Polyethylene Oxide Surface Research Articles

Preparation of sterically stabilized human serum albumin nanospheres using a novel Dextranox-MPEG crosslinking agent.

Human serum albumin (HSA) nanospheres with a size less than 200 nm in diameter were prepared using a modified coacervation method and crosslinking with methyl polyethylene glycol modified oxidized Dextram (Dextranox-MPEG) which created a sterically stabilizing polyethylene oxide surface layer surrounding the nanospheres. The crosslinking efficiency and the surface characteristics of glutaraldehyde and Dextranox-MPEG crosslinked HSA nanospheres were determined and compared. The zeta potential of the Dextranox-MPEG crosslinked particles was significantly lower than that of glutaraldehyde stabilized particles. The existence of a hydrated steric barrier surrounding the nanospheres was confirmed by an electrolyte and pH induced flocculation test. The Dextranox-MPEG crosslinked nanospheres showed a significantly reduced plasma protein adsorption on the particle surface compared with glutaraldehyde crosslinked nanospheres.

Plaque formation in vivo and bacterial attachment in vitro on permanently hydrophobic and hydrophilic surfaces.

Highly hydrated polyethylene oxide (PEO) films represent one type of surface modification which may interfere with biofilm formation. Protein adsorption and saliva-mediated bacterial adherence were investigated in vitro on normal and hydrophobized glass surfaces and on glass surfaces with immobilized PEO films. More protein and bacteria bound to untreated compared to hydrophobized and PEO-treated glass. Pellicle and plaque formation was also studied in vivo on ceramic crown surfaces either untreated, hydrophobized or with immobilized PEO films. Pellicle and plaque formation was similar on the untreated ceramic and PEO surfaces. Less plaque seemed to collect on these surfaces compared to adjacent normal tooth surfaces. Almost no plaque accumulated on the hydrophobic crown surface and it was virtually devoid of stainable pellicle. Even after 7 days in the mouth without oral hygiene this surface was very hydrophobic and the disclosing solution could not spread.

Biological responses to polyethylene oxide modified polyethylene terephthalate surfaces

Polyethylene oxide (PEO) of molecular weights 5,000, 10,000, 18,500, and 100,000 g/mol was covalently grafted to surfaces of otherwise cell adhesive polyethylene terephthalate (PET) films. Analysis of these surfaces by measurement of contact angles and ESCA verified the presence of the grafted PEO. Protein adsorption assays of radiolabeled albumin and fibrinogen showed a marked reduction in adsorbed protein for the 18,500 and 100,000 molecular weight PEO coupled surfaces. Cell growth assays using human foreskin fibroblasts in culture showed that the higher-molecular-weight PEO surfaces supported cell growth to a much lower extent than the two lower-molecular-weight PEOs. Flow of whole blood over these surfaces and visualization of platelet adherence using epifluorescence video-microscopy showed very low platelet adherence only on the two higher-molecular-weight PEO coupled surfaces. Scanning electron microscopy corroborated these results. It was concluded that PEO of molecular weights neighboring 18,500 and higher was effective in reducing protein adsorption and cellular interactions on these surfaces.

Protein—surface interactions in the presence of polyethylene oxide: II. Effect of protein size

Polyethylene oxide (PEO) surfaces exhibit low protein adsorption. PEO surface—protein interactions are examined theoretically as a function of surface density and chain length of PEO and variation in the size of the protein (assumed to be a sphere). Recent studies suggest that the PEO surface may have a small hydrophobic character. We study the effect of surface density of PEO and protein size and deduce the PEO surface density conditions for optimal protein resistance. For small proteins ( R ∼ 20 A ̊ ), D should be small (∼ 10 Å), while for large proteins ( R ∼ 60–80 A ̊ ), D should be larger (∼ 15 Å), where R is the protein radius and D is the average distance between end-attached PEO chains. These results evolve from the trade-offs between steric repulsion and the assumed weak hydrophobic interaction between the PEO layer and the protein. The longest chain length of PEO at optimum surface density appears best for protein resistance. As a number of assumptions and estimates are involved in the model, the results can be taken only as qualitative trends at this time. The trends should be helpful in the design and evaluation of surfaces resistant to protein adsorption.

