Nanoparticles are the smallest particles capable of reaching virtually all parts of the body. Researchers use various approaches to test ways in which nanoparticles could be used in medicine - for instance, to deliver substances to a specific site in the body such as a tumor. For this purpose, nanoparticles are generally coated with organic materials because their surface quality plays a key role in determining further targets in the body. If they have a water-repellent shell, nanoparticles are quickly identified by the body's immune system and eliminated.
How gold particles wander through the body
The team of scientists headed by Dr. Wolfgang Kreyling, who is now an external scientific advisor at the Institute of Epidemiology II within the Helmholtz Zentrum Muenchen, and Prof. Wolfgang Parak from the University of Marburg, succeeded for the first time in tracking the chronological sequence of such particles in an animal model. To this end, they generated tiny 5 nm gold nanoparticles radioactively labeled with a gold isotope*. These were also covered with a polymer shell and tagged with a different radioactive isotope. According to the researchers, this was, technically speaking, a very demanding nanotechnological step.
After the subsequent intravenous injection of the particles, however, the team observed how the specially applied polymer shell disintegrated. "Surprisingly, the particulate gold accumulated mainly in the liver," Dr. Kreyling recalls. "In contrast, the shell molecules reacted in a significantly different manner, distributing themselves throughout the body." Further analyses conducted by the scientists explained the reason for this: so-called proteolytic enzymes** in certain liver cells appear to separate the particles from their shell. According to the researchers, this effect was hitherto unknown in vivo, since up to now the particle-conjugate had only been tested in cell cultures, where this effect had not been examined sufficiently thoroughly.
"Our results show that even nanoparticle-conjugates*** that appear highly stable can change their properties when deployed in the human body," Dr. Kreyling notes, evaluating the results. "The study will thus have an influence on future medical applications as well as on the risk evaluation of nanoparticles in consumer products and in science and technology."
* Isotopes are types of atoms which have different mass numbers but which represent the same element.
** Proteolytic enzymes split protein structures and are used, for example, to nourish or detoxify the body.
*** Conjugates are several types of molecules that are bound in one particle.
Kreyling, W. et al. (2015). In vivo integrity of polymer-coated gold nanoparticles, Nature Nanotechnology DOI: 10.1038/nnano.2015.111
As German Research Center for Environmental Health, Helmholtz Zentrum Muenchen pursues the goal of developing personalized medical approaches for the prevention and therapy of major common diseases such as diabetes mellitus and lung diseases. To achieve this, it investigates the interaction of genetics, environmental factors and lifestyle. The Helmholtz Zentrum Muenchen has about 2,300 staff members and is headquartered in Neuherberg in the north of Munich. Helmholtz Zentrum Muenchen is a member of the Helmholtz Association, a community of 18 scientific-technical and medical-biological research centers with a total of about 37,000 staff members.
The Institute of Epidemiology II (EPI II) focuses on the assessment of environmental and lifestyle risk factors which jointly affect major chronic diseases such as diabetes, heart disease and mental health. Research builds on the unique resources of the KORA cohort, the KORA myocardial infarction registry, and the KORA aerosol measurement station. Aging-related phenotypes have been added to the KORA research portfolio within the frame of the Research Consortium KORA-Age. The institute's contributions are specifically relevant for the population as modifiable personal risk factors are being researched that could be influenced by the individual or by improving legislation for the protection of public health.
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Scientific contact at Helmholtz Zentrum Muenchen:
Dr. Wolfgang G. Kreyling, Helmholtz Zentrum Muenchen - German Research Center for Environmental Health (GmbH), External Scientific Advisor of the Institute of Epidemiology II, Ingolstaedter Landstr. 1, 85764 Neuherberg - Email: firstname.lastname@example.org