Growth-factor controlled release in silk fibroin-based corneal bandages

Abstract

Purpose : Amnion membrane (AM) dressing is a standard-of-care for the treatment of corneal wounds or burns, although limitations include potential for an immunological response, non-transparency, and relatively high cost. We have developed silk fibroin (SF) membranes as an accessible, transparent, manageable, and biocompatible treatment alternative. We describe the development and characterization of loading and release of GF on SF-based corneal bandages

Methods : SF was extracted from silkworm cocoons using standard procedures. Membranes were obtained by evaporation in a climatic chamber at and cross-linked using polyethylene glycol (SF-PEG bandage). Two GFs were used: epidermal (EGF) and hepatic (HGF). Two loading procedures were tested: immersion GFs for 24 hours at room temperature in 2 ml of 0.4 µg/ml for EGF for HGF (soak), and by covalent binding of GFs to the membrane by carbodiimide reaction (EDC). Aliquots of 200 µl were taken every 24 hours. The aliquots were analyzed using Human EGF and HGF enzyme-linked immunosorbent assay (ELISA) kits. Statistical differences (p<0.01) across GF loading methods and concentrations were evaluated by ANOVA with a subsequent parametric Bonferroni test for multiple comparisons.

Results : Soaking resulted in a more rapid release than EDC in all cases. With the soaking procedure, the EGF was released at a rate of 6%/day during the first 2 days, with 18% being released by day 5, and 15-20% released by day 32; the HGF was released at higher rates, with no measurable HGF content by day 22. In contrast, EDC release was longer sustained in time, with rates of 3% (1), 1.5% (5), and 0.75% (10) for EGF during the first 2 days and 5%/day (0.4) and 3%/day (0.8) during the first 2 days for HGF. Differences between soak and EDC processes were statistically significant (p<.0.001) both for EGF and HGF. Differences between concentrations were statistically significant for EFG (p=0.01) and HGF (p=0.01).

Conclusions : SF-PEG bandages aiming at replacing AM treatments for corneal wounds can be loaded with growth factors, and their release (rate and duration) can be modulated by the loading mode and the GF concentration. Growth Factor Loaded silk fibroin-PEG bandages can provide an affordable alternative to AM treatments.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.