There is provided a method of forming a hydrogel, the method comprising: providing a mixture of a polymer comprising a cross-linkable pendant phenolic group, peroxidase, H2O2, fibrinogen, and thrombin, at concentration sufficient to enzymatically cross-link the polymer and to cleave the fibrinogen to yield fibrin; and allowing the mixture to form a hydrogel. There is also provided a hydrogel comprising a cross-linked network of a polymer interpenetrated by fibrin fibers, the polymer cross-linked by oxidative coupling between phenolic groups pendant on the polymer.