| Research Abstract |
Polymer molecular structure, phase structure of polymer, formulation of mixtures and particle structure were designed to prepare functional microcapsules (MCs).
1. Coating of fine particles with compisite latices : (1) Physico-chemical properties of latex polymer required to successfully perform coating of subsieve-size particles were made clear. A composite latex with 12 : 6 : 4 poly (ethyl acrylate (EA) /methyl methacrylate (MMA) /2-hydroxyethyl methacrylate (HEMA)) core and 6 : 12 : 8 poly (EA/MMA/HEMA) shell was synthesized. This latex exhibited an excellent coating performance even for tens mum particles. (2) A composite latex with N-isopropylacrylamide shell newly synthesized exhibited excellent coating performance, self-film-formability in water and thermosensitive drug release.
2. Multi-functional MCs with lecithin membrane : (1) MCs with membrane copmosed of soybean lecithin (SL), cholesterol (CH), stearic acid (SA) and polyvinylpyrrolidone (PVP) exhibited short-term delayd, pro
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longed release and bioerosion in vivo. Phase structure in MC membrane was determined by differential scanning calorimetry, X-ray diffractometry and polarizing microscopy and a phase diagram of SL-CH-SA-PVP system was drawn. (2) The behaviors of SL MCs could be widely controlled even in vivo by changing their membrane formulation, membrane thickness and type of lecithin.
3. MCs for neutron-capture therapy : (1) Hydrophobic gadolinium chelate, Gd diethylene-pentaacetic acid distearylamide (Gd-DTPA-SAm), -containing MCs with 9 : 9 : 4 poly (EA/MMA/HEMA) membrane had a mass median diameter of 52 mum and a Gd-DTPA-SAm content of 29.3%, and released Gd of only 0.23% for 60 days. This showed the prepared MCs to be used as depots for neutron-capture therapy. (2) By hepatic arterial injection of 29.3 % Gd-DTPA-SAm-containing SL-Mcs, 41.6 % of the dose was retained by rat livers. Hepatic tissue damage by the intraarterial injection of the MCs was determined biochemically and histologically. The results suggested that the prepared SL-MSs could be used for treatment of hepatoma without serious tissue necrosis when appropriate formulation and dose were chosen. Less
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