Abstract
Purpose: :
To investigate the effect of NC-1059 peptide on riboflavin (RF) diffusion across an intact corneal epithelium into the stroma.
Methods: :
NC-1059 peptide was synthesized by solid-phase synthesis with 9-fluorenylmethoxycarbonyl chemistry, purified by reversed-phase HPLC and characterized with matrix-assisted laser desorption time-of-flight mass spectroscopy. The diffusion of RF across E18 chick corneal epithelium ex vivo was monitored using confocal microscopy. The depth distributions of RF in the cornea stroma were measured using a group of linear equations based on the relationship between RF fluorescence intensity and concentrations.
Results: :
Data presented in this study demonstrated that the NC-1059 peptide can open the epithelial barrier to allow the permeation of RF into the stroma. The effect of NC-1059 peptide on RF diffusion across an intact corneal epithelium appeared concentration-, and time-dependent. The concentration of RF at 50 µm depth of chick corneal stroma increased distinctly after exposure to NC-1059 for 10 minutes, reaching a much higher, stable level by 30 minutes. The concentrations of RF in the presence of NC-1059 at corneal stromal depths of 50, 100, and 150 µm were significantly higher than in the absence of the peptide. However, they were relatively lower when compared to corneas from which the epithelium first had been removed. In addition, a cell viability assay indicated that the NC-1059 peptide did not kill corneal epithelial cells.
Conclusions: :
NC-1059 peptide can significantly enhance the diffusion of RF across intact corneal epithelium into the stroma before UVA corneal crosslinking.
Keywords: keratoconus • cornea: stroma and keratocytes • cornea: epithelium