摘要:

In this paper we show how the Lowry method, designed for the determination of proteins in solution, can be used for the determination of proteins immobilized on the surface of microspheres (for protein concentrations higher than 10μg/ml). Measurements were made for human serum albumin (HSA) and for immunoglobulins [rabbit immunoglobulins-antibodies against human fibrinogen (IgGF) and against fragment D of human fibrinogen (IgGFgD)] immobilized on the surface of polystyrene microspheres.

ISSN:0920-5063    

DOI:10.1163/156856291X00223

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Of the interactions that govern protein adsorption on polymer surfaces, solvation interactions (repulsive hydration and attractive hydrophobic interactions) are thought to be among the most important. The solvation interactions in protein adsorption, however, have not been dealt with in theoretical calculation of the adsorption energy owing to the difficulties in modelling such interactions. We have evaluated the solvation interaction energies using the fragment constant method of calculating the partition coefficients of amino acids. The fundamental assumption of this approach is that the partition coefficients of amino acids between water and organic solvent phases are related to the free energies of transfer from bulk water to the polymer surface. The X-ray crystallographic protein structures of lysozyme, trypsin, immunoglobulin Fab, and hemoglobin from the Brookhaven Protein Data Bank were used. The model polymer surfaces were polystyrene, polypropylene, polyethylene, poly(hydroxyethyl methacrylate) [poly(HEMA)], and poly(vinyl alcohol). All possible adsorption orientations of the proteins were simulated to study the effect of protein orientation on the solvation interactions. Protein adsorption on either hydrophobic or hydrophilic polymer surfaces was examined by considering the sum of solvation and other interaction energies. The results showed that the contribution of the solvation interaction to the total protein adsorption energy was significant. The average solvation interaction energy ranged from - 259.1 to - 74.1 kJ/mol for the four proteins on the hydrophobic polymer surfaces, such as polystyrene, polypropylene, and polyethylene. On the other hand, the average solvation interaction energies on hydrophilic surfaces such as poly(HEMA) and poly(vinyl alcohol) were larger than zero. This indicates that repulsive hydration interactions are in effect for protein adsorption on hydrophilic polymer surfaces. The total interaction energies of the proteins with hydrophobic surfaces were always lower than those with more hydrophilic surfaces. This trend is in agreement with the experimental observations in the literature. This study suggests that consideration of the solvation interaction energies is necessary for accurate calculation of the protein adsorption energies.

ISSN:0920-5063    

DOI:10.1163/156856291X00232

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Proliferation of vascular smooth muscle cells is postulated to be one of the key events in the pathogenesis of atherosclerosis or during the development of focal glomerular sclerosis. Several studies have suggested that the antiproliferative effects of heparin appear to be regulated by different structural determinants. Our experiments show that dextrans substituted with carboxylic and benzylamide sulphonate groups markedly inhibit the growth of smooth muscle cells in vitro. Studies on the structure- function relationships of these products to their effect on rat aorta smooth muscle cells are reported. The antiproliferative capacity is similar to that of heparin.

ISSN:0920-5063    

DOI:10.1163/156856291X00241

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Thermosensitive co-polymers of isopropyl acrylamide (IPAAm) with butyl methacrylate (BMA) are capable of 'on-off' regulation of drug release in response to external temperature changes due to skin formation with increasing temperature. To clarify the role of the surface-modulated skin and controlled pulsatile drug release patterns, the surface shrinking process was regulated by changing the length of the methacrylate alkyl side-chain. Release of indomethacin in response to stepwise temperature changes between 20 and 30°C from co-polymers of IPAAm with BMA, hexyl methacrylate (HMA), and lauryl methacrylate (LMA) was studied. The drug release rate during the 'on' state (20°C) remained constant before and after the 'off' state (30°C) when the period of the 'off' state was increased. These results suggest that the drug in the polymeric matrices diffused from the inside to the surface during the 'off' state even when no drug release was seen. The length of alkyl side-chain was found to be an important parameter in controlling the thickness and density of the surface skin layer.

ISSN:0920-5063    

DOI:10.1163/156856291X00250

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Polystyrene substrates were modified by radio-frequency plasma deposition from mixtures of various organic vapors (acetone, methane, methanol, and formic acid) and oxygen. The resulting surfaces exhibited a wide range of surface oxygen concentrations, as measured by electron spectroscopy for chemical analysis (ESCA). The surface hydroxyl, carboxyl, and carbonyl groups were derivatized with trifluoroacetic anhydride, trifluoroethanol, or hydrazine, respectively, and their concentrations subsequently determined by ESCA. The growth of bovine aortic endothelial cells was found to increase with the surface carbonyl concentration but did not appear to correlate with the hydroxyl or carboxyl concentrations.

ISSN:0920-5063    

DOI:10.1163/156856291X00269

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The effects of phospholipid adsorption onto the polymer surface during adsorption of plasma proteins were investigated. When a polymer with the phosphorylcholine moiety, 2-methacryloyloxyethyl phosphorylcholine (MPC) co-polymer, was treated with dipalmitoylphosphatidylcholine (DPPC) liposome solution, an organized adsorption layer of DPPC was formed on the MPC co-polymer surface, which was confirmed by differential scanning calorimetric analysis and X-ray photoelectron spectroscopy. On the other hand, an organized layer of DPPC on poly(n-butyl methacrylate) and poly(2-hydroxyethyl methacrylate) could not be found. The amount of albumin adsorbed on the polymer surfaces was decreased by pretreatment of the surface with DPPC liposome solution in every polymer case. The smallest amount of adsorbed proteins was found on the MPC co-polymer. Protein adsorption on the surface of MPC co-polymers from the plasma was also small. The difference in protein adsorption on the polymers probably reflects the difference in the orientation of the phospholipid molecules which cover the polymer surface.

ISSN:0920-5063    

DOI:10.1163/156856291X00278

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor