PubMed · 4624241
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I M Blatt, A Failla. 1972. Acrylic implants for frontal bone defects.. https://pubmed.ncbi.nlm.nih.gov/4624241/
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To achieve a combination of spatial specificity in a passive manner with a stimuli-responsive targeting mechanism, a temperature-responsive polymeric micelle is prepared using block copolymers of (poly(N-isopropylacrylamide-b-butylmethacrylate) (PIPAAm-PBMA)). The micelle inner core formed by self-aggregates of PBMA segments successfully loaded with a drug (adriamycin), and the outer shell of PIPAAm chains played a role of stabilization and initiation of micellar thermo-response. Optimum conditions were investigated for the micelle formation and drug loading into the inner cores in a view of micellar stability and function as drug carriers. Outer shell hydrophilicity that prevents inner core interaction with biocomponents and other micelles can be suddenly switched to hydrophobic at a specific site by local temperature increase beyond the LCST (lower critical solution temperature) (32.5 degrees C). These micelles showed reversible structural changes allowing drug release upon heating/cooling thermal fluctuations through the LCST. Polymeric micelles incorporated with adriamycin showed a dramatic thermo-responsive on/off switching behavior for both drug release and in vitro cytotoxicity according to the temperature responsive structural changes of a micellar shell structure. The reversible and sensitive thermo-response of the micelle opens up opportunities to construct a novel drug delivery system in conjunction with localized hyperthermia.
The production and characterization of cationic microparticles based on Eudragit RS and cationic agents (i.e. a cationic acrylic polymer and three different cationic surfactants) for the delivery of nucleic acids is here described. It was found that morphological and dimensional characteristics of microparticles were influenced by the type and concentration of cationic agent employed and by some experimental parameters such as stirring speed, emulsifying agent and type of rotor. The desoxiribonucleotide Defibrotide (DFT) was associated with positively charged microparticles and its in vitro release kinetics from microparticles were determined. A study of the in vitro toxicity of cationic microparticles on cultured human cell line K562 was also performed, demonstrating that DDAB(18) microparticles display very low cytotoxicity.
Two different immobilized chymotrypsin derivatives were used to synthesize kyotorphin, using N-benzoyl-L-tyrosine ethyl ester and L-arginine ethyl ester as substrates, in water-DMF media. The first was adsorbed onto Celite particles and the second was multipoint covalently attached into polyacrylamide gel. In all cases, the conversion of the carboxyl substrate was carried out in first-order reaction conditions. For the adsorbed enzyme, the reaction kinetics deviated from first-order likely due to a fast irreversible inactivation of enzyme during the reaction time even at low DMF concentration (15-20% v/v). The covalent attachment of enzyme resulted in elimination of irreversible activity loss by organic solvent up to 60% (v/v) of DMF. The catalytic activity of the covalent derivative was conserved as appropriate for performing a synthetic reaction up to 60% v/v of DMF (in comparison to 30% v/v for the adsorbed derivative), showing a clear improvement in its stability against reversible denaturation by this solvent. The selectivity of the synthetic reaction was slightly enhanced (from 40-50%) with the increase in DMF concentration to 80% v/v, but it was significantly improved (to 80%) when L-argininamide was used as nucleophile.