| Biomedical materials has been widely used as drug carriers, but Loading and releasing drugfrom carriers in a controllable way is not very satisfied as well as the biodegradation/eliminationway in vivo. Hydroxyapatite (HAP) is one of the most crucial inorganic constituent of natualhard tisues such as bone and teeth. It has been widely used in a variety of biomedical fields, suchas bone reconstruction, drug carrier, and other biomedical applications due to its excellentbiocompatibility, osteo-conductivity and adsorptivity etc. However, a conventional existence ofthe initial burst release of drug and the intrinsic properties of poor degadation limit itsbioapplication. Therefore, improving its imperfect drug release dynamics and controllabledegradation is extremely important in injectable bone tissue engineering.In this paper, spherical CaCO3has been synthesized by hydrothermal method, the CaCO3particles were then used as a template to synthesize the hydroxyapatite microspheres under themicrowave irradiation. In additon, the in vitro degradation rate of different hydroxyapatitecontent after transformation was investigated. Moreover, the excellent adsorptivity ofhydroxyapatie microspheres allowed for an effective drug loading and controllable drug releasefrom it. Besides, the drug loaded hydroxyapatite microsphere was surface modificated bydifferent concentration of biocompatible materials. At last, MG-63human osteosarcoma cellswas seeded on the surface of hydroxyapatite and its biocompatibility was investigated. Thedetails and results of the study are as follows:1. Spherical CaCO3particles was prepared by a precipitation reaction of sodium carbonatewith calcium chloride in the presence of sericin(SS). The SS showed a strong preference to themineralization of vaterite and the fine controls over the shape, size and uniformity of vateritewere carried out by the variation of pH value and reaction time in the presence of SS. Using thevaterites as a template, the homogeneous and monodispersed hydroxyapatite microspheres with apore size of15nm and special surface areas of17.16m2/g were fabricated under the assistance ofmicrowave irradiation. The micro porous structure of hydroxyapatite was good for thesubsequent loading and release of drugs in it.2. Different hydroxyapatite content of composites were obtained after trasformation of CaCO3particles.The results showed that the percentage of obtained hydroxyapatite wasincreased with the increasing of microwave irradiation, reaction time and mole ratio of Ca/P. Thein vitro degradation study results indicated that pure CaCO3degraded quickly wihle the purehydroxyapatite degraded most slowly. Besides, the in vitro degradation rate of compositesincreased with increasing the content of CaCO3.3. Hydroxyapatite microsphere was used as carrier of Magnesium ascorbyl phosphate andDexamethasone Sodium Phosphate, the drug loading efficiency was about70%, the loaded drugskept a sustained release for more than45days, which demonstrated that obtained HAPmicrospheres had a better drug loading and sustained-release properties.4. Surface modification of drug loaded hydroxyapatite was carried out by immersing thedrug loaded HAP particles into different concentration of Sodium alginate(Alg) andPolyethyleneglycol (PEG). The results showed that surface modification of Alg and PEG couldinhibit the initial drug burst effectively. Compared with PEG, less Alg had a higher level tocontrol MAP release at early stage but had little influence on the subsequent release period ofMAP.5. MG-63cells was seeded on the surface of hydroxyapatite to study its biocompatibility.The results showed that cells could grow well accompanied with hydroxyapatite microspheres.Compared with HAP, the drug loaded HAP enhanced the cell proliferation greatly。The researchmay provide a potential value for the application of hydroxyapatite-based biomaterials in theinjectable tissue engineering. |
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