TiO₂ Nanorod Arrays As A Photocatalytic Coating Enhanced Antifungal And Antibacterial Efficiency Of Ti Substrates

Purpose:To investigate the photocatalytic inactivation of fungi and bacteria mediated by TiO2 nanorod arrays(TNRs).Method:The features of TNRs were characterized by scanning electron microscope(SEM),atomic force microscope(AFM),transmission electron microscope(TEM),X-ray diffraction(XRD)and contact angle measurement.The antimicrobial efficiency was detected on biofilm and planktonic forms of Candida albicans(C.albicans),Aggregatibacter actinomycetemcomitans(A.actinomycetemcomitans)and Porphyromonas gingivalis(P.gingivalis)by crystal violet and XTT assay,confocal laser scanning microscope(CLSM)and colony-forming assay.Fluorogenic quantitative assay was used to explore the underlying mechanism.Results:The rutile TNRs were successfully synthesized on pure Ti plates via hydrothermal reaction and sintering method.The synthesized TNRs were homogeneously and vertically oriented on Ti,possessing rougher surface and better hydrophilicity compared to Ti.The photocatalytic activity of TNRs was estimated by photocatalytic degradation of MO solution and this reaction was apparent first-order.The biomass and bioactivity of C.albicans biofilm on the surface of TNRs were significantly inhibited compared with Ti under the same UV irradiation(p<0.01).CLSM images showed that C.albicans biofilm formed on Ti surface showed more hyphae while on TNRs surface C.albicans mainly presented yeast phase.After the same UV irradiation,not only the dead cell proportion of C.albicans biofilm on TNRs was significantly(p<0.01)higher than that on Ti,but also the biofilm on TNRs was significantly(p<0.01)thinner than Ti.By analyzing the dead bacteria percentage of A.actinmycetemcomitans or P.gingivalis biofilm on TNRs and Ti surface after 2 h UV illumination,TNRs exhibited a significant inhibitory effect compared with Ti(p<0.01).Though A.actinomycetemcomitans or P.gingivalis biofilm in TNRs group was thinner than that in Ti group after 2 h UV irradiation,there was no significant difference(p>0.05).Moreover,the assembled TNRs as photocatalyst displayed a significant higher(p<0.01)lethal effect compared with Ti after 2 h UV irradiation towards planktonic C.albicans,A.actinomycetemcomitans and P.gingivalis at initial concentration of 1×106 CFU mL-1 in vitro.It was confirmed that the stronger antimicrobial effect of photocatalytic TNRs was due to the generation of more intracellular ROS when compared with Ti(p<0.05).Conclusion:TNRs possessed a rougher surface and better hydrophilicity,and exhibited significantly higher antifungal and antibacterial efficiency compared with Ti under UV irradiation,laying the foundation for surface modification of implants with TNRs.