摘要:

Five structurally related, aliphatic polyarylates were synthesized from tyrosine-derived diphenols and diacids. The diphenols were a homologous series of three desaminotyrosyl-tyrosine alkyl esters (ethyl, hexyl, octyl) which had previously been used in the synthesis of mechanically strong and tissue-compatible polycarbonates. The diacids (succinic acid, adipic acid, sebacic acid) were selected among compounds that were known to be of low systemic toxicity. By using different diacids as comonomers, the flexibility of the polymer backbone could be varied while the desaminotyrosyl-tyrosine alkyl esters provided pendent chains of various length. Some of the thermal and mechanical properties of the five polymers could be correlated to their chemical structure: the glass transition temperature decreased from 53 to 13°C, and the tensile modulus (measured at room temperature) decreased from 1500 to about 3 MPa when the length of the aliphatic diacid in the polymer backbone and/or the length of the alkyl ester pendent chain was increased. The presence of an arylate bond in the polymer backbone introduced a hydrolytically labile linkage into the polymer structure. Under physiological conditions in vitro all polymers degraded: thin films retained only about 30-40% of their initial molecular weight (Mw) after 26 weeks of storage in phosphate buffer solutions (pH 7.4) at 37°C. Release studies with p-nitroaniline as a model drug indicated that a diffusion controlled release process occurred. The rate of p-nitroaniline release could be correlated with the glass transition temperature of the polymer.

ISSN:0920-5063    

DOI:10.1163/156856294X00176

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Methanol extracts of four poly(etherurethane urea) (PEUU) materials were analyzed using Gel Permeation Chromatography (GPC). The additives in the materials were Santowhite® powder at 1 wt% and Methacrol® 2138 F at 5 wt% loading levels. One-to-two wt% of the original PEUU films was extractable with methanol. The extractables consisted of a low molecular weight (Mw) PEUU polymer, an MDI-rich oligomer, the additives Santowhite® (SW) powder and Methacrol® 2138 F, and aniline. The low Mw PEUU polymer had a Mwof 12 000 relative to polystyrene, and the MDI-rich oligomer had a Mwof 1000 relative to polystyrene. Quantitation of all extracted species was achieved using GPC; the use of dual-detectors on the GPC made it possible to determine the soft-to-hard composition of the PEUU extracts as a function of molecular weight.

ISSN:0920-5063    

DOI:10.1163/156856294X00185

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The attachment and growth of human endothelial cells and fibroblasts was studied on polymer surfaces fabricated by the polymerization of volatile amine and amide compounds in a low pressure gas plasma, and by the treatment of various surfaces in ammonia plasmas, which served to increase the nitrogen content of the surface layers. Infrared spectra showed the presence of amide groups, including those cases where the volatile compound ('monomer') did not contain oxygen. The performance of the surfaces in cell attachment correlated with the surface hydrophilicity and the nitrogen content, although for the latter a fair degree of scatter indicated that a more complex relationship applies. All these surfaces supported the attachment and growth of human cells. Generally, amide plasma polymers were best but the individual monomer and the plasma parameters also played a role. From comparisons of the various surfaces, it is suggested that the amide group is the main promoter of cell attachment in nitrogen-containing plasma surfaces.

ISSN:0920-5063    

DOI:10.1163/156856294X00194

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We have been studying adsorption and retention (resistance to desorption) behavior of temperature sensitive LCST polymers on different substrates as a function of temperature. According to our studies with Poly 64 (a copolymer of 60% (mol) NIPAAm and 40% (mol) NnBAAm, LCST = 8.5°C in water), the copolymer retention depends on the rinse temperature. When the rinse temperature is above the LCST, the polymer adheres well to most surfaces. On the contrary, at rinse temperatures below the LCST, most of the adsorbed polymer is easily rinsed off. These studies are relevant to our work on the thermally reversible adsorption of LCST polymers conjugated to peptides and proteins, such as affinity ligands, for uses in immunoassays and affinity separations. The interaction between the LCST polymer and most hydrophobic polymer surfaces is mainly due to hydrophobic interactions, and the critical surface tension (γc) and the solubility parameter (δ) of the solid polymer substrate are the most important factors which influence the LCST polymer adsorption and retention. The critical surface tension appears to correlate best with the LCST polymer adsorption levels on different substrates, while the solubility parameter correlates best with the retention of the adsorbed polymer. According to our preliminary study, n-butyl groups probably interact more strongly with the substrates than isopropyl groups because of the greater hydrophobic surface area of the former groups.

ISSN:0920-5063    

DOI:10.1163/156856294X00202

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Retention behavior of rat lymphocyte subpopulations (B- and T-cells) was investigated on poly(2-hydroxyethyl methacrylate)-graft-polyamine (HA) copolymers with various copolymer compositions. Separation mechanism of B- and T-cells was then evaluated by focusing on several parameters, such as pH, temperature, and ionic strength. The interaction of lymphocytes with HA surfaces was mainly through the electrostatic force from their retention profile at varying ionic strengths of the medium. Temperature also has a crucial effect on the response of lymphocytes toward pH-induced phase transition of polyamine grafts at the polymer interface with aqueous milieu. At 4°C, both B- and T-cells showed minimal retention on HA surfaces at pH 8. At this pH, polyamine grafts existed in a compact conformation with a low degree of protonation. However, at pHs below 8, at which polyamine grafts existed in extended conformation, the resolution of B- and T-cells was achieved. In contrast, at 23°C, the phase transition of polyamine grafts significantly influenced T-cell retention, resulting in a decrease in the retention of T-cells on HA with polyamine in a compact conformation. Consequently, preferential retention of B-cells was achieved under this condition. The polyamine content was found to be another important factor affecting the retention behavior of lymphocyte subpopulations. On HA copolymers with low polyamine content (HA7, HA10), conformational transition of polyamine grafts showed a significant influence for B-cell retention, although the influence decreased with increasing polyamine content. From the study estimating the effect of neuraminidase treatment of lymphocytes on their retention to HA surfaces, sialic acid residues on the plasma membrane surface of lymphocytes are suggested as feasible anionic sites showing electrostatic interaction with polyamine grafts.

ISSN:0920-5063    

DOI:10.1163/156856294X00211

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The in vitro degradation of samples of L- and D,L-lactic acid polymers, P(L)LA and P(DL) LA respectively, having different molecular weights, morphology and/or geometry, has been studied through the determination of viscometric molecular weight, mass and mechanical properties as function of the immersion time in Ringer solution at 37°C. In particular have been compared the degradation kinetics of P(L) LA, amorphous and crystalline, and of P(L)LA and P(DL)LA having different molecular weight and sample geometry. From the molecular weight versus the degradation time data, a degradation rate has been defined, as the derivative of the function best fitting the data, normalized to the molecular weight of the polymer at each time. The behavior of the degradation rate curves, plotted against the degradation time, has been interpretated and compared with relation to the initial physical and geometrical characteristics of the PLA samples.

ISSN:0920-5063    

DOI:10.1163/156856294X00220

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Five new trisiloxane quaternary ammonium compounds were synthesized from hydro-trisiloxane with allyl glycidyl ether to yield the epoxy function. Various amines were then reacted to yield trisiloxane amines which were further reacted to methyl substitute or oxidize the β-carbons in order to provide thermal stability. These new compounds were employed as melt additives in a nonwoven polypropylene fiber extrusion process to produce, through surface segregation, a new biomaterial with antibacterial properties.

ISSN:0920-5063    

DOI:10.1163/156856294X00239

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor