Photoreactive Polymers Bearing a Zwitterionic Phosphorylcholine Group for Surface Modification of Biomaterials

Photoreactive polymers bearing zwitterionic phosphorylcholine and benzophenone groups on the side chain were synthesized and used as surface modification reagents for biomaterials. A photoreactive methacrylate containing the benzophenone group, 3-methacryloyloxy-2-hydroxypropyl-4-oxybenzophenone (MHPBP), was synthesized via a ring-opening and addition reaction between glycidyl methacrylate and 4-hydroxybenzophenone. Then, water-soluble, amphiphilic polymers poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-MHPBP) (PMH) and poly(MPC-co-n-butyl methacrylate-co-MHPBP), with different monomer unit compositions, were synthesized through radical polymerization. Ultraviolet-visible (UV/vis) absorption spectra of these polymer solutions showed that these polymers have maximum absorption peaks at 254 and 289 nm that can be attributed to the benzophenone unit. The intensity of UV adsorption at 289 nm was decreased with increased UV irradiation time, and it was saturated within a few minutes, indicating that the polymers are highly sensitive to UV irradiation. A commercial material (i.e., cyclic polyolefin) was simply modified by a UV irradiation for 1.0 min. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis results indicated that the stability of the polymer on the surface was dramatically enhanced because of the photochemical reaction of the benzophenone moiety. The air contact angles of PMH surfaces measured in water were up to 160°. Thus, highly hydrophilic surfaces were obtained. The critical surface tension of the PMH-modified surface was 45.7 mN/m. By evaluating the biological reactivity of the treated surface, protein adsorption and cell adhesion were completely inhibited on the surface, which was prepared using a photopatterning procedure using PMH. In conclusion, photoreactive MPC polymers with a benzophenone moiety could be used as a novel and effective surface modifier.