Page 124 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani

COMPARISON WITH OTHER STUDIES
Numerous studies have focused on surface modifications of PCL and other polyester scaffolds, and studied the effect of these alterations on cellular responses. Gupta et al. showed that NaOH treatment of PCL scaffolds with controlled concentration and treatment time improves surface topography as well as cell attachment and proliferation [9]. Shuai et al. demonstrated that etching the surface of 3D-printed graphene oxide/poly(L-lactic acid) scaffolds with 1 M NaOH for different time periods forms micropores on the surface of the struts which results in higher surface roughness, and therefore facilitates cell attachment and bone tissue ingrowth [10]. Khampieng et al. altered the smooth topography of PCL scaffolds through hydrolysis with 1 and 5 M NaOH for 2 h, and observed that a rougher surface topography is created due to the formation of pores [11]. The size of the formed pores increased with increasing NaOH concentration [11]. Faia-Torres et al. studied the surface roughness gradient of PCL scaffolds [12]. They demonstrated that PCL scaffolds with a roughness of 0.93 to 1.53 μm optimally induce osteogenic differentiation of human mesenchymal stem cells [12]. At this surface roughness, moderate alkaline phosphatase activity, mineralization, and type I collagen deposition is observed, while at higher or lower roughnesses, these parameters are not optimal [12]. The results of Faia-Torres et al. [12] are consistent with our findings showing that 24 h NaOH-treated PCL scaffolds having pores with dimensions of 0.7×2.5 μm, more strongly enhanced osteogenic differentiation of pre-osteoblasts compared with RGD-immobilized scaffolds having no pores, and 72 h NaOH-treated scaffolds having pores with dimensions of 2.2×7 μm [7].
A number of studies have evaluated the performance of ordered pore scaffolds compared with random pore scaffolds in different tissue engineering applications [13, 14]. A general conclusion cannot be drawn from these studies since the results are highly dependent on the material and cell type used. Sun et al. compared 3D-printed silk fibroin/collagen scaffolds with freeze-dried scaffolds for the purpose of cartilage tissue engineering [13]. They observed that cells seeded on the 3D-printed scaffolds are more viable and produce higher amounts of glycosaminoglycans than those seeded on the freeze-dried scaffolds [13]. They concluded that compared to freeze drying technique, the 3D-printed scaffolds exhibit better overall performance and are more suitable for cartilage tissue engineering [13]. Mohanty et al. showed that poly(dimethyl siloxane) scaffolds with random pores fabricated by solvent casting-salt leaching have increased surface area compared to structured pore scaffolds, and therefore more HepG2 cells (human hepatoblastoma) are trapped and adhere to random pore scaffolds [14]. Moreover, there is more surface area in the random pore scaffolds for cell proliferation. However, when cut
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