Sustained Release of Antibacterial Lipopeptides from a Biodegradable Polymer

Objectives: Various pathogenic species inhabit the oral cavity. The development of antibacterial drugs confronts several challenges such as salivary flow and enzymatic activity that restrict the dosage retention. Owing to their amphipathic nature, antibacterial peptides (AMPs) serve as the first line of defense of the innate immune system. The ability to synthesize different types of AMPs enables the recruitment of their advantages as alternatives for antibiotics. Controlled release of AMPs incorporated into biodegradable polymers can be advantageous in maintaining high peptide levels. For this purpose, we examined four ultra-short lipopeptides, conjugated to aliphatic acids chain (16C). A potent lipopeptide was incorporated into a ricinoleic acid-based poly (ester-anhydride) P (SA-RA) copolymer for slow release.
A novel formulation of lipopeptide and P (SA-RA) was tested for antibacterial activity.
Methods: The minimal inhibitory concentration of four lipopeptides was determined on Enterococcus faecalis, Streptococcus mutans, Escherichia coli, Fusobacterium nucleatum, Porphyromonas gingivalis and Actinomyces naeslundii, using the micro-dilution assay. Formulated peptides were tested antibacterial activity during one week using turbidometric measurements of bacterial outgrowth. Additionally, the anti- biofilm activity was evaluated using live-dead staining. Bacterial membrane disruption was examined using fluorescence-activated cell sorting (FACS). Biocompatibility was tested using hemolysis. A fluorometric assay was used to test the release kinetics.
Results: Among the four lipopeptides, 16C-KGGK was the most potent. Decreased optical densities were depicted in all tested groups containing the formulation, indicating that the peptide was released from the polymer and had an antibacterial effect. Furthermore, the novel formulation exhibited an anti-biofilm effect. We showed that the bacterial membrane was disrupted by KGGK.
Conclusions: An antibacterial effect can be achieved using a formulation of the 16C-KGGK peptide incorporated in P (SA-RA).