Teiji Tsuruta

Contemporary Topics in Polymeric Materials for Biomedical Applications

Contemporary topics in polymeric materials for biomedical applications are reviewed, with the emphasis on the modes of interaction of water soluble polymers as well as their conjugates, and those of microdomain-structured polymers with proteins and cells. The nature of biocompatibility of these polymer surfaces is discussed in terms of the random-network concept of water molecules on the polymer surface. Several recent studies on biohybridized and biomimicking materials are also reviewed.

Adsorbed serum protein mediated adhesion and growth behavior of bovine aortic endothelial cells on polyamine graft copolymer surfaces

Polyamine-brushed substrata for cell culture were designed by solvent casting of polystyrene-graft-polyamine copolymer (SA) on hydrophobically modified glass surface, and adhesion, spreading, and proliferation of bovine aortic endothelial cells (BAEC) on these substrata were evaluated. Adhesion and spreading of BAEC increased with increasing polyamine content in the copolymer. Close correlation was found between cellular spreading and subsequent cell growth; the surface inducing better spreading of adhered cells showed higher endothelial cell growth. Adhesion and spreading of BAEC were significantly influenced by fetal calf serum (FCS)-pretreatment of the SA copolymer surfaces, being increased with increasing polyamine content, whereas on bovine serum albumin (BSA)-preabsorbed surfaces, BAEC adhesion was considerably prevented and eventually no cell spreading was observed. Then, adsorption of cell-adhesion proteins, fibronectin (FN), and vitronectin (VN), out of FCS onto SA copolymer surfaces were evaluated using enzyme immunoassay. Both FN and VN adsorption on SA copolymer surfaces were increased with increasing polyamine content in the copolymer, suggesting a crucial role of these cell-adhesion proteins in BAEC adhesion and subsequent growth behavior on SA copolymer surfaces.

Differential retention of lymphocyte subpopulations (B and T cells) on the microphase separated surface of polystyrene/polyamine graft copolymers

Abstract To characterize the nature of differential retention of lymphocyte subpopulations (B and T cells) on polymer surfaces having microphase separated structures, the retention behaviour of lymphnode lymphocytes was studied as a function of contact time by using a column method: the cell suspension was passed through a “column” packed with polymer-coated glass beads. Logarithm of proportion of effluent cells was found to be proportional to the contact time (τ) of the cell suspension with the polymer surfaces. A B and A T are the proportional constants for B and T cells, respectively. Selectivity for lymphocyte subpopulations can be estimated by the ratio of A B /A T . The higher the value of this ratio, the higher is the differential retention of B cells. With albumin precoating, the microphase separated surfaces of polystyrene-polyamine graft copolymer showed a dramatic increase in values of the A B /A T ratios, as high as 4.5, indicating that preferential retention of B cells over T cells took place on these surfaces. None of the homopolymer or random copolymer surfaces showed a value of A B /A T ratio higher than 2.0. A possible formation of microphase separated albumin layer is assumed on the surface of graft copolymer. This protein layer seems to play an important role in the differential retention of lymphocyte subpopulations.

Synthesis of optically active cobalt(salen) type complexes and their asymmetric reactivity toward propylene oxide

Abstract An optically active Co(I)(salen) type complex, lithium N,N′-bis(salicylaldehyde)-1(R), 2(R)-1,2-trans-cyclohexanediiminatocobalt(I), was prepared by reducing the CoII complex, N,N′-bis(salicylaldehyde)-1(R),2(R)-1,2-trans-cyclohexanediiminatocobalt(II), with LiAlH4. The structure of the CoI complex was determined on the basis of the structure of the corresponding CoII complex and was confirmed by usual physicochemical methods. Furthermore, characteristics of the absorption and circular dichroism(CD) spectra of the CoI complex were compared with those of the reported structure of Na+[Co(I)(salen)]−. Highly asymmetric selectivity was found in a resolution reaction of DL-propylene oxide by use of the above optically active lithium cobalt(I) complex as a catalyst.

Separation of B and T lymphocytes by a hybrid field-flow fractionation/adhesion chromatography technique

A hybrid of the techniques of cellular adhesion chromatography and field-flow fractionation has been used for the effective separation of rat mesenteric B and T lymphocytes with nearly complete recovery of both cell species. Use of this hybrid technique also allows the relative binding strengths of cells to biomaterials and other surfaces to be rapidly and simply estimated. For the copolymer surface used here, B cells appear to bind with a force five times greater than T cells.

