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Phospholipid-like polymers based on 2-methacryloyloxyethyl phosphorylcholine containing varying amounts of the cationically charged monomer choline methacrylate (CMA) from 0 to 30 wt% have been prepared. Substrates coated with these materials were shown to bind significantly lower amounts of specific proteins compared to the uncoated control. ELISA assays demonstrated that fibrinogen did not bind appreciably to coatings containing 0–30% CMA, whereas albumin binding was seen to increase significantly as the CMA content of the coating increased. Platelet activation assays, measurement of plasma coagulation time and whole blood contact scanning electron micrography demonstrated that the haemocompatibility of the coatings was shown to be unaffected by the CMA component. The CMA polymer coatings have been shown to absorb/adsorb many different drug compounds covering a wide range of molecular weights and release these in a controlled fashion. The range of cationic polymers assessed can interact with the net negative charge found in many large therapeutic biomolecules, such as DNA fragments used in gene therapy, that may be of interest in the preventative treatment of conditions such as restenosis. Coronary stents coated with 6% or 20% CMA-containing polymers have been shown to load and release this type of genetic material irrespective of molecular weight of the biomolecule. Ex vivo and in vivo studies have shown that these compounds can be delivered to the stented section of the vessel with very low quantities delivered outside the vessel target area. [Copyright &y& Elsevier]

Abstract: Phosphorylcholine (PC) moieties were chemically attached to surfaces of polymer microparticles by addition of 2-methylacryloyloxyethyl phosphorylcholine monomer to the seeded, semi-continuous polymerisations of methyl methacrylate (MMA) and butyl acrylate (BA). The surface of the bio-functionalised polymer microparticles was principally characterised using X-ray photoelectron spectroscopy (XPS), dynamic nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), photon correlation spectroscopy (PCS), acoustophoresis and enzyme-linked immunosorbent assays (ELISA). It was found that the persulphate initiating species are concealed behind the phosphorylcholine containing monomer sequence located on the surface of the microparticles. The combination of analytical techniques showed that the surfaces of the polymer microparticles are extremely mobile above the glass transition temperature of the co-polymer and able to rearrange depending on the environment in which they are placed. This allows the phosphorylcholine moiety to be preferentially expressed at the surface in aqueous media, but not so in the dry state or conditions of ultra-high vacuum. In terms of the nature of the biocompatibility of phosphorylcholine containing polymers, no evidence was found for the irreversible structuring of water molecules around the phosphorylcholine moiety in the wet state. The results of this work suggest that a more likely contributory reason for the protein-resistant nature of phosphorylcholine containing polymers is the mobility of the phosphorylcholine moiety. Increases in biocompatibility correspond with increases in the hydrophilicity of a polymer surface when phosphorylcholine is preferentially expressed. A large free water fraction may be present in the phosphorylcholine containing monomer sequence, as part of a hydrogel structure located at the surface of the polymer microparticles. This, coupled with concomitant modification of the local electrical double-layer very close to the surface may also play a critical role in reducing protein–surface interactions. [Copyright &y& Elsevier]