[Chlorhexidine-grafted coating to improve antibacterial property of the micro/nanoporous titanium surfaces]

Objective: To investigate the antibacterial properties and the osteoblast-compatibility of chlorhexidine (CHX)-modified porous titanium. Methods: Smooth pure titanium specimen with diameter of 10.0 mm and thickness of 1.5 mm treated with alkali heat method were set as control group. Those with covalent conjugation of aminosilane were set as silane group, and those with CHX grafted by glutaraldehyde were set as CHX group. Scanning electron microscope (SEM) was used to observe the surface morphology and element compositions were detected by X-ray photoelectron spectroscopy. Hydrophilicity was analyzed by surface water contact angle test (n=6), while surface amino/imine groups quantification were performed through acid orangeⅡ(n=5) and the CHX was quantified by optical densitometric method (n=5). Live/dead bacterial staining, the morphology of adherent bacteria by SEM, plate counting method and inhibition zone method were executed to evaluate the antibacterial property of the samples. Osteoblast compatibility was evaluated by methyl thiazolyl tetrazolium. Cell-bacterial co-culture was conducted to evaluated the cell viability on the samples under the circumstance with bacteria. Results: After CHX grafting, pores on the titanium surface were decreased, while the atom ratio of C, N, Cl increased and the water contact angle decreased to 37.5°±4.0°. The density of CHX on the surface was (5.07±0.39) μg/cm(2). The results of live/dead bacterial staining and the morphology of adherent bacteria showed that only little dead bacterial (bacterial wall rupture) adherent on the surface of CHX group, which proved that the modified surface could inhibit bacteria adhesion and even destroyed bacteria; the plate counting displayed sporadic colonies and a transparent inhibition zone could be observed, which demonstrated that CHX group could suppress bacteria multiplication from surrounding environment. When incubating for 1 and 3 days, the cell viability of CHX group showed no significant difference from that of control group (P>0.05) ; when incubating for 5 days, the value of cell viability of CHX group was 0.547±0.087, and this was significantly lower than that of the control group (0.751±0.056) (P<0.05), demonstrating a slight inhibition of cell proliferation by CHX. The results of bacteria-cell co-culture for 3 days showed that a mass of bacteria adhered on the surface of the control group while considerable cells adhered on the surface of CHX group and exhibited a good shape. Conclusions: Porous titanium surface grafted by CHX showed an excellent antibacterial properties and allowed cell adhesion in bacterial circumstance, providing immediate implantation options for patients with bad oral health.