title: In Vitro Spoilation of Silicone-Hydrogel Soft Contact Lenses in a Model-Blink Cell.
abstract: OBJECTIVE
  We developed an in vitro model-blink cell that reproduces the mechanism of in vivo fouling of soft contact lenses. In the model-blink cell, model tear lipid directly contacts the lens surface after forced aqueous rupture, mirroring the pre-lens tear-film breakup during interblink.
  
  
  METHODS
  Soft contact lenses are attached to a Teflon holder and immersed in artificial tear solution with protein, salts, and mucins. Artificial tear-lipid solution is spread over the air/tear interface as a duplex lipid layer. The aqueous tear film is periodically ruptured and reformed by withdrawing and reinjecting tear solution into the cell, mimicking the blink-rupture process. Fouled deposits appear on the lenses after cycling, and their compositions and spatial distributions are subsequently analyzed by optical microscopy, laser ablation electrospray ionization mass spectrometry, and two-photon fluorescence confocal scanning laser microscopy.
  
  
  RESULTS
  Discrete deposit (white) spots with an average size of 20 to 300 μm are observed on the studied lenses, confirming what is seen in vivo and validating the in vitro model-blink cell. Targeted lipids (cholesterol) and proteins (albumin from bovine serum) are identified in the discrete surface deposits. Both lipid and protein occur simultaneously in the surface deposits and overlap with the white spots observed by optical microscopy. Additionally, lipid and protein penetrate into the bulk of tested silicone-hydrogel lenses, likely attributed to the bicontinuous microstructure of oleophilic silicone and hydrophilic polymer phases of the lens.
  
  
  CONCLUSIONS
  In vitro spoilation of soft contact lenses is successfully achieved by the model-blink cell confirming the tear rupture/deposition mechanism of lens fouling. The model-blink cell provides a reliable laboratory tool for screening new antifouling lens materials, surface coatings, and care solutions.
authors.affiliation: *PhD †MS Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California (C-CP, NPF, CJR); Protea Biosciences Group, Morgantown, West Virginia (TR); and Vision Science Graduate Program, University of California, Berkeley, Berkeley, California (CJR).
authors.forename: Cheng-Chun
authors.initials: CC
authors.lastname: Peng
authors.forename: Neil P
authors.initials: NP
authors.lastname: Fajardo
authors.forename: Trust
authors.initials: T
authors.lastname: Razunguzwa
authors.forename: Clayton J
authors.initials: CJ
authors.lastname: Radke
mesh_terms: D003263:Contact Lenses, Hydrophilic; D005136:Eye Proteins / Q000737:chemistry; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D066298:In Vitro Techniques; D050356:Lipid Metabolism / Q000502:physiology*; D008055:Lipids / Q000032:analysis*; D065346:Lubricant Eye Drops / Q000737:chemistry*; D018613:Microscopy, Confocal; D036641:Microscopy, Fluorescence, Multiphoton; D008954:Models, Biological; D009077:Mucins / Q000378:metabolism; D011485:Protein Binding; D012828:Silicones / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D005136:Eye Proteins; D008055:Lipids; D065346:Lubricant Eye Drops; D009077:Mucins; D012828:Silicones; C042434:tear proteins; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate