摘要:

Protein-polymer conjugates to be used in the pretargeted delivery of a photosensitizer to cells were synthesized and characterized. Avidin was modified by N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers bearing the photosensitizer, mesochlorin e6mono(N-2-aminoethylamide) (Mce6). Synthesis of HPMA copolymer-avidin-Mce6conjugates was carried out so that either predominantly single point attachment or multipoint attachment of copolymer chains to avidin would result. HPMA copolymer-avidin conjugates were used which retained specific binding activity to a lower affinity biotin analog. Antigen specific anti-avidin immune response was shown to be reduced six-fold in some HPMA copolymer-avidin conjugates when compared to immune response to unmodified avidin. HPMA copolymer itself was shown to elicit a very low (IgM) immune response.

ISSN:0920-5063    

DOI:10.1163/156856200743454

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Both non swellable and swellable poly(EGDMA/HEMA) microbeads were produced by suspension copolymerization. These microbeads were modified by immobilization of a spacer-arm (hexamethylene diamine (HMDA)) and protein A. The optimal values for modifications were as follows: sodium periodate concentration, 1.0 mg ml-1; HMDA concentration, 4 mg ml-1; and glutaraldehyde concentration, 0.070μg ml-1. Adsorption of protein A onto the plain and periodate oxidized poly(EGDMA/HEMA) microbeads were very close to each other, and were 0.01-0.02 mg protein A on the 1-g Microbeads I and II, respectively. Protein A immobilization on poly(EGDMA/HEMA) microbeads were studied at different temperatures, times, and pHs using single protein solution containing different amounts of proteins. The optimal values for immobilization were as follows: the initial protein A concentration, 0.1 mg ml-1; temperature, 25°C; pH, 9.5; and immobilization time, 120 min. Incorporation of protein A resulted in 1.420 and 1.825 mg protein A on the 1-g Microbeads I and II, respectively. HIgG adsorption capacity on the protein A-incorporated poly(EGDMA/HEMA) microbeads is 27 and 35 mg HIgG g-1polymer for Microbeads I and II, respectively.

ISSN:0920-5063    

DOI:10.1163/156856200743463

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Poly(vinyl alcohol)-guar gum interpenetrating network microspheres were prepared by cross-linking with glutaraldehyde. Nifedipine, an antihypertesive drug, was loaded into these matrices before and after cross-linking to study its release patterns. The extent of cross-linking was analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Furthermore, the microspheres were characterized for drug entrapment efficiency, particle size, transport of water into the matrix and drug release kinetics. Scanning electron microscopic photographs confirmed the spherical nature and surface morphology. The mean particle size of the microspheres was found to be around 300μm. The molecular transport phenomenon, as studied by the dynamic swelling experiments, indicated that an increase in cross-linking affected the transport mechanism from Fickian to non-Fickian. Thein vitrorelease study indicated that the release from these microspheres is not only dependent upon the extent of cross-linking, but also on the amount of the drug loaded as well as the method of drug loading.

ISSN:0920-5063    

DOI:10.1163/156856200743472

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this report, the effect of ionic strength on the loading efficiency of three model polypeptide/protein drugs, namely angiotensin II, insulin, and cytochrome c, in pH- and temperature-sensitive terpolymers of poly(NIPAAm-co-butylmethacrylate-co-acrylic acid) (poly(NIPAAm-co-BMA-co-AA)) has been investigated. Loading efficiency of polypeptides in pH-/temperature-sensitive beads composed of poly(NIPAAm-co-BMA-co-AA) terpolymer is predominantly governed by hydrophobic interactions, both nonspecific surface interactions and/or specific interactions (binding pockets) between the protein and the polymer molecules. Thus, loading efficiency increases with ionic strength. However, as ionic strength increases further, polymer deswelling (collapse), which is also controlled by hydrophobic forces, becomes more pronounced, and consequently, a higher fraction of water is squeezed out during bead formation and the loading efficiency starts to decrease.

ISSN:0920-5063    

DOI:10.1163/156856200743481

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Vaccine efficacy can be enhanced by delivery of antigens in synthetic microspheres. The process of antigen incorporation into microspheres can expose fragile antigens to damaging conditions, such as high temperatures, and to bacterial contamination. Maintenance of immunogenicity of several antigens and reduction of bacterial load in alginate microspheres following boiling was evaluated. Mice were immunized subcutaneously, initially and again 21 days later, with either non-boiled or boiled microspheres containing ovalbumin (OVA), a culture supernatant vaccine ofPasteurella haemolytica(PHV), or a potassium thiocyanate extract ofP. multocida(PTE). Serum samples were obtained prior to immunization and at the time of euthanasia 28 days later. Culture of microspheres showed that boiling completely eliminated aerobic bacterial growth for OVA-containing microspheres, and reduced growth by a factor of 104for PTE microspheres. More bacteria were cultured after boiling than before for PHV microspheres. ELISA performed on serum and intestinal lamina propria explant supernatants showed that immunogenicity of PHV microspheres was not altered by boiling. Boiled OVA microspheres were still able to stimulate a significant serum IgG anti-OVA titer in mice, but boiled PTE microspheres completely lacked immunogenicity. Elispot assays of spleens showed that only PHV microspheres were able to retain immunogenicity after boiling. Results indicate that boiling is not an effective means for reducing the bacterial load of alginate microspheres and that the process is associated with a diminution of vaccine immunogenicity.

