Tuning electrospun substrate stiffness for the fabrication of a biomimetic amniotic membrane substitute for corneal healing

Corneal blindness is the fourth most common cause of vision impairment worldwide with a high incidence in global south countries. A recently developed surgical technique for treating corneal blindness is simple limbal epithelial transplantation (SLET), which uses small pieces of healthy limbal tissue (limbal explants) delivered to the damaged eye using the human amniotic membrane (AM) as a carrier. SLET relies on the use of tissue banks for the AM that reduces the availability of the technique. Replacing the AM with a synthetic membrane is key to making SLET more accessible to those who need it. Previous research has demonstrated the suitability of electrospun poly(lactide-co-glycolide) (PLGA) scaffolds as AM substitutes, and here, we report how these membranes can be tailored to mimic fundamental AM mechanical properties. To modify the stiffness of PLGA electrospun membranes, we explored different electrospinning solvent systems (1,1,1,3,3,3,-hexafluoroisopropanol (HFIP), dichloromethane (DCM), chloroform, and N,N-dimethylformamide (DMF)) and the use of plasticizers (PEG400 and glycerol). PEG400 was found to reduce stiffness from 60 MPa to around 4 MPa, approaching the values shown by the native AM. The biocompatibility of membranes with and without PEG400 was found to be comparable, and cell outgrowth from rabbit/porcine explants was successfully observed on the materials after 3 weeks. This research underpins the manufacture of next-generation fibrous biomimetic membranes that will ultimately be used as amniotic membrane substitutes for biomedical applications including SLET.