Wound closure: soldering with light and nanotechnology

With "iSoldering", the Particles Biology Interactions Laboratory at the Swiss Federal Laboratories for Materials Science and Technology (Empa) in St. Gallen and the Nanoparticle Systems Engineering Laboratory at ETH Zurich have developed a method that does not require surgical sutures or synthetic adhesives. Instead, nanoparticles and light enable secure wound closure.

In an interview with MEDICA-tradefair.com, Prof. Inge Herrmann describes the advantages and areas of application of this technology, which could also be used for minimally invasive surgery.

Prof. Hermann, how does this soldering process work?

Prof. Inge Herrmann: We use a protein-rich soldering paste containing gelatine and light-absorbing and light-emitting nanoparticles, which is applied to the wound. The nanoparticles are irradiated with a laser, heat up and the nanothermometers they contain then emit a signal with which we can measure the temperature without contact.

Heating the solder paste with the laser to around 60 degrees causes the proteins to change their shape, the chains open up and mix with the underlying biological tissue. This results in crosslinking with the tissue, which is only heated locally and to a small extent.

What are the advantages over other methods, such as classic suturing?

Herrmann: Intelligent soldering, iSoldering, is a very gentle method because we do not cause any additional injury to the tissue with the soldering material, as is the case with suturing or stapling with sewing needles or staples. When gluing wounds with a cyanoacrylate adhesive, the acrylates are not very well tolerated. Biological alternatives such as fibrin glue adhere very weakly, and bonding wet or moist tissue generally works poorly. As our solder paste consists mainly of proteins, we have fewer biocompatibility concerns than with synthetic adhesives.

What are the preferred areas of application?

Herrmann: The procedure is only suitable for very soft tissue that cannot be sutured with a needle and thread because the thread would otherwise cut through the tissue. This is mainly the case with the liver, but also with the intestine and very small nerve or blood vessels. These are the main applications. However, we will not replace the classic applications of suturing.

There are limits to wound closure in the microscopic area. But here the conditions for soldering are better than when working with a thread. We are currently working on developing an endoscopic and robotic method so that the soldering procedure can be used in a minimally invasive way.

What experience has already been gained and when will it be possible to implement it in practice?

Herrmann: Surgeons at Charles University in the Czech Republic have achieved a fast, stable and biocompatible connection of wounds, for example on the intestine, muscle or liver, in laboratory tests with various tissue samples. Other cooperation partners are doctors from the University Hospital Zurich and the Cleveland Clinic (USA), who advise us in the laboratory.

A patent application has been filed for the nanoparticle composite material. Based on experience, we expect it to take five to ten years before it can be used in practice. The procedure must be approved, and it must be ensured that there are no long-term effects.

Do the nanoparticles remain in the body?

Herrmann: This is something that the regulatory authorities will also be very interested in. This proof of absence, i.e. that nothing harmful happens, is difficult to obtain. We are doing everything we can to understand this: What happens to these particles? Are they broken down or redistributed? We see that they are not distributed in the body and are working on the choice of materials so that nanoparticles are as compatible and even degradable as possible.