Confocal microscopy and albumin penetration into contact lenses.
OBJECTIVE
To develop a novel in vitro method to detect the depth of penetration of the tear film protein albumin into contact lens materials using confocal laser scanning microscopy (CLSM).


METHODS
A poly-HEMA-based hydrogel (etafilcon A) and a silicone hydrogel material (lotrafilcon B) were examined. In vitro, bovine serum albumin (BSA) was labeled with 5-(4,6-dichloro-s-triazin-2-ylamino) fluorescein hydrochloride (DTAF). The lenses were incubated in this protein solution (0.5 mg/ml) at 37 degrees C. After 1 and 7 days incubation, the lenses were examined using CLSM (Zeiss 510, config. META 18) and the location of the fluorescently labeled BSA was identified.


RESULTS
BSA adsorption on the surface and penetration into the lens matrix occurred at a higher concentration for etafilcon compared to lotrafilcon (p < 0.001). For both materials, BSA was detected on the surface after 1 day of incubation. Significant levels of BSA were detected within the matrix of etafilcon after as little as 1 day (p < 0.001), but no BSA was detected in the matrix of lotrafilcon at any time (p > 0.05).


CONCLUSIONS
CLSM can be successfully used to examine the depth of penetration of fluorescently labeled proteins into various hydrogel polymers. Our results show that etafilcon lenses both adsorb BSA on the surface and absorb BSA within the matrix, whereas lotrafilcon B adsorbs small amounts of BSA on the surface only.
Luensmann
Doerte
D
Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada. dluensma@uwaterloo.ca
Glasier
Mary-Ann
MA
Zhang
Feng
F
Bantseev
Vladimir
V
Simpson
Trefford
T
Jones
Lyndon
L
D000327:Adsorption; D000818:Animals; D002417:Cattle; D003263:Contact Lenses, Hydrophilic; D005452:Fluoresceins; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D020100:Hydrogels; D008689:Methacrylates; D018613:Microscopy, Confocal; D009994:Osmolar Concentration; D012710:Serum Albumin, Bovine / Q000493:pharmacokinetics*; D012828:Silicones
D005452:Fluoresceins; D020100:Hydrogels; D008689:Methacrylates; D012828:Silicones; C114176:etafilcon; C524582:lotrafilcon B; C039083:5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)fluorescein; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D012710:Serum Albumin, Bovine