Laser Tissue Soldering Uses Light and Nanothermometers as Minimally-Invasive Alternatives for Wound Fusion

Not every wound can be closed by using a needle and thread. In a recent breakthrough, a team of experts have developed a novel process of gently fusing tissue for better wound healing.

Wound Suturing Technique

The idea of suturing a wound started sometime more than 5,000 years ago. Since then, this surgical technique has not changed much and remains one of the most commonly used methods in closing incisions.

A suture refers to a stitch or a row of stitches which holds together the edges of a wound or surgical incision. Suturing involves the application of stitches using a needle with an attached piece of thread which are secured with surgical knots.

Wound suturing is important to reduce the risk of bleeding and wound infection and to support and strengthen wounds until healing. Once both sides of a wound are fixed to each other neatly, then the body can begin to close the tissue gap permanently in a natural way.

However, there are times when the suture does not achieve what it is supposed to. Depending on the fingertip feeling of the person who performs the operation, cuts or tears from the wound can be joined together more or less perfectly. In very soft tissues, the thread can cut through the flesh and cause additional injury. And if the wound closure fails to seal on internal organs, permeable sutures can pose a life-threatening problem.

Innovative Laser Wound Soldering

Wound soldering is usually done by joining materials together by heat using a melting bonding agent. The fact that this thermal reaction must stay within narrow limits for biological materials while measuring the temperature in a non-invasive way has been a challenge in applying soldering processes in medicine.

In collaboration with ETH Zurich, scientists from Empa developed a smart wound system where laser soldering can be gently and efficiently controlled. Led by Oscar Cipolato and Inge Herrmann, they created a bonding agent with metallic and ceramic nanoparticles and used nanothermometry for temperature control. The result of their study is described in the paper "Nanothermometry-Enabled Intelligent Laser Tissue Soldering."

The novel soldering process is based on the interaction of the two types of nanoparticles in the bonding protein-gelatin paste. As the laser irradiates the paste, the light is converted by titanium nitride nanoparticles into heat. Meanwhile, the specially synthesized bismuth vanadate particles in the paste act as tiny fluorescent nanothermometers.

A specific wavelength of light is emitted in a temperature-dependent manner, enabling precise temperature regulation in real time. This makes this approach suitable for use in minimally invasive surgery, since it does not require stirring and determines temperature differences with extremely fine spatial resolution in deep wounds.

After optimizing the conditions for iSoldering through mathematical modeling in silico, Cipolato and his team were able to investigate the performance of composite materials. They achieved fast, stable, and biocompatible bonding of wounds on organs like the liver or pancreas in laboratory tests with different tissue samples.

Furthermore, the research team also succeeded in replacing the laser light source with infrared light, bringing the soldering technology another step closer to be used in hospitals. If this approach is medically applied, it can be used in conventional operating rooms without the need for additional laser protection measures.