Abstract
Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.
Highlights
Keratoconus (KC) is an ocular disease with a relatively high prevalence [1] usually diagnosed during the second or third decade of life that causes an irregularly shaped cornea leading to severe impairment of vision
We investigated the changes in the protein profile in tears collected from patients with dry eye syndrome and KC during treatment and explored the possible correlation of the electron paramagnetic resonance (EPR) parameters of spin probes that bind to some tear proteins with the composition of tears or ophthalmic parameters [12]
We aimed to find evidence of changes in collagen properties induced by riboflavin in the presence of UVA, and to identify the type of reactive species formed in various systems relevant for the CXL treatment of KC
Summary
1:2000) [1] usually diagnosed during the second or third decade of life that causes an irregularly shaped cornea leading to severe impairment of vision. This disease is characterized by progressive thinning of the cornea, giving rise to a cone-shaped cornea instead of the normal spherical shape [1,2]. A relatively new technique introduced in 2003 by Wollensak et al [4] is the corneal collagen cross-linking (CXL), based on the combined use of the photosensitizer riboflavin and UVA light of 370 nm This method exploits the property of riboflavin to generate, under
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