Hydrogel blood-compatible

Similarly to the phospholipid polymers, the MPC polymers show excellent biocompatibility and blood compatibility [43—48]. These properties are based on the bioinert character of the MPC polymers, i.e., inhibition of specific interaction with biomolecules [49, 50]. Recently, the MPC polymers have been applied to various medical and pharmaceutical applications [44-47, 51-55]. The crosslinked MPC polymers provide good hydrogels and they have been used in the manufacture of soft contact lenses. We have applied the MPC polymer hydrogel as a cell-encapsulation matrix due to its excellent cytocompatibility. At the same time, to prepare a spontaneously forming reversible hydrogel, we focused on the reversible covalent bonding formed between phenylboronic acid and polyol in an aqueous system. 

Blood compatibility of PEG-modified surfaces was discussed in terms of the mobility of water molecules at the interface of hydrogel materices. The property and application of poly(N-isopropylacrylamide) and its copolymers as thermoresponsive hydrogel were also reviewed. 

Very few polymeric materials exhibit good blood compatibility. The best currently available materials Include some hydrogels, some PEUUs, and some blolized materials. Biollzation involves affixing some biologically inactivated natural tissue to the polymer surface (31). 

Most blood vessels in the body are smaller than 4 mm, and no satisfactory replacement currently exists. The most promising materials seem to be certain polyether polyurethane ureas (PEUU) (48, 49) and some hydrogels (50). Both materials show good blood compatibility, and patency rates (in dogs) in excess of 75% have been reported for the PEUU system (49). Human studies have not been made, to date, with either material, but the PEUU material is about the same as that used in the artificial heart. 

Hydrophilic coatings have also been popular because of their low interfacial tension in biological environments [Hoffman, 1981]. Hydrogels as well as various combinations of hydrophilic and hydrophobic monomers have been studied on the premise that there will be an optimum polar-dispersion force ratio which could be matched on the surfaces of the most passivating proteins. The passive surface may induce less clot formation. Polyethylene oxide coated surfaces have been found to resist protein adsorption and cell adhesion and have therefore been proposed as potential blood compatible coatings [Lee et al., 1990a]. General physical and chemical methods to modify the surfaces of polymeric biomaterials are listed in Table 40.7 [Ratner et al., 1996]. 

These materials, which preferentially adsorb or absorb water (hydrogels), were initially postulated to be blood compatible based on the view that many naturally occuring phospholipids, comprising the cell membranes of... 

In contrast to the above mentioned hydrophobic polymers, the so-called hydrogel, which is a physically or chemically crosslinked polymer swollen with water, is hydrophilic and also known as a blood-compatible polymer Poly 2-hydroxyethyl meth-... 

In summary, with regard to the development of a blood-compatible polymer surface based on poly(ether sulfone), an athrombotic surface is achieved by hydrogel coating using plasma-induced graftpolymerization of HEMA. Nevertheless, this evaluation is based on only three in vitro parameters, i.e. blood compatibility, fibrinogen adsorption, and platelet adhesion, and hence is by no means comprehensive. 

IPNs and gradient IPNs based on polyether-urethane-urea (PEUU) block copolymers and acrylamide, 2-hydroxyethyl methacrylate (HEMA), or N-vinyl-2-pyrrolidone. Intended for biomedical uses, such compositions created high-strength, water-absorbing hydrogel surfaces showing good blood compatibility. 

G. C. Berry and M. Dror, Modification of Polyurethanes by Interpenetrating Polymer Network Formation with Hydrogels, Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Pap. 38(1), 465 (1978). Polyether-urethane-urea block copolymers with crosslinked HEMA, NVP, or acrylamide. IPNs and gradient IPNs for biomedical purposes. Strength, water swellability, and good blood compatibility. 

The most actively pursued areas are the design of polymers for drug and enzyme delivery or entrapment, the use of synthetic techniques to modify the blood compatibility of existing materials, and the production of new forms of biodegradable polymer. Hydrogels as a group of polymers still command attention. Various chapters in previously cited symposium collections provide useful illustrations of current trends. 

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