Physico-chemical Effects of Gelatin Addition in Carboxymethylcellulose and Calcium Phosphate Cement-based Nanocomposites

Nanocomposites comprising of biopolymers and calcium phosphate cements (CaP) are promising due to their biocompatibility, non-toxicity, biodegradability and suitable mechanical properties for biomedical applications. In here, a new composite material was synthesized with carboxymethylcellulose (CMC) and gelatin (GEL) as the liquid phase and CaP based powder as the solid phase. In this study, the effect of addition of different wt% of GEL including 0, 5, 10, 20 in the liquid phase was investigated on the physical properties of the nanocomposites. Physico-chemical characteristics of materials were determined by using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and mechanical tests. Swelling analysis was performed after 1, 8, 16, 24 and 48 hours and degradation of samples was studied after 7 and 14 days. FTIR results showed that there was physical interaction between CMC and GEL with H bonding which was evident from the peak at 3288cm-1. Disruption in GEL structure was observed from the band at 1600-1400 cm-1 Disruption of GEL structure may increase the interaction between CMC and GEL molecules. After mixing of solid and liquid phases, negative charged COO- groups on CMC and Ca2+ molecules from CaP start to interact with each other. This produces attraction sites for PO43- molecules. This lead to accumulation of hydroxyapatite-like structures. A homogenous and porous microstructure was observed by using SEM in all samples. Mechanical tests showed that GEL improved the strength of the samples up to 20 wt% of GEL. The addition of 20 wt% of GEL decreased the mechanical properties. The compressive strength values were found up to approximately 6 MPa. Swelling results revealed that increasing in GEL concentration cause decrease in swelling until the 16th hour, after that 10wt% GEL samples had the lowest swelling which was approximately 28%. Finally, degradation studies indicated that the highest degradation rate was for 10% GEL incorporated samples. Addition of further GEL also reduced the degradation rate. Overall, the addition of GEL improved physical properties of the samples for potential biomedical applications.