Sf solution

A total of 5% (w/v) SF solution (Sigma, St. Louis, MO, USA) derived from Bombyx mori cocoons was dialyzed against 10% polyethylene glycol (PEG) (Sigma, St. Louis, MO, USA, MW 10,000) solution in 3 mL 3.5K MWCO Slide-A-LyzerTM dialysis cassettes (Sigma, St. Louis, MO, USA) for 20 h to prepare a concentrated SF solution. After dialysis, the resulting SF solution volume should be around 3.5 mL, which is approximately 14.29% in concentration. The concentrated SF solution was then re-diluted to 8% (w/v) with ultrapure water (Invitrogen, Waltham, MA, USA) and mixed with 10% (w/v) polyethylene oxide (PEO) (Sigma, St. Louis, MO, USA, MW~900,000) solution to obtain a final concentration of 6.37% (w/v) SF and 2% (w/v) PEO solution for electrospinning. PEO solution of 10% (w/v) was obtained by adding PEO to ultrapure water and stirring for 24 h at room temperature.

HA (Mw ≈ 180 kDa, MB7259‐1) was obtained from Meilunbio®. SF solution (Mw ≈ 100 kDa, 5154) was obtained from Sigma. Hexafluoroisopropanol (HFIP, 920‐66‐1) was purchased from Aladdin. Dulbecco's modified Eagle's medium (DMEM, 10567022), fetal bovine serum (FBS, 12483020), penicillin/streptomycin (P/S, 10378016), trypsin (0.25%, 15,050,057), phosphate‐buffered saline (PBS, pH 7.4, 10,010,023), Rhodamine‐ and Alexa Fluor‐488 conjugated phalloidin (R415 and A12379), DAPI (62248) were purchased from Gibco. Primary antibodies to cytokeratin‐5 (K5, ab75869), uroplakin‐3 (ab187646), α‐smooth muscle actin (α‐SMA, ab5694), CD31 (ab24590), and Ki67 (ab15580), and secondary antibodies for fluorescence staining were purchased from Abcam.