Improving biomaterial properties of collagen films by chemical modification

Films of bovine collagen were chemically modified with the goal of improving their biomaterial properties. The modified films were investigated with respect to their affinity to fibroblast and endothelial cells, as well as their antibacterial properties tested by adhesion of Staphylococcus aureus. Modifications that only change the net charge of collagen, such as acetylation, succinylation, and treatment with glutaraldehyde (all increase the negative charge), and amination with ethylenediamine (EDA), N,N-dimethyl-EDA (DMEDA), or butylamine (all increase the positive charge), did not dramatically alter the mammalian cell attachment to the film. In contrast, derivatization of collagen using methoxypoly(ethylene glycol) (PEG) diminished the attachment of fibroblasts by 98 +/- 1% and of endothelial cells by more than 99% compared to unmodified collagen. Moreover, the rate of growth of fibroblasts dropped by 97 +/- 1% and that of endothelial cells by 88 +/- 3% as a result of PEGylation of collagen. Adhesion of S. aureus cells also plummeted by 93 +/- 2% as a result of this PEGylation. With these antifouling properties, PEG-collagen may be a promising coating material for coronary stents. Subsequent derivatization of PEG-collagen with EDA or DMEDA abolished its mammalian cell-repelling ability, whereas bacterial cell repulsion was partially retained: for example, DMEDA-modified PEG-collagen exhibits up to a 5-fold lower bacterial adhesion than collagen. It is worth noting that a material that allows mammalian cell attachment but reduces bacterial adhesion could be useful as an implant or coating.