Shuji Matsuzawa

Bio: Shuji Matsuzawa is an academic researcher from Shinshu University. The author has contributed to research in topics: Vinyl alcohol & Crystallization. The author has an hindex of 20, co-authored 95 publications receiving 1190 citations.

Properties of mixtures of silk fibroin/syndiotactic-rich poly(vinyl alcohol)

Abstract: The gelation of mixed solutions of silk fibroin (SF)/syndiotactic-rich poly(vinyl alcohol) (s-PVA), the thermal analysis of dry-gels, and the various properties of blend films were investigated. The rate of gelation of a mixed solution was lower than that of each SF or s-PVA solution of the same concentration. In the DSC thermograph of mixed dry-gel (SF/s-PVA = 2/8–8/2) 2 endothermic peaks corresponding to SF (at 288–299°C: decomposition) and s-PVA (at 233–241°C: melting) were found. Namely, microphase segregation took place. This was confirmed by optical and electron microscopes. The mechanical properties of blend films did not have additive properties. The degree of swelling in water of blend films was independent on water temperature or methanol treatment. The mechanochemical behaviors were barely observed by the pH exchange between pH 2 and 12 only under lower loads. The addition of SF into s-PVA films promoted the permeation of neutral salts.

Properties of gels obtained by freezing/thawing of poly(vinyl alcohol)/water/dimethyl sulfoxide solutions

Abstract: Melting points of poly(vinyl alcohol) (PVA) gels obtained by repeated freezing/thawing cycles of the solutions in mixed solvents of water and dimethyl sulfoxide (DMSO) were measured. PVA solutions in 1–30 and 90 vol % DMSO froze at −40°C. The melting point of a gel increased with an increase in freezing/thawing cycles for all the solutions frozen and with an increase in freezing time in 10–30 vol % DMSO. The solutions in 1–5 vol % DMSO gelled even at very low polymer concentration of 1.0 g/dL by repeated freezing/thawing. The melting point of all the gels with a 5% polymer concentration reached ca. 73°C after 14 freezing/thawing cycles except for the gels in 90 vol % DMSO. However, the melting point of the gels with the same polymer concentration prepared at −40°C using an unfrozen mixed solvent in 60 vol % DMSO was ca. 77°C and the largest. The maximum apparent enthalpy of fusion of the gels prepared by repeated freezing/thawing was ca. 40 kcal/mol. The gels in 90 vol % DMSO were transparent independent of cycles where as those in 1–80 vol % DMSO were opaque. The degree of opaqueness increased with decreasing DMSO content.

On the poly(vinyl alcohol)–iodine complexes

Abstract: The color development due to the complex formation of poly(vinyl alcohol) (PVA) with iodine increased with increasing syndiotacticity of PVA. Isotactic PVA showed no color development. The color development of syndiotacticity-rich PVA film decreased with increasing annealing temperature for films before complexization, whereas that of atactic (commercial) PVA increased with it. Lower temperatures, the elongation of complex film, and the presence of boric acid enhanced the absorbance at 600 nm due to I−5. The complexes are assumed to be made by incorporation of polyiodines into aggregates of syndiotactic sequences in PVA. The polarizability and electric conductivity of complex films are investigated. © 1993 John Wiley & Sons, Inc.

Self-Assembly of CdSe−ZnS Quantum Dot Bioconjugates Using an Engineered Recombinant Protein

Abstract: A novel and direct method is described for conjugating protein molecules to luminescent CdSe−ZnS core−shell nanocrystals (Quantum Dots) for use as bioactive fluorescent probes in sensing, imaging, immunoassay, and other diagnostics applications. The approach makes use of a chimeric fusion protein designed to electrostatically bind to the oppositely charged surface of capped colloidal quantum dots (QDs). Preparation of protein-modified QD dispersions with high quantum yield, little or no particle aggregation, and retention of biological activity was achieved. Combining the advantages of lipoic acid capped CdSe−ZnS quantum dots (photochemical stability, a wide range of size-dependent emission wavelengths, and aqueous compatibility) with facile electrostatic conjugation of bioactive proteins, this type of hybrid bioinorganic conjugate represents a powerful fluorescent tracking tool for diverse applications. The design and preparation of a model QD/protein conjugate based on E. coli Maltose Binding Protein is...

Structure and Applications of Poly(vinyl alcohol) Hydrogels Produced by Conventional Crosslinking or by Freezing/Thawing Methods

Abstract: Poly(vinyl alcohol) (PVA) is a polymer of great interest because of its many desirable characteristics specifically for various pharmaceutical and biomedical applications. The crystalline nature of PVA has been of specific interest particularly for physically cross-linked hydrogels prepared by repeated cycles of freezing and thawing. This review includes details on the structure and properties of PVA, the synthesis of its hydrogels, the crystallization of PVA, as well as its applications. An analysis of previous work in the development of freezing and thawing processes is presented focusing on the implications of such materials for a variety of applications. PVA blends that have been developed with enhanced properties for specific applications will also be discussed briefly. Finally, the future directions involving the further development of freeze/thawed PVA hydrogels are addressed.

Structure and Properties of Poly(vinyl alcohol)/Na+ Montmorillonite Nanocomposites

Abstract: Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compositions were created by casting from a polymer/silicate water suspension. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties. Namely, the hybrid polymer/silicate systems have mechanical, thermal, and water vapor transmission properties, which are superior to that of the neat polymer and its conventionally filled composites. For example, for a 5 wt % MMT exfoliated composite, the softening temperature increases by 25 °C and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale d...

Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry

Abstract: Optical spectroscopy, imaging, and therapy tissue phantoms must have the scattering and absorption properties that are characteristic of human tissues, and over the past few decades, many useful models have been created. In this work, an overview of their composition and properties is outlined, by separating matrix, scattering, and absorbing materials, and discussing the benefits and weaknesses in each category. Matrix materials typically are water, gelatin, agar, polyester or epoxy and polyurethane resin, room-temperature vulcanizing (RTV) silicone, or polyvinyl alcohol gels. The water and hydrogel materials provide a soft medium that is biologically and biochemically compatible with addition of organic molecules, and are optimal for scientific laboratory studies. Polyester, polyurethane, and silicone phantoms are essentially permanent matrix compositions that are suitable for routine calibration and testing of established systems. The most common three choices for scatters have been: (1.) lipid based emulsions, (2.) titanium or aluminum oxide powders, and (3.) polymer microspheres. The choice of absorbers varies widely from hemoglobin and cells for biological simulation, to molecular dyes and ink as less biological but more stable absorbers. This review is an attempt to indicate which sets of phantoms are optimal for specific applications, and provide links to studies that characterize main phantom material properties and recipes.