Mineralization of phosphorylated cellulose/sodium alginate sponges as biomaterials for bone tissue engineering

In recent years, the cellulose sponge has become an attractive material for bone tissue materials in tissue engineering. However, cellulose with hydroxyl groups shows weak apatite nucleation ability in simulated body fluid (SBF). In this study, cellulose/sodium alginate (SA) composite sponges were prepared via freeze-drying technique. The incorporation of SA in the cellulose matrix effectively increased the macroporous ability of composite scaffolds. Furthermore, the phosphate groups were grafted onto the surface of the composite sponges by esterification reaction in order to induce the formation of an apatite crystal. The morphology and structure were characterized by Fourier transform infrared spectrometer, scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that the deposition of apatite nanoparticles on the surface of phosphorylated composite sponges was very robust, and the spherical apatite nanoparticles were aggregated into rod-like apatite crystals. The Ca/P molar ratio of HA on the surface of the phosphorylated cellulose/SA composite sponge was 1.45. In addition, sponges with biocompatibility were demonstrated by CCK8 assay and Live/Dead fluorescence staining of L929 cells. The L929 cell activity of both cellulose/SA and phosphorylated cellulose/SA composite sponge extracts were higher than 80%. We draw a conclusion that the biocompatible mineralized phosphorylated cellulose/SA composite sponges show potential to be applied as a bone repair material.