Raman, IR and thermal study of a new highly biocompatible phosphorylcholine-based contact lens

In this study, vibrational Raman and IR spectroscopy coupled to thermogravimetry (TG) and differential scanning calorimetry (DSC) have been used to characterize the Proclear (TM) lens, a biomimetic soft contact lens composed of Omafilcon A, a phosphorylcholine (PC)-modified poly(2-hydroxyethyl-methacrylate) (PHEMA), whose main monomer is 2-methacryloyloxy-ethylphosphorylcholine. Raman and IR spectra showed that the PC component is actually incorporated into the polymer. The vOH Raman stretching region demonstrated that the Proclear (TM) lens contains a higher amount of water (59% by TG analysis) than commercial PHEMA lenses, confirming that the PC incorporation has noticeably altered the material properties. DSC comparative analysis was carried out on Proclear (TM) and PHEMA lenses as well as Acuvue (TM) (Etafilcon A), a commonly used soft contact lens with a water content comparable to that of Proclear (TM). The latter revealed to be characterized by a significantly higher free water fraction than PHEMA; this result explains why the former lens absorbs few tear components than the latter. Conversely, free water fraction was found to be nearly the same for Proclear (TM) and Acuvue (TM) lenses; the noticeably lower protein adsorption reported for the former was explained, partially at least, in relation to the different organization of water molecules in the two lenses. (c) 2004 Elsevier B.V. All rights reserved.