Factors affecting the biocompatibility of novel phosphorylcholine based biomaterials
Phosphorylcholine (PC) based polymers have been used in medical devices to
improve biocompatibility. In this study, PC based polymers were modified with
either a cationic charge or combined with poly(butylmethacrylate) (PBMA) and
their biocompatibility assessed through a series of biological assays.
Protein adsorption assays revealed that the presence of a cationic charge
significantly increased the number of proteins adsorbed. The total amount of
protein adsorbed to PC with 30% cationic charge was considerably more then that
adsorbed to the other samples. Fibronectin, albumin, complement factor B and
immunoglobulins were found adsorbed to all samples. Clq however, was only
adsorbed on samples containing 10% cationic charge or more.
The presence of a cationic charge increased cell adhesion for both the fibroblast
cells and the epithelial cells. Adhesion did not increase linearly with cationic
charge, possibly due to alterations in protein adsorption, coating stability, and or
cytotoxicity. Endothelial cells showed little to no cell adhesion on any of the PC
cationic samples. Pre-coating materials in fibronectin increased endothelial cell
adhesion, although this effect generally decreased as serum concentration
increased. Pre-coating samples in laminin facilitated cell adhesion on PC with
20% cationic charge but not on PET or PC with 0% cationic charge. The
combination of cationic charge and laminin may encourage cell adhesion,
possibly through alterations in conformation of adsorbed proteins.
Serum type affected adhesion and activation of mononuclear cells and
granulocytes. The presence of a cationic charge increased the adhesion and
activation of these two cell types. Adhesion and activation did not increase
linearly with cationic charge, possibly due to differences in protein adsorption,
coating stability and or cytotoxicity.
The biocompatibility of PC and PBMA copolymer samples were assessed,
looking at adhesion of corneal epithelial cells and macrophage cells. Adhesion of
both of these cell these cell types increased as PBMA content increased and PC
decreased. This is probably due to alterations in protein adsorption as a result of
changes in surface hydrophobicity.