Protein—surface interactions in the presence of polyethylene oxide: I. Simplified theory

The protein resistance character of polyethylene oxide (PEO) chains terminally attached to a hydrophobic solid substrate is theoretically studied. Steric repulsion, van der Waals attraction, and hydrophobic interaction free energies are considered. The results are dependent on the chain length and surface density of PEO. The protein approaches the PEO surface by diffusion and is affected by the van der Waals attraction between the PEO surface and protein through water. Further approach of the protein initiates the compression of PEO chains, which induces a steric repulsion effect; an additional van der Waals attraction becomes important between the substrate and protein through the water solvated PEO layer. The van der Waals component with the substrate decreases with increasing surface density and chain length of terminally attached PEO chains. Other synthetic polymers were also studied, indicating that the protein resistance character is related to the refractive index, with PEO having the lowest refractive index of the common water-soluble synthetic polymers. The osmotic and elastic constants of steric repulsion for terminally attached PEO were estimated as ∼0.007 and 0.02, respectively, from literature data for PEO adsorbed to mica. The steric repulsion free energy and the combined steric repulsion and hydrophobic interaction free energies were calculated as a function of surface density and chain length of PEO. The free energy calculations as a function of surface density and chain length of PEO reveal that a high surface density and long chain length of terminally attached PEO should exhibit optimal protein resistance, with the attainment of high surface density of PEO being more important than long chain length. These theoretical results should be helpful in the design and development of materials resistant to protein adsorption.

Surface properties of copolymers of alkyl methacrylates with, methoxy (polyethylene oxide) metiiacrylates and their application as protein-resistant coatings

New polymeric surfactants, copolymers of alkyl methacrylates with methoxy (polyethylene oxide) methacrylates, were synthesized and characterized by gel permeation chromatography. They were studied as possible means to produce polyethylene oxide-rich surfaces by a simple coating treatment on common Hydrophobie medical materials. They were further studied as cleaners for the removal of proteins preadsorfaed on hydrophobic surfaces. The surface properties of the copolymers such as the adsorption properties of the copolymer on a hydrophobic surface, low density polyethylene, the protein-resistant character of the prepared polyethylene oxide surfaces and the effectiveness of the copolymers for removal of proteins pre-adsorbed on the surface, were investigated by X-ray photoelectron spectroscopy and by using 125l-labelled copolymers and 125l-labelled proteins. The surface properties of the synthesized copolymers were compared with those of commercially available polyethylene oxide containing block copolymer surfactants.

Protein adsorption on functionalized and ESCA-characterized polymer films studied by ellipsometry

The adsorption of bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen, and poly- l-lysine (PLL) on polyvinylchloride (PVC), a copolymer of methacrylic acid/methacrylate (PMA) and surface-grafted polyethylene oxide (PEO) films, has been studied by means of ellipsometry. The films were spin-cast on silicon wafers covered with silicon oxide (SiO x ). Under physiological conditions, most proteins, but not the polyelectrolyte PLL, adsorbed to a larger extent to the hydrophobic PVC than to the hydrophilic PMA or PEO surfaces. For PLL extensive adsorption to PMA occurred as a result of strong electrostatic interaction. A correlation was found between the amount of protein adsorbed as measured by ellipsometry, and the relative surface content of nitrogen as recorded using ESCA. None of the proteins adsorbed to a constant plateau level. Instead, a monotonically increasing degree of adsorption was found in the concentration range studied, 0–1000 g/m 3. For the hydrophobic PVC, the isotherms were similar in shape to those theoretically obtained by I. Lundström ( Prog. Colloid Polym. Sci. 70, 76–82 (1985)) upon assuming a dynamic adsorption process which takes into account several modes of adsorption characterized by different affinities to the surface. Generally, a low degree of protein adsorption, Γ < 0.5 mg/m 2, was observed for surfaces covered with PEO chains (mol wt 1900) which were covalently linked, by means of terminal CHO groups, to surface amino groups.

Preparation and protein adsorption properties of photopolymerized hydrophilic films containing N-vinylpyrrolidone (NVP), acrylic acid (AA) or ethyleneoxide (EO) units as studied by ESCA

Films of acrylic acid, N-vinylpyrrolidone and monoacrylated polyethyleneoxide (PEO) with different molecular weight were attached to PVC and sulphated PE (PE-OSO 3) substrates and cross-linked with hexanedioldiacrylate (HDDA) by UV-polymerization. For PVC, but not for sulphated PE, the solvent choice was critical for the film adhesion. The ESCA C-O-/-CH 2-ratio obtained from the C(1 s) peak had a maximum for PEO films prepared with a molar ratio of PEO to HDDA of approximately 1:2. Good wetting by water was found for such films. Generally, film wetting correlated with the C-O-/-CH 2- ratio. As measured by the ESCA N(1 s) peak bovine serum albumin formed thick adsorbates on PVC, sulphated PE, acrylic acid and N-vinylpyrrolidone films in 1% solutions. On PEO films, however, very thin protein adsorbates (submonolayer) were found. A strong correlation was found between a high substrate C-O-/-CH 2- ratio and a low degree of protein adsorption. The exceptionally low degree of protein adsorption on PEO surfaces is attributed to the absence of ionic groups as well as the lack of hydrophobic interaction possibilities. Hence, water binding effects are predominant.