Preparation and in vitro drug release performance of morphine-loaded chitosan microspheres / 南方医科大学学报

<p><b>OBJECTIVE</b>To prepare morphine-loaded chitosan microspheres by emulsion ionic cross-linking and investigate the effect of initial morphine quantity and different cross-linking degrees on drug loading, encapsulation efficiency and in vitro drug release.</p><p><b>METHODS</b>Chitosan (with a relative molecular mass of 50,000 and deacetylation degree no less than 90%) at 100 mg and morphine at 20, 30, 40, or 50 mg were dissolved by 2% acetate and dripped slowly into 15 ml soy-bean oil containing 0.75 ml Span80. After full emulsification at 35 degrees C; for 1.5 h, the mixture was dripped slowly into sodium tripolyphosphate (10 mg/ml) at the mass ratio of 5:1, 7:1, or 9:1 to allow cross-linking for 2 h. The drug loading, encapsulation efficiency and in vitro drug release of the preparations were measured.</p><p><b>RESULTS</b>The drug loading in the microsphere increased while the encapsulation efficiency reduced with the increment of the initial morphine quantity. High cross-linking degree resulted in prolonged release time of the drug loaded in the preparations.</p><p><b>CONCLUSION</b>The microspheres loaded with morphine allows sustained release of morphine.</p>

Role of enamel matrix proteins in inducing biomimetic mineralization of the enamel: a study with quartz crystal microbalance technique / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the adsorption behavior of enamel matrix proteins (EMPs) on the enamel surface and study their effect on biomineralization of enamel using quartz crystal microbalance (QCM) technique.</p><p><b>METHODS AND RESULTS</b>The EMPs were adsorbed on the enamel surface to form a protein film, which was soaked in simulated body fluid solutions. After 30 days of biomimetic mineralization, the hydroxyapatite nucleation, growth and aggregation occurred with hydroxyapatite crystal formation on the enamel surface.</p><p><b>CONCLUSION</b>The EMPs play a key role in regulating enamel mineralization.</p>

Grafting functional groups on enamel surface by a self-assembled monolayer technique / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the influence of various active groups grafted on the enamel surface by means of self assembly on enamel biomineralization.</p><p><b>METHODS</b>The enamel was prepared by immersing the bicuspid tooth into 1 mmol/L ethanolic solution of a omega-functionalized (omega=PO4H2, SO3H, COOH or OH) group and deionized water solution of HSCH2CH2SO3Na for 24 h at room temperature. The contact angles and infrared (IR) images were used to identify the morphological changes of the enamel with chemisorption of the functional groups.</p><p><b>RESULTS</b>The contact angles and IR images showed that the omega-functionalized (omega=-PO4H2, -SO3H, -COOH, -OH or -CH3) group was chemisorbed on the enamel surface.</p><p><b>CONCLUSION</b>Self assembled monolayers with omega-functionalized (omega=-PO4H2, -SO3H, -COOH, -OH or -CH3) group can be successfully formed on the enamel surface by hydrolyzation.</p>

Development and potential of a biomimetic chitosan/type II collagen scaffold for cartilage tissue engineering / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Damaged articular cartilage has very limited capacity for spontaneous healing. Tissue engineering provides a new hope for functional cartilage repair. Creation of an appropriate cell carrier is one of the critical steps for successful tissue engineering. With the supposition that a biomimetic construct might promise to generate better effects, we developed a novel composite scaffold and investigated its potential for cartilage tissue engineering.</p><p><b>METHODS</b>Chitosan of 88% deacetylation was prepared via a modified base reaction procedure. A freeze-drying process was employed to fabricate a three-dimensional composite scaffold consisting of chitosan and type II collagen. The scaffold was treated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. Ultrastructure and tensile strength of the matrix were carried out to assess its physico-chemical properties. After subcutaneous implantation in rabbits, its in vivo biocompatibility and degradability of the scaffold were determined. Its capacity to sustain chondrocyte growth and biosynthesis was evaluated through cell-scaffold co-culture in vitro.</p><p><b>RESULTS</b>The fabricated composite matrix was porous and sponge-like with interconnected pores measuring from 100-250 microm in diameter. After cross-linking, the scaffold displayed enhanced tensile strength. Subcutaneous implantation results indicated the composite matrix was biocompatible and biodegradable. In intro cell-scaffold culture showed the scaffold sustained chondrocyte proliferation and differentiation, and maintained the spheric chondrocytic phenotype. As indicated by immunohistochemical staining, the chondrocytes synthesized type II collagen.</p><p><b>CONCLUSIONS</b>Chitosan and type II collagen can be well blended and developed into a porous 3-D biomimetic matrix. Results of physico-chemical and biological tests suggest the composite matrix satisfies the constraints specified for a tissue-engineered construct and may be used as a chondrocyte carrier for cartilage tissue engineering.</p>