title: Treatment of Silk Fibroin with Poly(ethylene glycol) for the Enhancement of Corneal Epithelial Cell Growth.
abstract: A silk protein, fibroin, was isolated from the cocoons of the domesticated silkworm (Bombyx mori) and cast into membranes to serve as freestanding templates for tissue-engineered corneal cell constructs to be used in ocular surface reconstruction. In this study, we sought to enhance the attachment and proliferation of corneal epithelial cells by increasing the permeability of the fibroin membranes and the topographic roughness of their surface. By mixing the fibroin solution with poly(ethylene glycol) (PEG) of molecular weight 300 Da, membranes were produced with increased permeability and with topographic patterns generated on their surface. In order to enhance their mechanical stability, some PEG-treated membranes were also crosslinked with genipin. The resulting membranes were thoroughly characterized and compared to the non-treated membranes. The PEG-treated membranes were similar in tensile strength to the non-treated ones, but their elastic modulus was higher and elongation lower, indicating enhanced rigidity. The crosslinking with genipin did not induce a significant improvement in mechanical properties. In cultures of a human-derived corneal epithelial cell line (HCE-T), the PEG treatment of the substratum did not improve the attachment of cells and it enhanced only slightly the cell proliferation in the longer term. Likewise, primary cultures of human limbal epithelial cells grew equally well on both non-treated and PEG-treated membranes, and the stratification of cultures was consistently improved in the presence of an underlying culture of irradiated 3T3 feeder cells, irrespectively of PEG-treatment. Nevertheless, the cultures grown on the PEG-treated membranes in the presence of feeder cells did display a higher nuclear-to-cytoplasmic ratio suggesting a more proliferative phenotype. We concluded that while the treatment with PEG had a significant effect on some structural properties of the B. mori silk fibroin (BMSF) membranes, there were minimal gains in the performance of these materials as a substratum for corneal epithelial cell growth. The reduced mechanical stability of freestanding PEG-treated membranes makes them a less viable choice than the non-treated membranes.
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. shuko.suzuki@qei.org.au.
authors.forename: Shuko
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. r2.dawson@qut.edu.au.|School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia. r2.dawson@qut.edu.au.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Dawson
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. traian.chirila@qei.org.au.|Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland 4001, Australia. traian.chirila@qei.org.au.|Faculty of Medicine and Biomedical Sciences, University of Queensland, Herston, Queensland 4029, Australia. traian.chirila@qei.org.au.|Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Queensland 4072, Australia. traian.chirila@qei.org.au.|Faculty of Science, University of Western Australia, Crawley, Western Australia 6009, Australia. traian.chirila@qei.org.au.
authors.forename: Traian V
authors.initials: TV
authors.lastname: Chirila
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. audra.shadforth@qei.org.au.|School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia. audra.shadforth@qei.org.au.
authors.forename: Audra M A
authors.initials: AM
authors.lastname: Shadforth
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. thomas.hogerheyde@qei.org.au.|School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia. thomas.hogerheyde@qei.org.au.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland 4059, Australia. thomas.hogerheyde@qei.org.au.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Hogerheyde
authors.affiliation: Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Queensland 4072, Australia. g.edwards1@uq.edu.au.
authors.forename: Grant A
authors.initials: GA
authors.lastname: Edwards
authors.affiliation: Queensland Eye Institute, South Brisbane, Queensland 4101, Australia. d.harkin@qut.edu.au.|School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia. d.harkin@qut.edu.au.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland 4059, Australia. d.harkin@qut.edu.au.
authors.forename: Damien G
authors.initials: DG
authors.lastname: Harkin
keywords: Bombyx mori silk fibroin; cell attachment; corneal epithelial cells; membranes; permeability; poly(ethylene glycol); porosity; silk; surface topography