Peg ac

To form the hydrogel network, 2, 4, or 8-arm PEG-VS, PEG-Ac and PEG-Mal (JenKem Technology, Beijing, China) macromer powder was dissolved in sterile Dulbecco’s Phosphate Buffered Saline(DPBS) (pH 7.4, Gibco, USA) solution and 0.4 mg/100μL of photo-initiator Irgacure 2959 (Ciba, Basel, Switzerland, MW=224.3) to create a solid concentration of 5% w/v. Furthermore, a co-monomer, N-vinyl-2-pyrrolidone (NVP) (Sigma-Aldrich, USA), was added in some compositions at a final concentration of 0.1%, as NVP has been shown to enhance the gelation mechanism without impacting the cell compatibility [35 (link)]. To form the gels, the precursor solution (PEG, Irgacure 2959 and NVP (in some compositions)) was exposed to UV light at a constant intensity (1090 μW/cm² at a distance of 4 cm) for a designated duration.

PEG hydrogels were prepared by Michael-type addition reaction between PEG-dithiol (PEG-diSH; Laysan Bio Inc., Arab, AL) and 4-arm PEG acrylate (PEGAc; Jenkem Technology, Piano, TX).²¹ To prepare a 10% w/v gel, PEG-diSH and PEGAc were combined in a 1:1 molar ratio of Ac:SH in 0.3 M triethanolamine (TEA), pH 7.4. PRGF was added at 10% w/v. The solution was placed between two parafilm-lined glass slides separated by 0.5 mm silicon spacers and incubated at 22°C for 1 h for gelation.