Genipin is a naturally occurring cross-linker derived from the plant Gardenia jasminoides that has low cytoxicity and can form stable and biocompatible cross-linked products [1]. Many laboratory studies have been conducted into the use of genipin cross-linking to enhance the biostability of collagen/chitosan scaffolds for ocular surface reconstruction [2-3], myocardial [4] and cartilage tissue regeneration [5] and numerous other applications. Its ability to strengthen the sclera has also highlighted the potential usefulness of genipin cross-linking in stabalising ocular tissue to prevent myopia progression [6]. In terms of the cornea, laboratory studies have also shown that removal of the corneal epithelium, followed by a 30-minute application of 0.25% genipin produces a stiffening effect that is comparable to that achieved with riboflavin/UVA cross-linking [7].  However, unlike riboflavin/UVA cross-linking which results in a loss of corneal cells (keratoyctes) from the anterior 300μm of the corneal stroma, minimal keratocyte apoptosis occurs immediately after genipin cross-linking [8], and even after 14-days there is only a small amount of keratocyte loss in the anterior 50μm of the stroma [7]. Further to this, significant corneal flattening has been recorded in genipin-treated rabbit corneas at 60-day follow-up, with minimal blue staining of the cornea (caused by the blue pigment of genipin) and no damage to the endothelium [9]. Although the potential of this cross-linker is clear and further testing is warranted, the dose-dependent discolouration of the transparent cornea may prove to be a limiting factor in its clinical usefulness for the management of corneal disorders, such as keratoconus.

1.. Sung H., et al. Feasibility study of a natural crosslinking reagent for biological tissue fixation. J Biomed Mater Res. 1998; 42: 560-567.

2. Grolik M., et al. Hydrogel membranes based on genipin-cross-linked chitosan blends for corneal epithelium tissue engineering. J Mater Sci Mater Med. 2012; 23: 1991-2000.

3. Li Y., et al. Characterization of the modified chitosan membrane cross-linked with genipin for the cultured corneal epithelial cells. Colloids and Surfaces B: Biointerfaces. 205; 126: 237-244.

4. Fang Y., et al. Assessment of various crosslinking agents on collagen/chitosan scaffolds for myocardial tissue engineering. Biomed Mater. 2020. 15: 045003.

5. Yan L., et al. Genipin-cross-linked collagen/chitosan biomimetic scaffolds for articular cartilage tissue engineering applications. J Biomed Mater Res A. 2010; 95: 465-475.

6. Liu T and Z Wang. Collagen crosslinking of porcine sclera using genipin. Acta Ophthalmologica. 2013; 91: e253-e257.

7. Tang Y., et al. A study of corneal structure and biomechanical properties after collagen crosslinking with genipin in rabbit corneas.Mol Vis. 2019; 25: 574-582.

8. Song W et al. The comparative safety of genipin versus UVA-riboflavin crosslinking of rabbit corneas. Mol Vis. 2017; 23: 504-513.

9. Avila M., et al. Effects of genipin corneal crosslinking in rabbit corneas. J Cataract Refract Surg. 2016. 42: 1073-1077.