Study On Growth,Structure And Property Of Hydroxyapatite Based On The Polymer Substrates

Ideal bone-repair materials should be of good biocompatibility and high bioactivity.Besides,their mechanical properties should be equivalent to natural bone. Hydroxyapatite(HA) is the main inorganic composition of bone tissue and is of good biocompatibility and high bioactivity which makes it possible to chemically bond to bone tissue.However,the brittleness and hard machining limit its extensive clinical use.To fabricate the complicate structure of bone,poly(vinyl alcohol)(PVA) and poly(ε-caprolactone)(PCL) were selected as matrices by mixed with carboxymethyl cellulose(CMC) and nano-HA respectively to induce HA growth in order to prepare PVA/CMC/HA composites and PCL/HA fibrous scaffolds via biomimetic approach and alternate soaking process.The composition,structure and morphology of HA formed under different conditions were investigated.The biocompatibility of PVA/CMC/HA composites and PCL/HA fibrous scaffold were also studied.The blend membranes of(PVA/CMC) were prepared by co-solution method.The morphology of the blend membranes was observed by means of SEM,and other mechanical properties were measured.The results show that the compatibility of the blend films was good,and the comprehensive mechanical properties can satisfy the demand of cartilage repair materials.For the first time,the membranes were treated in H₃PO₄ or CaCl₂ solutions,which improved its stability in water effectively.And HA could be deposited on PVA/CMC membranes by alternative soaking process.The apatite size and deposition amount were increased with increased cycles of alternate soaking.In addition,the incomporation of CMC could accelerate the growth of HA on PVA/CMC membranes.The formed HA were characterized by FT-IR and XRD analyses and the results confirmed the structure of HA in which some positions were replaced by CO₃^2- and HPO₄^2-.PVA/CMC/HA composite was also prepared by a biomimetic process.In this method,The PVA/CMC membranes were first blended by using H₃PO₄ and CaCl₂. The treatment by CaCl₂ was more effective to grow HA than by H₃PO₄ at the same condition,while HA could only be formed on membranes treated by H₃PO₄ after the Ca-P treatment previously.The amount of HA deposited on membranes increased with CMC content and immersion period.FT-IR and XRD confirmed the structure of formed HA.Citric acids of different concentrations were added into 1.5SBF for studying its effect on the formation of HA.When the concentration of citric acid was less than 1mmol/L,the HA formed on the membranes treated by H₃PO₄ were increased with the addictive amount of citric acid,while the formed HA decreased with the concentration of citric acid when citric acids was more than 1mmol/L.Diversely the formed HA on the membranes treated by CaCl₂ were decreased with the addictive amount of citric acid.PCL/HA fibers were prepared by melt spinning of the PCL/HA blends.The fibrous scaffolds were produced by hot-pressing according to latitude and longitude arrangement of fibers.PCL/HA fibers were characterized by SEM,TG,DSC and DMA.The results show that nano-HA particles were dispersed well in PCL substrates and the thermal stability was improved due to the addition of nano-HA particles.The HA/PCL scaffolds were immersed in 1.5SBF and the production of a new calcium phosphate layer on the scaffolds surface was monitored by SEM and FTIR.The amount of formed calcium phosphate was increased with the increasing amount of nano-HA added.This PCL/HA fibrous scaffold processes good bioactivity and could be expected desirable for bone tissue engineering.The results obtained in this paper would be useful in the research of HA formation on the surface of polymer and help to get a better understanding of preparation of polymer/HA composites.And it may provide valuable information to the study and development of bone tissue engineering.