Controlled Release System for Delivery of the WLBU2 Antimicrobial Peptide

Oral bacteria initiate localized inflammatory processes leading to bone resorption in conditions such as periodontitis and peri-implantitis. The first step to bone regeneration is to eliminate/minimize bacterial burden. Most effective for this purpose is site-specific, controlled release of anti-infective agents, which can be achieved by incorporating biomolecules in biodegradable materials, such as the polymer blend system of cellulose acetate phthalate and Pluronic F-127 (CAP/PF-127). OBJECTIVE: The objective of this study was to determine the efficacy of de-novo engineered antimicrobial peptide WLBU2 incorporated in CAP/PF-127 on S. gordonii, which is a commensal early colonizer that coaggregates with other bacteria to initiate biofilm formation. METHODS: S. gordonii suspensions were prepared at 0.3 OD₆₀₀ in 10 mM phosphate buffer (PB) and a 1/10^th volume used per treatment. The combined effect of CAP/PF-127 at 3.125% and WLBU2 at 50, 25 and 12.5 µM, with or without equimolar sucrose for enhancing the interaction of WLBU2 with the bacteria, was examined. Controls included treatment of bacteria in PB, 3.125% polymer, or 3.125% polymer supplemented with 50 µM sucrose. After 30 min treatment, ten-fold serial dilutions of each suspension were plated on blood agar and grown at 37^oC overnight. The data from triplicate plates was calculated as number of bacterial colonies compared to control. RESULTS: The number of S. gordonii colonies was negligible with 50 µM WLBU2 treatment alone, but was decreased to only approximately 1000-fold reduction in the presence of 3.125% CAP/PF-127. Addition of 50 µM sucrose to polymer-peptide solutions reduced S. gordonii colonies as effectively as did peptide treatment alone. This effect could be due to sucrose reducing interaction between polymer and WLBU2 and thereby making it more available to kill bacteria. CONCLUSIONS: CAP/PF-127 can be effectively used to deliver WLBU2 to kill S. gordonii. Supported by U.S. Army (W81XWH-09-1-0461) and NIH/NIDCR DE018177.