Info
Background:
Inflammatory bowel disease (IBD) affects over 3 million people in the United States and is driven by chronic inflammation, immune dysregulation, and elevated reactive oxygen species (ROS) in the gastrointestinal tract (GIT).1,2 Computed tomography (CT) is widely used for non-invasive GIT imaging, however conventional iodinated and barium-based contrast agents lack specificity for inflamed regions, reducing diagnostic accuracy.3 Cerium oxide nanoparticles (CeNP) offer a promising alternative due to their K-edge energy profile and enhanced X-ray attenuation, as well as their reported catalytic antioxidant activity via reversible redox cycling.4,5
Hypothesis/Objective:
This study investigates dextran-coated cerium oxide nanoparticles (Dex-CeNP) as a scalable theranostic platform for IBD, by assessing whether scale-up based production preserves their imaging performance, catalytic ROS-scavenging activity, and dextran-mediated targeting to inflamed tissues to enable imaging and modulation of inflammation in relevant in vitro and in vivo models.
Methods:
Dex-CeNP (dextran molecular weight = 5 kDa) were synthesized using a confined impinging jet mixer (CIJM), enabling rapid and scalable production through turbulent mixing of two aqueous precursor streams (Fig. 1A). Nanoparticles were characterized using transmission electron microscopy (TEM) and complementary physicochemical techniques. CT imaging performance was evaluated using a Dex-CeNP phantom scanned on a clinical CT scanner at 80 and 140 kV. Cytocompatibility was assessed in RAW 264.7 macrophages and C2BBe1 colon epithelial cells by evaluating cell viability post-treatment with varying Dex-CeNP concentrations. To elucidate the uptake mechanism of Dex-CeNP in macrophages, inhibition studies were performed using phenylarsine oxide (PAO), cytochalasin D (CyD), and nocodazole (Noco) to probe receptor-mediated endocytic pathways and route of internalization. In vivo imaging, dose optimization, and safety were evaluated in a dextran sodium sulfate (DSS)-induced colitis mouse model and naïve controls following oral administration of Dex-CeNP across multiple doses or PBS. CT attenuation was measured pre- and post-treatment, while safety was assessed through body weight monitoring, blood chemistry, and histological analysis of major organs.
Results:
CIJM synthesis produced Dex-CeNP with consistent morphology while enabling scalable and reproducible batch production (Fig. 1B-C, S1. A-B). CT phantom imaging demonstrated concentration-dependent X-ray attenuation (Fig. 1D).5 Dex-CeNP maintained high cytocompatibility in both macrophage and epithelial cell models in vitro (Fig. 1E-F). In RAW 264.7 macrophages, nanoparticle uptake was significantly reduced in the presence of PAO, CyD, and Noco (Fig. 1G-I), indicating that internalization occurs through active, receptor-mediated endocytic pathways rather than passive uptake. In vivo CT imaging revealed enhanced GIT contrast in colitis mice following Dex-CeNP administration, with time-dependent attenuation in intestinal regions and dose-dependent imaging performance which identified 125 mg/kg as the optimal imaging dose (Fig. 1J-L, S2. A-C). Importantly, scaled-up Dex-CeNP demonstrated a favorable in vivo safety profile, as treated mice exhibited stable body weight, blood chemistry markers within normal ranges, and no histological evidence of toxicity in major organs.
Conclusion:
Dex-CeNP synthesized via CIJM represents a scalable and theranostic nanoplatform that retains CT contrast generation and macrophage-targeted uptake. Notably, the dose-dependent in vivo imaging performance and favorable safety profile of Dex-CeNP, together with previously reported antioxidant activity, support their translational potential for imaging guided diagnosis and treatment of IBD.
Image/Figure:
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Image/Figure Caption:
Figure 1. A) Schematic of Dex-CeNP. B) Transmission electron micrograph of 5 kDa Dex-CeNP. C) UV-Visible absorption spectra of Dex-CeNP. D) Dex-CeNP phantom at clinical energy range of 80 kV and 140 kV. In vitro viability assay with E) RAW 264.7 cells and F) C2BBe1 cells post-treatment with different Dex-CeNP concentrations. Cellular uptake of Dex-CeNP in the presence of inhibitors G) phenylarsine oxide, H) cytochalasin D, and I) nocodazole using RAW 264.7 macrophages. Representative CT scans of DSS-induced colitis mice and naïve control mice acquired post-administration of 5 kDa Dex-CeNP at varying dosages at J) 5 minutes in the stomach, K) 120 minutes in the small intestine, and L) 120 minutes in the large intestine.
Author
Sylvia Cho
University of Pennsylvania