Biomimetic chitosan–nanohydroxyapatite composite scaffolds for bone tissue engineering

We describe a comparative assessment of the structure–property–process relationship of three-dimensional chitosan–nanohydroxyapatite (nHA) and pure chitosan scaffolds in conjunction with their respective biological response with the aim of advancing our insight into aspects that concern bone tissue engineering. High- and medium-molecular-weight (MW) chitosan scaffolds with 0.5, 1 and 2 wt.% fraction of nHA were fabricated by freezing and lyophilization. The nanocomposites were characterized by a highly porous structure and the pore size (∼50 to 120 μm) was in a similar range for the scaffolds with different content of nHA. A combination of X-ray diffraction, Fourier transform infrared spectroscopy and electron microscopy indicated that nHA particles were uniformly dispersed in chitosan matrix and there was a chemical interaction between chitosan and nHA. The compression modulus of hydrated chitosan scaffolds was increased on the addition of 1 wt.% nHA from 6.0 to 9.2 kPa in high-MW scaffold. The water uptake ability of composites decreased with an increase in the amount of nHA, while the water retention ability was similar to pure chitosan scaffold. After 28 days in physiological condition, nanocomposites indicated about 10% lower degree of degradation in comparison to chitosan scaffold. The biological response of pre-osteoblasts (MC 3T3-E1) on nanocomposite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to chitosan scaffold. In composite scaffolds, cell proliferation was about 1.5 times greater than pure chitosan after 7 days of culture and beyond, as implied by qualitative analysis via fluorescence microscopy and quantitative study through MTT assay. The observations related to well-developed structure morphology, physicochemical properties and superior cytocompatibility suggest that chitosan–nHA porous scaffolds are potential candidate materials for bone regeneration although it is necessary to further enhance the mechanical properties of the nanocomposite.