## 4 Discussion  
To develop an advanced dental implant, surface treatments are widely used, including physical and chemical methods, to provide a suitable environment for improving the quantity and quality of osseointegration. The physical method-based surface treatment can increase the surface area by increasing roughness, and chemical method-based surface treatment with biochemical materials can confer proper bioactivity to cells [30; 31; 32]. In this study, we used a material-based surface treatment, with the advantages of incorporating the two types of surface treatments (i.e., physical and chemical method-based surface treatments). Graphene has a unique physicochemical property with unparalleled nanotopographic features, and its good biocompatibility has led to its recognition as an efficient tool for improving the functions of biomaterials [33; 34]. The various works demonstrated that the incorporation of graphene can improve the mechanical strength owing to the high surface area and unique chemical properties of graphene [33]. [PERSON] et al. developed the electrodeposited GO-titanium substrates, showing the enhanced mechanical properties of the fabricated GO-titanium substrates than those on the pure titanium substrates [34]. The modulus of fabricated GO-titanium substrate was increased compared to that of the hydroxyapatite-coated titanium substrate (e.g., 1.7 GPa), and the hardness was increased (e.g., 18 MPa). [PERSON] et al. [35; 36] revealed that a graphene-layered eggshell membrane substrate can acquire a micro- and nanoscale hierarchical wrinkled morphology without inducing damage to the protein-based eggshell membrane, and the limitations of raw materials such as the  
Figure 3: Effects of graphene–chitosan hybrid implants on the activity of mammalian cells. (**a**) Representative scanning electron microscope (SEM) images of MC3T3-E1 cells on graphene–chitosan hybrid implants (1%, 3%, and 5% GC) and the chitosan (C) implant. (**b**) Quantification of the cell proliferation of MC3T3-E1 cells (\(n=4\) per group). The data were analyzed using one-way ANOVA and Tukey’s test (* \(p<0.05\)). structural property, chemical property, and wettability were overcome through the combination of the advantages of the two materials. Furthermore, the authors confirmed the ability of the fabricated substrates as an artificial extracellular matrix using stem cells. Interestingly, the stem cell morphologies were controlled according to varying the concentration of graphene, resulting in enhanced cytoskeleton development. In addition, the different degree of attachment of stem cells with various graphene concentrations subsequently affected the stem cell functions, including proliferation, differentiation, and the production of growth factor through cell-substrate interactions. To suppress bacteria activity and biofilm formation, methods for controlling the wettability of a surface, such as hydrophilic and hydrophobic properties, are typically employed. In particular, a superhydrophobic and superhydrophobic surface can prevent the attachment of bacteria, which has been applied into secondary application fields, including food packaging and storage [37; 38]. The proposed GC hybrid implant showed only a slightly hydrophilic surface, but biofilm formation was nonetheless inhibited. These findings showed that the structural and chemical properties of graphene can influence bacterial activity. [PERSON] et al. [39] investigated the antibacterial effects of a graphene-based nanocomposite, which was fabricated using simple electrostatic binding. The graphene-based nanocomposites resulted in a small inhibition zone, whereas the silver-decorated graphene nanocomposite had a greater inhibitory effect. The authors proposed that the nanoplane structure of graphene may directly penetrate the bacteria membrane as the possible inactivation mechanism. Although the mechanism underlying the indirect antibacterial effects is unclear, it was attributed to the synergistic effect of graphene with microbial-produced substances.