Surface characterization and biocompatibility of micro- and nano-hydroxyapatite/chitosan-gelatin network films

Hydroxyapatite (HA)/polymer composites have been widely used in bone tissue engineering due to their chemical similarity to natural bone. And the surface characters of the composites are crucial to influence their biological properties. Here, nano-hydroxyapatite/chitosan-gelatin (nHCG) films were prepared via biomineralization of chitosan-gelatin (CG) network films in Ca(NO3)2-Na3PO4 Tris buffer solution at alkaline condition. And the micro-hydroxyapatite/chitosan-gelatin (mHCG) films were formed through immersing the CG network films into the HA crystal (with average size 5 μm) suspensions. The surface chemical characteristics of nHCG and mHCG were evaluated by Fourier transformed infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Surface topographies of the samples were observed by atomic force microscopy (AFM) and scanning electron microscope (SEM). Results suggest that the ion/polar interactions are the main drive forces for nHCG formation via biomineralization. And the hydrogen bonds between COOH, OH, -NH2 of CG films and OH groups of HA crystals take the important role in the formation process of mHCG. A comparative study of mesenchymal stem cells (MSCs) behaviors on the nHCG and mHCG surface layer was carried out. Both nHCG and mHCG have excellent biocompatibility, moreover, the MSCs on nHCG present higher osteogenic differentiation activity than on mHCG. The nHCG is a potential biomaterial in bone tissue engineering.