Mussel glue to replace surgical sutures

A surgeon has completed surgery: whatever needed to be removed or corrected has been attended to, and the surgical wound now needs to be closed.

The classic solution is to use a needle and surgical thread – sutures. The surgeon sews up the wound and then removes the sutures once the wound has healed, unless they use sutures which gradually dissolve.

Another solution is the surgical staple – small, sterile staples of stainless steel or titanium, which the surgeon uses to staple the wound together. Once the wound has healed, typically after one to two weeks, the staples are removed.

But what if we could rethink this entirely, eliminating sutures and staples in many cases and using glue instead – for both external and internal surgical wounds.

This is a highly challenging solution in many ways, because surgical wounds are moist and it is not easy to glue wet surfaces together. Nevertheless, a team of researchers from iNANO at the Department of Chemistry, Aarhus University, are fully convinced that they can develop a surgical glue of this kind:

‘We’re in full swing and we’re basing our work on studies of the common mussel,’ says Associate Professor Henrik Birkedal, who is the team leader.

He began studying the common mussel several years ago, and funded by the Lundbeck Foundation, among others, he has mapped a range of fascinating aspects of the chemical properties of the protein threads – byssal threads – used by the common mussel and a number of other marine mussels to anchor themselves to wet, slippery rocks. Even when pounded by one brutal wave after another.

‘And the chemical properties of these byssal threads form the basis for our work to produce a surgical glue that really sticks. Compared to sutures, the advantage of a glue of this kind is that it will fit and flow into the very places where the wound surfaces need to meet. In the case of sutures, for example, it can be difficult to find the perfect thread dimension to close the surgical wound optimally,’ Henrik Birkedal explains.

Global interest

The researchers at iNANO at Aarhus University are not the only ones to study the chemical properties of the byssal threads of mussels. Chemists at universities the world over have this field in their sights, and there are plans to use mussel chemistry for a wide variety of purposes. Henrik Birkedal elaborates:

‘For instance, a South Korean group has discovered that we can produce a material to stop the bleeding from a pinprick by copying the chemical tricks used by marine mussels. And another research team in the US has demonstrated the potential to build an imitation of the so-called self-healing properties of mussel byssal threads into functional materials such as plastic.’

These self-healing properties are another astounding characteristic of the byssal threads. They enable the threads to heal themselves as they wear.

It is this unique self-healing chemical property that the American researchers have made applicable in practice, and it can now be integrated into a variety of synthetic materials.

This means that a range of medical implants incorporating highly durable plastic tubes may suddenly be plausible.

However, the characteristic needs to be stabilised before the long-term safety of this self-healing, chemical property can be ensured in a synthetic material for incorporation in an implant – for instance, a special plastic tube for transporting blood across a section of a person’s vascular system. This requires an independent chemical process, and the researchers at iNANO at Aarhus University are the first in the world to devise a formula for it. Henrik Birkedal explains:

‘So far, this is our most significant contribution to the research based on the common mussel’s amazing ability to cling to surfaces under water.’

Stopping the bleeding

While the Aarhus scientists are working on developing the surgical glue, they also have their eye on another, closely related field. Henrik Birkedal elaborates:

‘It’s all about trying to develop barrier materials, and this is also one of our key focus areas. Barrier materials are glue which can be used to stop internal bleeding or prevent the seepage of bacteria into the abdominal cavity, which can occur during bowel surgery and which is potentially highly dangerous. It would be extremely useful if, instead of suturing, we could apply some type of tightly sealing adhesive to surgical incisions in the bowel.’

Henrik Birkedal explains that we already have adhesives for internal surgical use. However, they are not particularly effective: ‘So byssal chemistry could provide us with good solutions here, too – if it is integrated into the right materials.’

According to Henrik Birkedal, it is difficult to guess when the various types of surgical glue and barrier materials will reach the market: ‘We’ve got to the stage of preparing for animal trials, and if all goes well, and we can get the funding, we should be able to start in three to four years’ time. The glue will then have to be tested on humans, so the entire process will take some years.’