Dye-Based Nanoparticles Could be Used in New Imaging Techniques

In a new study, physicists and chemists from Martin Luther University (MLU) have demonstrated a new approach in which tiny nanoparticles can be equipped with dyes and how these particles could be used in novel imaging techniques.

The research team was also the first to fully establish the internal structure of the particles. The study results were published in the leading journal, Angewandte Chemie International Edition.

Single-chain nanoparticles, or SCNPs, are fascinating materials for biomedical and chemical applications. These particles are produced from only a single chain of molecules that folds into a single particle, the circumference of which measures just 3 to 5 nm.

Because they are so small, they can travel everywhere in the human body and be used for a wide variety of purposes.

Wolfgang Binder, Professor, Institute of Chemistry, Martin Luther University

Since it is a new field of research, a few queries continue to remain unanswered. For instance, the internal structure of the particles had only been suspected, but was not ultimately resolved, until now.

After designing the new single-chain nanoparticles that can possibly be used in medicine, Binder and his research team wanted to learn more about the structure of these particles.

We concluded that the nanoparticles we developed must have a special, internal structure.

Wolfgang Binder, Professor, Institute of Chemistry, Martin Luther University

But to establish this claim, Binder contacted collaborators from the departments of physics and chemistry at MLU. Then, using a combination of fluorescence spectroscopy and electron spin resonance, the researchers successfully observed the SCNP structure, for the first time.

“They form a kind of nano-pocket that can protect a dye or other molecules,” Binder explained. The team’s findings correspond with the earlier assumptions about the potential spatial structure inside these microscopic particles.

The goal of Binder’s research team is to design nanoparticles for diagnostic testing purposes, but it is very difficult to produce nanoparticles.

“They have to be virtually invisible to the body,” explained Justus Friedrich Hoffmann, a PhD student in Binder’s research team. The nanoparticles cannot be damaged by the body’s immune system, and they should also have the right internal binding locations so that another molecule or a dye can be preserved and protected. Apart from this, the nanoparticles should be water-soluble, so that they can be easily carried through the bloodstream.

They often form large clumps, but we have now been able to produce individual particles.

Justus Friedrich Hoffmann, PhD Student, Martin Luther University

The researchers then used a chemical trick to condense the chain of molecules into the required form.

The dye, which is integrated at the time of the manufacturing process, needs to be used for the supposed photoacoustic imaging. The process provides an alternative option to computer tomography but without the harmful radiation. It enables scientists to look several centimeters deep into the tissue beyond the body.

Generally, the human body rapidly destroys the dye, Binder added.

The dye is protected by the tiny nanoparticles and it could perhaps be used, for instance, for observing tumors that would penetrate through blood vessels.

SCNPs can also be used in many different applications. For example, they could be utilized as nanoreactors, where chemical reactions occur.

The study was financially supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation).

Journal Reference:

Hoffmann, J. F., et al. (2020) Fluorescent and water dispersible single‐chain nanoparticles: core‐shell structured compartmentation. Angewandte Chemie International Edition. doi.org/10.1002/anie.202015179.