Abstract:
Antibacterial properties have been demonstrated by propolis and its products in the past. By encapsulating propolis in chitosan nanoparticles, the intrinsic property of propolis can be enhanced. The resulting chitosan-propolis nanoparticle formulation had ideal physicochemical properties viz. spherical shape, smooth surfaces, average particle size around 100 nm, good stability (zeta potential +40 mV) and encapsulation efficiency of 88.8%. Chitosan-propolis nanoparticles demonstrated a steady and sustained release over time. The improved effect of chitosan-propolis nanoparticles can be attributed to their penetration into the biofilms as tested on Enterococcus faecalis and Staphylococcus epidermidis, which are clinically significant microbes causing human ailments. This formulation inhibited both E. faecalis and S. epidermidis biofilm formation and reduced the number of bacteria in the biofilm by ~90% at 200 μg/mL concentration. When tested on pre-formed biofilms, the formulation reduced E. faecalis and S. epidermidis bacterial number in the biofilm by ~75% and ~90% at 300 μg/mL, respectively. The chitosan-propolis nanoparticles physically disrupted the biofilm architecture, as evident by imaging studies. Treatment of biofilms with chitosan-propolis nanoparticles altered the expression of cytolysin genes (cylB, cylLL, cylLS, cylR1, cylR2, cylM and cyl1) and virulence genes (gelE, ace, asa, fsrB, fsrC, ebpA, ebpB, ebpC, efa, gls24 and bopD) genes in E. faecalis. This formulation also altered the expression of matrix and adhesive genes (embp, rsbU, sarA, sepA, atlE, and icaABCD) in S. epidermidis. Therefore, chitosan-propolis nanoparticles can be a prospective therapeutic agent to prevent biofilm formation and/or improve clearance of chronic biofilm infections.
