Biomedical use for tick ‘cement’
The sticky substance used by ticks to anchor to their prey has potential as a bioadhesive. Kathryn Allen reports.
Found in tall grass, ticks are tiny, wingless insects that anchor themselves to warm-blooded animals to feed on their blood. Known for their strength in attaching themselves to skin, ticks have become the focus of researchers at the Medical University of Vienna and Vienna University of Technology, Austria, who aim to chemically recreate the protein-based, cement-like substance ticks use to latch on to their prey.
The composition of the substance secreted by 300 ticks is being studied at the Medical University of Vienna. As ticks bite through a skin-like membrane, they secrete the adhesive substance, which is then collected and analysed. Later this year, the substance secreted by giant ticks in South Africa will also be studied. The researchers expect the substance produced by the giant ticks to be similar to that of the Austrian ticks, but it is hoped that, if there are differences, it will help them better understand the composition and mechanisms of both substances.
Funded by the Austrian Science Fund, the study is part of the EU Cooperation in Science and Technology (COST) Action – an international network for collaborating on research projects. The COST Action European Network of Bioadhesion Expertise unites experts studying bio-adhesives. Various organisms, from bacteria to plants and animals, produce chemical substances to anchor themselves to surfaces. Some of these adhesives function better than their synthetic alternatives, withstanding broader temperature ranges and adapting to different environments.
Sylvia Nürnberger, from the Medical University of Vienna’s Department of Trauma Surgery and project leader, is working alongside Martina Marchetti-Deschmann from Vienna University of Technology to develop a bio-adhesive from the tick ‘cement’. Nürnberger commented, ‘It is totally conceivable that, in future, it will be possible to use this substance to produce a biological adhesive for human tissue. For example, anchoring tendons and ligaments to bone without using any metal.’ Currently, tendons and ligaments are fixed by sewing or screwing and typically require metal components. Nürnberger expects that liver ruptures and skin defects can also be treated using this bio-adhesive.
As Nürnberger points out, current tissue adhesives can be toxic to an extent and others are not strong enough for medical purposes. ‘Currently used tissue glues are either based on fibrin, and are in this case biocompatible but with weak bonding forces, or are based on toxic substances such as cyanoacrylate, formaldehyde or glutaraldehyde,’ said Nürnberger. The researchers hope that the tick substance is stronger than established biocompatible glues.
Other biological alternatives to current tissue adhesives that have the potential to be developed include substances secreted from certain salamander species and adhesive threads from sea cucumbers. The sticky threads produced by marine mussels, containing the adhesive protein 3,4-dihydroxy-L-phenylalanine (DOPA), have been studied in depth by an international research team that has successfully replicated the adhesive and produced a synthetic alternative. Synthetic mimics of this adhesive have been produced by polymerising compounds containing catechol, such as DOPA. However, due to DOPA’s low bonding strength, Nürnberger predicts that it won’t be suitable for a wide range of medical applications, meaning the search is still on.
Nürnberger explains that, ‘Biological substances are frequently produced by biotechnological methods. This means that gene sequences responsible for the creation of the substance are introduced, for example, into bacteria that then produces this substance in the course of their normal metabolic activities.’