A biocompatible and electrically conductive three-dimensional (3D) hydrogel comprising nanocellulose, wherein the 3D hydrogel in its final form for bioprinting or injecting into tissue is non-dried, wherein the nanocellulose comprises one or more of bacterial cellulose, cellulose nanofibrils, cellulose nanocrystals, or disintegrated bacterial cellulose, wherein the nanocellulose is isolated from tunicates, bacteria, plants, and/or algae, wherein the non-dried 3D hydrogel further comprises graphitic-based electrically conductive nanomaterials, and wherein the non-dried 3D hydrogel in its final form is bioprinted to form three-dimensionally bioprinted structures or injected into tissue.