Abstract
Transparent composite hydrogel in the form of a contact lens made from poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) was subjected to in vitro biocompatibility evaluation with human corneal epithelial cells (HCE-2 cells). The cell response to direct contact with the hydrogels was investigated by placing the samples on top of confluent cell layers and evaluating cell viability, morphology, and cell layer integrity subsequent to 24 h culture and removal of the hydrogels. To further characterize the lens–cell interactions, HCE-2 cells were seeded on the hydrogels, with and without simulated tear fluid (STF) pre-conditioning, and cell viability and morphology were evaluated. Furthermore, protein adsorption on the hydrogel surface was investigated by incubating the materials with STF, followed by protein elution and quantification. The hydrogel material was found to have affinity towards protein adsorption, most probably due to the interactions between the positively charged lysozyme and the negatively charged CNCs embedded in the PVA matrix. The direct contact experiment demonstrated that the physical presence of the lenses did not affect corneal epithelial cell monolayers in terms of integrity nor cell metabolic activity. Moreover, it was found that viable corneal cells adhered to the hydrogel, showing the typical morphology of epithelial cells and that such response was not influenced by the STF pre-conditioning of the hydrogel surface. The results of the study confirm that PVA-CNC hydrogel is a promising ophthalmic biomaterial, motivating future in vitro and in vivo biocompatibility studies.
Highlights
Cornea is the transparent tissue that, together with sclera, forms the anterior surface of the human eye
We have previously reported the synthesis process of cellulose nanocrystal (CNC)-reinforced poly(vinyl alcohol) (PVA) hydrogel following a physical route of crosslinking by cryogelation from a mixed dimethyl sulfoxide (DMSO)/water solvent system [38,39]
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Summary
Cornea is the transparent tissue that, together with sclera, forms the anterior surface of the human eye. The ability to see properly depends on the optical properties of the cornea, since two-thirds of the refractive power of the eye is due to the cornea while the remaining one-third is due to the eye lens [1]. The tear film has an important role in enabling optical functions of the cornea by forming a thin smooth liquid surface, which minimizes undesired surface scattering. Any damage to the cornea due to accident or infection leads to impaired vision and blindness. It is estimated that about 23 million people worldwide are corneal blind at least in one eye [4]
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