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

Abstract

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.

Bioparameter-directed nanoformulations as MRI CAs enable the specific visualization of hypoxic tumour

“…10d and e). 62 Another novel redox-active approach for a Gd-based complex occurs through disulphide reduction by reducing biothiols, intramolecular macrocyclization and finally selfassembling into nanoparticles with a 60% enhanced r 1 relaxivity. 63 Cobalt (Co), whose divalent ion is one of the premier metal ions with the highest shifts in paramagnetic NMR spectroscopy, also transforms magnetic properties and changes valence states.…”

Red Upconverter Nanocrystals Functionalized with Verteporfin for Photodynamic Therapy Triggered by Upconversion

“…An effective coupling of imaging and therapy is represented by imaging-guided surgery, for tumor resection and post-surgery evaluation, where the precise visualization of malignant tissues is fundamental for ensuring the complete resection of the tumor [3,4]. More traditionally, therapeutic active moieties can be delivered and released to the target site by using nanometric carriers which are active in optical imaging [5][6][7][8] or magnetic resonance imaging [9][10][11]. As an alternative to drug delivery, the therapeutic agent can be generated in situ through photo activation, such as in Photodynamic Therapy (PDT), where a photosensitizer (PS) is able to generate cytotoxic reactive oxygen species once activated by illumination with light of proper wavelength [12][13][14][15][16], or in the case of Photothermal Therapy, where the nonradiative conversion of absorbed photon energy into heat causes cell death [17,18].…”