Preparation and MRI of CB86-DTPA-Gd targeting TSPO in rheumatoid arthritis model / 中华核医学与分子影像杂志

ABSTRACT

Objective:To synthesize Gd labeled probe targeting transporter protein(TSPO) 2-(8-amino-2-(4-chlorophenyl)imidazo[1, 2-a]pyridine-3-yl)- N, N-dipropylacetamide (CB86)-diethylene triamine pentaacetic acid (DTPA), and investigate its MRI effect in rheumatoid arthritis (RA) model. Methods:CB86-DTPA was prepared by coupling a bifunctional chelating agent, and then chelated with Gd to obtain MRI targeted contrast agent CB86-DTPA-Gd. The cytotoxicity, MR relaxation rate and in vitro stability of CB86-DTPA-Gd were determined. RA model was established with Freund′s adjuvant and the biodistribution study and MRI was performed. The RA lesion and its surrounding normal tissue were used as regions of interest (ROI) to calculate the signal to noise ratio (SNR). Independent-sample t test was used to analyze the data. Results:CB86-DTPA-Gd had excellent biosafety and a good MR relaxation rate ( r1=11.05 mmol·L -1·s -1). The survival rate of RAW264.7 cells and 4T1 cells was still more than 90% at the maximum concentration (20 μmol/L) of Gd 3+. CB86-DTPA-Gd also exhibited good stability in human serum and phosphate buffer saline solution (PBS; pH=7.4). The in vivo biodistribution showed that CB86-DTPA-Gd had better inflammatory targeting efficiency, and the uptake of Gd in the inflamed site of the ankle joint was still (2.33±0.29) percent dose rate per gram of tissue (%ID/g) at 120 min after injection. MicroMRI showed that the inflammation of the right ankle joint displayed significant enhancement after the injection of CB86-DTPA-Gd and Gd-DTPA. The SNR of CB86-DTPA-Gd group was up to 23.21±1.44, and the maximum intensification time was 90 min after injection, and can be significantly inhibited by CB86-DTPA at all time points ( t values 6.083-12.451, all P<0.05), while the Gd-DTPA group had a strengthening time of 30 min after injection with the SNR of 16.12±1.24. Conclusion:CB86-DTPA-Gd shows good macrophage targeting and good uptake in arthritic reaction sites, and is expected to be a novel MRI molecular probe for peripheral inflammation imaging.