A new type of gadodiamide-conjugated amphiphilic chitosan nanoparticle and its use for MR imaging with significantly enhanced contrastability

Magnetic resonance imaging (MRI) has been one of the most frequently-used diagnostic tools with high dimensional precision and positioning accuracy in clinical practices. To achieve contrast enhancement, utilization of high-efficient MR imaging contrast agents becomes a prime consideration and is indispensably reinforced the diagnosis precision, especially for the emerging precision medicine. Gadolinium (Gd)-based complexes has been widely used in current clinical MRI operations, however, numerous side effects were reported and highlighted in clinic. Those drawbacks render specific unmet needs to be clinically and technically improved with a new version of Gd-based compound. Here we report a newly-synthesized amphiphilic Gadodiamide-conjugated carboxymethyl-hexanoyl chitosan (termed as CHC-Gd) hybrid. The gadodiamide was selected is due to its smallest molecular size among other Gd-based complexes reported in literature, which assumed to give least influence on the resulting physicochemical properties such as colloidal stability, nanostructural evolution, and cytocompability, particularly self-assembly capability, of the resulting hybrid upon practical uses. Experimental outcomes showed a successful synthesis of the CHC-Gd hybrid using a one-pot synthesis protocol, where the gadodiamide complexes were covalently attached to the carboxyl groups along the CHC backbone. Self-assembly behavior can be observed to form a sphere-like nanoparticle of 100-200 nm in size as of amphiphilic native CHC macromolecule. Experimental outcomes indicated a largely improved cytocompatibility of the hybrid, compared with free Gd, suggesting the Gd+3 ions were well stabilized in the CHC nanostructure. Excellent contrastability in-vitro and in particular in vivo were measured, where for in-vivo test, a 10-40-folded reduction in dosage, compared with clinical Gd dose, was used and demonstrated a comparative-to-better imaging resolution and brightness. Therefore, from this preliminary investigation, a potential translation to clinical practice through the use of newly-synthesized amphiphilic CHC-Gd hybrid appears to be relatively promising.