Assessment of collagen-induced arthritis using cyanine 5.5 conjugated with hydrophobically modified glycol chitosan nanoparticles: Correlation with ¹⁸F-Fluorodeoxyglucose positron emission tomography data

Objective: To evaluate the potential and correlation between near-infrared fluorescence (NIRF) imaging using cyanine 5.5 conjugated with hydrophobically modified glycol chitosan nanoparticles (HGC-Cy5.5) and ¹⁸F-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG-PET) imaging of collagen-induced arthritis (CIA). Materials and Methods: We used 10 CIA and 3 normal mice. Nine days after the injecting collagen twice, microPET imaging was performed 40 minutes after the intravenous injection of 9.3 MBq ¹⁸F-FDG in 200 μL PBS. One day later, NIRF imaging was performed two hours after the intravenous injection of HGC-cy5.5 (5 mg/kg). We assessed the correlation between these two modalities in the knees and ankles of CIA mice. Results: The mean standardized uptake values of ¹⁸F-FDG for knees and ankles were 1.68 ± 0.76 and 0.79 ± 0.71, respectively, for CIA mice; and 0.57 ± 0.17 and 0.54 ± 0.20 respectively for control mice. From the NIRF images, the total photon counts per 30 mm2 for knees and ankles were 2.32 ± 1.54 x 10⁵ and 2.75 ± 1.51 x 10⁵, respectively, for CIA mice, and 1.22 ± 0.27 x 10⁵ and 0.88 ± 0.24 x 10⁵, respectively, for control mice. These two modalities showed a moderate correlation for knees (r = 0.604, p = 0.005) and ankles (r = 0.464, p = 0.039). Moreover, both HGC-Cy5.5 (p = 0.002) and ¹⁸F-FDG-PET (p = 0.005) imaging also showed statistically significant differences between CIA and normal mice. Conclusion: NIRF imaging using HGC-Cy5.5 was moderately correlated with ¹⁸F-FDG-PET imaging in the CIA model. As such, HGC-Cy5.5 imaging can be used for the early detection of rheumatoid arthritis.