In-situ Synthesis And Properties Of Collagen/Chitosan/Hydroxyapatite Composite Microspheres

Microspheres as biomaterials have been developed rapidly in the past few decades, especially in the fields of drug delivery and bone repair. Hydroxyapatite(HA) has been considered as one of the most important inorganic biomaterials due to its good bioactivity, biocompatibility and osteoinductivity. The composite microspheres of collagen, chitosan and HA are expected to not only improve poor toughness and low degradation rate of the pure HA materials, but combine the advantages of three components adequately, thus producing a composite microsphere material with comprehensive performances. In this thesis, the in-situ synthesis method was used to prepare collagen/chitosan/HA composite microspheres with a good spherical form, narrow particle size distribution, high dispersity, and homogeneous structure in a water-in-oil(W/O) emulsion system. The influence of various experimental parameters on the synthesis of microspheres was discussed, and the optimal parameters were determined. Furthermore, the drug-loading efficiency and drug release behavior of the composite microspheres were preliminarily studied. The main research results of the present thesis can be summarized as follows:(1) Collagen/chitosan/HA composite microspheres were prepared in a W/O emulsion system by the in-situ synthesis method. The FT-IR, XRD, SEM, TEM and TG measurements were used to analyze the collagen/chitosan/HA composite microspheres. Morevoer, the influence of the various experimental parameters on the preparation of the collagen/chitosan/HA composite microspheres was investigated. The main parameters include the amount and time of glutaraldehyde(GA) during the pre-crosslink period, the concentration of Na OH, reaction time, the amount of surfactant and the contents of HA. The results showed that the optimal experimental conditions were determined as follows: glutaraldehyde was added twice, and 0.2 m L of GA was added to cross-link for 30 min during the pre-crosslink period; the concentration of Na OH was 1.5 mol/L; reaction time should be 5 h; the amount of surfactant was 1.0 g; the contents of HA should be 20%. The SEM images showed that the collagen/chitosan/HA composite microspheres which were prepared at the optimal experimental conditions listed above displayed a regular spherical form and high dispersity. Their average particle diameter was 8 ?m. The FT-IR and XRD results indicated that the inorganic component in the composite microspheres was poorly crystalline HA containing carbonate ions. The TEM results revealed that HA was uniformly dispersed in the collagen/chitosan matrix. The TG results showed that, the actual contents of HA was lower than 20%.(2) In order to futher incresase the HA content, the experimental conditions were slightly modified on the basis of the ones listed above. The phosphate solution was added into the mixed solution of collagen, chitosan and the calcium solution, and other conditions remained the same. The composition, morphology and the inorganic component of the composite microspheres were characterized. The TG results showed that the content of HA was increased obviously under the modified experimental conditions, but the composite microspheres presented an irregular spherical form and poor dispersity. These defects will affect the clinical applications of the composite microspheres. Therefore, we decided to still use the original experiment conditions to prepare the collagen/chitosan/HA composite microspheres.(3) Drug-loaded collagen/chitosan/HA composite microspheres were prepared by soaking the microspheres in the Vancomycin Hydrochloride(VH) solution, and their drug loading and releasing behaviors were preliminarily evaluated via the UV spectrophotometric method. The results showed that, both encapsulation efficiency and drug loading amount of the collagen/chitosan/HA composite microspheres were higher than those of the collagen/chitosan microspheres. Moreover, both of them were increased with the increase in the amount of HA. The collagen/chitosan/HA composite microspheres exhibited a sustained release of VH in the composite microspheres. The cumulative release amount of VH from the composite microspheres was achieved at 60% within 60 h.