I am trying to make a hydrogel from the bovine Urinary Bladder Matrix (UBM), but can't get any hydrogel from the digested matrix using pepsin.

Despite the complete digestion of both 10 and 20 % matrix as well as the bladder itself using 0.1 % of the enzyme as in the published papers, but no hydrogel was formed at all after the neutralization of the enzyme action at pH 10, and incubation of the pre-gel solution (pH 7.4) for a long period at 37oC.

Any suggestions regarding this issue?