A peptide hydrogel with an antimicrobial activity is developed as a bandage contact lens. The antimicrobial activity is enhanced with the addition of the biomolecules penicillin G or poly‐ε‐lysine and is positive against Staphylococcus aureus and Escherichia coli. The lens is also noncytotoxic toward a human corneal epithelial cell line and as a consequence is of great potential as a drug‐eluting bandage lens replacing conventional corneal ulcer treatment.

Microbial keratitis is a serious sight threatening infection affecting approximately two million individuals worldwide annually. While antibiotic eye drops remain the gold standard treatment for these infections, the significant problems associated with eye drop drug delivery and the alarming rise in antimicrobial resistance has meant that there is an urgent need to develop alternative treatments. In this work, a nitric oxide releasing contact lens gel displaying broad spectrum antimicrobial activity against two of the most common causative pathogens of microbial keratitis is described. The contact lens gel is composed of poly-ε-lysine (pεK) functionalized with nitric oxide (NO) releasing diazeniumdiolate moieties which enables the controlled and sustained release of bactericidal concentrations of NO at physiological pH over a period of 15 h. Diazeniumdiolate functionalization was confirmed by Fourier transform infrared (FTIR), and the concentration of NO released from the gels was determined by chemiluminescence. The bactericidal efficacy of the gels against Pseudomonas aeruginosa and Staphylococcus aureus was ascertained, and between 1 and 4 log reductions in bacterial populations were observed over 24 h. Additional cell cytotoxicity studies with human corneal epithelial cells (hCE-T) also demonstrated that the contact lens gels were not cytotoxic, suggesting that the developed technology could be a viable alternative treatment for microbial keratitis.

Dysfunction of the corneal endothelium (CE) resulting from progressive cell loss leads to corneal oedema and significant visual impairment. Current treatments rely upon donor allogeneic tissue to replace the damaged CE. A donor cornea shortage necessitates the development of biomaterials, enabling in vitro expansion of corneal endothelial cells (CECs). This study investigated the use of a synthetic peptide hydrogel using poly-ε-lysine (pεK), cross-linked with octanedioic-acid as a potential substrate for CECs expansion and CE grafts. PεK hydrogel properties were optimised to produce a substrate which was thin, transparent, porous and robust. A human corneal endothelial cell line (HCEC-12) attached and grew on pεK hydrogels as confluent monolayers after 7 days, whereas primary porcine CECs (pCECs) detached from the pεK hydrogel. Pre-adsorption of collagen I, collagen IV and fibronectin to the pεK hydrogel increased pCEC adhesion at 24 h and confluent monolayers formed at 7 days. Minimal cell adhesion was observed with pre-adsorbed laminin, chondroitin sulphate or commercial FNC coating mix (fibronectin, collagen and albumin). Functionalisation of the pεK hydrogel with synthetic cell binding peptide H-Gly-Gly-Arg-Gly-Asp-Gly-Gly-OH (RGD) or α2β1 integrin recognition sequence H-Asp-Gly-Glu-Ala-OH (DGEA) resulted in enhanced pCEC adhesion with the RGD peptide only. pCECs grown in culture at 5 weeks on RGD pεK hydrogels showed zonula occludins 1 staining for tight junctions and expression of sodium-potassium adenosine triphosphase, suggesting a functional CE. These results demonstrate the pεK hydrogel can be tailored through covalent binding of RGD to provide a surface for CEC attachment and growth. Thus, providing a synthetic substrate with a therapeutic application for the expansion of allogenic CECs and replacement of damaged CE.

The role of biomaterials in tissue engineering and regenerative medicine strategies to treat vision loss associated with damage to tissues in the anterior segment of the eye has been studied for several years. This has mostly involved replacement and support for the cornea and conjunctiva. These are complex tissues with specific functional requirements for different parts of the tissue. Amniotic membrane (AM) is used in clinical practice to transplant autologous or allogenic cells to the corneal surface. Fibrin gels have also progressed to clinical use under specific conditions. Alternatives to AM such as collagen gels, other natural materials, for example keratin and silks, and synthetic polymers have received considerable attention in laboratory and animal studies. This experience is building a body of evidence to demonstrate the potential of tissue engineering and regenerative medicine in corneal and conjunctival reconstruction and can also lead to other applications in the anterior segment of the eye, for example, the trabecular meshwork. There is a real clinical need for new procedures to overcome vision loss but there are also opportunities for developments in ocular applications to lead to biomaterials innovations for use in other clinical areas.

