Two-component probe

The new MRI technique made it possible to carry out early diagnosis of small tumors

Sofia Jabotinskaya, Naked Science

For cancer treatment, it is extremely important to detect tumors as early as possible. A new technique developed by researchers from the University of California, Davis, makes it possible to use magnetic resonance imaging to detect even very small tumors in normal tissue. An article about the development was published in Nature Nanotechnology (Wang et al., Two-way magnetic resonance tuning and enhanced subtraction imaging for non-invasive and quantitative biological imaging).

The new technique is based on the effect of magnetic resonance tuning, which manifests itself when two nanoscale magnetic elements interact: one of them amplifies the signal, and the second extinguishes it. In this case, the degree of signal attenuation depends on the distance between these elements.

Researchers have created a two-component MRI probe that generates two signals that mutually suppress each other and enhance the contrast between normal and tumor tissue. The first component of this probe is a chelated complex of pheophorbide A with divalent magnesium (P–Mn), a complex organometallic compound with paramagnetic properties. The second is a superparamagnetic iron oxide particle (SPIO).

Both types of particles are "packed" in a lipid envelope that holds them together. Being close to each other, P-Mn and SPIO almost instantly extinguish the "partner" signal. When such a probe enters the tumor tissue, the shell disintegrates, releasing the components. SPIO and P-Mn are separated, and both signals manifest.

Scheme of interaction of P-Mn and SPIO components of the probe / © Wang et al.

The authors of the technique called it TMERT (two-way magnetic resonance tuning, two-way magnetic resonance tuning). The use of two-component nanoparticles in combination with specially developed software allowed researchers with very high sensitivity to detect brain tumors in model mice.

For most MRI probes, the signal from the tumor is about twice as strong as from normal tissue. Using a new nanoprobe, scientists were able to obtain a tumor–norm ratio of 10.

The TMERT technique will significantly improve the quality of tumor diagnosis, especially at the early stages of the pathological process. The scientists plan to apply for approval of the development for clinical use. But before that, researchers need to conduct large-scale toxicological studies.

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