摘要:

—Copolymers (IABb) composed of N-isopropylacrylamide (I), N-(3-dimethylaminopropyl)-acrylamide (A), 3-acrylamidophenylboronic acid (B), and a hydrophobic comonomer, n-butyl methacrylate (b), were synthesized as cell culture substrata since we previously learned that bovine aortic endothelial cells (BAECs) cultured on the phenylboronic acid-containing copolymer (IAB) differentiated into capillary structures after 26 days culture. The synthesized IABb copolymers contained higher boron and amine moieties than the IAB copolymer. The results of the dynamic contact angle measurement revealed that IABb copolymer-coated surfaces showed a relatively hydrophobic nature, changing to hydrophilic in response to the aqueous environment. BAECs cultured on the copolymer substrata developed into capillary networks after 7 days. This is probably due to the enrichment of boron and amine segments in the vicinity of the hydrophilic copolymer surface, enhancing more pronounced interaction of boronates with cell membrane glycocalyx. The introduction of n-butyl methacrylate into the polymers might enhance the diffusion of the hydrophobic segments to the bulk polymers and the concentration of relatively hydrophilic segments at the outermost polymer surfaces by contact with water. A copolymer (IAP) without boronic acid groups was also prepared using N-phenylacrylamide (P) as a comonomer instead of 3-acrylamidophenylboronic acid in the IAB copolymer to investigate the effect of boronic acid moieties on the capillary formation of the cultured cells. Although the endothelial cells seeded on the copolymer without boronic acid groups adhered during the early culture period, these cells showed neither proliferation nor differentiation and detached from the surface after 13 days. These results strongly support the opinion that the phenylboronic acid groups in the copolymers are responsible for the specific induction of tissue formation of BAECs through the interaction with glycoconjugates on the cell membranes.

ISSN:0920-5063    

DOI:10.1163/156856297X00227

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

—It has been suggested in the literature that 'large' size bioabsorbable aliphatic polyester devices degrade heterogeneously when exposed to an aqueous environment. That is, following saturation, the material degrades preferentially from the center to the exterior due to an auto catalytic effect. Oriented absorbable films were developed using a new solid state method in order to assess the influence of molecular orientation on degradation pattern. The method entails uniaxial deformation and thus is referred to as solid state uniaxial orientation (SS-UO). This work examines solely the physicochemical changes occurring in the degrading polylactide film and their relevance to changes in key molecular parameters, as part of a broad based study on the effect of orientation on absorption. The results indicate that the orientation has a large effect on the glass transition temperature and the heat of fusion.

ISSN:0920-5063    

DOI:10.1163/156856297X00236

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

—Lipoglutamides with tetraethylene glycol tails were synthesized. Physicochemical features of the DNA/lipoglutamide complexes were investigated by light scattering method, phase transition, and CD-spectrum. Aggregation of the DNA/lipoglutamide complex was significantly depressed compared with DNA complexes without ethylene glycol tails, and the solution showed no turbidity. The DNA/lipoglutamide complex showed a high resistance to nuclease, and an efficient internalization into tumor cells, compared with those of DNA alone. Furthermore, the DNA complex was found by confocal laser scanning fluorescence microscopy to distribute in the cytoplasmic region.

ISSN:0920-5063    

DOI:10.1163/156856297X00245

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

—To develop a polymeric matrix for efficiently loading cationic biomolecules, polyelectrolyte hydrogels carrying pendant phosphate groups were synthesized by copolymerizing 2-methacryloyloxyethyl dihydrogen phosphate with N-isopropylacrylamide and N,N'-methylene-bis-acrylamide. The phosphate-carrying monomer yielded anionic hydrogels, which formed ionic complexes with the cationic protein, lysozyme. It was shown that the amount of complexed lysozyme reached 2.1 gg-1dry gel, corresponding to 1.3 x 10-3mol phosphate group per gram lysozyme, when 40 mol% of phosphate-carrying monomer was incorporated in a hydrogel. When the hydrogel complexed with lysozyme was placed in deionized water and various KCl solutions, of varying concentrations of up to 0.5 M KCl, no lysozyme was released in deionized water, while increasing amounts of lysozyme were released as the KCl concentration increased. This confirmed that lysozyme was loaded in the hydrogel through electrostatic interactions. It was further found that the complexed lysozyme retained its enzymatic activity after being released from the hydrogel. These results suggest the use of this system for the controlled release of cationic protein drugs.

ISSN:0920-5063    

DOI:10.1163/156856297X00254

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

—This paper presents a review of the theories based on wetting measurements/interfacial thermodynamics most frequently used to explain bacterial adhesion to solid surfaces. The physical meaning of data stemming from the application of the different theories is discussed and compared with current knowledge on interactions between components of matter. It is underlined that existing theories are either in disagreement with accepted knowledge on interfacial interactions or yield conflicting results from a quantitative point of view. It is concluded that, according to the present state of the art, no completely satisfactory theory exists, and that theoretical and experimental difficulties still hinder the understanding of the relationship between surface/interface free energy and bacterial adhesion to solid substrates. The recognition of existing shortcomings should be the first step towards a more satisfactory state of the art.

ISSN:0920-5063    

DOI:10.1163/156856297X00263

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

—Previously synthesized lactic/glycolic acid (PLGA) oligomers with different compositions (i.e. different ratio of lactic to glycolic acid in the oligomers) were further studied regarding their biodegradation and drug delivery application. The PLGA oligomers have fast biodegradation characteristics. They degrade to water soluble substances, i.e. lactic and glycolic acids, at a rate of 31.43-40.68 mg day-1in a medium of constant pH and 28.04-37.87 mg day-1in a medium of non-constant pH. The biodegradation rate is affected by the composition of the PLGA oligomers and the pH of the incubating medium. The higher the content of glycolic acid moiety in the oligomer, the faster the biodegradation rate. The lower the pH of the incubating medium, the slower the biodegradation of PLGA oligomers. A sustained-release drug delivery system based on the PLGA oligomers was fabricated as injectable microgranules by thermal blending of the PLGA oligomers and drug. Aspirin was used as a model drug. The oligomeric microgranules have advantages of easy fabrication, high drug loading efficiency, easy administration, and fast biodegradation. This thermal blending preparation method has a high loading efficiency of more than 90%. The PLGA oligomeric microgranules can release drug from 9 to 13 days depending on the oligomer composition. Both drug release rate and release duration are influenced by composition of the oligomers. The PLGA oligomeric matrix has the capability of protecting aspirin from hydrolysis. The lactic/glycolic acid oligomeric microgranules have potential use for sustained-release drug delivery.

ISSN:0920-5063    

DOI:10.1163/156856297X00272

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor