Bactericidal and Antibiofilm Activity of Anacardic Acid Loaded-Zein Nanoparticles Against Enterococcus faecalis Ex Vivo

Abstract

Anacardic acid has demonstrated extraordinary antibacterial properties. This study aimed to evaluate the bactericidal activity of zein nanoparticles containing anacardic acid and its effectiveness against Enterococcus faecalis biofilms. The minimum inhibitory and bactericide concentrations of zein blank and loaded nanoparticles were determined using the microdilution method. Fifty-four human root specimens were used in 4 groups as follows: anacardic acid nanoparticles; blank zein nanoparticles; chlorhexidine gluconate 2% solution; sterile saline solution 0.9% (negative control) to evaluate the antibiofilm activity over 30 days. An inoculum-free group was used to validate the experimental protocol. Microbial collections were done before and 7, 14, 21 and 30 days after the treatments. Anacardic acid nanoparticles presented remarkable inhibitory (0.042 yiig/ml) and bactericide (0.083 yiig/ml) activity against E. faecalis. The groups anacardic acid and blank zein nanoparticles presented a considerable reduction on the viable bacteria levels over 30 days (99.93 and 99.55%, respectively), comparable to chlorhexidine. No treatment was able to fully eliminate E. faecalis biofilms overtime. Blank nanoparticles also demonstrated satisfactory results, even so no inhibition was observed in the microdilution method. Scanning Electron Microscopic images revealed the presence of residual biofilms on the dentin surfaces of all groups and stages evaluated. Anacardic acid nanoparticles were found to be a potent bactericide agent against E. faecalis. While chlorhexidine and anacardic acid nanoparticles acted chemically; blank zein nanoparticles possibly functioned as a physical barrier preventing E. faecalis proliferation.