Minimized platelet interaction with poly(2-hydroxyethyl methacrylate-block-4-bis(trimethylsilyl)methylstyrene) hydrogel showing anomalously high free water content

Novel hydrophilic-hydrophobic block copolymers - poly(2-hydroxyethyl methacrylate-block-4-bis(trimethylsilyl)methylstyrene) (poly(HEMA-block-BSMS) or BH polymer) - were prepared as materials potentially useful for blood-contacting devices. Among the BH(X) series including poly(HEMA) itself, platelet adhesion and activation are minimum on the surface of BH(10), the block copolymer composed of 10 mol% of the hydrophobic segment. The unique physicochemical characteristics of BH(10) such as the high free water content and the increased mobility of PHEMA segments seem to play an important role in the prevention of platelet adhesion and activation. The water content of BH(10) was twice that of poly(HEMA) itself, even in the presence of 10 mol% of the hydrophobic moiety [poly(BSMS)]. Further, an anomalous increase in free water content was observed for the BH(10) sample measured by DSC. The glass transition temperature of BH(10) in the dry state was determined to be c. 10 degrees C, which was much lower than that observed for each of the homopolymers (c.f.: Tg [poly(HEMA)] = 70 degrees C; Tg [poly(BSMS)] = 160 degrees C), suggesting an increased mobility of tethered PHEMA segments in the BH(10) film.

Effect of microphase separated structure of polystyrene/polyamine graft copolymer on adhering rat platelets in vitro

Rat platelet adhesion on microphase separated surface of polystyrene/polyamine graft copolymers (SA copolymers) was investigated. Shapes of adhering platelet were very much changeable in response to the mode of microphase separation of SA copolymer surfaces. We assume that the microphase separated structure of SA copolyer may regulate the shape change of platelet through its effect on a redistribution of proteins and/or lipids present at the plasma membrane of platelets.

Quantitative evaluation of rat lymphocyte adsorption on microdomain structured surfaces of poly(2-hydroxyethyl methacrylate)/ polyamine

The adsorption behaviour of rat lymphocytes on poly(2-hydroxyethyl methacrylate)-graft-polyamine (HA) copolymers was evaluated using a newly developed chromatographic method. The quantity of lymphocyte adsorption can be varied by regulating the polyamine content in the HA copolymer. A remarkable depression in lymphocyte adsorption was observed on the surface of HA copolymer, consisting of 7 wt% of polyamine graft and 93 wt% of poly(2-hydroxyethyl methacrylate) (pHEMA) backbone. Further introduction of a polyamine graft on pHEMA resulted in the increase of lymphocyte retention on the copolymer surfaces. Lymphocytes adsorbed on HA copolymer surface retained their original round shape. Detailed analysis of the chromatogram showed that interaction of lymphocytes with HA copolymer was very much weaker than that with homopolymer of pHEMA or polyamine.

Immunoaffinity chromatography of lymphocyte subpopulations using tert-amine derived matrices with adsorbed antibodies

New polymeric solid-phase matrices for cell affinity chromatography were prepared and their advantageous characteristics compared with conventional matrices were highlighted. These new matrices are derivatives of poly(2-hydroxyethyl methacrylate) (PHEMA) containing a slight quantity of amino compounds as a co-monomer. They were applied to immunoaffinity selection between IgG+ and IgG- lymphocytes of the rat mesenteric lymph node. Simple physical adsorption was sufficient for anti-rat IgG antibodies to be immobilized on these matrices, allowing us to omit the laborious procedure of covalent-linking of antibodies on a matrix. As these matrices themselves showed extremely low non-specific adsorption of lymphocytes, a very dilute solution of antibody (0.02-0.08 mg/ml) was enough for column conditioning. This separation method gave IgG- lymphocytes of more than 90% purity and almost 95% yield within as short a time as 7 min. Further, IgG+ lymphocytes were obtained in good yield (80-90% of loaded number) by recovering the adsorbing cell fraction from the column by gentle pipetting of the matrix.

The ionic character of organolithium compounds in the presence of lithium methoxyethoxide: “Coordination-agent-separated” ion pairs

Small amounts of the lithium salts of methoxyethanol or 2-(dimethylamino)ethanol have been found to have an enormous effect on the ionic character of alkyl(or aryl-)lithium. Measurements of the electronic spectra of 1,1-diphenyl-n-hexyllithium coupled with these additives have indicated that the organolithium system possesses a species with the composition RLi·2XCH2XCH2CH2OLi [where X = CH3O or (CH3)2N]. No peak assignable to such a contact ion pair was observed in the 9-fluorenylithium-CH3OCH2CH2Oli system at a one to two mole ratio, the only peak observed here being in accordance with that expected for the solvent-separated ion pair. The term “coordination-agent-separated” ion pair is proposed to distinguish such species from “solvent-separated” ion pairs.