Supramolecular and biomacromolecular enhancement of metal-free magnetic resonance imaging contrast agents

Abstract

Supramolecular/macromolecular organic radical contrast agents (smORCAs) overcome many of the limitations of nitroxide radicals for use in magnetic resonance imaging in vivo like poor stability and weak contrast.

Human Serum Albumin Labelled with Sterically-Hindered Nitroxides as Potential MRI Contrast Agents

“…In fact, the r2 per nitroxide group (4.3-5.3 mM −1 s −1 ) for both conjugates, at 37 °C and 7 T, match or exceed those reported for other ORCAs (0.17-4.7 mM −1 s −1 ) [23]. This was achieved at a relatively light loading of 3.9 nitroxides per HSA (Table 4).…”

“…The r2/r1 values of 10.4-14.3 obtained in a 7 T magnetic field suggest that at high field strengths the conjugates may work most effectively as T2 contrast agents [15,19]. The r2/r1 values per nitroxide exceed those of most other nitroxide-based ORCAs [15,20,23] and the r1 relaxivities are similar to values at 7 T for other ORCAs.…”

Viral nanoparticles for drug delivery, imaging, immunotherapy, and theranostic applications

“…Furthermore, by conjugating fluorescent dyes on the internal surface and ORCA on the outer surface, the TMV probes could be used as a concentration marker regardless of the ORCA oxidation state. In a more recent study by the same group, TMV was conjugated to a derivative of the aminoxyl radical TEMPO (coined Compound 6) by a coppercatalyzed azide-alkyne cycloaddition reaction (TMV-6) [205]. Subsequent binding to cucurbit [8]uril (CB [8]) forms an ORCA inclusion complex called a semirotaxane that helps shield the aminoxyl radicals from reduction into hydroxylaminesa process which makes aminoxylbased ORCAs MRI-silent.…”

Role of gadolinium-based contrast agents in neurological disorders

“…On the basis of this, they can be employed as contrast media in MRI [98] Iron sucrose (IS) IS IS shortened both the T1 and T2 of blood, indicating its suitability as a contrast agent for CE-T1WI magnetic resonance angiography (MRA) and dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) Animal model Routinely used for treatment of Fe-deficiency anaemia.…”

“…Compared to GBCAs, they have low relaxivity and are reduced rapidly to MRI-silent hydroxylamines in physiological conditions. In order to improve their efficiency, the attachment of supramolecular and biomacromolecular is needed [98].…”