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PubMed2000

Blood compatible aspects of poly(2-methoxyethylacrylate) (PMEA)--relationship between protein adsorption and platelet adhesion on PMEA surface.

Platelet adhesion and spreading is suppressed when a poly(2-methoxyethylacrylate) (PMEA) surface is used, compared with other polymer surfaces. To clarify the reason for this suppression, the relationship among the amount of the plasma protein adsorbed onto PMEA, its secondary structure and platelet adhesion was investigated. Poly(2-hydroxyethylmethacrylate) (PHEMA) and polyacrylate analogous were used as references. The amount of protein adsorbed onto PMEA was very low and similar to that absorbed onto PHEMA. Circular dichroism (CD) spectroscopy was applied to examine changes in the secondary structure of the proteins after adsorption onto the polymer surface. The conformation of the proteins adsorbed onto PHEMA changed considerably, but that of proteins adsorbed onto PMEA differed only a little from the native one. These results suggest that low platelet adhesion and spreading are closely related to the low degree of the denaturation of the protein adsorbed onto PMEA. PMEA could be developed as a promising material to produce a useful blood-contacting surface for medical devices.

Acrylates↗
PubMed2002

AFM and SFG studies of pHEMA-based hydrogel contact lens surfaces in saline solution: adhesion, friction, and the presence of non-crosslinked polymer chains at the surface.

The surfaces of two types of soft contact lenses neutral and ionic hydrogels--were characterized by atomic force microscopy (AFM) and sum-frequency-generation (SFG) vibrational spectroscopy. AFM measurements in saline solution showed that the presence of ionic functional groups at the surface lowered the friction and adhesion to a hydrophobic polystyrene tip. This was attributed to the specific interactions of water and the molecular orientation of hydrogel chains at the surface. Friction and adhesion behavior also revealed the presence of domains of non-crosslinked polymer chains at the lens surface. SFG showed that the lens surface became partially dehydrated upon exposure to air. On this partially dehydrated lens surface, the non-crosslinked domains exhibited low friction and adhesion in AFM. Fully hydrated in saline solution, the non-crosslinked domains extended more than tens of nanometers into solution and were mobile.

Adsorption↗
PubMed2003

Mechanical behaviour and biocompatibility of poly(1-vinyl-2-pyrrolidinone)-gelatin IPN hydrogels.

IPN hydrogels based on poly(1-vinyl-2-pyrrolidinone) and gelatin were obtained by casting of aqueous solution using potassium persulphate and glutaraldehyde as respective crosslinking agents. Studies of swelling and mechanical behaviour showed that the samples of different composition can incorporate high content of water and still exhibit high compression strength. The composition has influence at the global crosslinking density what affects the mechanical performance. In vitro biocompatibility and hemocompatibility were also investigated. The materials do not interfere on the cellular functions and neither induce platelet adhesion. From this preliminary evaluation, it is possible to conclude that these hydrogels have potential for applications in the biomedical field.

Biocompatible Materials↗
PubMed2003

Albumin and fibrinogen adsorption on PU-PHEMA surfaces.

Materials that adsorb specific proteins may find a variety of applications in the biomedical field. The aim of this study was the preparation of a hydrophilic surface, with low protein adsorption, to be used in the future as a support for the immobilisation of several species, e.g. Cibacron Blue F3G-A, which has been described to induce specific albumin adsorption. Poly(hydroxyethylmethacrylate) (PHEMA) and poly(hydroxyethylacrylate) (PHEA) were chosen as the hydrophilic surface because they can be easily polymerised and possess hydroxyl groups that can be used for the immobilisation of different compounds. Thin films of PHEMA and PHEA were successfully graft polymerised onto the surface of a commercial poly(etherurethane) (PU) using ceric ion as initiator. Grafting polymerisations were followed by mass gain and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Since stability tests demonstrated that only PU-PHEMA was stable in alkaline solutions, a necessary condition to future immobilisations, the investigation was focused on the coating of PU with PHEMA. PU-PHEMA films were characterised in detail using several techniques as mass gain, ATR-FTIR, contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Protein adsorption was evaluated using radiolabelled albumin and fibrinogen from pure solutions and from mixtures of both proteins. PU surfaces modified with PHEMA have demonstrated low protein adsorption, showing their potential use as substrates. This opens the possibly of exploring the advantages of selective adsorption by appropriate immobilisation of specific molecules.

Adsorption↗
PubMed1998

High-strength, ultra-thin and fiber-reinforced pHEMA artificial skin.

Membranes of pHEMA-based composites were manufactured by adding various kinds of weaved and knitted fabrics and fibers into a deionized water solution of HEMA monomer, EGDMA cross-linker and BIE initiator, and followed by polymerization under ultraviolet radiation. By varying the amount of initial water addition (IWA), the dimensional change of pHEMA matrix from the newly fabricated state to the eventually swollen state could be adjusted to reduce the swellability mismatch with the fabrics and the possibility of the swollen membranes becoming folded and curled was avoided. Mechanical properties of the fiber-reinforced pHEMA composites, including yielding strength, maximum strength, Young's modulus and elongation at break, are improved evidently depending on the mechanical characteristics of additives applied. The involvement of fabrics and fibers in the soft pHEMA matrix also provides an alternative of making the ultra-thin membranes to overcome the problem of easily being torn during handling. In addition, some of these membranes also exhibit an improvement in water transmission rate.

Biocompatible Materials↗