|Needle And Thread? Mussels Inspire New Type Of Surgical Glue|
|SciMed - Healthcare|
|TS-Si News Service|
|Sunday, 09 December 2007 19:00|
Is it a bio-adhesive of the Future?
Although many adhesives are already used in medicine today, their applications are limited as they can release toxins (such as formaldehyde).
Mussels have provided a solution.
A research team has developed a new approach based on the mussels' ability to stick on any surface, be it porous rock or the smooth hull of a ship. Over the course of evolution, these mollusks have developed a special glue that not only works under water, but is also a particularly firm and lasting bonding agent. Moreover, the mussel adhesive is relatively well tolerated by the human body.
It sounds risky at first: implants such as artificial heart valves and vessels are to be welded to the body’s own tissue using a special glue, a synthetic version of a mussel gland's secretion. This will eliminate the need for bothersome sutures. The bond will rapidly harden under ultraviolet (UV) light, so that only 30 seconds later, the foreign object is firmly implanted in the patient’s body.
Dr. Klaus Rischka, a chemist at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research (IFAM), is confident that this scenario will soon become reality. The scientists envisage it one day replacing stitches in surgery, for the treatment of cuts and gashes, joining broken bones or serving as a fixative aid for ligaments. Other potential areas of applications are in retina repair, as a fixative for dental prostheses or for anchoring tissue samples on slides for microscopic examination.
The common mussel is a master of adhesive bonding. The mussels' secretions keep them stuck fast even to surfaces that are as smooth as glass. They also stick to iron, wood and stone, painted surfaces, and Teflon coatings. The molluscs can hold on to walls and posts by their adhesive threads for years, even when pounded by mighty salt-water waves and surf.
Because of their adhesive properties in a damp environment, where other adhesives fail, the mussel secretion can be relied upon to stay put. That is why it is ideal for medical applications like dressing wounds, fixing broken bones, and suturing incisions in a "wet" environment.
The Fraunhofer researcher and his partners will initially demonstrate the glue’s suitability on the basis of a dental implant made of titanium. It is current practice to anchor tooth implants in the jaw bone without an adhesive. This often leaves gaps between the gums and the metal, allowing bacteria to enter and cause infections. A glue that firmly connects the gums to the implant would serve as an effective barrier against aggressive germs. Conventional products are not suited to such a purpose, however, as they would sooner or later dissolve in the moist environment inside the mouth.
The strength of the bond is due to a particular growth protein that can be synthetically produced using the classic technique of solid-phase peptide synthesis. Its purpose is to stimulate cell growth so that the body’s own tissue — in this case the gums — bonds as closely as possible with the implant. A third component, in the form of a classic polymer, is then added as a carrier substance.
The typical coupling step in solid peptide synthesis (according to L. P. Miranda.
The amino acid chain AAHYHTHKE with side chain protecting groups bonds with glutamate (E) to a PAM resin. Lysine is protected with Boc (Nα) and 2-chloro-benzyl-oxy-carbonyl (sidechain).
It is activated with OBt.
The work of the IFAM team to produce this natural product in the laboratory has paved the way for its eventual production on an industrial scale. The chemists are able to synthetically reproduce the key elements of the substance in sufficient quantity for use in a joint project with the European Space Agency (ESA). That joint effort is intended to develop an adhesive for everyday repairs during manned spaceflight.
Until recently, mussel secretions were extracted naturally at a barely affordable price. Since some 10,000 molluscs are needed to produce one gram of the material, it can cost approximately €200,000. It is understandable that to date the costly substance has only been used in minimal amounts for selected scientific applications. Doctors and medical technology companies are extremely interested in the prospect of a low-cost method of synthetic production.
Over the next two years, the participating chemists, medics and engineers intend to create a basis for practical medical applications. According to Rischka, it may then take another five to ten years before the glue is ready to be used on humans.
Dr. Klaus Rischka (Fraunhofer) has partnered with colleagues at Frankfurt University Hospital, the Center of Biotechnical Engineering BitZ at Darmstadt University of Technology, the State Materials Testing Institute MPA and the implant manufacturer Straumann in Freiburg.
The Fraunhofer IFAM is one of 80 research establishments within the Fraunhofer-Gesellschaft (FhG). It is a leading independent organization for applied research in Europe.
|Last Updated on Monday, 10 December 2007 01:50|