Antimicrobial Activity Of Drug-loaded Nanoparticles On Enterococcus Faecalis In Vitro

ObjectiveThe study was aimed to compare the bacteriostasis of Erythromycin nano-hydroxyapatite microspheres (nHA-PHBV-PEG-EM),Erythromycin nanoliposome (EMNP) and Calcium hydroxide (Ca(OH)2) on Enteroco-ccus faecalis in vitro, providing evidences for drug-loaded nanoparticles used in root canal disinfection.Method1. nHA-PHBV-PEG-EM was prepared by solvent evaporation method and EMNP was made by ethanol injection-ammonium sulfate gradients-motor method.After that, nanoparticles were examed by particle diameter, encapsulation efficiency,drug loadings and the characteristics of drug release in vitro.2. Calcium hydroxide suspension was made by Ca(OH)2powder mixed with brain heart infusion.3. Liquid dilution method was used to examine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of nHA-PHBV-PEG-EM, EMNP and Ca(OH)2on Enterococcus faecalis.4. Diameter of bacteriostatic zones on Enterococcus faecalis of nHA-PHBV-PEG-EM and EMNP were compared with Ca(OH)2by liquid diffusion technique.5.0.1ml Enterococcus faecalis solution was anaerobic cultured after respectively adding2.0mg/ml nHA-PHBV-PEG-EM2ml,2.5mg/ml EMNP2ml and3.5mg/ml Ca(OH)22ml. The explants were cultured in brain heart infusion agar medium for1day,2days,3days,4days,5days,6days.The number of colonies found were counted by macroscopic observation.Result1. With the average particle size was106.6nm, particle size distribution of nHA-PHBV-PEG-EM was uniformity. The drug loadings was8.34%and the encapsulation rate is85.84%.2. With the average particle size was102.7nm, particle size distribution of EMNP was uniformity. The drug loadings was8.22%and the encapsulation rate is82.40%.3. The results of MIC and MBC by the liquid dilution method:The MIC of nHA-PHBV-PEG-EM was2.5mg/ml and MBC was3.0mg/ml. The MIC of EMNP was3.0mg/ml and MBC was3.5mg/ml. The MIC of Ca(OH)2was4mg/ml and MBC was4.5mg/ml. The MIC result determined by MTT assay was similar to the result by conventional direct observing assay4. The bacteriostatic action of nHA-PHBV-PEG-EM, EMNP and Ca(OH)2on Enterococcus faecalis in different concentration showed significant statistical difference(P<0.05). The bacteriostatic action of both nHA-PHBV-PEG-EM and EMNP had no statistical difference (P>0.05).5. The bacteriostatic action of2.0mg/ml nHA-PHBV-PEG-EM increased when time extended over. The5days later, the bacteriostasis action was stable on certain level; The bacteriostatic action of2.5mg/ml EMNP changed when time increased; The bacteriostatic action of3.5mg/ml Ca(OH)2decreased when time increased. After the6th day, the effect of drug abated and the colonies increased.Conclusion1. Antibacterial experiment in vitro showed that nHA-PHBV-PEG-EM, EMNP and Ca(OH)2all had certain bacteriostatic action on Enterococcus faecalis. The bacteriostatic effect of nanoparti-cles was better than that of calcium hydroxide.2. nHA-PHBV-PEG-EM and EMNP had controlled-release effect. In a certain time period, The bacteriostatic action increased over time increased.