Fresh porcine liver tissues were obtained from local slaughterhouses, cut into ~1 cm cubes, and put in a 2 L Erlenmeyer flask. The cubes were rinsed with doubly deionized (DDI) water then soaked in 1.5 L decellularization solution composed of 0.5% Triton X-100 (A16046.AP, Thermo Fisher, Pittsburgh, PA, USA) and 47.6 mM ammonium hydroxide (AX1303-3, MilliporeSigma, St. Louis, MO, USA) and placed on a stir plate in 4 °C, stirring at 180 rpm. The decellularization solution was changed every 24 hours for 7 days. The decellularized ECM (dECM) was then thoroughly rinsed with DDI water, patted dry with paper towels, placed in two 250 mL weigh boats (10803-170, VWR International, Radnor, PA, USA), and frozen at -80 °C, after which it was lyophilized and ground into a coarse powder. A total of 300-400 mg of coarsely powdered dECM was digested with 40 mL of 3500 U/mL pepsin (P7000, MilliporeSigma, St. Louis, MO, USA) in 0.01 M HCl solution for 24 hours at 37 °C on an orbital shaker, 60 rpm. The solution was neutralized with 0.1 M NaOH to pH 8.0 to permanently denature the pepsin. The digested dECM solution was centrifuged for 20 min at 10,000 x g, 4 °C in a high-speed centrifuge (Avanti J-E, Beckman Coulter, Brea, CA, USA), the supernatant collected in 50 mL conical tubes, lyophilized for 72 hours and stored in -20 °C.