Synthesis of Iron Oxide Nanoparticles coated with Nonpolymeric Azidopropyl-Uracil Triphosphate (UTP) and Adenosine triphosphate (ATP) for Multimodality Imaging

Objectives The surface modification of superparamagnetic iron oxide nanoparticles (SPION) with non polymeric materials had many advantages for clinical use. We synthesized azidopropyl-uracil triphosphate (UTP) material and iron oxide nanoparticles coated with adenosine triphosphate (ATP) and UTP. It had ability to click reaction for nuclear medicine imaging and we evaluated it as multiplatform.

Methods 5-iodo uridine used as starting material and added propyl alcohol by Sonogashira coupling followed substitution with azide. 5-propyl uridine triphosphate (UTP) was obtained finally by tri-phosphorylation and purified it by HPLC. Prepared iron oxide nanoparticles coated with mompolymer ATP and UTP (UTP@SPION) by co-precipitation method. We characterized the UTP@SPION with dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD). UTP@SPION was modified with gluconic acid (GA-UTP@SPION) to reduce phagocytic uptake for biomedical application. We labeled with F-18 by click reaction using 3-butynyl tosylate as precursor for nuclear imaging. Prepared UTP@SPION conjugated with RGD (RGD/GA-UTP@SPION) for specific targeting and Cy5.5 (Cy5.5/GA-UTP@SPION) using Cy5.5-NHS for optical image. We performed in vivo study using U87MG cancer rodent model.

Results The intermediates of each step to synthesize UTP were confirmed by 1H NMR (400 MHz), 13C NMR (100 MHz) and LC-Mass/LRMS and UTP obtained finally was by 31P NMR (162 MHz). UTP was similar structure with ATP contained three phosphate group that was able to affinity strongly to SPION surface. Also, ATP had the amine group that was able to conjugate with other molecules. Prepared GA-UTP@SPION showed that the mean diameter of and size distribution was 10±3 nm from TEM image. The molar ratio of UTP used in UTP@SPION synthesis was very low as below 0.02 but there was no problem in labeling F-18 and obtaining the nuclear image such as PET/CT without additional other step. We could modify surface of UPT@SPION with coating material such as gluconic acid, labeling with Cy5.5 and conjugation with RGD, and that showed possibility to use it for multiplatform. The result of image and bio-distribution using U87MG cancer rodent model after injection of RGD/UTP@SPION by intravenous injection showed specific uptake having the increase in tumor with time and it had potential to use in clinic for nuclear imaging.

Conclusions UTP@SPION could be used as a multimodality molecular imaging, especially nuclear imaging by easy and simple click reaction without additional process, and as multiplatform for targeting and imaging.