title: Lysozyme sorption in hydrogel contact lenses.
abstract: OBJECTIVE
  To examine the processes involved in formation of protein deposits on hydrogel contact lenses.
  
  
  METHODS
  The adsorption and/or penetration of lysozyme on or into three types of contact lenses, etafilcon A, vifilcon A, and tefilcon, were investigated in vitro using a radiolabel-tracer technique, x-ray photoelectron spectroscopy, and laser scanning confocal microscopy.
  
  
  RESULTS
  Binding of lysozyme to high-water-content, ionic contact lenses (etafilcon A and vifilcon A) was dominated by a penetration process. The extent of this penetration was a function of charge density of the lenses, so that there was a higher degree of penetration of lysozyme in etafilcon A than in vifilcon A lenses. In contrast, the binding of lysozyme to tefilcon lenses was a surface adsorption process. The adsorption and desorption kinetics showed similar trends to those found in human serum albumin (HSA) adsorption on lens surfaces. However, the extent of lysozyme adsorption on tefilcon is much higher than HSA adsorption, probably because of the self-association of lysozyme on the tefilcon lens surface. Furthermore, either penetration or adsorption of lysozyme involved reversible and irreversible processes and were both time dependent.
  
  
  CONCLUSIONS
  Binding of lysozyme to hydrogel lenses involves surface adsorption or matrix penetration. These processes may be reversible or irreversible. The properties of the lens materials, such as charge density (ionicity) and porosity (water content) of the lenses, determine the type and rates of these processes.
authors: Cooperative Research Centre for Eye Research and Technology, The University of New South Wales, Sydney, Australia.
authors: Q
authors: Q
authors: Garrett
authors: R W
authors: RW
authors: Garrett
authors: B K
authors: BK
authors: Milthorpe
mesh_terms: D000327:Adsorption; D003263:Contact Lenses, Hydrophilic; D016650:Fluorescein-5-isothiocyanate; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007700:Kinetics; D018613:Microscopy, Confocal; D009113:Muramidase / Q000378:metabolism*; D011485:Protein Binding; D013052:Spectrometry, X-Ray Emission; D013997:Time Factors
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D009113:Muramidase; D016650:Fluorescein-5-isothiocyanate