title: Extraction efficiency of an extraction buffer used to quantify lysozyme deposition on conventional and silicone hydrogel contact lens materials.
abstract: OBJECTIVE
  Extracting lysozyme from Food and Drug Administration group IV etafilcon lenses by using 0.2% trifluoroacetic acid and acetonitrile (TFA/ACN) is a well-established procedure. TFA/ACN has been the extraction buffer of choice for extracting proteins from silicone hydrogel contact lenses. The purpose of this study was to determine the efficiency of TFA/ACN in extracting lysozyme from silicone hydrogel and etafilcon lenses by using an in vitro model.
  
  
  METHODS
  ACUVUE 2, Focus NIGHT & DAY, O2 Optix, PureVision, and ACUVUE Advance lenses were incubated in simple lysozyme solution and a complex artificial tear solution consisting of multiple tear components containing lysozyme labeled with iodine 125. All the silicone hydrogel lenses were incubated for 28 days, whereas the ACUVUE 2 lenses were incubated for 7 days at 37 degrees C with constant rotation. After the incubation period, radioactive counts were determined, and the lenses were placed in an appropriate volume of the buffer for 24 hours in darkness. The lenses were removed from the buffer, and radioactive counts were determined again.
  
  
  RESULTS
  Extraction efficiencies for lysozyme from the artificial tear solution were 97.2% +/- 1.2% for ACUVUE 2, 64.3% +/- 6.2% for Focus NIGHT & DAY, 62.5% +/- 5.6% for O2 Optix, 53.5% +/- 5.8% for PureVision, and 89.2% +/- 3.4% for ACUVUE Advance. Results were similar for the lysozyme extracted after incubating in the simple lysozyme solution.
  
  
  CONCLUSIONS
  TFA/ACN is extremely efficient at extracting lysozyme deposited on etafilcon lenses. However, it does not extract all the lysozyme deposited on silicone hydrogel lenses, and alternative extraction procedures should be sought.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada. lnagapat@uwaterloo.ca
authors.forename: Lakshman N
authors.initials: LN
authors.lastname: Subbaraman
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Glasier
authors.forename: Michelle
authors.initials: M
authors.lastname: Senchyna
authors.forename: Heather
authors.initials: H
authors.lastname: Sheardown
authors.forename: Lyndon
authors.initials: L
authors.lastname: Jones
mesh_terms: D002021:Buffers; D018639:Contact Lens Solutions / Q000737:chemistry; D003263:Contact Lenses, Hydrophilic; D004795:Enzyme Stability; D004867:Equipment Design; D006801:Humans; D008689:Methacrylates / Q000737:chemistry*; D009113:Muramidase / Q000032:analysis*; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000379:methods
chemical_list: D002021:Buffers; D018639:Contact Lens Solutions; D008689:Methacrylates; C114176:etafilcon; D009113:Muramidase