Development of porous chitosan/tripolyphosphate scaffolds with tunable uncross-linking primary amine content for bone tissue engineering

Abstract The primary amine along the chitosan backbone plays a key role in biomedical applications. Although chitosan-based porous scaffolds have been widely used in tissue engineering, it remains very challenging to regulate uncross-linking primary amine content ( C N ) in scaffolds in order to realize particular mechanical and biological properties. In the present study, chitosan/tripolyphosphate (TPP) scaffolds with controlled C N (i.e., degree of cross-linking) were prepared based on the ionic-dependent solubility of chitosan together with the freezing process. The effects of the concentration of TPP ( C TPP ) and NaCl ( C NaCl ) in the cross-linking solution on C N were studied by infrared spectroscopy, ninhydrin assays and elemental analysis. The results showed that C N decreased with increasing C TPP and decreasing C NaCl . C N affected physicomechanical properties such as swelling behavior and the mechanical strength of the chitosan/TPP scaffolds. The uncross-linking primary amine in scaffolds can be used for chemical and biological modifications. The protein loading of the scaffolds demonstrated that the pH-responsive adsorption and release behavior was influenced by C N . Cell experiments also illustrated that C N affected the proliferation of bone marrow mesenchymal stem cells ( BM-MSCs ). All of these results indicate that these porous chitosan/TPP scaffolds containing uncross-linking primary amines are potentially useful for applications in regenerative bone medicine.