Abstract
Purpose:
To assess the attraction of hyaluronate (HA), present in Biotrue MPS, to the surface of samfilcon A, senofilcon A, and comfilcon A silicone hydrogels (SiHy). Chemical evidence for the presence of the lubricant hyaluronate on SiHy surfaces was addressed using X-ray Photoelectron Spectroscopy (XPS) characterization. HA staining with Basic Red 2 coupled with detection by confocal, differential interference contrast as well as phase contrast imaging techniques was used to directly illustrate the hyaluronate network across lens surfaces.
Methods:
Lenses were soaked overnight with Biotrue MPS. All samples were stained with Basic Red 2 stain for three minutes, rinsed with DI water, and assembled on custom-made glass holders. A polarized light Nikon Eclipse 2000 and an Olympus FV1000 confocal laser scanning microscope (CLSM) equipped with differential interference contrast (DIC) attachment were used to monitor hyaluronate distribution over silicone hydrogel surfaces. Additionally, SiHy materials were incubated with a range of pure HA concentrations 0.1 to 0.01 % (w/v) and exposed to the dye solution. In addition, lenses soaked with the stain only but not exposed to MPS or HA were characterized. All images were captured with 20X microscope objective. When needed, confocal magnification was applied to resolve the HA network details. The surface chemistry of the lenses soaked in Biotrue MPS was examined for hydrated samples by cold probe XPS.
Results:
Microscopy imaging illustrated a homogenous, stained hyaluronate network that covered the samfilcon A surface. The morphology of HA transferred from Biotrue MPS was similar to the HA-stain network recorded for control samples. Presence of a uniform hyaluronate network on senofilcon A and comfilcon A surfaces was also demonstrated. HA covered the examined lens surfaces as demonstrated by cold probe XPS analysis.
Conclusions:
Microscopy imaging by DIC, phase contrast, and CLSM illustrated compatibly of the humectant hyaluronate with samfilcon A, senofilcon A, and comfilcon A lenses. High molecular weight HA present in Biotrue MPS partitioned on to the lens surface and it was homogeneously distributed over all lens surfaces. The morphology of the HA network adsorbed to samfilcon A, senofilcon A, and comfilcon A soaked with Biotrue and lenses incubated with pure hyaluronate solutions was similar.