Abstract
Purpose: :
Proteins in the ocular tear film deposit on contact lenses during wear and can become denatured. The components of multi-purpose solutions (MPS) may affect protein denaturization of tear film proteins as a result of contact lens wear. This in vitro study investigates the impact of commonly used surfactants of MPS, including poloxamine 1107, Tetronic 904, Pluronic F127, and polyoxyethylene-polybutylene (EOBO), on the stability of the tear film protein lysozyme.
Methods: :
Lysozyme, an antimicrobial protein, was dissolved in four MPS products, as well as in solutions of their corresponding surfactants at different concentrations in a Borate Buffered Saline solution (BBS). The resulting solutions were then exposed to the chemical denaturant sodium dodecyl sulfate (SDS). The activity of lysozyme was evaluated by then adding each test solution to a tube containing a suspension of Micrococcus luteus. Native lysozyme is able to lyse the M. luteus cells causing the turbidity of the suspension to decrease. The percentage of lysozyme maintained in the native form was determined by comparing the initial turbidity of the M. luteus suspension to its turbidity after exposure to the test solutions.
Results: :
The amount of lysozyme maintained in its native form by four different surfactants evaluated at an equal concentration ranged from 92.4% to 7.0%. The percent of stabilized lysozyme correlated with the concentration of the surfactant. One surfactant tested stabilized less than 10% of the lysozyme over the concentration range tested. The MPS products tested exhibited a range from 90.1% to 3.0% lysozyme stabilized, and the results correlate with the type and concentration of surfactant found in the product.
Conclusions: :
This data indicates that the ability of a MPS to prevent denaturation of lysozyme in this model system can be affected by the type and concentration of surfactant present in the MPS. The structure, hydrophobicity, molecular weight of a surfactant may affect its ability to stabilize lysozyme. These results suggest that further study is needed to understand the effect of ingredients commonly used in MPS and their impact on tear film protein stabilization and protective antimicrobial benefits conveyed to contact lens wearers.
Keywords: protein structure/function • contact lens • anterior segment