The effect of bacteriochlorophyll derivative WST-D and near infrared light on the molecular and fibrillar architecture of the corneal stroma

Abstract

A cross-linking technique involving application of Bacteriochlorophyll Derivative WST-11 mixed with dextran (WST-D) to the epithelium-debrided cornea and illumination with Near Infrared (NIR), has been identified as a promising therapy for stiffening pathologically weakened corneas. To investigate its effect on corneal collagen architecture, x-ray scattering and electron microscopy data were collected from paired WST-D/NIR treated and untreated rabbit corneas. The treated eye received 2.5 mg/mL WST-D and was illuminated by a NIR diode laser (755 nm, 10 mW/cm2). An increase in corneal thickness (caused by corneal oedema) occurred at 1-day post-treatment but resolved in the majority of cases within 4 days. The epithelium was fully healed after 6–8 days. X-ray scattering revealed no difference in average collagen interfibrillar spacing, fibril diameter, D-periodicity or intermolecular spacing between treated and untreated specimens. Similarly, electron microscopy images of the anterior and posterior stroma in healed WST-D/NIR corneas and untreated controls revealed no obvious differences in collagen organisation or fibril diameter. As the size and organisation of stromal collagen is closely associated with the optical properties of the cornea, the absence of any large-scale changes following treatment confirms the potential of WST-D/NIR therapy as a means of safely stiffening the cornea.

Enzymatic Digestion of Porcine Corneas Cross-linked by Hypo- and Hyperosmolar Formulations of Riboflavin/ultraviolet A or WST11/Near-Infrared Light

“…We showed significant and persistent stiffening of the cornea in vivo, with X-ray diffraction and electron microscopy studies showing unaltered corneal microstructure and transparency. 13,19 Increased proteolytic activity is believed to be a major driver of disease progression in KC and corneal melting in IK. 20 Thus, after establishing biomechanical and structural effects of WST11/NIR treatment, in this study we assess its effect on resistance against enzymatic digestion.…”

Recent advances in medicinal compounds related to corneal crosslinking

“…Arie L Marcovich et al proved that WST-11 and dextran T-500 (WST-D) treatment upon near infrared (NIR) illumination consistently resulted in significant and prolonged corneal stiffening with minimal side effects. WST-D/NIR would not fundamentally change the distribution pattern of collagen fibrils, which further highlighted its safety (Hayes et al, 2020). Brekelmans et al (2017a) compressed the irradiation time to 1 min ex vivo and 5 min in vivo without affecting the stiffening effect, which saved the corneas from prolonged exposure to NIR.…”

A Review of Bacteriochlorophyllides: Chemical Structures and Applications

“…Therefore, the authors summarized that this form of treatment may become a potential therapy in low-risk cancer. In addition, a new complex contained WST-11 and dextran (WST-D) was used to treatment of stiffening pathologically weakened corneas [ 55 ]. WST-D was illuminated with near infrared and used to treat rabbit corneas.…”