Development of a Geometrically Tunable Cardiovascular Shunt for Pediatric Heart Reconstruction
Thursday, June 25, 2026
10:00 AM-12:00 PM
BIOMED PhD Thesis Defense
Title:
Development of a Geometrically Tunable Cardiovascular Shunt for Pediatric Heart Reconstruction
Speaker:
Akari Seiner, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University
Advisor:
Christopher Rodell, PhD
Associate Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University
Details:
Congenital heart defects (CHDs) are the most common class of birth anomalies, affecting approximately 1% of live births globally and representing a leading cause of infant morbidity and mortality worldwide. A critical subset, collectively termed single ventricle (SV) defects, are characterized by the functional or morphological inadequacy of one ventricle, leaving a single dominant ventricle to simultaneously support both pulmonary and systemic circulations. Among these, hypoplastic left heart syndrome (HLHS) is the most prevalent and severe, accounting for 25 – 40% of all neonatal cardiac deaths. Without surgical intervention, SV defects are universally fatal. The current standard of care is staged palliative reconstruction, the Norwood–Glenn–Fontan procedure, in which the initial Norwood procedure establishes parallel circulation via implantation of a fixed-diameter modified Blalock–Taussig–Thomas (mBTT) shunt. Despite decades of iterative refinement of surgical procedures and post-operative care, interstage mortality remains as high as 39%, with nearly 48% of patients requiring invasive shunt revision due to the device's inability to accommodate the rapid somatic growth of the developing infant. These persistent limitations motivate the development of a geometrically adaptive shunt capable of dynamically adjusting its lumen diameter without reoperation.
To address these limitations, this work develops a geometrically tunable cardiovascular shunt for pediatric heart reconstruction. Photoresponsive methacrylated dextran (DexMA) hydrogels were synthesized and integrated as luminal linings within polytetrafluoroethylene (PTFE) and expanded PTFE (ePTFE) shunt conduits. A dual-stage crosslinking strategy — combining covalent Michael addition crosslinking with a secondary blue-light photopolymerization step — was established to achieve controlled volumetric contraction of the hydrogel lining upon irradiation, thereby expanding the inner lumen diameter. Systematic investigation of polymer modification, concentration, and dithiothreitol (DTT)-to-methacrylate molar ratios yielded an optimized formulation of 50% modified DexMA at 10%w/v with a 40% DTT/methacrylate ratio. With this formulation, volume changes exceeding 39% were achieved, enabling clinically relevant increases in lumen diameter. Building on this material platform, comprehensive biological safety was established in accordance with ASTM and ISO standards. Hydrogels exhibited excellent long-term hydrolytic stability (> 3 months), cytocompatibility (including both 3T3 fibroblast and HUVEC cell lines), lack of immune response (RAW264.7 cells, primary human PBMCs), and hemocompatibility (absence of complement activation, platelet aggregation, or hemolysis) across hydrogel formulations, collectively demonstrating the platform's suitability for a blood-contacting vascular environment.
The hydrogel platform was integrated into full-scale shunt prototypes using polydopamine (PDA)-mediated surface functionalization to ensure robust hydrogel-to-PTFE interfacial bonding. Incremental exposure to catheter-delivered blue light via a fiber-optic radial diffuser produced precise lumen diameter expansion up to 40%. Programmable expansion patterns, including incremental weekly increases and one-time targeted adjustments, remained structurally stable over one month. These results were subsequently translated to clinical-grade ePTFE, where comprehensive multi-axial mechanical characterization demonstrated dimensional stability under physiological arterial pressures up to 160 mmHg, and light-activated expansion in ePTFE was statistically equivalent to that achieved in rigid PTFE prototypes.
Evaluation of the tunable shunt under simulated physiological flow conditions was performed using ASTM F1841-19 compliant dynamic hemocompatibility testing and an ex vivo perfusion platform. Dynamic hemocompatibility confirmed that the hydrogel lining does not introduce additional hemolytic shear compared to controls. Hemodynamic perfusion testing over a flow range of 300 – 1000 mL/min demonstrated a highly linear pressure-flow relationship (R² = 0.99), consistent with the physiological range of neonatal cardiac output. Non-invasive nanoCT imaging of shunts before and after flow exposure confirmed structural integrity and dimensional stability of the inner lumen, with no significant differences in lumen diameter or circularity. Together, these findings establish proof-of-concept for a light-responsive, geometrically tunable cardiovascular shunt capable of accommodating infant growth through minimally invasive catheter-based actuation, offering a promising strategy to reduce interstage mortality and reintervention burden in pediatric SV palliation.
Contact Information
Natalia Broz
njb33@drexel.edu