Biomedical subjects
Publications and source records attributed to Masa-aki Morikawa.
Gold nanoparticles (Au-NPs) are encased in aqueous nanospheres of alpha-helical poly(gamma-benzyl L-glutamate)s (PBLG, number average degree of polymerization: n = 32), with spatially controlled self-assembly structures of solid core-shell nanospheres or double-layered hollow nanocapsules.
alpha-Helical peptide microcapsules were prepared by the emulsion-templated self-assembly of amphiphilic poly(gamma-benzyl L-glutamate)s (PBLG) 1. By mixing solutions of 1 in dichloromethane (in the form of a sodium salt) with water, oil-in-water emulsions were obtained. Spontaneous stripping of the dichloromethane phase caused a decrease in the diameter of the microdroplets and finally stable microcapsules formed. The microcapsules contain an inner aqueous phase as observed by confocal laser scanning microscopy (CLSM). Binding of hydrophobic pyrene molecules to the polypeptide shell was also demonstrated. The present polypeptide microcapsules are stable even after drying in air and they would serve as supramolecular vehicles for both hydrophobic and water-soluble molecules.
A new colorimetric detection technique for glucose, based on electron transfer from glucose oxidase (GODred) to iron(III) acetylacetonate(acac)/phenanthroline(phen) mixed complexes, is developed. When GOD is added to an aqueous mixture that contains tris(acetylacetonato)iron(III) complex (FeIII-(acac)3), 1,10-phenanthroline (phen), and glucose, the color immediately changes from pale yellow to red. The red color originates from formation of tris(1,10-phenanthroline)iron(II) complex ([FeII(phen)3]2+). Differential pulse voltammetry indicates that cationic, mixed-ligand complexes of [Fe(acac)3-n-(phen)n]n+ are formed upon mixing the labile FeIII(acac)3 complex and phenanthroline. The cationic mixed-ligand complexes electrostatically bind to GOD (pI 4.2), and are easily reduced by electron transfer from GODred. This electron transfer is not affected by the presence of oxygen. The reduced complex [FeII(acac)3-n(phen)n](n-1)+ then undergoes rapid ligand exchange to FeII (phen)3. Formation of the colored FeII complex is repressed when the salt concentration in the mixture is increased, or when anionic bathophenanthroline disulfonate (BPS) is employed in place of phenanthroline. The use of labile metal complexes as electron acceptors would be widely applicable to the design of new biochromic detection systems.