Merck
  • Home
  • Search Results
  • Enzymatic quantification of cholesterol and cholesterol esters from silicone hydrogel contact lenses.

Enzymatic quantification of cholesterol and cholesterol esters from silicone hydrogel contact lenses.

Investigative ophthalmology & visual science (2010-01-22)
Andrew D Pucker, Mirunalni Thangavelu, Jason J Nichols
ABSTRACT

The purpose of this work was to develop an enzymatic method of quantification of cholesterol and cholesterol esters derived from contact lenses, both in vitro and ex vivo. Lotrafilcon B (O2 Optix; CIBA Vision, Inc., Duluth, GA) and galyfilcon A (Acuvue Advance; Vistakon, Inc., Jacksonville, FL) silicone hydrogel contact lenses were independently incubated in cholesterol oleate solutions varying in concentrations. After incubation, the lenses were removed and underwent two separate 2:1 chloroform-methanol extractions. After in vitro studies, 10 human subjects wore both lotrafilcon B and galyfilcon A contact lenses for 7 days. The lenses also underwent two separate 2:1 chloroform-methanol extractions. All in vitro and ex vivo samples were quantified with a cholesterol esterase enzymatic reaction. Calibration curves from quantifications of in vitro contact lens samples soaked in successively decreasing concentrations of cholesterol oleate yielded coefficients of determination (R(2)) of 0.99 (lotrafilcon B) and 0.97 (galyfilcon A). For in vitro contact lens samples, galyfilcon A was associated with an average cholesterol oleate extraction of 39.85 +/- 48.65 microg/lens, whereas lotrafilcon B was associated with 5.86 +/- 3.36 microg/lens (P = 0.05) across both extractions and all incubation concentrations. For ex vivo contact lens samples, there was significantly more cholesterol and cholesterol esters deposited on galyfilcon A (5.77 +/- 1.87 microg/lens) than on lotrafilcon B (2.03 +/- 1.62 microg/lens; P = 0.0005). This is an efficient and simple method of quantifying total cholesterol extracted from silicone hydrogel contact lenses and, potentially, the meibum and/or tear film. Certain silicone hydrogel materials demonstrate more affinity for cholesterol and its esters than do others.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cholesterol Esterase from bovine pancreas, lyophilized powder, ≥200 units/g protein
Sigma-Aldrich
Cholesteryl oleate, ≥98% (HPLC; detection at 205 nm)
Sigma-Aldrich
Sodium phosphate dibasic, for molecular biology, ≥98.5% (titration)
Sigma-Aldrich
Sodium phosphate monobasic, BioReagent, for molecular biology, anhydrous, ≥98%
Sigma-Aldrich
Peroxidase from horseradish, Type VI-A, essentially salt-free, lyophilized powder, 950-2000 units/mg solid (using ABTS), ≥250 units/mg solid (using pyrogallol)