Thermosensitive and biodegradable polymeric micelles with transient stability.
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Biocompatible Materials↗
Biomedical subjects
O Soga
Publications and source records attributed to O Soga.
The effect of the processing and formulation parameters on the size of nanoparticles based on block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) with and without hydrolytically sensitive groups.
Block copolymers of poly(ethylene glycol) (PEG) as a hydrophilic block and N-isopropylacrylamide (PNIPAAm) or poly (NIPAAm-co-N-(2-hydroxypropyl) methacrylamide-dilactate) (poly(NIPAAm-co-HPMAm-dilactate)) as a thermosensitive block, are able to self-assemble in water into nanoparticles above the cloud point (CP) of the thermosensitive block. The influence of processing and the formulation parameters on the size of the nanoparticles was studied using dynamic light scattering. PNIPAAm-b-PEG 2000 polymers were not suitable for the formation of small and stable particles. Block copolymers with PEG 5000 and 10000 formed relatively small and stable particles in aqueous solutions at temperatures above the CP of the thermosensitive block. Their size decreased with increasing molecular weight of the thermosensitive block, decreasing polymer concentration and using water instead of phosphate buffered saline as solvent. Extrusion and ultrasonication were inefficient methods to size down the polymeric nanoparticles. The heating rate of the polymer solutions was a dominant factor for the size of the nanoparticles. When an aqueous polymer solution was slowly heated through the CP, rather large particles (> or = 200 nm) were formed. Regardless the polymer composition, small nanoparticles (50-70 nm) with a narrow size distribution were formed, when a small volume of an aqueous polymer solution below the CP was added to a large volume of heated water. In this way the thermosensitive block copolymers rapidly pass their CP ('heat shock' procedure), resulting in small and stable nanoparticles.
Acrylic Resins↗
Evaluation of peroxisomal heme in yeast.
Heme is supposed to be transported into peroxisomes to form peroxisomal catalase [EC 1.11.1.6] in harmony with proliferation of the organelle because of the absence of the heme synthetic pathway in peroxisomes. We tried to understand the transport mechanism of peroxisomal catalase through the peroxisomal membrane from the aspects of a cofactor, heme, by measuring cellular and subcellular heme contents with the pyridine hemochrome method, independent of measuring the catalase activity. n-Alkane-grown Candida tropicalis cells, in which peroxisomes develop profusely, contained a larger amount of heme than the glucose-grown cells, and the increase well matched that of the catalase activity. The results of subcellular fractionation of the n-alkane-grown cells showed that, in peroxisomes, the catalase subunit and heme existed in a molar ratio of 1:1, indicating that excessively transported catalase subunit proteins or heme could not be present in peroxisomes and they formed a tetramer having four molecules of heme. From this quantification of peroxisomal heme, it was strongly suggested that the amounts of the catalase subunit protein and heme transported into peroxisomes should be stoichiometrically regulated at the step of their synthesis or/and transport.
Alkanes↗