In vitro delivery, cytotoxicity, swelling, and degradation behavior of a liquid-to-solid gelling polymer system for cerebral aneurysm embolization

This study examines the in vitro characteristics of a crosslinking polymer system for cerebral aneurysm embolization. The polymeric material is composed of poly(propylene glycol)diacrylate (PPODA) and pentaerythritol tetrakis(3-mercaptopropionate) (QT), formulated with the liquid contrast agents Conray™ or Omnipaque™ 300. The PPODA-QT system was tested for delivery feasibility through mock delivery into a model aneurysm. Cytotoxicity was performed by exposing 3T3 cells to gel formulations, followed by a cell viability assay. Swelling was measured on samples submerged in 150 mM phosphate buffered saline at 37 or 50°C. The same samples underwent compression testing to assess degradation, characterized by reduction in Young's modulus over time. The PPODA-QT system was easily deliverable to mock aneurysms. Cytotoxicity results indicated that Conray-formulated gels are initially less toxic than Omnipaqueformulated gels, but show greater susceptibility to swelling and degradation over time. In general, these experiments represented more challenging conditions than would be present in vivo, and therefore, reported results are likely overestimations of in vivo outcomes. However, these results highlight potential issues with each PPODA-QT formulation. Given the desired outcome of neointimal tissue growth over the polymer material, initial cytotoxicity may be more important than longterm factors when choosing an optimal formulation for aneurysm embolization.