RESUMEN
The bone formation promoter recombinant human parathyroid hormone 1-34 [PTH (1-34)] has a short half-life and low bioavailability. In this study, we prepared a biodegradable and temperature-sensitive hyaluronic acid-poly-N-isopropyl acrylamide (AHA-g-PNIPAAm), and further investigated its effects of PTH (1-34) release and cell behavior as drug carrier. The structure of AHA-g-PNIPAAM was confirmed by hydrogen nuclear magnetic resonance spectroscopy and infrared spectroscopy. Next, PTH (1-34) loaded thermo-sensitive hydrogels were prepared by physical swelling method and their stability was investigated. The morphology of hydrogel was observed by scanning electron microscope. The minimum critical transition temperature and drug release behavior of hydrogels were investigated by ultraviolet spectrophotometry. The tetrazolium-based colorimetric assay (MTT assay) was used to investigate the toxicity and proliferation effects of PTH (1-34)-loaded thermo-sensitive hydrogel on mouse mononuclear macrophage RAW264.7 and mouse precranial osteoblasts MC3T3-E1. The effect of PTH (1-34)-loaded thermo-sensitive hydrogel on the differentiation of RAW264.7 was investigated by the tartrate-resistant acid phosphatase assay. The results showed that the PTH (1-34)-loaded thermo-sensitive hydrogel prepared in this study displayed regular three-dimensional honeycomb structure, and had good stability, thermo-sensitivity and sustained and controlled release properties, which could promote the proliferation of MC3T3-E1 cells more effectively and inhibit the differentiation of RAW264.7 into osteoclasts.
RESUMEN
<p><b>AIM</b>To isolate and purify the brain microvessels without intact neural cells used for cloning specific gene at the blood-brain-barrier.</p><p><b>METHODS</b>Magnetic beads ranging from 200-500 nm were synthesized and infused into cerebral spheres through carotid arteries. The brain tissues were dissected by mechanic and enzymatic methods, and sieved to discharge tissues and large blood vessels. The brain microvessels labelled by magnetic beads were sorted in magnetic fields, and identified by morphology, molecular biology and biologic activity.</p><p><b>RESULTS</b>Scanning electric micrograph of the obtained brain microvessels showed the vessels grossly free of adjoining neural cells except an occasional nerve ending. RT-PCR products of microtube-associated protein 2a, glutamine synthetase and CD31 from brain tissue had positive lanes, but only CD31 had positive lanes from isolated microvessels. The endothelial cells from isolated microvessels had more fluorescence than that from cultured endothelial cells.</p><p><b>CONCLUSION</b>Highly purified microvessels without intact neural cells can be obtained by this method.</p>