Tag Archives: University of Freiburg

Trick your kidneys with sugar (molecules, that is)

A February 4, 2020 news item on Nanowerk announces research that makes it possible for kidneys to remove nanoparticles after they’ve been used in therapeutic remedies (Note: A link has been removed),

In the past decade nanomedicine has contributed to better detection and treatment of cancer. Nanoparticles are several 100 times smaller than the smallest grain of sand and can therefore easily travel in the blood stream to reach the tumor.

However, they are still too big to be removed by the kidneys. Since several doses of nanoparticles are necessary to treat a tumor, over time the nanoparticles can accumulate in the kidney and cause irreversible damage.

In a study published in the scientific journal Biomaterials (“Renal clearance of polymeric nanoparticles by mimicry of glycan surface of Viruses”), materials scientists at the University of Freiburg [Germany] led by Prof. Dr. Prasad Shastri from the Institute of Macromolecular Chemistry now present a natural solution to this problem: they built nanoparticles with the carbohydrate polysaccharides, which led to the excretion of the particles.

A February 4, 2020 University of Freiberg press release (also on EurekAlert), which originated the news item, expands on the theme,

In nature viruses such as the herpes simplex virus-1 and the cytomegalovirus, which are able to pass through the kidney filtration apparatus despite their large size compared to nanoparticles. Shastri and his team identified that both viruses presents sugar molecules on their surface. Inspired by this observation, the scientists engineered nanoparticles containing polysaccharides. These carbohydrates are frequently found in the human tissue environment. Using a real-time imaging technique, which they have established in their laboratory, the team investigated in a mouse model the fate of these nanoparticles. They observed that the polysaccharide-enriched nanoparticles readily pass through the kidney and are excreted with the urine within a few hours after intravenous administration. The decisive factor for the researchers was that the nanoparticles continued to act as intended and were still able to target tumors.

“The ability to combine tumor accumulation and kidney clearance in the same nanoparticle represents a tipping point in ensuring that nanomedicines can be safely administered” says Shastri. “Our nature-inspired approach enabled us to trick the kidney environment to let nanoparticles pass through” adds Dr. Melika Sarem who was a co-author of the study.

Prasad Shastri is Professor of Biofunctional Macromolecular Chemistry at the Institute for Macromolecular Chemistry and Professor of Cell Signalling Environments in the Excellence Cluster BIOSS Centre for Biological Signalling Studies and at the University of Freiburg.

Here’s a link to and a citation for the paper,

Renal clearance of polymeric nanoparticles by mimicry of glycan surface of viruses by Pradeep P.Wyss, Surya P.Lamichhane, Ahmed Abed, Daniel Vonwil, Oliver Kretz, Tobias B. Huber, Melika Sarema, V. Prasad Shastri. Biomaterials Volume 230, February 2020, 119643 DOI: https://doi.org/10.1016/j.biomaterials.2019.119643 First published online November 23, 2019

This paper is behind a paywall.

Opposite world: developing anti-adhesion surfaces

The power of the metaphor/analogy is demonstrated in a Sept. 24, 2013 news item on ScienceDaily where they’ve mentioned insects in the context of anti-adhesion—the opposite of how insects are usually referenced, i.e., how well they stick to surfaces and the search for better adhesives. Or you could put it down to lazy reading on my part as it took me a minute or so to make sense of what I was reading (from the news item),

Beetles, cockroaches, and ants will have a harder time walking up the sides of buildings or air conditioners in the future — thanks to the bio-inspired, anti-adhesive surfaces Prof. Dr. Thomas Speck, Dr. Bettina Prüm, and Dr. Holger Bohn are developing together with the Plant Biomechanics Group of the University of Freiburg. The team studied plant surfaces in order to determine what influence cell form and microstructure as well as surface chemistry exert on the adhesion behavior of insects.

The Sept. 24, 2013 University of Freiburg (Germany) press release,which originated the news item, describes the research and the new anti-adhesive surface in more detail,

The researchers conducted adhesion experiments in which Colorado potato beetles walked across differently structured plant surfaces as well as replicas made of synthetic resins. The team used a highly sensitive sensor to measure the traction forces of the beetles on various surfaces. They discovered that wavy or strongly curved cells can increase the adhesive powers of beetles, whereas microstructures composed of wax crystals or cuticular folds reduce them. The latter are tiny folds in the cuticle, a protective layer on the surface of the leaf resembling polyester. The beetles had the hardest time walking on surfaces with cuticular folds with a height and width of approximately 0.5 micrometers and a spacing of between 0.5 and 1.5 micrometers. “That is the perfect anti-adhesion surface. The insects slip off of it much easier than off glass,” says project director Thomas Speck. The cuticular folds reduce the contact area between the adhesive hairs on the beetles’ legs and the plant surface. Unlike on more coarsely structured surfaces, the beetle can’t dig its feet firmly into the cuticular folds. Thus, the microstructure of the surface has a stronger effect on the adhesion of the beetle than the cell form.

The team also took contact angle measurements to investigate the wettability of the various surfaces. The researchers used hydrophobic and hydrophilic artificial moldings of the microstructured plant surfaces in order to study the influence of the surface chemistry on surface wettability and the beetles’ walking behavior. Much like wax crystals, cuticular folds are very good at repelling water. In contrast to the wettability, which depends on both the microstructure and the surface chemistry, the walking behavior of the beetles is not influenced by the surface chemistry. This means that the beetle’s adhesive power depends solely on the physical microstructure of the surface.

Here’s a link to and a citation for the researchers’ paper,

Plant surfaces with cuticular folds and their replicas: Influence of microstructuring and surface chemistry on the attachment of a leaf beetle by Bettina Prüm, Holger Florian Bohn, Robin Seidel, Stephan Rubach, and Thomas Speck. Acta Biomaterialia Volume 9, Issue 5, May 2013, Pages 6360–6368

This paper is behind a paywall.