If the heart muscle is damaged, repairing this constantly active organ can be a challenge. Researchers at Empa are therefore developing a tissue adhesive inspired by nature which can repair defects in muscle tissue perfectly. To achieve this, they have taken advantage of the adhesion ability of marine mussels.
The new biopolymer with mussel proteins exhibits a fine but robust microstructure (scanning electron microscopy, 1000x magnification).
Empa
On windy and wave-pounded coasts, mussels adhere to rocks, boats and jetties. With super strength, the mussel's foot holds on to the surface. Its glands produce fine adhesive threads (byssus) which, unlike spider silk, remain firm but highly elastic underwater. The components of the muscle silk include the proteins mfp-3 and mfp-6. As structural proteins, they are relevant for biomedicine particularly due to their fascinating mechanical properties and their biocompatibility with living tissues.
Getting to the heart of the issue
The Empa (Swiss Federal Laboratories for Materials Science and Technology) researchers from the "Biomimetic Membranes and Textiles" laboratory in St. Gallen made use of these properties. Claudio Toncelli's team was looking for a biocompatible tissue adhesive which would adhere to a beating heart and remain elastic, even under challenging conditions. This is because if heart muscle tissue is damaged, for example due to an infarction or a congenital disorder, the wounds must be able to heal, even though they are still working permanently. "Actually, collagen is a suitable basis for a wound glue, a protein that is also found in human connective tissue and tendons", says Toncelli. For example, gelatin consists of collagen in a linked structure, which would be very attractive for a tissue adhesive. "The structure of gelatin already comes very close to some of the natural properties of human connective tissue", adds the researcher. However, the hydrocolloid is not stable at body temperature, but instead liquefies. So in order to develop an adhesive material that can hold wounds on internal organs firmly together, the researchers had to find a way to incorporate additional properties into the gelatin.
Perfect mussel silk
"The muscular foot of mussels excretes strongly adhesive threads with which the mussel can adhere to all kinds of surfaces in water", explains Toncelli. Several proteins contained within this mussel silk interact perfectly. As soon as the gelatin mussel silk gel comes into contact with tissue, the structural proteins link with each other and ensure a stable connection to the wound surfaces. The researchers have already investigated how well the new hydrogel actually adheres in lab experiments that are used to determine technical standards for what is known as bursting strength. "The tissue adhesive can resist a pressure equivalent to human blood pressure", says Empa researcher Kongchang Wei. The scientists were also able to confirm the outstanding tissue compatibility of the new adhesive in cell culture experiments. They are now trying hard to advance the clinical application of this "mussel glue".