Development of a geometrically-tunable blood shunt for pediatric heart reconstruction surgery

Single-ventricle malformations are severe congenital heart defects that require life-saving reconstructive surgery, placing a blood shunt (fixed-diameter tubing) to divert blood flow to the lungs. Mortality rates are the highest in all cardiothoracic surgery. This is because shunts are unable to grow with the child, necessitating repeated surgeries to implant larger shunts. Here, we develop a light-responsive shunt that changes in diameter on demand, allowing blood flow to be tuned to meet the child’s growing needs without surgery.

Dextran was methacrylated by glycidyl methacrylate (50% substitution) and crosslinked into hydrogels (10%_w/v) by Michael-addition with dithiothreitol (DTT; DTT/methacrylate ratios of 20-50%). Hydrogel volumes and moduli were assessed at baseline and after secondary photopolymerization performed to induce de-swelling. 40% DTT/methacrylate afforded excellent volume reduction (40%) with moduli (8.46±0.67kPa) comparable to soft connective tissues and was selected for prototype development. Hydrogels did not hinder cell proliferation (PrestoBlue), induce inflammatory response (RAW-Blue reporter assay) or hemolysis (ASTM 756-13). PTFE tubing was surface modified by polydopamine to enable hydrogel adhesion. When irradiated via a fiberoptic catheter, hydrogels contracted towards the outer tubing. Clinically-indicated increases in lumen diameter (15-18%) necessary to support infant growth were obtained in <1min; changes far-exceeding clinical demands (40%) were possible. The dual-stage crosslinking approach is a promising strategy to create responsive biomedical implants that change in size, and the geometrically-tunable shunt design may prevent repeated surgeries in this fragile patient population.