Experimental Study Of Nano-hydroxyapatite /Carboxymethyl Chitosan Composite On Injectable Soft Tissue Filler

Background Since 1899 liquid paraffin wax was used as skin and soft tissure filling agent for the first time , clinical scholars research a lot of filling materials on injection and its clinical application and Achieved many progress. More and more injection filler is used in cosmetic and plastic surgery to correct deformity of human body . From liquid paraffin wax to fat,collagen, hyaluronic acid, fibrin, polyacrylamide gel and the same leather powder,but their defect was exposed with the increasingly application. Hydroxyapatite was used as soft tissue filling agent,but it was mobile and unstable. However Hydroxyapatite has good biocompatibility, biologicalactivity, and Nano-hydroxyapatite has unique biological activities. The surface area of Unit quality nanoparticles is greater than the micron particles, the number of atoms are significantly increased in the particle surface.so the ctivity of particle is improved and it is very helpful in combination with the organization . Chitosan is used very early in the field of medicine, because it has extensive resources, good biocompatibility , biodegradation ,formability, anticoagulation, anticorrosive antibacterial properties and it was not toxic and excitant. Nano hydroxyapatite/chitosan composite has all of them advantages, so it is expected to become a kind of ideal soft tissue filling agent. At present, it has been widely applied in the bone tissue engineering. There are still not the reports that nano hydroxyapatite/chitosan composite was used as soft tissue filler material. Objective The purpose of this study was to observe and evaluate the intracutaneous filling effect of Nano-hydroxyapatite /Carboxymethyl Chitosan composite( N-HA/CMCTS) as a new kind of soft tissue filling agent in order to control tissue reaction,fibrous capsule formation and reduce complication rate.Methods N-HA and CMCTS were used to make three kinds of composite (A,B,C ) for different proportion (1:1,4:6,3:7),and another material D is Physiological saline. Sixty-four wistar rats were divided into 4 groups. These different kinds of materials were injected randomly and subcutaneously on the back of each rat. At time points 1 , 4 , 8 and 12 weeks after injection , some of the rats were sacrificed to be evaluated with anatomy and histology.Results No apparent reject reaction was found. A mild inflammatory infiltrate was found on the back of the other rats of A,B and C at 1 week. No apparent inflammatory reaction was found on the back of all over the rats at 4 weeks. At 1-12 weeks postoperatively, fiber tissue surrounding the composite was not pronounced,and the collagen of A,B and C was more toD ,p<0.05,difference was statistically significant, the collagen of A,B and C was gradually increasing as time goes on and nano hydroxyapatite concentration was higher,but p>0.05, difference was not statistically significant, abnormal fiber cells were not found.Conclusion Nano-hydroxyapatite /Carboxymethyl Chitosan composite has good histocompatibility and plasticity in vivo. It was not toxic and excitant. It was absorbed slowly and promoted collagen secretion. As such, this material may become a new kind of injectable soft tissue filling agent.