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Diagnostic imaging equipment has improved the resolution of its results and reduced the radiation patients receive, but the main advance has occurred in contrast agents. Through nanoparticles 'decorated' with dyes or nanoantibodies, which travel through blood vessels, the scientific community works to detect cancer and metastasis early, and check if the treatment works.
While attending a character design class with Pixar animators, researcher Cristina Zavaleta, a lifelong fan of Disney and art, noticed the type of paints dissolved in water and with very high pigment that they were using, the so-called gouaches. .
Its texture, brightness and color reminded him of the dyes used in humans in the form of tattoo inks or even food coloring. It was at that moment when this biomedical engineer from the University of Southern California in the United States, with a degree in Nuclear Medicine, thought that these pigments could have interesting optical properties and be used as fluorescence image contrast agents to detect certain diseases. So it was.
He turned to Adam Sky, a San Francisco-area tattoo artist, who filled the 96 wells used as test tubes in Zavaleta's microplates with tattoo inks. The scientist then examined them with a Raman scanner, which allowed the sample to be illuminated with a monochromatic laser beam to check how it interacted with the molecules.
The result was the discovery of 'amazing' spectral fingerprints that could be used to encode and label nanoparticles, tiny spheres that carry dyes through blood vessels in search of malignant cells.
"We encapsulate various pigments in nanoparticles, which can carry several dyes at the same time and target cancer cells, and we then detect them using optical imaging methods," explains Zavaleta, who focuses on finding effective contrast agents to diagnose more accurately. cancer.
Early detection of cancer
In her laboratory, this researcher's team is developing new molecular imaging strategies using fluorescence and Raman imaging, aimed at detecting this disease, which covers up to 200 different types. The goal is to guide doctors to the cancer cells and provide them with functional information in addition to the structural details of the tumor that they can already see.
"If we could give them visual cues that could help them differentiate in real time (in the operating room) the tumor from the adjacent normal tissue, it could guarantee the removal of the entire tumor and improve the patient's overall outcome," the researcher emphasizes.
These tools, still in the experimental phase and in the absence of more evidence to guarantee their safety in humans, allow patients to be injected with these materials covered in coloring pigments that increase the sensitivity of images obtained by magnetic resonance or computed tomography.
Thus, when nanoparticles are directed and concentrated in a specific place in the body, they make malignant cells 'glow' and thus allow different types of cancer to be identified. Researchers can thus check, for example, whether a polyp in the colon is cancerous or simply benign, without the need for a biopsy, according to the study recently published in the journal 'Biomaterials Science'.
However, until now there was a safety problem with the use of nanoparticles because they tended to be retained for a long time in the liver and spleen, the organs responsible for breaking them down. But the food dyes that coat, for example, M&Ms, are biodegradable materials and also have a specific size to passively penetrate the tumor areas and be retained for longer for detection.
Currently, only three pigments have been approved by the US Food and Drug Administration (FDA) as contrast agents for optical imaging. "They all have fluorescent properties and can be used to illuminate structures in the body, usually during surgery or endoscopy," says Zavaleta.
The scientific community now has to expand its 'color palette' to better guide doctors in the early identification of cancers, the expert believes.
Virtual biopsies for metastasis
But once the tumor has been detected, other harmless imaging techniques are being developed that will allow virtual biopsies to be performed. These methods will allow us to see biologically in a few minutes what is happening in the tissue without having to open it. They will also be able to detect possible metastasis, and predict whether the treatment will work or not.
This is how the Molecular Imaging Unit team led by Francisca Mulero, a specialist in Nuclear Energy at the National Cancer Research Center (CNIO), can see the inside of the organism thanks to work still in the experimental phase with model animals. , like the mouse.
In their case, instead of dyes, scientists use contrast agents that emit positrons, the antiparticle of the electron. "This gives us an advantage over other types of contrast because they pass through the entire body. In these devices, the patient is introduced and the tumor is seen anywhere because these particles pass through all tissues and can be monitored," emphasizes Mulero. To achieve this, the researcher's group labels nanoantibodies, which are sent directly to the specific part of the tumor. There there is an increase in signal and concentration of gamma photons. "There we see what is happening without taking tissue samples. It is a non-invasive method and will serve to monitor patients," explains the expert.
Unlike Zavaleta's technique in the US, which allows early diagnosis of the tumor, Mulero's research is very useful for studying its extension to other places and monitoring treatment. "Once treatment has started, we can see if there are responses and if we should continue with it or not," she continues.
