Polyethylene glycol-coated biocompatible surfaces

Surfaces covered with polyethylene glycol (PEG; HO-(CH(2)-CH(2)-O)(n)-H) have been shown to be biocompatible because PEG's properties yield nonimmunogenicity, nonantigenicity, and protein rejection. To produce a biocompatible surface coating, we have developed a method for grafting PEG onto activated silica films. We first deposited an amorphous silica film by plasma-enhanced chemical vapor deposition from SiH(4) and O(2) gases, which provided the flexibility to coat diverse materials with different chemistries and shapes. The silica films were activated by exposure to water plasma, increasing the number of silanol groups (Si-OH) on their surface. The surface silanol groups were then chemically reacted with the hydroxyl end of PEG to form an ester bond, Si-O-C, and to cover the surface with PEG. The surface reactions were monitored using attenuated total reflection Fourier transform infrared spectroscopy. The vibrational absorption bands of the C-O and -CH(2) bonds increased with time and saturated, indicating that PEG was adsorbed to saturation coverage on the surface. Simultaneously, the Si-OH absorption band decreased, showing that the surface silanols reacted with PEG and were depleted. The PEG-covered surfaces were physically characterized by atomic force microscopy, Auger electron spectroscopy, ellipsometry, and contact angle measurements. These characterization techniques provided additional evidence for the existence of chemically bonded PEG on the surfaces. Efficacy of protein rejection on PEG-covered surfaces was studied through measurements of the fluorescence intensity of Texas red-labeled bovine serum albumin brought in contact with such surfaces in solution. Significantly less protein adsorption was observed on surfaces covered with PEG compared to uncovered surfaces.