Effects of Wettability
A large number of materials are deficient in proper protein adsorption and cell adhesion, which may result from the high hydrophobicity. Though it is widely accepted that proteins adsorb stronger on hydrophobic than hydrophilic surfaces [22-24], hydrophobic surface is easier to induce changes in protein structure and activity than hydrophilic one . Accordingly, much attention has been paid to the scaffold
Fig. 5.3 Reorganization of adsorbed fibronectin on various chemistries after osteoblasts were seeded in serum free medium for 12 h. Immunofluorescence staining images of F-actin (red), FN (green) and nuclei (blue). Scale bar indicates 10 gm 
modification. For example, by treating of nitrogen plasma, highly hydrophobic poly(caprolactone) (PCL) nanofibers showed more significant reduction in water contact angle than microfibers and micro/nano fibers, which enhanced their serum protein adsorption and increased cell attachment and proliferation . Moreover, the wettability of scaffolds can be improved by compositing with other hydrophilic components like chitosan and hyaluronan. Li et al.  reported that the incorporation of hyaluronan to polycaprolactone (PCL)/silk fibroin (SF) nanofibers significantly reduced the hydrophobicity of the scaffolds and subsequent non-specific protein adsorption, which may account for the reduction of fibrosis formation after implantation in vivo (Fig. 5.4) The presence of chitosan in PCL nanofibrous also aided a prominent improvement in the hydrophilicity of the scaffold and enhanced the serum protein adsorption on the scaffold . Jose et al. showed that adding collagen to hydroxyapatite/poly[(D,L-lactide)-co-glycolide] nanofibrous scaffolds
Fig. 5.4 (a) Water contact angle decreased with the increasing of hyaluronan (HA) ratio. (b) Fluorescence images of fibers after incubating with 2.5 mg/ml FITC-BSA for 2 h 
helped to enhance fibronectin and vitronectin adsorption . Furthermore, the wettability of scaffolds can be altered by reinforcing with nanotubes. Although pure carbon nanotube surface is extremely hydrophobic (contact angle of more than 160°), CNT-poly(carbonate urethane) became more hydrophilic and enhanced protein adsorption after compositing with high ratios of CNT because of higher nano surface roughness .