| Summary: | Purpose
To study the impact of incubation solution complexity on protein deposition to silicone hydrogel (SH) contact lenses and the effect of contact lens cleaning solutions on protein activity and removal.
Methods
The SH materials investigated in this thesis included senofilcon A (SA), lotrafilcon B (LB), and balafilcon A (BA). Contact lenses were incubated in both a simple saline solution containing only one protein and a more complex artificial tear solution (ATS) containing numerous proteins, lipids, and mucins. Protein deposition was determined at days 1, 7, 14, and 28.
??? For the first in vitro experimental chapter (Chapter 3), 125Iodine radiolabeled albumin, lactoferrin, and lysozyme were the proteins of interest. Protein deposition to the different SH contact lenses was quantified using a gamma counter.
??? For the second in vitro experimental chapter (Chapter 4), 125Iodine radiolabeled lysozyme was the protein of interest and the effect of a contact lens care regimen (OPTI-FREE RepleniSH) on lysozyme deposition to SH lenses was determined.
The effect of contact lens cleaning solutions on lysozyme activity and removal was also determined.
??? For the third in vitro experimental chapter (Chapter 5), the effect of cleaning solutions on lysozyme activity was determined. OPTI-FREE RepleniSH (OFR), BioTrue (BT), and Clear Care (CC) were the cleaning solutions used in this study. Lysozyme activity was determined at hours 1, 12, 24, and 48 using the turbidity assay.
Results
The three proteins investigated exhibited unique deposition profiles which were impacted by the complexity of the incubation solution and the SH materials. In Chapter 3, BA lenses incubated in a complex analogue of the human tear film accumulated the most lysozyme and albumin. Lactoferrin deposited in greater amounts when LB lenses were incubated in a simple saline solution containing only lactoferrin. Protein deposited similarly on SA lenses, independent of incubation solution used.
In Chapter 4, the cleaning efficacy of OFR was determined for different SH materials. Lysozyme was more efficiently removed when both SA and LB lenses were incubated in a complex ATS. As seen in Chapter 3, SA lenses were not impacted by the complexity of the incubation solution. The protein removal efficacy of multi-purpose solution (MPS) for BA lenses was similar independent of incubation solution used. BA lenses incubated in ATS attracted the greatest amount of lysozyme; however, LB lenses incubated in the same solution allowed for the greatest protein removal by OFR.
In Chapter 5, MPS had varying effects on lysozyme activity. For OFR, there was an enhanced lysozyme activity throughout the 48-hour time period. For BT, the activity at hr 1 was relatively low, but an increase was seen by hr 12, which remained stable up to hr 48. For CC, there was a denaturing effect on lysozyme, and the activity was decreased significantly throughout the duration of the experiment.
Conclusions
Protein deposition profiles varied when lenses were incubated in either a simple saline solution or a complex artificial tear solution and deposition patterns varied between SH materials. The efficacy of a contact lens care regimen (OFR) to remove deposited lysozyme from SH lenses was dependent on both lens material and incubation solution. Lysozyme activity was impacted differently by the three care regimens, with OFR seemingly enhancing activity, BT stabilizing it, and CC exhibiting decreased activity. Future in vitro studies should use more appropriate analogues of the human tear film in order to better mimic the in vivo situation, as the complexity of the incubation solution has a clear impact on protein deposition profiles.
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