Antimicrobial Mechanism Research On HAPw/N-ZnO Composite As A Novel Antimicrobial Bone Restorative Material

[Objectives] The aim of the research was to modify hydroxyapatite whisker (HAPw) by means of sol-gel technology and prepare HAPw/n-ZnO bone repair composite, study the antimicrobial capability of the composite and investigate the probable antimicrobial mechanism preliminarily, lay the foundation for the subsequent experiments.[Materials and Methods] Employing microplate reader to evaluate and compare the antibacterial activity of HAPw/n-ZnO, commercial n-ZnO and home-made HAPw under darkness and simulated solar excitation; quantitative determinating the generation of H2O2in HAPw/n-ZnO and commercial n-ZnO suspensions, analyzing the influence on the yield of H2O2under simulated solar irradiation, UV-light and darkness; exploring the mode of the antibiotic action of HAPw/n-ZnO, utilizing Transmission Electron Microscope (TEM) to observe the change of bacterial morphology and intracellular microstructure, Confocal Laser Scanning Microscope (CLSM) and fluorescent staining technique to examine the proportion of live/dead bacteria with intact or damaged bacterial cytomembrane.[Results] The bacteriostasis rate of HAPw/n-ZnO and commercial n-ZnO under darkness and simulated solar against Streptococcus mutans, Candida albicans and Staphylococcus aureus was higher than Escherichia coli, Pseudomonas aeruginosa and Actinomyces viscous. The bacteriostasis rate of HAPw/n-ZnO under simulated solar against S. aureus, E. coli, C. albicans and S. mutans was statistically significant compared to darkness (p<0.05), HAPw exhibited no antibacterial effectiveness whatever light conditions; the H2O2production in each gram of HAPw/n-ZnO and commercial n-ZnO suspensions was (0.3210.045) μg and (0.289±0.030) μg under darkness,(0.937±0.096) μg and (0.860±.083) μg under simulated solar irradiation,(0.362±0.071) μg and (0.368±0.053) μ.g under UV-light, respectively, the yield of H2O2of HAPw/n-ZnO under simulated solar was statistically significant compared to under darkness and UV-light (p<0.01); contrasting with blank control in the presence of HAPw/n-ZnO, TEM images showed that the bacterial cell wall was irregular with superficial depression, the cytomembrane was atrophic, destroyed and dissolved, nucleus contents were disordered and leaked, CLSM graphs revealed that a large proportion of fluorescent red and a small percentage of fluorescent green.[Conclusions] HAPw/n-ZnO synthesized by sol-gel technology possessed certain antibiotic efficacy both under darkness and simulated solar excitation, and was more effective on S. mutans, C. albicans and S. aureus than E. coli, P. aeruginosa and A. viscous, its inhibition rate against S. aureus, E. coli, C. albicans and S. mutans under simulated solar irradiation was apparently enhanced compared to darkness, the antibacterial efficiency of HAPw/n-ZnO was primarily originated from ZnO nanoparticles; a certain mount of H2O2was yielded under darkness, simulated solar excitation and UV-light in HAPw/n-ZnO suspensions, the generation of H2O2was the most under simulated solar irradiation, in addition, the variety of H2O2yield was accordant with the variation of corresponding HAPw/n-ZnO antimicrobial activity, the oxidative decomposed function from H2O2as the primary generated reactive substance maybe one of the antibiotic mechanism of HAPw/n-ZnO; the mode of antibacterial action of HAPw/n-ZnO was to destruct the normal physiological structure of the bacteria involving cytomembrane resulting in the leakage of intracellular contents and the bacterial death, explaining another probable antimicrobial mechanism of HAPw/n-ZnO.