Figure 6.

2B hydrogel systems, which have a secondary mechanism of action, and need manufacturing validation, are summarized. (A) This schematic outlines an extrusion-based method of collagen 3D printing with alternating layers of keratinocytes and fibroblasts. [197] (B) A schematic of the approach to alginate-based 3D printing of MSCs along with sweat gland ECM containing growth factors for sweat gland regeneration. [198] (C) This study develops a 3D printed human airway epithelium using thermoresponsive collagen hybrid gel embedded with human bronchial epithelial cells and human bronchial fibroblasts. [199] (D) This depicts 3D-printing of GelMA along with ASCs that secrete neurotrophic factors in a secondary mechanism of action as nerve guidance conduits that promote peripheral nerve regeneration. [200]