Synthetic materials have played a significant role in ophthalmic applications to improve vision for many years. This has been in four main areas in ophthalmology: ocular surface reconstruction, lens replacement, vitreous replacement and structural support and cell transplantation in the retina. Corneal replacement therapies have been developed using both synthetic acrylic-based materials and more recently naturally derived materials such as amniotic membrane.

Purpose: To investigate the effect of dehydration on human donor corneal stroma for biobanking. Methods: Epithelium and endothelium of research-grade human donor corneas (n = 12) were scraped off, leaving a bare stroma with attached sclera. The tissues were placed in a large Petri dish prefilled with silica gel in the periphery and stored at room temperature for 14 days. At the end of preservation, the tissues were rehydrated by being submerged in phosphate-buffered saline for 15 minutes. Transparency (using a custom-built device) and thickness (using optical coherence tomography) measurements were recorded before dehydration, after dehydration, and after rehydration of the tissues. Periodic acid-Schiff and alpha-smooth muscle actin (a-SMA) staining before dehydration and after rehydration were performed to determine the presence of keratocytes and expression of a-SMA. Tensile stress-strain before dehydration and after rehydration was performed to evaluate the biomechanical properties. Results: No difference in corneal transparency before dehydration (69.57 6 6.41%) and after rehydration (67.37 6 2.82%), P = 0.36, was observed. The corneas were more compact after dehydration. A significant change in thickness between before dehydration (625.8 6 75.58 mm) and after rehydration (563.6 6 15.77 mm) stage, P = 0.03, was noticed. The thickness was reduced to 147.6 6 3.71 mm when dehydrated. Periodic acid-Schiff staining showed presence of stromal keratocytes and a-SMA protein expressed in control, dehydrated, and rehydrated corneas. There was no significant difference in the stiffness between control (27.86 6 11.65 MPa) and rehydrated corneas (31.46 6 11.41 MPa). Conclusions: Human donor corneal stroma can be biobanked for up to 2 weeks in a dehydrated condition without losing their molecular or biomechanical properties after rehydration.

Microbial keratitis (MK) is a serious issue in many countries and is often caused by contact lens wear. Antimicrobial peptides (AMPs) are a potentially useful tool for creating antimicrobial surfaces in light of increasing antibiotic resistance. Poly‐ε‐lysine (pεK) is an AMP that has been used extensively as a food preservative and Mel4 has recently been synthesized and studied as an antimicrobial coating for contact lenses. A hydrogel synthesized of pεK cross‐linked with biscarboxylic acids provides a potential lens material which has many surface free amines, that can be subsequently used to attach additional AMPs, creating an antimicrobial lens. The aim of this study is to investigate pεK hydrogels against a clinical strain of Pseudomonas aeruginosa (P. aeruginosa) for preventing or treating MK. Covalent attachment of AMPs is investigated and confirmed by fluorescently tagged peptides. Bound pεK effectively reduces the number of adherent P. aeruginosa in vitro (>3 log). In ex vivo studies positive antimicrobial activity is observed on bare pεK hydrogels and those with additionally bound pεK or Mel4; lenses allow the maintenance of the corneal epithelium. A pεK hydrogel contact lens with additional AMPs can be a therapeutic tool to reduce the incidence of MK.

Forming thin tissue constructs with minimal extracellular matrix surrounding them is important for tissue engineering applications. Here, we explore and optimize a strategy that enables rapid fabrication of scaffold-free corneal tissue constructs using the liquid–liquid interface of an aqueous two-phase system (ATPS) that is based on biocompatible polymers, dextran and polyethylene glycol. Intact tissue-like constructs, made of corneal epithelial or endothelial cells, can be formed on the interface between the two liquid phases of ATPS within hours and subsequently collected simply by removing the liquid phases. The formed corneal cell constructs express essential physiological markers and have preserved viability and proliferative ability in vitro. The corneal epithelial cell constructs are also able to re-epithelialize the corneal epithelial wound in vitro. The results suggest the promise of our reported strategy in corneal repair.