Dr. Rumiana Bakalova, chief researcher at the Department of Molecular Imaging & Theranostics (NIRS-MIT), National Institutes for Quantum and Radiological Science and Technology (QST), along with her colleagues Dr. Ichio Aoki (group leader) and Tatsuya Higashi (department director), have undertaken international joint research with Bulgaria’s Sofia University and the Bulgarian Academy of Sciences to successfully develop a quantum sensor that is switched on and off by quantum dot fluorescence and MRI signals in response to oxidative stress. The results were published in Analytical Chemistry.
Reactive oxygen is associated with the onset of a variety of illnesses, but it is not as though there is a set quantity at which a person will become ill, and there are likewise individual differences in antioxidant capacity. Consequently, unless the surplus state of active oxygen (oxidized state) and the antioxidant capacity (oxidation-reduction state) can both be grasped, it is not possible to determine whether or not there is a state of oxidative stress.
The international joint team developed a quantum sensor that is switched on and off by quantum dot fluorescence and MRI signals in response to oxidative stress within cells. This sensor was created by coating the surface of an approximately two-nanometer-diameter quantum dot with a cyclodextrin that is safe for the body, and coupling it with a nitroxyl radical that functions as an MRI contrast agent. In a state of oxidative stress the quantum dot’s fluorescence vanishes (off) and the MRI signals increase (on). In a state of oxidation-reduction the quantum dot’s fluorescence is emitted (on) and the MRI signals decrease (off).
Because quantum dot fluorescence has high luminance, by improving the measuring technology it will be possible to measure oxidative stress from blood samples. If oxidative stress is detected in blood tests etc., conceivably it will have medical applications. Namely, investigate the entire body using an MRI, examine which regions of the body are experiencing strong oxidative stress, and begin treatment at the stage prior to the onset of the illness.
With that in mind, the research team produced a mouse whose kidneys were slightly inflamed but were still not suffering serious damage, with protein leaking into the urine (on the verge of hypercholesterolemia). When the team administered the quantum sensor it had developed and took MRI images, they succeeded in capturing images showing that the kidneys were in a state of oxidative stress at the stage prior to serious kidney damage occurring.
By applying an oxidative stress evaluation technique that employs this quantum sensor and developing it, it should become possible to observe states of oxidative stress at any time when blood tests are carried out in medical examinations, for example. This promises to lead to preemptive medical treatment by making it possible to detect the risk of developing cancers based on precancerous conditions or chronic inflammation, or to detect mild inflammation occurring as a result of diabetes, dementia, kidney disease, infections and other ailments, and intervening preventatively, prior to the onset of serious illness.
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