Laser Coagulation: an alternative to stitches

Interview with D.Eng. Martin Wehner of the Fraunhofer Institute for Laser Technology ILT

Wounds in the oral and maxillofacial area are often difficult to suture. Sometimes only simple compression bandages are being used in the oral cavity, which temporarily close the wound. This is why the BI-TRE project, coordinated by the Fraunhofer ILT, is searching for a reliable post-surgical wound closure method. spoke with Dr. Martin Wehner, the project leader of the Fraunhofer Institute.


Photo: Laboratory sample of a handpiece

Laboratory sample of a handpiece for temperature controlled laser coagulation; © Fraunhofer ILT, Aachen

Dr. Wehner, could you briefly define the goal of the BI-TRE project?

Wehner: This grant project intends to bring biophotonic processes into clinical implementation. More precisely, we are developing a laser coagulation method for the fixation of wound dressings as an alternative to stitches and sutures. Oral and maxillofacial surgeries often require the closure of larger wounds in the oral cavity. Suturing in this area is very difficult to perform. Laser coagulation is designed to be an alternative that meets all requirements of wound care. We need an adequate seal, making it impossible for germs to enter the wound from outside. In addition, the method is meant to be easier to handle than current suturing techniques.

What is the exact assignment of the Fraunhofer Institute for Laser Technology during this project?

Wehner: We are testing a specific version of laser tissue soldering. We are working with a liquid protein that is heated using laser radiation and subsequently hardens. This is how we achieve the adhesion process. This works similarly to frying an egg. At first, the egg white is a transparent mass. The increasing heat links the protein and the egg white becomes - as the name already indicates- white. Of course you need to avoid carbonization if the egg is fried for too long. This is why our handpiece that facilitates laser radiation to the surgical site is equipped with a temperature sensor intended to prevent overheating.  One special feature is that we use two different laser wavelengths at the laser source that are absorbed by tissue in varying degrees. That is to say, we have one wavelength that is absorbed in a very thin layer near the surface. We are talking about a range within just a few hundred micrometers. By contrast, a second wavelength enters deeper up to one millimeter.  We proceed this way since the optical properties change drastically during the coagulation process. Back to the example of a fried egg: first it is clear and transparent, then very scattered and no longer transparent. Switching between the two wavelengths enables us to adjust the optical penetration depth. This way, it allows the adhesive to fully harden but doesn’t affect the tissue behind it.
Photo: Laboratory sample of a handpiece for temperature controlled laser coagulation

Testing temperature controlled laser coagulation for the fixation of wound dressings in a pig model; © Fraunhofer ILT, Aachen

The other project partners are currently working on the collagen membrane intended for this use. You focus on the aforementioned laser. When do you expect to use the finished product for the first time?

Wehner: During the course of the two-year project, we are hoping to advance the technology to where it is subsequently ready for use. The requirements for the device-related applications also need to be established. This pertains to the handpiece, the laser source, and the certification since there are several special features involved. After all, a medical laser with temperature control is not the current industry standard. The control circuit is an important point that needs to be considered in terms of manipulation safety. This is why it needs to be certified separately. If the preclinical studies that are first conducted on preparations and small animals show positive results, we are able to continue with further animal studies. If these also show positive results, we can finally advance to a clinical trial. However, it will still take several years until we get to that point.
Photo: Simone Ernst; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Simone Ernst and translated by Elena O'Meara.