Exploiting synergistic effect of CO/NO gases for soft tissue transplantation using a hydrogel patch.

Autologous skin flap transplantation is a common method for repairing complex soft tissue defects caused by cancer, trauma, and congenital malformations. Limited blood supply range and post-transplantation ischemia-reperfusion injury can lead to distal necrosis of the flap and long-term functional loss, which severely restricts the decision-making regarding the optimal surgical plan. To address this issue, we develop a hydrogel patch that releases carbon monoxide and nitric oxide gases on demand, to afford a timely blood supply for skin flap transplantation during surgery. Using an ischemia-reperfusion dorsal skin flap model in rats, we show that the hydrogel patch maintains the immediate opening of blood flow channels in transplanted tissue and effective blood perfusion throughout the perioperative period, activating perfusion of the hemodynamic donor site. We demonstrate that the hydrogel patch promotes distal vascularization and long-term functional reconstruction of transplanted tissues by inhibiting inflammatory damage and accelerating blood vessel formation.