Biological characterization of the osteogenic, antibacterial and anti-inflammatory properties of fullerene-modified zirconia and titanium alloy implant surfaces

Peri-implant disease due to bacterial infection is the most common cause for dental implant failure. Similarly, surgical site infections (SSI) after orthopedic surgery utilizing Ti-based fracture fixation devices pose a dire clinical problem. Although it is well-known that fullerenes possess excellent biocompatibility, antibacterial and anti-inflammatory properties, their use for surface functionalization of dental and orthopedic implants is poorly investigated. Previously, we established a high-vacuum sublimation process which facilitates coating Ti-6Al-4V implants with complex geometry and a threaded screw design with homogeneous and stable C₆₀ films. This work assessed the effect of fullerene coated zirconia and titanium alloy screw-shaped implants subjected to various surface treatments on the osteogenic, antibacterial and anti-inflammatory properties of these implant surfaces in vitro. Quantitative analysis of osteogenic marker expression by MC3T3-E1 cells was used to characterize the osteogenic properties of the test surfaces. To evaluate the anti-inflammatory properties, expression levels of pro-inflammatory cytokines from macrophages under LPS challenge were assessed, and the anti-bacterial rate of different surface variants was evaluated by quantification of E.coli adherence and growth. This was in addition to determining the antibacterial rate against P.gingvalis for permucosal surface variants. The results showed that fullerene functionalization rendered excellent antibacterial properties of the implant surfaces and minimized the inflammatory response to zirconia dental implants, while yielding no benefit for osteogenic differentiation. Therefore, a fullerene surface modification of the per-mucosal portion of dental implants or of fracture fixation devices may hold great promise for designing dental implants as well as fracture fixation devices which an enhanced capacity of withstanding the bacterial and inflammatory challenges leading to peri-implantitis and SSI.