Compared with traditional gadolinium-based products, new contrast agents have been greatly improved
Image: (a) High-resolution 3D MRI cerebrovascular map using SAIO. You can see various blood vessels in the rat brain. In addition to clinically important cerebral blood vessels including the anterior cerebral artery, middle cerebral artery, and posterior cerebral artery, small blood vessels with a diameter of about 100 microns can be clearly seen. (b) 3D MRI cerebrovascular map using Dotarem (gadolinium contrast agent). The resolution is low and the capillaries are not visible. (c) For 3D reconstruction, multiple MRI images of the rat heart were obtained after SAIO injection. Successfully observed rat coronary arteries (180 microns) that are 10 times thinner than human coronary arteries. Coronary arteries supply blood to the heart muscle. Blockage or narrowing of these arteries can cause myocardial infarction or angina. However, due to the limited resolution of current MRI contrast agents, these arteries cannot be seen. see more
Image source: Institute of Basic Science
Heart attack and stroke are the first and second leading causes of death in developed countries, respectively. Since the disease often leads to sudden death, and there are few special prognostic symptoms, early diagnosis is very important. For this reason, imaging techniques such as magnetic resonance imaging (MRI) are widely used to identify narrowing or blockage of blood vessels.
In MRI, contrast agents increase the visibility of structures, such as the smaller blood vessels in the body. Just as satellites or global positioning systems (GPS) provide traffic jam information, MRI contrast agents can provide accurate information about blood vessel conditions, such as blood vessel blockage and stenosis. Commonly used products are gadolinium-based contrast agents. Free gadolinium ions are highly toxic and must be administered in chelated form. However, even so, for patients with poor renal function, renal-derived systemic fibrosis still has some health risks. There have been some attempts to use paramagnetic iron-based nanoparticles as contrast agents, but their renal clearance must be improved to prevent undesirable accumulation in the liver and other organs.
A collaborative research team led by Professor CHEON Jinwoo, director of the Center for Nanomedicine (CNM) of the Institute of Basic Science (IBS), Yonsei University, Seoul, South Korea, and Professor CHOI Byoung Wook of the Yonsei University School of Medicine, developed a high-precision high-resolution imaging system for 3D vascular mapping. Performance MRI contrast agent. Researchers have developed a nanoparticle-based MRI contrast agent called SAIO (Supramolecular Amorphous Iron Oxide). The particle size is 5 nanometers, which is about 1,500 times smaller than the diameter of the capillaries. This allows it to circulate in the blood vessels in the body.
SAIO is a special kind of nanoparticle, which consists of a polysaccharide core composed mainly of dextran and other molecules cross-linked. Then, the magnetic core is coated with an iron oxide surface to make it paramagnetic at room temperature. The blending properties of SAIO give them excellent biocompatibility and imaging performance. The researchers compared SAIO with Dotarem (a gadolinium-based reagent) and iron oxide nanoparticles in terms of performance, retention and renal clearance curves.
SAIO is one of the highest resolution imaging agents, and its accuracy is 10 times that of images generated using current contrast agents. It realizes 3D brain blood vessel mapping, and in animal experiments, brain capillaries as thin as hair (100 microns) can be clearly identified. In addition, in order to obtain excellent resolution, the enhancement duration is much longer (> 10 minutes) compared to Dotarem (< 2 minutes), which gives radiologists plenty of time to perform the imaging procedure. These excellent characteristics of SAIO enable researchers to observe the heart blood vessels, which are almost invisible with current MRI contrast agents.
In addition to having high resolution, the excretion of contrast media through urine is particularly important to avoid its accumulation in the body, which can cause various side effects. SAIO has excellent renal clearance and does not accumulate in the liver or spleen. It was also found that SAIO was stable for up to a year, with no aggregation and no iron leaching.
Director Cheon said: "SAIO is a next-generation contrast agent that meets both high resolution and safety." Professor Choi said, "SAIO is expected to play an important role in improving the accuracy of the diagnosis of cerebral cardiovascular diseases. Stroke, myocardial infarction, angina pectoris And diseases such as dementia."
The results of this research were supported by the Korean Healthcare Technology R&D Project of the Ministry of Health and Welfare and the Institute of Basic Science of the Republic of Korea. The research was published in the journal Nature Biomedical Engineering on March 8, 2021.
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Copyright © 2021 American Association for the Advancement of Science (AAAS)
Copyright © 2021 American Association for the Advancement of Science (AAAS)