Hydrogel tubes were generated as previously described.52 (link) Briefly, 20% w/v 8-arm polyethylene glycol maleimide (PEG-MAL, 20 kDa; JenKem, Plano, TX) was crosslinked with 5 mM slow-degrading-plasmin-sensitive YKND cross-linking peptide (Ac-GCYKNDGCYKNDCG; Genscript, Piscataway, NJ)55 (link) to form microspheres through water-oil emulsion with diameters ranging between 15 and 150 μm and an average of 45 μm. The PEG-YKND solution was homogenized in silicone oil (Fisher, Hampton, NH) with 2% TWEEN-20 (Sigma, St. Louis, MO) at a speed of 4000 rpm for 1 minute. Microspheres were rinsed by centrifugation three times. Irgacure 2959 photoinitiator (Sigma) dissolved in N-vinylpyrrolidinone (660 mg/mL; Sigma) was added to the microspheres at a final concentration of 1% w/v. The resulting microspheres were then packed into polydimethylsiloxane (PDMS, Dow Corning, Midland, MI) molds to generate PEG tubes (approximate OD: 600 μm, ID: 250 μm, porosity: 66%)and exposed to an ultraviolet lamp for 3 minutes to initiate free radical polymerization. Tubes were rinsed three times, dehydrated, and stored at −80 until use. Tubes were cut to length during surgery to ensure fit within the defect.