Biological responses to cationically charged phosphorylcholine-based materials in vitro

Phosphorylcholine (PC)-based polymers have been used in a variety of medical device applications to improve biocompatibility. The use of PC-based materials for biomaterials is associated with low protein adsorption, reduced complement activation, low inflammatory response and cell adhesion. For some medical device applications however, materials that support cell adhesion are also beneficial, allowing host interaction and encouraging full incorporation within the body. As previous studies have suggested that cell adhesion to materials is enhanced by the addition of charge, PC-based polymers have therefore been modified to incorporate various concentrations of cationic charge. In this study, the affect of cationic charge on a range of biological responses was investigated. In vitro assays have been used to assess the adsorption of protein onto the materials surface, the adhesion of mouse fibroblasts and rabbit corneal epithelial cells and the adhesion of human mononuclear cells and granulocytes. The results corroborate previous work showing that PC without charge significantly reduces protein adsorption, cell adhesion and inflammatory cell activation. The addition of cationic charge to PC polymers however, resulted in an increase in all of the above responses. This increase did not however, increase linearly with cationic monomer concentration. The differences in cell adhesion are discussed in terms of differences in protein adsorption, cytotoxicity and/or stability of the different cationic polymer coatings.