Lateral Size Dependence of Graphene Oxide in Modifying Shape Memory Fibers

Graphene oxide (GO) with different lateral sizes was doped into the shape memory capable fibrous membranes of poly(L-lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PLLA/PHBV) composite via electrospinning. A series of characterizing techniques such as Raman spectroscopy (Raman), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to characterize the structure and thermal properties of the fibrous composite membranes. Thereafter, shape memory properties were determined by dynamic mechanical analysis (DMA), shape recovery stress, and photothermal effect test. Finally, the effect of GO lateral sizes on the osteodifferentiation capacity of bone mesenchymal stem cells (BMSCs) cultured on the fibrous composite membranes was examined by conducting cell proliferation and osteodifferentiation relevant assays. It was found that incorporation of small-sized GO (sGO) into the fibrous composite membranes gave rise to the most significant reinforcing effects on the mechanical strengthening and shape recovery capability of the fibrous PLLA/PHBV membranes, with the tensile Young's modulus increased by about 124%, the shape recovery stress increased by about 29%, the shape recovery rate increased by about 47%, and the thermal responsive rate increased by about 30 fold. In terms of osteogenic performance, the fibrous PLLA/PHBV membranes doped with large-sized GO (lGO) demonstrated the best osteogenic induction capacity in BMSCs, with the secreted alkaline phosphatase (ALP) increased by 92% and the calcium deposits by 133%.