PEG Microgel Electrospraying for Tissue Engineering

PEG microgel electrospraying setup was similar to the previously reported approach.³³ Based on the gel table (Table S1), PEG-Nb and PEG-DT were mixed off-stoichiometrically so that 25% excess norbornene groups were available for further photocrosslinking of microgels. The mixed precursor solutions were electrosprayed into a bath of light mineral oil with Span 80 (0.5 wt%) and photopolymerized into microgels with UV irradiation (60 mW cm⁻², 365 nm). The UV light was kept on for 2 minutes after all precursor solutions were sprayed. The microgels were rinsed with phosphate buffered saline (PBS) three times and centrifuged at 4,400 rpm for 5 minutes to remove the mineral oil. The microgels were stored in PBS at 4 °C and allowed to reach equilibrium swelling before use.