A lead abellaite–alginate nanocomposite as a contrast agent for post-mortem CT imaging

High-resolution visualization of vascular networks is critical for studying biological mechanisms, disease progression, and tissue repair. Although micro-computed tomography (microCT) enables non-destructive three-dimensional imaging, post-mortem angiography remains limited by existing contrast agents that exhibit high viscosity, premature solidification, incomplete distal vessel filling, and/or insufficient radiopacity. Here, we evaluated a triggerable alginate-based nanocomposite containing lead abellaite nanoparticles (ANPs) as a post-mortem vascular casting and imaging material. ANPs (22 ± 1 nm crystallite size; ~ 40 ± 10 nm particle size) were suspended in 1% alginate at concentrations of 0.10–0.40 g/mL and gelation was initiated using gluconic acid δ-lactone (GDL). Rheological testing demonstrated an extended low-viscosity period followed by concentration-dependent gelation, indicating suitability for triggerable post-perfusion solidification. Although ultimate failure properties were lower than benchmark materials, mechanical performance at physiologically relevant strains (≤ 25%) was comparable to or exceeded that of Microfil and gelatin controls. Brief exposure to physiologically relevant calcium concentrations substantially improved hydrogel stiffness and prevented subsequent reliquefaction, maintaining structural stability for at least 44 days. All formulations exhibited exceptionally high radiopacity that exceeded dried bone and supported feasibility for simple threshold-based segmentation from mineralized tissues. Preliminary mouse perfusion studies demonstrated vascular delivery, persistence of contrast within harvested tissues, visualization of microvascular structures following microCT imaging, and threshold-based segmentation of mineralized tissues and vessels. Together, these findings identify ANP-alginate hydrogels as a multifunctional platform that combines triggerable gelation and extreme radiopacity within a single nanoparticle system and supports their further development as post-mortem vascular casting agents for microCT applications.