Poly(ethylene glycol)-poly(ε-caprolactone) iodinated nanocapsules as contrast agents for X-ray imaging

Synthesis and formulation of iodinated PCL-mPEG nanocapsules as new original blood pool contrast agents for computed tomography.

PCL-mPEG was synthesized and formulated following the emulsion-solvent diffusion process, in the form of iodinated nanocapsules. Physico-chemical characterization of such nano-materials was performed by DLS and transmission electron microscopy. A stability study of the nanocapsules suspension was followed-up to 3 month. Blood biocompatibility was performed. Finally, the nanocapsules suspension radiopacity was evaluated in vitro then in vivo in mice as micro-CT contrast agent.

In this study, the iodine concentration in nanocapsules suspension was about 70 mgI/mL. Besides, these nanocarriers appeared non-toxic, and stable in suspension. In vivo, i.v. administration of 10 μL/g of mouse body weight of theses nano-particles induced a vascular contrast enhancement of 168 HU and a half-life in blood of 4.2 +/- 0.5 h. Elimination route of these particles appears mainly performed by the liver, without sequestration in spleen and lymph nodes confirming their stealth properties.

This study proposes the first example of iodinated biodegradable polymeric blood pool contrast agent, able to induce an exploitable contrast enhancement. The main advantage of polymeric system compared to lipid ones, lies in their stability and handling, e.g. towards drying for storage.