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Adhesion of transferrin to Tisifilcon A contact lenses

Tear proteins accumulate on contact lenses causing lens deterioration and conjunctival irritation. We examined the adhesion of transferrin to contact lenses made of tisifilcon A, a rigid gas‐permeable silicone hydrogel (FDA Group III). Lenses were incubated 2.0 mg/ml solutions of human holo‐transferrin for 1, 2, 3, and 4 days, and protein adhesion was determined by bicinchoninic acid assay. Transferrin adhesion increased from day 0 to day 3 and then dropped after days 4 and 5. This pattern resembled transferrin adhesion to lenses made of polymacon (FDA Group I), alphafilcon (FDA Group II), omafilcon (FDA Group II) and balafilcon (FDA Group III) materials, but differed from the pattern of transferrin adhesion to etafilcon (FDA Group IV) material. Transferrin adhesion to tisifilcon A was greater than transferrin adhesion to all other materials except balafilcon, which had equivalent transferrin adhesion. These differences may be related to the positive charges on transferrin originating from arginine residues and the N‐terminus. These cause transferrin to adhere better to the low water ionic Group III materials than to the non‐ionic materials (FDA Groups I and II) and the high water ionic material (FDA Group IV).