| Gelatin microspheres (GMs) have been known to display a variety of applications in different technological fields including medicine, biology, chemical and electronic information industry because of their diverse and excellent physical, chemical, biological and amphoteric properties. As the widely use of GMs in different field, People has brought forward higher call for its morphology, structure and properties. Although nano- and micro- GMs could be prepared thanks to the development of emulsifying devices, uniform-sized microspheres are still difficult to synthesized. In this dissertation an attempt was made to optimize the manufacturing conditions, in order to prepare homogeneous and size-controlled GMs.Gelatin/hydroxyapatite (HAP) composite microspheres have been extensively investigated because of their similar composition and structure to natural bone, perfect biocompatibility and osteoconductive activity. However, to be an ideal bone repair material, low elastic modulus, high fracture toughness and tensile strength are needed. Therefore, an attempt of optimizing the preparation conditions was performed with the aim to improve the microstructure and properties of the composite microspheres. The main research work in the present dissertation can be summarized as follows:1. A series of GMs were prepared by emulsification-coacervation method in water-in-oil (w/o) emulsions. The influence of preparation parameters on particle size, surface morphology and dispersity of GMs were examined. The experimental results indicated that increasing the concentration of gelatin solution and water /oil ratio would increase the particle size of GMs. On the contrary, increasing the concentration of the emulsifier and stirring speed would decrease the particle size of GMs. At proper emulsifying time and temperature would get the best sphericity of GMs. According to the practical application, size tunable GMs can be prepared.2. Four kinds of oil phase were used to study its influence on the particle size and morphology of GMs. The experimental results indicated that GMs with smaller size can be obtained by using the oil phase with higher hydrophobicity. Accordingly, lower hydrophobic oil can lead to larger particle size.3. The influences of CTAB, Tween/Span, SDS and composite emulsifiers on the formation of GMs were investigated. The results showed that Span was a tender emulsifier, lower dosage of CTAB could have good effect, and SDS was not an ideal choice for this study. We also found that the mean diameter of GMs was just 6.5μm when the ratio of CTAB and Tween 80 was 1:1.4. The mechanism of GMs'formation was carried out preliminarily by study the changes of morphology and physicochemical properties of gelatin during the emulsifying time.5. By changing the concentration of gelatin solutions, a series of Gelatin/ HAP composite microspheres were prepared through in-suit synthesis method in water-in-oil (w/o) emulsions. The products were characterized by XRD,FTIR,SEM,TEM and TGA. The experimental results indicated that the concentration of gelatin solutions had great influence on the formation of HAP. The initial rod-like crystalline shape of HAP changed to needle-like, and then to granules. The binding of gelatin and HAP had a maximum value at gelatin concentration around 0.025 g/mL. In addition, the reasons of the HAP crystal formation were presupposed theoretically.
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