ISSN:0920-5063    

DOI:10.1163/156856200743490

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Collagen, either alone or in combination with other materials, is an important natural biomaterial that is used in a variety of tissue-engineering applications. Cell adhesion and migration of cells within collagen-based biomaterials may be controlled by modifying the adhesive properties of collagen. Furthermore, spatially controlling the adhesiveness of the collagen may allow controlled localization or redistribution of cells. A method is presented for covalently coupling peptides that contain the well-characterized arginine-glycine-aspartic acid adhesion sequence directly to type I collagen monomers prior to fibrillogenesis. A heterobifunctional coupling agent was used to create stable amide and disulfide bonds with the lysine residues of the collagen monomers and the cysteine termini of the peptide molecules, respectively. The degree of conjugation could be controlled by changing the reaction conditions (ratios of reactants added and the length of incubation). The microstructure and gelation times of gels composed of covalently modified collagen were similar to those of unmodified gels. Cell adhesion on adsorbed monolayers of modified collagen was quantified using a well-established clonal cell line (K1735 murine melanoma). Cell adhesion was found to increase with both increasing degree of conjugation and increasing ratio of modified to unmodified collagen.

ISSN:0920-5063    

DOI:10.1163/156856200743508

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A new synthetic route is reported for the synthesis and covalent bonding of electrically conductive polypyrrole to a poly(ethylene terephthalate) fabric. It involves a three-step process including surface phosphonylation and graft polymerization from the gaseous phase. In the first step, the fibre surfaces are activated using phosphorus trichloride. Then, 1-(3-hydroxypropyl) pyrrole is introduced and grafted to the phosphorus chloride to create an ester bond between the fibres and the pyrrole. Finally, the pyrrole-grafted fibres are dipped in an aqueous FeCl3catalyst and exposed to pyrrole monomer vapor for the final polymerization. This last step creates an electrically conductive polypyrrole layer covalently linked to the poly(ethylene terephthalate) fibres. ESCA analysis indicates a high degree of phosphonylation and grafting of the anchor molecules. Scanning electron microscopy reveals an overall smooth and uniform surface coating of polypyrrole on the polyester fibres. The use of ATR-FTIR spectroscopy is not able to distinguish between polypyrrole-coated and non-coated fabrics because of the extremely thin polypyrrole layer. Measurements of dynamic surface wetting indicated that the polypyrrole-coated fabric is more hydrophilic than the untreated control. With values for surface resistivity in the range 104-105Ω/square, such polypyrrole-coated fabrics are considered attractive candidates for biomedical applications.

ISSN:0920-5063    

DOI:10.1163/156856200743517

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

To introduce reactive groups into temperature-responsive polymeric chains of poly(N-isopropylacrylamide) (PIPAAm), IPAAm is copolymerized with other monomer such as acrylic acid (AAc). IPAAm homopolymer exhibited temperature-responsive properties and phase transition at 32°C, however, the lower critical solution temperature (LCST) of the IPAAm-AAc copolymer shifts to a higher temperature and the phase transition becomes insensitive with increasing AAc content. To achieve a useful bifunctional copolymer containing both reactivity and temperature-sensitivity, we assumed that the homopolymer-like structure in the polymer chain would be required to maintain a sensitive temperature response with functional groups. Therefore, we designed a reactive monomer, 2-carboxyisopropylacrylamide (CIPAAm), and investigated its copolymerization with IPAAm. The important characteristic of the poly(IPAAm-co-CIPAAm) structure is that it was composed of the same polymer backbone and isopropylamide groups and some additional carboxyl groups. The transmittance measurement of the polymer aqueous solution revealed that phase transition of IPAAm-co-CIPAAm random copolymer occurred within a very narrow temperature range in pH 6.4, 7.4, and also even 9.0 phosphate buffered solution. These profiles were almost same as that of IPAAm homopolymer. While, under the same conditions, phase transition properties of poly(IPAAm-co-AAc)s solution were considerably influenced by small AAc content. We succeeded with the preparation of bifunctional polymer that possessed reactive functional groups and very sensitive response to temperature change.

ISSN:0920-5063    

DOI:10.1163/156856200743526

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A mixed (n-octadecyltrichlorosilane (OTS)/[2-(perfluorooctyl)ethyl]trichlorosilane (FOETS)) monolayer was prepared on the water subphase and was subsequently immobilized onto the silicon wafer surface by chemical bonds. Atomic force microscopic (AFM) observation of the mixed (OTS/FOETS) monolayer revealed the formation of a phase-separated structure.In situAFM observation of the adsorption behavior of bovine serum albumin (BSA) onto the mixed (OTS/FOETS) monolayers, successfully showed the adsorption behavior of BSA onto the phase-separated surface. It also revealed that in the case of pH 7.5, BSA was preferentially adsorbed onto the lower surface free energy FOETS phase of the mixed (OTS/FOETS) monolayer. On the other hand, BSA was adsorbed homogeneously onto the OTS and FOETS phases at the isoelectric point of BSA (pI4.7). These results indicate that the preferential adsorption of BSA onto the FOETS phase in the mixed (OTS/FOETS) monolayer system may be due to: (1) the minimization of interfacial free energy between a monolayer surface and an aqueous solution; and (2) the electrostatic repulsion among BSA molecules bearing negative charges.

ISSN:0920-5063    

DOI:10.1163/156856200743535

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor