Alexander Roussas

Biomedical engineering

Hometown: Scottsdale, Arizona, United States

Graduation date: Spring 2026

Additional details: Honors student

FURI | Spring 2026

Effect of Iron Nanoparticle Concentration, pH, and Buffer Strength on the Gelation Kinetics and Mechanical Strength of PPODA-QT Hydrogels for Aneurysm Embolization

Cerebral aneurysms remain a significant clinical concern, particularly in cases where current endovascular treatments require adjunctive support to achieve stable occlusion. PPODA-QT hydrogels are promising liquid embolic candidates because they polymerize in situ under mild conditions and may be adapted for minimally invasive neurovascular delivery. This project examines how iron nanoparticle concentration, pH, and buffer strength influence two key performance metrics of PPODA-QT hydrogels: gelation time and mechanical stiffness. The broader objective is to support development of an embolic formulation that is not only injectable and image-compatible, but also capable of rapid setting and sufficient post-gelation strength for aneurysm stabilization.

Analysis of gelation time data indicates that pH is the dominant factor controlling curing speed, with increasing pH causing a dramatic reduction in gelation time. Formulations at pH 10 required many hours to set, whereas gels formulated at pH 12 cured within minutes. Increasing buffer strength also accelerated gelation, with higher ionic conditions further reducing cure time across many groups. In contrast, increasing nanoparticle concentration generally slowed gelation, suggesting that added particles may interfere with rapid crosslinking, potentially through steric hindrance or disruption of polymer interactions. Statistical analysis further suggests that these variables act largely independently, with minimal interaction effects, meaning pH and buffer primarily accelerate gelation while nanoparticle loading tends to delay it.

Mechanical testing revealed a different but complementary pattern. For nanoparticle-loaded gels, stiffness increased sharply from pH 10 to pH 11, but often declined again at pH 12, indicating that the fastest-setting formulations were not necessarily the strongest. Higher buffer strength generally improved Young’s modulus, with 5x buffer frequently producing the most mechanically robust gels. Nanoparticle addition also showed a non-linear effect on stiffness: moderate loading improved reinforcement in several cases, while excessive loading reduced performance, likely due to aggregation or disruption of effective network formation. Together, these findings suggest that the optimal formulation is not the one that gels fastest, but rather one that balances gelation kinetics with structural integrity.

Overall, the data point to a promising formulation window near pH 11 with elevated buffer strength and moderate nanoparticle loading, where gels achieve relatively rapid curing while maintaining strong mechanical performance. This balance is especially important for embolic applications, where a material must set quickly enough for procedural practicality but remain strong enough to resist deformation after delivery. These results provide an important foundation for future development of magnetically guided PPODA-QT embolics that combine injectability, tunable curing behavior, imaging functionality, and mechanical stability for improved treatment of cerebral aneurysms.

Mentor: Brent Vernon