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.