The effects of processing variables on electrospun poly(ethylene glycol) fibrous hydrogels formed from the thiol-norbornene click reaction

Electrospinning has been used to create scaffolds with tunable micro/nano architecture, stiffness, and porosity to mimic native extracellular matrix. This study investigated the effects of electrospinning parameters and hydrogel formulation (solvent and crosslinker type) on the architecture and properties of fibrous poly(ethylene glycol) (PEG) hydrogels formed from a photoclick thiol-norbornene reaction. Fibrous hydrogels were prepared using hydrogel precursors (four-arm PEG norbornene and multi-thiol crosslinker), sacrificial poly(ethylene oxide) (PEO, 400 kDa), and photoinitiator (I2959) in either 2,2-triflouroethanol (TFE) or water. Three thiol crosslinkers- 2,2′-(ethylenedioxy)diethanethiol (EDT), pentaerythritol tetrakis(3mercaptopropionate) (PTMP), and PEG dithiol (PEGDT)- were investigated. Fibrous PEG networks with uniform fibers were produced at applied voltages of 10 or 12 kV for TFE and 16 kV for water. Fiber diameters of electrospun hydrogels were largely affected by the solvent when combined with PEO concentration and ranged from 0.5 to 3.5 mm in dry state. While the effect of crosslinker type on fiber diameter, morphology, and porosity of the fibrous hydrogel was minimal, it did modulate its shear modulus. To this end, this study provides the groundwork for selecting processing parameters to achieve desired properties of fibrous PEG thiol-norbornene hydrogels for intended tissue engineering applications ranging from neural, cardiovascular to musculoskeletal.