Papain digest

Lyophilized decellularized cardiac extracellular matrix samples were massed to obtain dry weight prior to digestion. The papain digest solution was prepared by adding 0.125 mg papain / mL (Sigma, St. Louis, MO) and 0.10M L-cysteine (Sigma, St. Louis, MO) to phosphate-buffered EDTA (PBE) buffer (0.1 M Na₂HPO₄, 0.01 M Na₂EDTA, pH 6.5). Samples were digested in 1 mL of papain digestion solution and incubated at 60C for 12-16 hours or until samples were fully digested. Following complete digestion, samples would be split for either hydroxyproline quantification or glycosaminoglycan quantification.