Wound healing: Fraunhofer Institutes develop bioresorbable membrane RENACER

Treating large-area and internal wounds and promoting their often protracted healing remains a challenging task for medicine. Researchers at the Fraunhofer Institute for Silicate Research (ISC) and the Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM) have developed the bioresorbable membrane RENACER®.

In an interview with MEDICA-tradefair.com, Dr. Bastian Christ explains how RENACER® was developed, what is possible with the membrane and how it could be further developed.

Dr. Christ, what is RENACER®?

Dr. Bastian Christ: RENACER® was developed by the Fraunhofer ISC. The membrane consists of amorphous, for instance non-crystalline, silica gel that completely dissolves into a bioactive molecule, monosilicic acid, when in contact with physiological solutions. On the basis of this material platform, we were able to produce a fibrous membrane that can be used in wound healing.

What makes RENACER® so special?

Christ: The material dissolves in monosilicic acid and does so in an almost pH-neutral manner. Monosilicic acid is ubiquitous in nature and can be detected natively in the body - in tissue, in body fluids. In the human organism, this acid can even contain attributed bioactive properties. For example, it is involved in the formation of connective tissue. Products available up to now do not have such properties.

Many biodegradable materials dissolve to form organic acids such as lactic acid or glycolic acid. This can lead to local hyperacidity in the tissue, which triggers inflammatory reactions of the immune system. Tests on our RENACER® in cell culture have once again confirmed that the dissolution product, monosilicic acid, is also completely compatible with cells and is neither toxic nor genotoxic. The material can therefore be introduced into the body. This proof was carried out in cell culture at Fraunhofer ITEM.

Are there any other advantages?

Christ: The material exhibits special degradation behavior. With RENACER®, the membrane retains its shape over a very long period of biodegradation. Accordingly, the mesh size set in the membrane during the spinning process remains intact over a long period. In contrast, many other membranes contract in contact with physiological solution and cells.

Which of the two Fraunhofer institutes was able to contribute what?

Christ: Fraunhofer ISC has a lot of experience in the development of bioresorbable materials and in process engineering. In discussions with doctors and colleagues from Fraunhofer ITEM, we came up with the idea of developing a bioresorbable membrane that helps prevent postoperative adhesions.

Fraunhofer ITEM investigated how the material affects the body's cells and whether the barrier effect is sufficient to prevent unwanted scarring without, for example, disrupting the physiological supply to the wound edges and the metabolism. Fraunhofer ISC developed the material formulation and the manufacturing processes for the fiber membrane.

What was your initial situation?

Christ: A wound dressing based on silica gel fibers already has approval as a medical product. It was shown that our fiber system and the degradation product monosilicic acid have a positive effect on wound healing.

We now wanted to improve these effects even further with RENACER® and have further developed the molecular structure. Parallel to the molecular structure, we have expanded our technologies for spinning such fibers. In addition to the already established pressure spinning process, which produces fibers with a diameter of around 50 µm, we can now also spin fibers with diameters smaller than 1 µm by electrospinning. As a result, the "mesh sizes" of the fiber nonwovens that can be produced from them can be greatly reduced.

New areas of application are opening up. For example, it is possible to prevent connective tissue cells from growing through (the material) without disrupting the supply of nutrients to the cells. Depending on how the fiber diameter and density of the nonwoven are adjusted, a growth barrier can be created to prevent unwanted adhesions and scarring; or, if the mesh is large enough, a regenerative wound dressing that supports natural tissue formation.

What was the challenge in the project?

Christ: To integrate all the important properties into a final demonstrator. In other words, the RENACER® membrane had to be non-toxic, dissolve completely under physiological conditions and be intrinsically stable as a membrane. These fine-tunings had to be successively adjusted in iterative steps over the course of the project.

What happens now with RENACER®?

Christ: Many steps are still necessary for further testing and approval. For this, we need additional partners from medical device manufacturing and from the clinic. But we have been able to take the first steps - the proof-of-concept and the toxicological tests - in the Fraunhofer in-house research project and know that we are on the right track.

We are also working on other interesting applications. For example, we can integrate additional active ingredients into the nonwoven. If, for example, we were able to integrate chemotherapeutic agents against certain types of brain tumors into the RENACER® fiber, we might be able to circumvent the problem of the blood-brain barrier. The blood-brain barrier protects the brain from foreign substances. This is absolutely necessary, but in the case of drug-based therapy for brain tumors, it is a major obstacle. With drug-loaded RENACER® membranes applied to the remaining wound cavity during tumor surgery, the active substances could be delivered directly into the adjacent tissue and combat tumor cells that have already settled. Since November 2022, we have been collaborating on this with the neurosurgery department of Würzburg University Hospital in the GlioGel project.