Study On The Phosphochitosan-based Biomimetic Scaffolds

Biomimetic growth of calcium phosphate over chitosan might be an effectivemethod to constitute inorganic/organic composite scaffold for bone tissue engineering.In this work, N-methylene phosphonic chitosan (NPCS) was synthesized by using aone-step reaction that allowed homogeneous modifications without sharp decrease ofits properties. FT-IR, XPS and ICP analysis confirmed their structures. The resultssuggested that there was an optimal reaction temperature (i.e. 70℃) for preparation ofNPCS with the highest DS, ca 0.5 as the reaction was extended at 70℃ for 10h. Two biomimetic methods, a stimulated body fluid (SBF) or alternative CaCl2and Na2HPO4 solutions respectively, were used to deposit hydroxyapatite (HA) on thesurfaces of CS and NPCS films. SEM and water contact angle measurement wereperformed to evaluate the surface structure and hydrophilicity of the materials. Thedata of XRD and EDX demonstrated that HA which formed on the NPCS filmimmersed in CaCl2 and Na2HPO4 solutions, compared with that formed in SBF, hadhigher crystallinity and Ca/P, and it had obvious effects on osteoblast adhesion,proliferation and differentiation functions. The macroporous scaffolds were fabricated through freeze-dry technique. Thecomparative study on NPCS and CS scaffold biomimetic mineralization was carriedout in different media, i.e, a SBF or alternative CaCl2 and Na2HPO4 solutionsrespectively. The microstructures of scaffolds were characterized by FT-IR and SEM.The results indicated that the freeze-drying temperature had great impact on theformation of HA in the scaffold walls. The later method was better than that of theformer for designing composite scaffolds. The number and size of deposited HAparticles increased with the number of alternate immersion cycles. The compressivemodulus and yield stress also greatly improved. The biocompatibility was evaluatedby implanting the scaffolds into the subcutaneous site of rabbits. The result revealedthat the composite scaffolds had a good compatibility for moderate inflammatoryresponse were observed, and its intensity were declining with gradually degradationof the scaffolds.