## 4 Discussion  
The n-HA had been well-known as potential material for bone implant applications, because it has similar component with bone [25]. However, several limitations of n-HA have necessitated the development of HA-based composite with various reinforce [3]. Here, we combined n-HA with Ch and CMC to form a composite. Ch, in this case, could be formed as a porous structure for bone cell growth, while CMC serves to increase the mechanical strength of the composite.  
The samples were fabricated by various Ch/CMC compositions, to understand the effects of this compound on the physical and biocompatibility properties of the composites, whereas the freeze-drying method was chosen to synthesize this composite-based scaffold due to simplicity, low cost, and ease of preparation. According to the chemical and structural examinations, we found that the porosity and mechanical strength are strongly correlated. The Ch, which is pore-forming [12], has the hydrophilic ability to generate a strong bonding with CMC. Consequently, the porosity decreases [18], but it can enhance the compressive strength. This conjecture is also supported by mechanical property examinations, where the compressive strength of 3.89 MPa was obtained, higher than the required minimum mechanical strength for scaffold for BTE. Moreover, the best sample, containing 10 wt% of CMC, has 49.77% porosity, with average sizes of about 92.10-136.00 \(\upmu\)m. This value is adequate for the template for bone cell regeneration. The thermal analysis also shows that the n-HA/Ch/CMC nanocomposite is suitable as a scaffold, since this nanocomposite has a much lower expansion coefficient, compared to human bone, at 25 to 75 \({}^{\circ}\)C.  
The information from DSC measurements is very important for the feasibility of the composite as a scaffold to be implanted in the human body. The feasibility and quality of the scaffold could be determined from the values of the Tb, Tg, Tc, and Td of the nanocomposite. In particular, the Td is important to determine, because it is related to the stability of the chemical composition of the composite, which further influences the functionality of the scaffold during implantation in the human body. Moreover, the TGA results show that the composite did not show any significant changes. The expansion coefficient of the composite, derived from TMA measurements, is also relatively small, compared to the coefficient expansion of bone, therefore the nanocomposite is implantable.  
The abovementioned results imply that the CMC gives significant impact to the feasibility of the composite. In fact, various material combinations with HA are possible to increase the feasibility of HA-based composites and to increase the functionality, especially for BTE application. In this present research, the CMC serves as a composite filler to enhance the mechanical strength of the composite-based scaffold, while keeping the functionality intact. Hence, the n-HA/Ch/CMC nanocomposite is suitable for BTE application. In the present study, we analyzed the morphology, mechanical, and thermal behavior of the prepared n-HA/Ch/CMC nanocomposite for bone application, focusing on the effect of varying the percentage of CMC. The results of this research indicate that attention should be given to the preparation procedure of preparing nanocomposite, with required compressive strength, sufficient porosity, and biodegradation rate being observed. The n-HA/Ch/CMC composite-based scaffolds are the most promising for bone tissue engineering application, because of their transformation in strengthening and degradation capabilities [28].