Non-biofouling materials prepared by atom transfer radical polymerization grafting of 2-methacryloloxyethyl phosphorylcholine: separate effects of graft density and chain length on protein repulsion.

Biomimetic poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) brushes with graft density 0.06-0.39 chains/nm2 and chain length 5-200 monomer units were prepared from silicon wafer surfaces by combining self-assembly of initiator and surface-initiated atom transfer radical polymerization (ATRP). Water contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy were used to characterize the modified surfaces. These surfaces with well-controlled poly(MPC) brushes were tested for protein repelling performance. Fibrinogen adsorption from tris-buffered saline at pH 7.4 decreased significantly with increasing graft density and/or chain length of poly(MPC) and reached a level of < 10 ng/cm2 at graft density > or = 0.29 chains/nm2 and chain length > or = 100 units, compared to ca. 570 ng/cm2 for the unmodified samples. While the fibrinogen adsorption was determined by both graft density and chain length, it showed a stronger dependence on graft density than on chain length.