Nitric Oxide Radical-Based Nanoparticles as Magnetic Resonance Imaging Probes for Ascorbic Acid Quantification

Ascorbic
acid (AsA) is intravenously administered as a drug for
disease therapy, fatigue recovery, antiaging, and cancer therapies.
However, the traditionally quantitative AsA detection needs blood
draws followed by mainly hyper-pressure liquid chromatography utilizing
diluted samples. Meanwhile, NO radical-based nanoparticles (NONPs)
have been widely used in biomedicine and as functional materials.
This study demonstrated the quantitative detection of AsA by using
NONPs as probes for magnetic resonance imaging (MRI). Simply organic
NO radicals such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and
2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PROXYL), which form as a monomer
in solutions, promptly react with AsA and diminish the paramagnetic
property during the MRI time scale (several minutes to several tens
of minutes), yielding difficulty in the acquisition of MRI images.
In contrast, NONPs consisted of the designed organic radicals, which
are based on an amphiphilic PROXYL framework, maintained the paramagnetic
property with appropriate decay during the MRI time scale, yielding
AsA-dose-dependent MRI images. This facilitated the direct measurement
of AsA concentrations upon probe addition, thereby realizing in vitro
quantitative AsA detection via MRI. In the future of AsA therapy,
noninvasive diagnosis of the diseases via the MRI
will be a promising method. Furthermore, this method reduced patient
burden by eliminating the need for blood draws, facilitating quick
and cost-effective medical examinations for wider generations.