Biodegradable Polymers as Potential Carrier Substrates for Ocular Surface Reconstruction

Abstract

Purpose: : In order to find alternatives for ocular surface reconstruction, we investigated several polymers that mimic the characteristics of extracellular matrix. Surgical stitch resistance, cell proliferation, viability, and characterization were tested on seven types of biopolymers based on chitosan (CH), polylactic acid (PLA) and PLA-collagen (PLA-C).

Methods: : : PLA and CH were prepared as thick films by a solvent casting technique. A 2% PLA solution was prepared by dissolving the polymer in dioxane and evaporated over 24 h. 1% and 2% CH solutions were prepared by dissolving the CH in 1% acetic acid in ultrapure water. Additionally, 4 types of PLA films were used: pure PLA and PLA-C were activated with NaOH and made functional with 3 collagen type I concentrations (25, 50, 100 µg/ml). Corneal epithelial cells (HCE cell line) were seeded onto these films and cultured for 8 days. Amniotic membrane (AM) was used as control substrate. To study cell proliferation, culture medium was collected after 1, 2, 4, and 8 days and Alamar blue test was used. Cell viability was assessed after 6h, 1, 2, and 4 days using the Calcein/EthDIII kit. Immunostaining and real time PCR was performed for several cytokeratins (K3, K7, K12, and K19) and adhesion proteins (E-cadherin, ZO-1, desmoplakin, connexin 43, and sprr2).

Results: : Surgical stitches could be placed in 2% PLA, 1% CH, and 2% CH. Only cells grown on 2% PLA showed an increased proliferation after 8 days in culture when compared to AM. Cell viability was higher on pure PLA and 2% PLA (99-100%) compared to that on AM (97%) after 2 days; however, after 4 days, cell viability was increased (98-100%) with all polymers compared to that of AM. Epithelial cells grew and proliferated on all films and they expressed all the corneal and adhesion markers tested. The highest gene expression was obtained for 2% PLA biopolymers.

Conclusions: : : Among all films tested, 2% PLA was the best substrate to support epithelial cell attachment and growth and to resist surgical stitches. Therefore, these biopolymers can be further considered as potential candidates for ocular surface reconstruction.

Keywords: cornea: epithelium • cell adhesions/cell junctions • proliferation