Surface Modification And Biomimetic Mineralization Of Cellulose Gel Composite Scaffold

In this study,cellulose gel scaffolds were prepared by chemical cross-linking method.Scaffolds with different pore structure,porosity,swelling rate and mechanical properties were obtained by adjusting the concentration of cellulose solution.Thereafter,a novel three-dimensional phosphorylated cellulose/hydroxyapatite composite scaffold was prepared via a facile route of oxidation with sodium periodate and reductive amination reaction of sodium alendronate followed by biomimetic mineralization.Fourier transform infrared spectrometer,scanning electron microscopy(SEM),X-ray diffraction,X-ray photoelectron spectroscopy,laser scanning confocal microscopy and cell viability test were employed to characterize the composite scaffolds.In order to further improve the mineralization ability of the cellulose scaffold,cellulose/sodium alginate and carboxymethylcellulose/chitosan composite gel scaffolds were prepared by chemical cross-linking method.The results show that sodium alginate is rich in carboxyl groups,which can improve the hydrophilicity of the gel,so that by adjusting the ratio of cellulose and sodium alginate,the pore size,porosity,swelling rate and mechanical properties of composite scaffold can be adjusted.Meanwhile,the electrostatic interaction between carboxymethylcellulose and chitosan can improve the mechanical properties of the composite scaffold.After the surface phosphorylation modification of the two composite gel scaffolds,the biomimetic mineralization ability has been correspondingly improved.Our experimental results indicate that the content,the crystal size and crystallinity as well as the Ca/P ratio of the deposited hydroxyapatite on the surface of the phosphorylated scaffolds are close to those of the natural bones.Moreover,compared with the unmodified composite scaffolds and the modified cellulose gel scaffolds,the phosphorylated cellulose/alginate scaffolds possess stronger electronegativity that favors for the synthesis of adequate amounts of hydroxyapatite in the process of biomimetic mineralization.Results of the cell counting kit-8 test reveal that all the scaffolds possess no cyto-toxicity.Observation via SEM demonstrates that the cultured cells can be well attached and further proliferate on the surface of the composite scaffolds,indicating the excellent bioactivity of the substrates.Our investigation demonstrates that the presented(bis)phosphonate-modified cellulose/alginate/hydroxyapatite composite material is an appropriate candidate for the fabrication of scaffolds and has great potential to be applied to bone tissue engineering.