a composite biocompatible hydrogel material includes a porous polymer matrix , the polymer matrix including a plurality of pores and providing a young &# 39 ; s modulus of at least 10 gpa . a calcium comprising salt is disposed in at least some of the pores . the porous polymer matrix can comprise cellulose , including bacterial cellulose . the composite can be used as a bone graft material . a method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix , the polymer matrix including a plurality of pores and providing a young &# 39 ; s modulus of at least 10 gpa , and inserting the hydrogel material into cartilage or bone tissue of an animal , wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding .