Conventional magnetic resonance imaging (MRI) uses the magnetic
properties of protons contained within the hydrogen atoms of the organism. This
non-invasive technique is certainly powerful, although it lacks sensitivity for
studies at the molecular level. Xenon MRI is a promising approach to
increase sensitivity and therefore the accuracy of the images. Unlike
conventional MRI, which detects the organism’s protons, this technique uses the
exogenous and harmless xenon atom, whose magnetic resonance signal can be
greatly amplified through hyperpolarization techniques. However, xenon is
“blind” in its native state; the idea of the researchers is thus to make small
systems enabling xenon to recognize its biological targets.
The scientists are working on caged molecules, in which xenon is
encapsulated, to easily navigate within the body. The currently proposed
molecules are constructed around a core of cryptophane; this cage-like
macromolecule is commonly synthesized to encapsulate all sorts of compounds of
interest. However, their drawback is their lack of solubility in water, which is
an obstacle to their use in a biological context.
| To remedy this and allow xenon to recognize its targets, the researchers
designed and synthesized a new cryptophane with two innovative features.
First of all, it is water soluble due to the addition of a group of
polyethylene glycol chains (PEGylation), resulting in good solubility and
diffusion through the body. Furthermore, it is equipped with alkyne groups
(CnH2n-2) for an easy functionalization by “click chemistry”. Preliminary
tests have shown the effectiveness of this new cryptophane compound, as well as
it safety at experimental imaging concentrations. It will be tested during in
vivo imaging experiments in small animal models. | |