Search

Contact lens materials include polymers that are ionized in the ocular pH condition and are susceptible to protein deposition due to their surface characteristics. Herein, we investigated the effect of the electrostatic state of the contact lens material and protein on protein deposition level using hen egg white lysozyme (HEWL) and bovine serum albumin (BSA) as model proteins and etafilcon A and hilafilcon B as model contact lens materials. Only HEWL deposition on etafilcon A showed a statistically significant pH-dependency (p < 0.05); protein deposition increased with pH. HEWL showed a positive zeta potential at acidic pH, while BSA showed a negative zeta potential at basic pH. Only etafilcon A showed a statistically significant pH-dependent point of zero charge (PZC) (p < 0.05), implying that its surface charge became more negative under basic conditions. This pH-dependency of etafilcon A is attributed to the pH-responsive degree of ionization of its constituent methacrylic acid (MAA). The presence of MAA and its degree of ionization could accelerate protein deposition; more HEWL deposited as pH increased despite the weak positive surface charge of HEWL. The highly negatively charged etafilcon A surface attracted HEWL, even overwhelming weak positive charge of HEWL, increasing the deposition with pH. [ABSTRACT FROM AUTHOR]

[Display omitted] • Benzalkonium chloride (BKC) is used as preservative in eye drops. • BKC binding on commercial contact lenses and effects on physical properties studied. • Lenses with and without wetting agent polyvinylpyrrolidone (PVP) investigated. • Maximum adsorbed BKC 2.88 and 2.32 mM for those without and with PVP, respectively. • PVP may reduce BKC adsorption, physical changes, and associated discomfort. Benzalkonium chloride (BKC) is a cationic surfactant used as a component in ophthalmic eye drops. The effects of BKC on the eye and the simple binding of BKC on the contact lens surface have been reported in other studies. However, the exact value of the BKC binding affinity on the contact lens surfaces and its effects on the physical properties of contact lenses have not been studied. Here, the binding affinity of BKC toward two types of contact lenses, those with the wetting agent polyvinylpyrrolidone (PVP) and those without, was calculated. In addition, the refractive power, UV–vis transmittance, contact angle, water content, base curve, and diameter of the contact lenses after treatment with BKC were examined to evaluate the effects of its adsorption on the contact lens. We found that the maximum amount of adsorbed BKC was 2.88 mM for the contact lens without PVP whereas it was 2.32 mM for that with PVP. In contrast, the BKC binding affinities were similar. Crucially, the physical properties of the contact lens changed significantly because of the adsorption of BKC. Although BKC is a widely used preservative, our results suggest that use of PVP-containing contact lenses reduces BKC adsorption and discomfort. [ABSTRACT FROM AUTHOR]