Fluorescent chitosan-based nanohydrogels and encapsulation of gadolinium MRI contrast agent for magneto-optical imaging

Abstract

In the field of medical imaging, multimodal nanoparticles combining complementary imaging modalities can give rise to new forms of imaging techniques that are able to make diagnosis more precise and confident. In this context, resolution and sensitivity have often to be gathered into a single imaging probe, by combination of MRI and optical imaging for instance. Gadolinium chelate (Gd-CAs) loaded nanohydrogels, obtained from chitosan (CS) and hyaluronic acid (HA) matrix, have shown their efficiency to greatly improve MRI contrast (r1 ≥ 80 mM−1 s−1). In this study, nanohydrogels were made intrinsically fluorescent by chitosan pre-functionalization and a series of fluorescent chitosans were obtained by covalent grafting of rhodamine (Rhod: 6.3µM) or fluorescein (Fluo: 7.3µM) tags. By combining DOSY and fluorescence data, fluorescent chitosans (CS-Rhod and CS-Fluo) with a low degree of substitution were then selected and used to encapsulate high gadolinium loadings to obtain efficient magneto-optical nanohydrogels.