An Experimental Study Of The Biocomposities Of Macroporous Calcium Phosphate Cements As Bone Substitutes By Using Gelatin Micospheres

There are various origins of cranial defects including trauma, tumours,or cerebrovascular accident postoperative defects due to the surgical procedure itself.Defects of the skull require adequate reconstruction in order to provide biomechanical stability, cerebral protection and optimal cosmetic results. A variety of techniques have been utilized to cover cranial defects including skull reconstructions with material from the patient's own body (autologous),implants of natural origin (allogenic) as well as artificial (alloplastic) substitutes. Autologous bone has excellent osteoconductive properties and was the"gold standard"over a long time period. Along with the development of tissue engineering technology in the past few years, trying to solve the problem above through bone tissue engineering. There are three elements of bone tissue engineering includes seed cells, scaffold material and biological active factors. The problem of scaffold material is the key point and essential element of bone tissue engineering. We develop macroporous calcium phosphate cements (CPCs) by incorporating the gelatin microspheres (GMs) and use them in the reparation of rabbit critical-sized skull defect to investigate application prospect of the scaffold be used in bone tissue engineering for the reparation of skull defect.Objective To determine the best proper proportion of GMs and CPC powers in the composite macroporous CPC by analyzing porosity and biomechanical property. To investigate the biocompatibility,biodegradation and clinical maneuverability by using them in the reparation of rabbit critical-sized skull defect.Methods (1)A series of gelatin microspheres prepared by the emulsified cold-condensation method , were were crosslinked by Glutaraldehyde(GA). After being dispersed in acetone, the kinds of microspheres were observed in terms of morphology and swelling properties;and the particle size, surface morphology of gelatin microspheres were examined with scanning electron.(2)Macroporous CPCS was developed using GMs with five weight ratios(0%,2.5%,5%,7.5%,10%).All of the scaffolds were 4-mm-thick,15-mm-diameter circular macroporous GMs/CPCs disks.After the scaffold were soaked in PBS for 2, 4 and 8 weeks, its porosity and compressive strength was analyzed.(3) The New Zealand white rabbits were randomly divided into five groups(10 each),group A,control group,0wt% CPC; group B,2.5wt% Macroporous CPCs; group C,5wt% Macroporous CPCs; group D,7.5wt% Macroporous CPCs;group E10wt% Macroporous CPCs.The round defect of diameter 20 mm were created in the parietal bone,and the same size Macroporous CPC of using GMs with different weight ratios different were used to cover these defect.The rabbits were killed after 2,4,8 and 12 weeks. General observation and histological examinations were used to evaluate the bioactivity and biodegradation in different groups.Results (1)The gelatin microspheres were spherical ,and had more uniform size and satisfactory dispersibility. The average diameter of microspheres was120±15μm. The gelatin microspheres had satisfactory swelling rate(91±4.8%).(2) After the scaffold were soaked,the CPCs scaffold only had micropore that its diameter was smaller than 10μm,and the macropore had not apparente formation;Porosity and macroporosity of the GMs/CPCs increased with the GMs increasing after 1, 2 and 4 weeks of soaking.The 7.5 wt% GM/CPC was the most favourable composite with high porosity and relative strong compressive strength. (3)The scaffolds showed no adverse inflammatory reaction after weeks of implatation. New tissues grew into the pores of the GM/CPC scaffold which resulted from GMs degradation, and coenocytes were present into the composite to degrade CPCs, but no new born could been seen inside of CPCs scaffold.Conclusion The macroporous GMs/CPCs scaffold had satisfactory biocompatibility. Macroporous calcium phosphate cements can be developed by incorporating gelatin microspheres,and the CPCs's degradation can accelerate because the macropores were good for growth of tissues and circulation of body fluid. And 7.5wt% GMs/CPCs is the most favourable with high macroporosity and strong compressive strength. Therefore,the composite is a good bone substitute with repaired no weight-Bearing bone defect.