ABSTRACT
The influence of different surface modifications with poly(ethyleneglycol) (PEG) layers on the adsorption of fibrinogen and the adhesion and activation of macrophage-like human leukocytes was investigated. Poly(ethylene terephthalate) (PET) was modified using pulsed AC plasma polymerization with two types of starting monomers to generate: 1) a reactive acid surface using maleic anhydride (MAH) as monomer, and 2) a PEG-like surface using diethyleneglycol methyl vinyl ether (DEGVE) as monomer. The MAH surface was used as a reactive platform to graft linear chains of non-fouling mPEG via an intermediate layer of poly(ethyleneimine) (PEI) under lower critical solution temperature (LCST) conditions of the mPEG. The DEGVE monomer is used to create PEG-like layers by use of low power plasma conditions. The ability of the surfaces to resist protein adsorption was investigated quantitatively using (125)I-radiolabeled human fibrinogen, and the conformation of the adsorbed protein was tested using an anti-fibrinogen monoclonal antibody in an enzyme-linked immunosorbent assay. The results showed that PEGylated surfaces adsorbed significantly less (up to 90% less) fibrinogen, and that unfolding of adsorbed fibrinogen was more pronounced on the linear mPEG layers than on the PEG-like plasma polymer surfaces. Adhesion of in-vitro differentiated macrophage-like U937 cells was reduced on both the PEG-like plasma polymer surfaces and the linear mPEG layers compared to the unmodified PET surface, but cells adhering to the PEG-like plasma polymer surfaces secreted less tumor necrosis factor-alpha (TNF-alpha) than cells adhering to the linear mPEG layers. In conclusion, the method for preparing non-fouling surfaces for long-term implanted devices influence surface-induced cellular responses of the host.
Subject(s)
Cell Adhesion/drug effects , Leukocytes/physiology , Macrophages/physiology , Polyethylene Glycols/chemistry , Surface Properties , Absorption/drug effects , Cell Differentiation , Fibrinogen/chemistry , Humans , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Tumor Necrosis Factor-alpha/metabolism , U937 CellsABSTRACT
Grafting of poly(ethylene glycol) (PEG) is a common strategy for reducing nonspecific interactions of surfaces with proteins. We have used grafting at "cloud point" solution conditions that ensures maximum grafting density of linear methoxy terminated PEG-aldehyde (mPEG-ald, M(w) = 5000 and 30000). In an alternative approach, surfaces were modified with layers prepared from isocyanate terminated, star shaped poly(ethylene glycol-stat-propylene glycol) prepolymers (80% ethylene glycol, six arms, M(w) = 3000, 12,000, and 18,000; this compound will be referred to as "Star PEG" in the text). Due to the highly reactive endgroups, these molecules form a dense network on the substrate with a high polymer surface coverage. The two systems were compared regarding their ability to prevent unspecific adsorption of insulin and lysozyme. The layers were analyzed by ellipsometry, contact angle measurements, and XPS. Protein adsorption was monitored by surface MALDI-TOF MS and fluorescence microscopy. No protein adsorption could be detected on Star PEG coatings and on mPEG-ald 5000, whereas mPEG-ald 30,000 could only prevent adsorption of lysozyme but not of the smaller insulin.
Subject(s)
Coated Materials, Biocompatible/chemistry , Polymers/chemistry , Adsorption , Insulin , Molecular Conformation , Muramidase , Polyethylene Glycols/chemistry , Propylene Glycols/chemistryABSTRACT
Surfaces covered with polyethylene glycol (PEG) have been shown to be biocompatible because PEG yields nonimmunogenicity, nonantigenicity and protein rejection. To produce a biocompatible surface coating, we have developed a method for grafting PEG onto modified poly(vinylidene fluoride) (PVDF) films. The first step was to create carboxy groups on the PVDF surface following covalente coupling of polyethylenimine (PEI) to achieve high density of amino groups. These surface amines were reacted with formyl-terminated PEG's with various molecular weight. The modified PVDF surface was characterized by means of static contact angle measurements, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The influence of the chain length on lysozyme repellence was investigated by means of surface-MALDI-Tof mass spectrometry (Surface-MALDI-Tof-MS). Lysozyme adsorption was significantly suppressed on the PEG 5000 modified PVDF surface.
Subject(s)
Coated Materials, Biocompatible/chemistry , Muramidase/pharmacokinetics , Polyethylene Glycols/chemistry , Polyvinyls/chemistry , Adsorption , Coated Materials, Biocompatible/chemical synthesis , Materials Testing , Proteins/pharmacokinetics , Sensitivity and SpecificityABSTRACT
Density measurements of aqueous albumin solutions as a function of concentration and temperature are reported. The solvents were H(2)O, D(2)O, and a physiological H(2)O-based buffer. An anomaly of the density at very small concentrations of albumin in D(2)O was found. Furthermore, the partial specific volume of albumin is remarkably different in D(2)O and H(2)O. We attribute both effects to structural differences of the solvents. Copyright 2001 Academic Press.
