Figure 6.

Handheld in situ printers used in vivo to induce tissue regeneration and functional recovery. (A) A custom handheld printer with an integrated photocrosslinking mechanism was used for in situ printing of VEGF-eluting GelMA scaffolds to treat full-thickness porcine wounds (i). The handheld printed VEGF-positive scaffolds improved wound healing quality (ii). Significant reduction in wound contraction (iii) and enhancement in the number of Rete Ridges (iv) was reported. (B) The handheld printer was implemented to deposit filaments of nano-engineered Muscle Ink for skeletal muscle regeneration. The printer enabled the deposition of filaments aligned with remnant muscle fascicles (i). The effect of Muscle Ink printed within a murine VML injury model on functional recovery was evaluated using a treadmill (ii). The use of VEGF-eluting Muscle Ink reduced scar area (iii) improved the maximum running speed (iv) and maximum running distance (v) over uninjured controls and VEGF-negative scaffolds. (C) The printer was used to deposit filaments with multiscale porosity for VML treatment. The porous bioink was developed by stirring a GelMA precursor (i). The printed foam resulted in a scaffold with hierarchical porous structures (ii). In situ printing of the porous bioink increased muscle volume, reduced fibrosis, improved myogenesis, and enhanced innervation after VML injury (iii). The foam scaffold induced functional recovery of the injured muscle, shown by in situ twitch (iv) and tetanus strength (v) results. Adapted with permission from Elsevier [12] (A), Wiley [53] (B), and AIP publishing [18] (C).