Regulating the Behavior of Human Gingival Fibroblasts by sp² Domains in Reduced Graphene Oxide

Long-term function of dental implants relies on not only stable osseointegration but also strong soft tissue-sealing ability. Ideal soft tissue sealing around implants is an effective protective barrier between the external environment and alveolar bone, preventing the invasion of bacteria that is considered as a vital trigger of irreversible marginal bone loss. Carbon-based materials have been reported to be beneficial to soft tissue sealing, which can be regulated through the hybridization type of carbon atoms (sp2 or sp3), but its internal mechanism is still not clear. In this work, graphene oxide with both sp2- and sp3-hybridized carbons was electrophoretic deposited on titanium and reduced to regulate the hybridization type of carbon atoms to investigate its effect and possible mechanism on human gingival fibroblasts (HGFs). X-ray photoelectron spectroscopy and Raman mapping test show the increase of sp2 domain content and the decrease of their size after reduction. Through computer simulation, the possible mechanism of the decrease of sp2 domain size was proposed. In vitro studies disclose that the HGFs exhibit higher proliferation rate, better adhesion, and migration ability with the increase of sp2 domains and the decrease of their sizes. It may be due to the amount and size of sp2 domains that synergistically regulate the amount and properties of adsorbed proteins, thereby influencing the cellular behaviors of HGFs. Our results may offer a different perspective on material designing and academic research to enhance the soft tissue integration of implants.