Direct quantitative super(13)C-filtered super(1)H magnetic resonance imaging of PEGylated biomacromolecules in vivo

• Published in: Magnetic resonance in medicine Vol. 77; no. 4; pp. 1553 - 1561
• Main Authors: Alvares, Rohan DA, Lau, Justin YC, Macdonald, Peter M, Cunningham, Charles H, Prosser, RScott
• Format: Journal Article
• Language: English
• Published: 01.04.2017
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.26237

Purpose super(1)H MRI is an established diagnostic method that generally relies on detection of water. Imaging specific macromolecules is normally accomplished only indirectly through the use of paramagnetic tags, which alter the water signal in their vicinity. We demonstrate a new approach in which macromolecular constituents, such as proteins and drug delivery systems, are observed directly and quantitatively in vivo using super(1)H MRI of super(13)C-labeled poly(ethylene glycol) ( super(13)C-PEG) tags. Methods Molecular imaging of super(13)C-PEG-labeled species was accomplished by incorporating a modified heteronuclear multiple quantum coherence filter into a gradient echo imaging sequence. We demonstrate the approach by monitoring the real-time distribution of super(13)C-PEG and super(13)C-PEGylated albumin injected into the hind leg of a mouse. Results Filtering the super(1)H PEG signal through the directly coupled super(13)C nuclei largely eliminates background water and fat signals, thus enabling the imaging of molecules using super(1)H MRI. Conclusion PEGylation is widely employed to enhance the performance of a multitude of macromolecular therapeutics and drug delivery systems, and super(13)C-filtered super(1)H MRI of super(13)C-PEG thus offers the possibility of imaging and quantitating their distribution in living systems in real time. Magn Reson Med 77:1553-1561, 2017.