Preparation And Modification Of High Performance Calcium Phosphate Ceramic Fibers

Calcium phosphate ceramic is the main inorganic phase of natural hard tissues including tooth and bone. Because of their excellent biocompatibility and biological activity, hydroxyapatite (Ca₁₀?PO₄?₆OH₂, HA) and beta tricalcium phosphate ?Ca₃?PO₄?₂, ?-TCP? as well as biphasic calcium phosphate ?BCP? draw widespread attention in biomedical field. In this study, we synthesized HA,?-TCP and BCP fibers by combination of sol-gel method with electrospinning technology. In order to improve the bioactivity, Zn doped calcium phosphate fibers have been further prepared and characterized.Firstly, with triethyl phosphate ?TEP? and calcium nitrate as the phosphorus and calcium source, respectively, preparation of calcium phosphate fibers was investigated with different designs in order to study the influence of various parameters on the final products. XRD results confirmed that the prepared HA, beta-TCP and BCP ceramic fiber were obtained as expected without impurities. It was found that low reaction temperature and slow addition rate of calcium nitrate into the hydrolyzed TEP solution were the two critical factors to avoid the formation of CaO in the final calcium phosphate.Normally, the prepared calcium phosphate fibers demonstrated porous surface after calcination at high temperature. However, their morphology depended heavily on the aging time of the precursor sol-gel solution and the calcination temperature and time. The diameter of the ceramic fibers was reduced as the aging time being prolonged, and 24 hours of aging was found proper for fiber formation. With the increase in the heat treatment temperature, the resulted calcium phosphate fiber would change from the calcium-deficient HA ?CDHA? phase into BCP phase.Besides, Zn-doped calcium phosphate fibers were successfully synthesized. The effect of Zn doping amount on the properties of calcium phosphate fibers was studied. By element mapping analysis, the Zn element was proven uniformly distributing within the calcium phosphate fibers. XRD analysis revealed that the doping of Zn would not alter the crystalline structure of calcium phosphate, however, would influence its stability. Quantitative analysis basing on XRD data demonstrated that the size of crystal cells decreased as the doping amount of Zn²⁺ increasing, which led to less stability and faster release of both Zn²⁺ and Ca²⁺ ions. The co-culture of bone mesenchymal stromal cells with the Zn-doped calcium phosphate fibers displayed that the fibers had non-cytotoxicity, which suggested that the resulted ceramic fibers were expected to be used as guided bone regeneration materials.