Biomolecule-grafted GO enhanced the mechanical and biological properties of 3D printed PLA scaffolds with TPMS porous structure

Graphene oxide (GO) exhibits excellent mechanical strength and modulus. However, its effectiveness in mechanically reinforcing polymer materials is limited due to issues with interfacial bonding and dispersion arising from differences in the physicochemical properties between GO and polymers. Surface modification using coupling agents is an effective method to improve the bonding problem between polymer and GO, but there may be biocompatibility issues when used in the biomedical field. In this study, the biomolecule L-lysine, was applied to improve the interfacial bonding and dispersion of GO in polylactic acid (PLA) without compromising biocompatibility. The PLA/L-lysine-modified GO (PLA/L-GO) bone scaffold with triply periodic minimal surface (TPMS) structure was prepared using fused deposition modeling (FDM). The FTIR results revealed successful grafting of L-lysine onto GO through the reaction between their -COOH and -NH2 groups. The macroscopic and microscopic morphology characterization indicated that the PLA/L-GO scaffolds exhibited an characteristics of dynamic diameter changes, with good interlayer bonding. It was noteworthy that the L-lysine modification promoted the dispersion of GO and the interfacial bonding with the PLA matrix, as characterized by SEM. As a result, the PLA/0.1L-GO scaffold exhibited higher compressive strength (13.2 MPa) and elastic modulus (226.8 MPa) than PLA/0.1GO. Moreover, PLA/L-GO composite scaffold exhibited superior biomineralization capacity and cell response compared to PLA/GO. In summary, L-lysine not only improved the dispersion and interfacial bonding of GO with PLA, enhancing the mechanical properties, but also improved the biological properties. This study suggests that biomolecules like L-lysine may replace traditional modifiers as an innovative bio-modifier to improve the performance of polymer/inorganic composite biomaterials.