Small nanoparticles can be dyed and could be used for new imaging techniques, as chemists and physicists at Martin Luther Halle-Wittenberg University (MLU) show in a recent study. The researchers have also been the first to determine the internal structure of the grains. Their findings were published in the prestigious journal Cemie Angewandte.
Single-chain nanoparticles (SCNP) are attractive materials for chemical and biochemical applications. They are formed from just one layer of molecules that fold into particles that have a circumference measuring three to five nanometers. “Because they are so small, they can travel everywhere in the human body and be used for a number of purposes,” says Professor Wolfgang Binder from MLU’s Institute of Chemistry. As it is a new area of research, some questions remain unanswered. So far, for example, the internal structure of the fragments has not been accepted, but has not been finally resolved.
After Binder and his team developed new single-chain nanoparticles that could be used in medicine, they wanted to learn more about their structure. “We concluded that the nanoparticles we developed must have a specific internal structure,” Binder said. To establish this, he contacted colleagues from the chemistry and physics departments at MLU. Using a combination of electron spin repositioning and a fluorescence spectroscope, the scientists were able to see the structure of SCNP for the first time. “They are a type of nano-pocket that can protect color or other molecules,” Binder explained. Their results are in line with previous assumptions about the possible spatial structure of tiny particles.
The goal of the Binder research group is to develop nanoparticles for diagnostic tests. However, extraction of the nanoparticles is a complex task. “They have to be almost invisible to the body,” explained Justus Friedrich Hoffmann, a PhD student in the Binder research group. They cannot be destroyed by the body’s immune system and must also have proper internal binding sites in order for color or other molecules to be stored and protected. In addition, they need to be soluble in water to be transported through the bloodstream. “They often form large lumps, but we have now been able to produce individual grains,” Hoffmann says. They used a chemical trick to compress the chain into the shape they wanted.
The color, which is absorbed through the manufacturing process, is to be used for so-called photocoustic images. The method represents an alternative to computed tomography but without the dangerous radiation. It allows one to look several centimeters deep into material from the outside of the body. The color is usually quickly destroyed by the body, says Binder. The tiny nanoparticles protect the dye, which could be used, for example, in seeing tumors that would pass through blood vessels.
SCNP can be used in many other types of applications as well. For example, they could be used as nanoreactors in which a chemical reaction occurs.
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The research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation).
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