CT imaging of and therapy for inflammatory bowel disease via low molecular weight dextran coated ceria nanoparticles

Abstract

Inflammatory bowel disease (IBD) affects approximately 3.1 million individuals in the U.S., causing deleterious symptoms such as bloody diarrhea and leading to an increased risk of colorectal cancer. Effective imaging is crucial for diagnosing and managing IBD, as it allows for accurate assessment of disease severity, guides treatment decisions, and monitors therapeutic responses. Computed tomography (CT) with contrast agents is the gold standard for imaging the gastrointestinal tract (GIT). However, current agents are less effective in obese patients and lack specificity for inflamed regions associated with IBD. Moreover, IBD treatments often have limited efficacy and do not address the role of oxidative stress in IBD progression. This study explores dextran-coated cerium oxide nanoparticles (Dex-CeNP) as a CT contrast agent and therapeutic for IBD, leveraging cerium's superior K-edge energy profile, dextran's inflammation-specific targeting, and cerium oxide's antioxidant properties. Herein, we synthesized Dex-CeNP formulations using 5, 10, 25, and 40 kDa dextran to explore the effect of dextran coating molecular weight. In vitro assays showed formulation biocompatibility and demonstrated that 5 kDa Dex-CeNP had the highest catalytic activity, which translated into improved suppression of inflammation. As a result, this formulation was selected for in vivo use. In vivo CT imaging of mice subjected to dextran sodium sulfate (DSS) colitis showed that Dex-CeNP provided better contrast in the GIT of mice with colitis compared to iopamidol (ISO), with pronounced attenuation in the large intestine and disease- specific retention at 24 h. Additionally, Dex-CeNP significantly decreased Disease Activity Index (DAI) scores, and diminished gastrointestinal bleeding when compared with a currently approved drug, indicating that it is an effective treatment for colitis. Studies also revealed that the Dex-CeNPs were safe and well-excreted following administration. In summary, Dex-CeNP has significant promise as a dual-purpose agent for CT imaging and treatment of IBD.

Fig. 1. Schematic depictions of Dex-CeNP functions (A) as a contrast agent and (B) as treatment for inflammation in the GIT.

Fig. 2. Characterization data of Dex-CeNPs. TEM of Dex-CeNP whose dextran was (A) 5 kDa, (B) 10 kDa, (C) 25 kDa, or (D) 40 kDa in molecular weight. The scale bars represent 50 nm in all panels. (E) UV-Vis spectra of Dex-CeNP dispersed in water. (F) XRD data from the Dex-CeNP.

Fig. 3. In vitro analysis of the Dex-CeNP formulations. (A) Representative images of the formulations before and after 2 h. (B) Formulation stability assessment via hydrodynamic diameter measurement using DLS. (C) CAT and (D) SOD-mimetic like activity of the different Dex-CeNP formulations. Error bars represent standard error of the mean. p < 0.005 unless indicated otherwise. *p < 0.05. All P values, including significant ones, can be found in the ESI Tables S1 and S2.

Fig. 4. Contrast generation scanned with a clinical CT system of a phantom composed of varying concentrations of Dex-CeNP. (A) Attenuation Rates for Dex-CeNP formulations obtained from CT scans at different X-ray tube voltages: 80, 100, 120, and 140 kV. Error bars represent the standard error of the mean, with asterisks indicating statistical significance levels: *P < 0.05, **P < 0.01, and ****P < 0.0001. (B) Representative CT images of a phantom containing 5 kDa Dex-CeNP (80 kV vs 140 kV). (C) SPCCT images of Dex-CeNP samples. Left to right: MonoE 70 keV image, virtual non-contrast (VNC) image and a cerium material map.

Fig. 5. In vitro assays. (A) Effect of Dex-CeNP formulations on the viability of RAW 264.7 and (B) C2BBe1 as determined by the MTS assay. In vitro assessment of anti-inflammatory activity by (C) MTS assay and (D) TNF-α ELISA using RAW 264.7 cells. Error bars represent the standard error of the mean, with asterisks indicating statistical significance levels: *P < 0.05, **P < 0.01, and ****P < 0.0001. All P values, including significant ones, can be found in the ESI Table S3–S6.n = 6 per group.

Fig. 6. Representative CT images of healthy and DSS colitis mice, before oral administration of CT contrast agents and for 24 h after. (A) Healthy control mice with 5 kDa Dex-CeNP, (B) DSS colitis mice with 5 kDa Dex-CeNP, and (C) DSS colitis mice with ISO.

Fig. 7. Evaluation of Dex-CeNP as a contrast agent. Time-dependent attenuation variations in various organs including (A) stomach, (B) small intestine, and (C) large intestine. Error bars represent the standard error of the mean, with asterisks indicating statistical significance levels: *P < 0.05, **P < 0.01, and ****P < 0.0001.

Fig. 8. Efficacy of Dex-CeNP as a treatment for IBD. (A) Fecal occult blood test results for mice treated with 5 kDa Dex-CeNP, 5-ASA, and water. (B) Comparison of colon length for mice treated with 5 kDa Dex-CeNP, 5-ASA, and water (n = 6). (C) Quantitative results for average weight lost and (D) DAI across different treatment groups, with statistical significance markers. Error bars represent the standard error of mean, with asterisks indicating statistical significance levels: *P < 0.05, **P < 0.01, and ****P < 0.0001.

Fig. 9. Dex-CeNP is an effective treatment for mice with acute DSS colitis. (A) Histological analysis of large intestines in colitis mice 24 h after Dex-CeNP, 5-ASA or water administration (the left micrographs were taken at 5x magnification, and the insets are magnifications of the boxed areas). (B) Histological scoring of disease severity by a blinded veterinary pathologist using a standardized system. (C) Serum biomarkers for liver and kidney function were assessed in mice 24 h after injection with either the water control, 5-ASA, or Dex-CeNP (n = 3 per group).