Disruption of Enterococcus Faecalis Biofilms Using Plasma Polymer Encapsulated D-amino Acids

Objectives: Enterococcus faecalis (Ef) is a predominant species present in the root canal system of failed endodontically treated teeth as it has the ability to form biofilms. We have shown that a mixture of D-amino acids (DAAs) disrupt established and developing Ef biofilms. Our objectives are to investigate the effectiveness of individual DAAs on Ef biofilms and to use encapsulation technologies to provide a sustained release of DAAs that may be used to improve the success of root canal therapy.
Methods: Micro-titre tray and static biofilm assays were used to compare the effect of DAAs and plasma polymer encapsulated DAAs (PPEDAAs) on Ef biofilms. A mixture and individual DAAs of D-Methionine, D-Tyrosine, D-Leucine and D-Tryptophan were encapsulated with a plasma polymer (1-7 octadeine) for 10, 20, 40 and 60 minutes to allow for variations in shell thickness of the particles. PPEDAAs were analysed with scanning electron microscopy. Diffusion of DAAs from the PPEDAAs was measured over 7 days using HPLC.
Results: Using SEM, the shell thicknesses of the PPEDAAs ranged between 36-77nm - indicating a substantial coating of plasma polymer and the thickness of polymer coating increased with plasma coating time. HPLC results showed a sustained diffusion of DAAs from the PPEDAAs over 7 hours for most PPEDAAs and 7 days for 60 minute encapsulated D-Tyrosine and D-Tryptophan. Visible and statistical biofilm disruption was observed with DAAs and PPEDAAs with 24, 72 and 144 hour biofilms.
Conclusions: Polymer encapsulation is a promising technology to maintain a sustained release of DAAs and may greatly improve the success rates of endodontic treatment.