A Novel Biofunctional Cryogel Scaffold for Corneal Stromal Tissue Repair

Reconstructing three-dimensional tissue structures has been a challenge for quite some time. Fortunately, the development of the scaffold-based tissue engineering approach that regulates key cellular events such as cell proliferation and matrix synthesis and delivers these engineered cell/material constructs to the sites of tissue defects, has come as a reprieve for many in this field. During scaffold fabrication, the creation of pore space is generally considered to be an important process which may facilitate nutrient accessibility and waste disposal in later cell cultivation stage, and has therefore been widely used in various tissue engineering fields. Presently, the scaffold design in a variety of gelatin-based cryogel formats is available in the scientific community. Recent studies have also demonstrated that multicomponent and responsive cryogel matrices can be reproduced to fabricate biomimetic cellular scaffolds, reflecting the importance of cryogel processing to endow the materials with multi-functionalities for tissue engineering. Nevertheless, up to date, the development of gelatin-based cryogels for ophthalmic applications is yet to be reported.

Recently, a team of researchers at Chang Gung University in Taiwan and led by professor Jui-Yang Lai developed a new biomaterial of gelatin/ascorbic acid cryogels for corneal keratocyte carriers. Consequently, they hypothesized that the introduction of varying amounts of ascorbic acid molecules into the gelatin materials could affect the structure, property, and function of cryogel matrices. Their work is currently published in the research journal, Acta Biomaterialia.

The research method employed commenced with the cross-linking of gelatin and ascorbic acid blends using carbodiimide via cryogelation technique in order to fabricate the cryogel samples. Next, they characterized the cryogels by determinations of total phenol content, functional groups, cross-linking index, porous structure, mechanical and biological stability, and in vitro and in vivo biocompatibility. Finally, the effects of the ascorbic acid content on cell culture performance was investigated and the antioxidant activity, the therapeutic efficacy of cell/cryogel constructs for corneal stromal repair examined by intrastromal implantation in alkali burn-induced model of corneal injury.

The authors observed that the hydrophilic ascorbic acid content in the carriers significantly affected the cross-linking degree and pore dimension of cryogels, thereby dictating their mechanical and biological stability and ascorbic acid release profile. The researchers also noted that the cryogel carriers with low-to-moderate ascorbic acid loadings were well tolerated by rabbit keratocyte cultures and anterior segment eye tissues, demonstrating good ocular biocompatibility. Additionally, the cytoprotective activity against oxidative stress was shown to be strongly dependent on ascorbic acid release, which further determined cell culture performance and tissue reconstruction efficiency.

Li-Jyuan Luo and colleagues study presented the successful development of gelatin/ascorbic acid cryogels for keratocyte carriers in vitro and in vivo. Experimentally, the cryogel samples were fabricated by blending of gelatin with varying amounts of ascorbic acid and carbodiimide cross-linking via cryogelation technique. Generally, it was observed that with the optimum ascorbic acid content in carrier materials, intrastromally implanted cell/cryogel constructs exhibited better capability to enhance tissue matrix regeneration and transparency maintenance as well as to mitigate corneal damage in an alkali burn-induced animal model. Altogether, their present findings give insight into the antioxidant molecule-mediated structure-property-function interrelationships in gelatin/ ascorbic acid cryogel materials for corneal stromal tissue engineering applications.