# Enhancement of Mechanical Properties of PCL/PLA/DMSO2 Composites for Bone Tissue Engineering
## 3 Results  
### Hydrophilicity of Composites  
The water contact angles (WCAs) of pure PLA, pure PCL, PLA/PCL composites, and PLA/PCL/DMSO\({}_{2}\) composites were measured to investigate the hydrophilicity of the composites. The contact angle shapes and results of the composites are shown in Figures 2 and 3.  
The hydrophilicity of PLA/PCL/DMSO\({}_{2}\) composites was better than that of other composites (Figure 2). As the DMSO\({}_{2}\) content increases, the water contact angle is also decreased. As shown in Figure 3, the WCAs of pure PLA, pure, PCL, PLA/PCL composites, and PLA/PCL/10, 20, and 30 wt% DMSO\({}_{2}\) composites were 86.93\({}^{\circ}\)\(\pm\) 0.60\({}^{\circ}\), 88.52\({}^{\circ}\)\(\pm\) 0.70\({}^{\circ}\), 85.25\({}^{\circ}\)\(\pm\) 0.49\({}^{\circ}\), 81.88\({}^{\circ}\)\(\pm\) 0.37\({}^{\circ}\), 80.49\({}^{\circ}\)\(\pm\) 0.65\({}^{\circ}\), and 76.97\({}^{\circ}\)\(\pm\) 0.29\({}^{\circ}\), respectively. The WCAs of pure PLA, PLA/DMSO\({}_{2}\) composites, and PLA/PCL/DMSO\({}_{2}\) composites decreased by 1.8, 3.7, 7.5, 9.0, and 13% compared to that of pure PCL.  
The WCA is one of the critical properties to investigate surface hydrophilicity that significantly influences biological activities, including cell attachment [39]. The WCA can vary depending on the molecular weight of the material, surface treatment, specimen structure, and other factors. In previous studies, the contact angles for PLA, PCL, and PLA/PCL composites were measured to be from 59.46\({}^{\circ}\)\(\pm\) 0.43\({}^{\circ}\) to 100.0 \({}^{\circ}\)\(\pm\) 1.0\({}^{\circ}\), from 75.40\({}^{\circ}\)\(\pm\) 0.35\({}^{\circ}\) to 107.0 \({}^{\circ}\)\(\pm\) 2.0\({}^{\circ}\), and from 66.60\({}^{\circ}\)\(\pm\) 0.19\({}^{\circ}\) to 100.0\({}^{\circ}\)\(\pm\) 3.0\({}^{\circ}\), respectively, under various conditions [40; 41; 42; 43; 44]. The water contact angles measured in this study for PLA, PCL, and PLA/PCL composites fell within the contact angle ranges reported in previous studies. The contact angles for PLA, PCL, and PLA/PCL composites were observed to be in the following order: PCL > PLA > PLA/PCL composites. This study's results, showinga decrease in the contact angle for composite materials, are consistent with previous findings [45; 46].  
A high contact angle, as observed in pure PCL and pure PLA, indicated low surface energy, which hampered the initial adhesion of cells [36; 39; 47]. DMSO\({}_{2}\) showed a decrease in contact angle due to its high surface energy. As DSMO\({}_{2}\) was added, the hydrophilicity was improved compared to ones of other composites.  
Hydrophilicity can anticipate cell attachment. However, in recent studies, the results indicate that cell attachment cannot be predicted based on only hydrophilicity [48; 49; 50]. Some studies showed that the water contact angles were not correlated with cell attach  
Figure 3: Contact angle of PLA, PCL, PLA/PCL, and PLA/PCL/10, 20, and 30 wt% DMSO\({}_{2}\) composites with DI water.  
Figure 2: Contact angle shapes of pure PLA, pure PCL, PLA/PCL, and PLA/PCL/10, 20, and 30 wt% DMSO\({}_{2}\) composites with DI water.  
ment [45; 51]. However, many studies have been researching the correlation between water contact angle and cell attachment [40; 41; 42; 43; 44; 46]. Therefore, various surface modification studies aim to enhance the wettability and cell attachment properties of PLA- and PCL-based surfaces in the literature [52; 53].