Glycol Chitosan Functionalized with a Gd(III) Chelate as a Redox‐responsive Magnetic Resonance Imaging Probe to Label Cell Embedding Alginate Capsules.

One possibility for the non‐invasive imaging of encapsulated cell grafts is to label the lumen of cell embedding capsules with a redox‐responsive probe, as an increased extracellular reducing potential can be considered as a marker of hypoxia‐induced necrosis. A Gd(III)‐HPDO3A‐like chelate has been conjugated to glycol‐chitosan through a redox‐responsive disulphide bond to obtain a contrast agent for Magnetic Resonance Imaging (MRI). Such a compound can be interspersed with fibroblasts within the lumen of alginate‐chitosan capsules. Increasing reducing conditions within the extracellular microenvironment lead to the reductive cleavage of the disulphide bond and to the release of gadolinium in the form of a low molecular weight, non‐ionic chelate. The efflux of such chelate from capsules is readily detected by a decrease of contrast enhancement in T1‐weighted MR images. [ABSTRACT FROM AUTHOR]