Reactive oxygen species accelerated glycation for oxygen-independent corneal cross-linking

The pentose-initiated Maillard reaction may serve as an oxygen-independent, non-enzymatic crosslinking (CxL) mechanism, but its slow kinetics limit clinical applicability. We hypothesize that glycation-mediated CxL can be accelerated by reactive oxygen species (ROS), potentially enabling its use in the treatment of keratoconus.

Rabbit corneal buttons were exposed to 20% ribose and irradiated with femtosecond oscillator laser pulses at 450 mW (1,069 nm) and 250 mW (400 nm). In addition to laser-based light sources, a 365 nm UVA lamp at 3 mW/cm² was used in combination with either ribose or riboflavin-5-phosphate to generate comparison and control groups. ROS-Glycation-CxLed corneas were flattened with a glass coverslip to minimize oxygen replenishment. Crosslinking efficacy was assessed using 5 µm micro-indentation to measure the equilibrium modulus and viscoelastic ratio post-treatment.

Corneal tissues subjected to ROS-glycation-CxL exhibited a significant increase in equilibrium modulus. The modulus change in ribose-exposed tissues treated with UVA light was comparable to that observed with the conventional UVA-riboflavin CxL pathway. In contrast, infrared and blue laser-treated samples showed less stiffening, likely due to the limited tissue volume affected by the laser's focal region. Notably, only the UVA-riboflavin-treated tissues demonstrated a pronounced elastic load-relaxation response.

ROS-Glycation-CxL offers a potential alternative to existing crosslinking techniques, with crucial advantages such as reduced oxygen reliance, light-source agnostic mechanism, and customizable treatment patterns with laser light sources. Further investigation is needed to evaluate the clinical viability of ROS-glycation CxL through optimization of sugar concentration, treatment duration, and assessment of stromal extracellular matrix ultrastructure.