Synthesis and characterization of novel radiopaque poly(allyl amine) nanoparticles.

Contrast agents are currently used in a variety of diagnostic imaging techniques, including computer tomography for early cancer detection. Radiopaque nanoparticles have recently been proposed as an alternative method to traditional contrast agents that may allow for long-term image tracking. The aim of this study was the preparation and characterization of aqueous suspensions of radiopaque nanoparticles made of poly(allyl amine) derivatives. Poly(allylamine) (PA) was modified by grafting either 4-iodobenzoyl chloride or 2,3,5-triiodobenzoyl chloride to make the polymer x-ray visible. Nanoparticles of the modified PA were prepared by the nanoprecipitation method and purified with respect to residual organic solvents. Stable suspensions of spherical particles of sub-micronic diameter were characterized by dynamic light scattering and transmission electron microscopy. In addition, the 4.5 wt% suspensions of nanoparticles displayed an x-ray visibility ranging between 185 and 235 HU. The non-clustering ability of the novel PA radiopaque nanoparticles suggests they could be injected via a catheter without clogging or sedimentation.

Elaboration of radiopaque iodinated nanoparticles for in situ control of local drug delivery.

Drug delivery systems can benefit from intrinsic radiopacity as this property will allow following up the diffusion path of the nanoparticles containing the therapeutic drug after their local administration. Herein, we report the synthesis of iodinated derivatives of cellulose acetate (CA) and their formulation into aqueous radiopaque nanoparticle suspensions. Modification and purification of CA with mono- or tri-iodobenzoyl chloride were characterized by NMR spectroscopy and elemental analysis of iodine. In particular, measurements of diffusion coefficients by the DOSY 2D NMR method allowed controlling the complete elimination of non-grafted iodinated materials. Pure radiopaque CA was successfully achieved with an iodine content varying between 14 and 32%. Aqueous suspensions of nanoparticles were successfully formed, characterized by being spherical, <100 nm in size and stable as a suspension over 3 months. The degree of substitution, in particular the triiodo moieties, imparted a good level of radiopacity whether in dry powder form (2627 HU) or as a nanoparticle suspension (298 HU). These values are comparable to radiopacity of systems reported in literature to be in vivo visible. Loading of paclitaxel was successfully attempted, suggesting that the developed radiopaque nanoparticles can ultimately function as a drug delivery system.