Effects of Lysine-Grafted Graphene Oxide on the Mechanical and Osteogenesis Properties of Shape Memory Capable PLCL Fibers

Graphene oxide (GO) nanosheets with varied mass fractions were introduced into the shape memory capable poly(lactide-co-caprolactone) (PLCL) copolymer to prepare GO/PLCL composite nanofibers via electrospinning. Based on the tensile and shape memory properties of the produced GO/PLCL nanofiber films, an optimal GO mass fraction(m(GO)∶m(PLCL)), 0.5% was determined to maximize the reinforcing effect of the GO nanosheets to the PLCL fiber matrix. Thereafter, an alkaline amino acid lysine (Lys) was selected to functionalize the GO (0.5%) via 1-(3-dimethy laminopropyl)-3-ethylcarbodiimide/N-hydroxysuccinimide chemistry followed by electrospinning for the generation of multifunctional Lys-GO/PLCL nanofibers. A series of characterization including mechanical properties, shape memory performance, acidity neutralization capacity and osteogenic differentiation were subsequently carried out with the produced Lys-GO/PLCL nanofibers. The results showed that among the four groups of GO/PLCL nanofibers loaded with different GO mass fractions (i.e., 0, 0.5%, 1% and 2%), incorporation of 0.5% GO within the PLCL nanofibers gave rise to the most remarkable enhancement efficiency, which was evidenced by 28.4% increase in Young's modulus and 28.3% increase in shape recovery stress. With the introduction of merely 0.5% of Lys-GO into the PLCL nanofibers, it was found that the fiber morphology, tensile properties and shape recovery stress of the GO/PLCL could be largely preserved (>85%). Most importantly, it was demonstrated that the developed Lys-GO/PLCL nanofibers not only enabled neutralize the acidic degradation products of the PLCL (e.g., the pH acidity was neutralized to 5.2 for the Lys-GO/PLCL nanofibers, compared to that of the GO/PLCL counterpart with a pH of 4.2), but also possessed good cytocompatibility and osteogenic differentiation capacity in the mouse bone mesenchymal stem cells (rBMSCs). This newly developed shape memory capable Lys-GO/PLCL fibers may find applications in the construction of multifunctional bone tissue engineering scaffolds.