The CoraLite Plus 488-conjugated Collage Type I Monoclonal antibody (CL488-67288, Proteintech, Rosemont, IL, USA) was used to label the dECM inserts to visualize collagen from the extracted ECM in the nanofibers. The inserts were rinsed 3x with PBS, fixed for 10 min in 4% paraformaldehyde solution, rinsed 3x in wash buffer (PBS + 0.1% Tween 20) for 5 min, and gently rocked in blocking solution (PBS + 0.1% Tween 20 + 1% bovine serum albumin (0332-25G, VWR International, Radnor, PA, USA)) for 60 min at room temperature. The blocking solution was then replaced with 1 mL of antibody solution (1:200 dilution of antibody in blocking solution). The insert was rocked gently overnight at 4 °C, covered with foil to protect it from light. The insert was then washed 3x in wash buffer for 5 min and placed on a WillCo glass bottom dish (HBSB-5040, WillCo Wells, Amsterdam, The Netherlands) with 20 µL SlowFade Diamond Antifade Mountant (S36972, Thermo Fisher, Pittsburgh, PA, USA).