontitis are biofilm-mediated diseases in which Porphyromonas.gingivalis plays a central pathogenic role. The organism's cysteine-proteases, particularly gingipains, contribute to virulence and may reduce the effectiveness of antimicrobial therapies by degrading peptide-based agents. Synthetic-nanoengineered-antimicrobial-peptide-polymers (SNAPPs) exhibit potent activity against a broad spectrum of bacterial pathogens, including multidrug-resistant-organisms, and represent a potential therapeutic strategy against P.gingivalis. This study investigated the influence of gingipains on SNAPP susceptibility and evaluated the antimicrobial, antibiofilm, and biocompatibility profiles of SNAPPs.

Methods:
The antibacterial activity of several SNAPP formulations was assessed against wild-type and gingipain-deficient P. gingivalis strains under reducing, non-reducing, and gingipain-inhibited conditions using minimum inhibitory and bactericidal concentration assays (MIC, MBC). Antibiofilm activity was evaluated using biofilm prevention and eradication assays. Mechanistic investigations included flow cytometry to assess membrane-permeability, membrane-depolarisation, and intracellular reactive-oxygen-species (ROS) generation. Helium-ion-microscopy was employed to examine bacterial morphological changes under SNAPP treatment. Biocompatibility of SNAPPs towards mammalian cells were evaluated using LDH cytotoxicity and MTS proliferation assays.

Results:
SNAPP activity against P.gingivalis was influenced by Lys-gingipain. Wild-type strains exhibited limited susceptibility to SNAPPs, whereas a Lys-gingipain-deficient mutant was susceptible. Experimental conditions that reduced gingipains activity restored SNAPP efficacy against wild-type strains. Biocompatible pharmacological gingipain inhibitors were developed, enabling SNAPP-mediated killing of wild-type P.gingivalis. SNAPPs were found to significantly inhibited biofilm formation and disrupted mature biofilms (4×MIC, p < 0.001). Microbial flow cytometry showed that SNAPPs disrupted and depolarised the cytosolic membrane and increased ROS production. Microscopic analysis revealed that SNAPP treatment caused membrane rupture and bacterial cell collapse, even at sub-MIC/MBC concentrations. All formulations exhibited favourable biocompatibility with mammalian cells.

Conclusions:
Optimised SNAPP formulations demonstrate considerable potential as peptide-based therapeutics for periodontal and peri-implant infections. Their broad-spectrum antibacterial activity, biofilm-disruptive effects, and favourable biocompatibility support further development as innovative treatments for oral biofilm-associated diseases.