Adhesives from nature

Almost invisible, they lurk at the edge of the forest and in the high grass waiting for their next potential host: ticks. Known as carriers of dangerous diseases, the small arachnids do not have a particularly good reputation. Yet they can be of great use for research.

In order to be able to suck blood for several days, ticks have to anchor themselves firmly in the skin. Some species use a cement-like substance that is applied to and under the skin and acts like an adhesive dowel for the mouthparts. Due to its enormous adhesive properties, tick cement has become the focus of medical research. A group at the Medical University of Vienna, led by Sylvia Nürnberger, is working on characterising the cement and making it usable for clinical application. This is because many tissue adhesives currently used in the clinic contain toxic substances, they irritate the surrounding tissue and have a negative effect on healing processes. Since ticks often remain undetected for a long time, the researchers assume that tick cement is better tolerated.

Over the past four years, ticks of various species have been studied at the Medical University Vienna. A special feeding device, a skin-like membrane, was used to obtain the cement. Experiments in cell culture indeed showed that cells feel comfortable around and on the cement, giving initial indications of good tolerance. Together with Martina Marchetti-Deschmann, from the Vienna University of Technology, the chemical composition is being deciphered and the biomechanical properties are determined with Philipp Thurner and Markus Valtiner, also from the Vienna University of Technology.

The project was funded by the Austrian Science Fund FWF. Additionally, the researchers are part of the COST Action of the European Union. COST networks promote cooperation between national and international research activities in science and technology. The network for bioadhesives “ENBA” (European Network of BioAdhesives) is coordinated by the Ludwig Boltzmann Institute for Experimental and Clinical Traumatology (LBI Trauma) and includes 150 researchers from 30 countries.

Bioadhesives are found everywhere in nature. Many animals use the sticky substances for hunting or defence, including the salamander Ambystoma opacum, the Roman snail Helix pomatia, the dwarf squid Idiosepius biserialis, Mytilus mussels and many more. Plants also secrete bioadhesives, probably most famously the sticky traps of carnivorous plants. Knowledge about these materials in terms of composition, structure and interaction with surfaces may reveal possibilities for future clinical applications.

Janek von Byern, scientist at LBI Trauma and head of ENBA, is conducting research at the University of Vienna on the bioadhesives of newts and salamanders. The small animals secrete sticky substances through their skin that act as a defence mechanism against predators. They harden particularly quickly and often stick to the attacker’s mouth for hours. The adhesive is characterised by its high adhesive strength.

The Roman snail is also attracting great interest among bioadhesive researchers. Its mucus allows it to climb vertical surfaces and the adhesive withstands its weight even overhead. Both the keeping of the animals and the harvesting of the slime are particularly easy – important aspects for future use.

The molecule DOPA, obtained from the adhesive filaments of the blue mussel, is being researched particularly intensively and is already in the preclinical test phase. A major advantage of DOPA is its natural application environment under water. It therefore also hardens in a moist environment. The adhesive strength is even somewhat greater than that of fibrin glue, a tissue adhesive widely used in the clinic that is modelled on blood clotting. However, it cannot compete with the less compatible synthetic adhesives in terms of resilience – the scientists are therefore still challenged. In their research, they like to continue to be inspired by nature.