Dual-modality imaging enables longitudinal biodistribution profiling of intracerebroventricular CAR-T therapy in orthotopic glioma

Abstract Locoregional CAR-T delivery is increasingly explored for glioblastoma to improve intracranial tumor exposure; however, organ-level biodistribution kinetics after intracranial administration remain poorly quantified in vivo, limiting route-informed optimization and preclinical risk assessment. Here, we report a dual-modality cell labeling and tracking strategy based on indocyanine green–conjugated iron nanoparticles (ICG-NPs) for in vivo assessment of B7-H3-targeting CAR-T cell (TX103) biodistribution using second near-infrared window (NIR-II) fluorescence imaging and magnetic resonance imaging (MRI). Using a heparin–protamine-assisted protocol, TX103 cells were labeled with high efficiency (83.1%) without detectable changes in viability, CAR expression, immunophenotype (including activation/exhaustion marker profile and CXCR3 expression), or cytotoxic function. In vitro imaging demonstrated a linear correlation between NIR-II fluorescence intensity and labeled cell numbers (R 2 = 0.973, p < 0.001), while MRI provided complementary anatomical context at higher cell densities. In an orthotopic glioma mouse model, longitudinal MRI and NIR-II imaging captured route-dependent differences in tumor-associated localization and whole-body biodistribution following intracerebroventricular and intravenous administration. Furthermore, organ-level NIR-II exposure showed a positive association with CD3⁺ T-cell density across organs (R 2 = 0.552, p < 0.001), supported by multi-organ pathological validation. Collectively, we establish a biocompatible dual-modality workflow that links intracranial anatomical localization with longitudinal whole-body biodistribution readouts for preclinical CAR-T tracking in solid tumor models. Graphical abstract Schematic of the ICG–iron nanoparticle (ICG-NP) labeling workflow for B7-H3–targeting CAR-T cells (TX103) and dual-modality in vivo tracking using MRI (tumor-associated localization) and NIR-II fluorescence imaging (whole-body biodistribution) in an orthotopic glioma model, with pathological validation.