Karin Bergström

Comparison of polysaccharide and poly(ethylene glycol) coatings for reduction of protein adsorption on polystyrene surfaces

Abstract There has been much recent interest in the use of poly(ethylene glycol)s (PEGs) for a variety of biotechnical applications. In the present work we have immobilized several cellulose derivatives and dextran on polystyrene surfaces and have measured the extent of fibrinogen adsorption onto the coated surfaces. Immobilization was achieved by adsorption onto clean polystyrene and by covalent linkage of oxidized polysaccharides to polyethylenimine which was ionically bound to polystyrene. Covalently bound polysaccharides, and adsorbed polysaccharides that are strongly held, compare well with poly(ethylene glycol) in preventing fibrinogen adsorption. The same polymers were coupled to polystyrene latex particles to permit examination by analytical microparticle electrophoresis. This investigation suggests that adsorbed polysaccharides form thicker layers than do covalently bound polysaccharides. Despite the polysaccharides being bound at many points along the polymer chain while PEG is bound only at the polymer terminus, the functional equivalence of polysaccharide and PEG coatings is of significance in interpreting the protein-rejecting ability of polymer-modified surfaces.

Immobilization of Proteins via PEG Chains

Grafting of poly(ethylene glycol) (or PEG) to solid surfaces has been recognized as a technique for obtaining low protein adsorption and low cell adhesion characteristics.1,2 For instance, PEG coating is reported to give a marked suppression of plasma protein adsorption and platelet adhesion leading to reduced risk of thrombus formation, as demonstrated both in vitro and in vivo.3–5

Microemulsions as reaction media for immobilization of proteins to hydrophilized surfaces

The effect of microemulsion as reaction medium for immobilization of proteins to polystyrene hydrophilized with poly(ethylene glycol) or polysaccharide has been investigated. The amount of albumin, immunoglobulin G (IgG) and collagen immobilized from microemulsion was increased 10–100 times, compared with immobilization from an aqueous buffer system. The stability of anti-IgG and interleukin-2 was studied in different microemulsion systems. Anti-IgG was found to be stable in microemulsions based on sodium bis(2-ethylhexyl)sulphosuccinate (AOT) and C12EO5, whereas the non-ionic surfactant di-C9φEO9 almost instantly destroyed the antigen-binding properties. Interleukin-2 completely lost its biological activity in an AOT-based microemulsion. We have also found that the choice of microemulsion influences coupling efficiency of the protein. An AOT-based system is preferred for immobilization of mycoplasma antibody, while a microemulsion based on C12EO5 is preferred for borrelia antigen.

Synthesis and characterization of cleavable surfactants derived from poly(ethylene glycol) monomethyl ether

A series of noncyclic acetal-linked cleavable surfactants were simply prepared by condensation of aldehydes with poly(ethylene glycol) monomethyl ethers. All of the products were characterized by1H nuclear magnetic resonance. Their hydrophile-lipophile balance, surface tension, cloud point, critical micelle concentration, and foam height were determined. Hydrolysis kinetic studies, followed by gas chromatography, showed that they had higher hydrolytic reactivity in acidic solution than cyclic acetal-linked cleavable surfactants.

Effects of surfactants and thermodynamic activity of model active ingredient on transport over plant leaf cuticle

The main objective of this study was to investigate the mechanism of molecular transport across the cuticle of Clivia leaves. In vitro diffusion methodology was used to investigate the transport of a systemic fungicide, tebuconazole, over a model silicone membrane, enzymatically isolated cuticle membranes, and dermatomed leaves. It was shown that dermatomed leaves may replace enzymatically isolated cuticles. Furthermore, the effects of two surfactants, C(10)EO(7) and C(8)G(1.6), on the fungicide transport were investigated. Tebuconazole cuticle permeation was described using Ficks first law of diffusion, expressed by the thermodynamic activity of the solute in the membrane. A new method for calculation of diffusion coefficients in the membrane is proposed. To access the thermodynamic activity of the fungicide in the membranes, sorption isotherms of tebuconazole in the membrane materials studied were recorded. The thermodynamic activity of the fungicide in aqueous solutions was calculated from solubility data. For that purpose, the effect of surfactants on tebuconazole solubility was studied. The results show that addition of surfactants allows for higher concentrations of tebuconazole available for penetration. Nonetheless, at a fixed fungicide thermodynamic activity, all formulations produced the same flux over the silicone membrane independently on the fungicide concentration. This shows that the driving force across non-responding membranes is the gradient of thermodynamic activity, rather than the gradient of the fungicide concentration. In case of leaves, surfactants induced the same quantitative increase in both flux and diffusion coefficient of solute in the cuticle, while the cuticle-water partition coefficient was unaffected.