The experimental work encompassed two main work-packages: The first work package consisted of proposing a novel type of skin bandage having synergistic capabilities, enhancing tissue repair and controlling infection simultaneously. Thus, several antimicrobial candidates, as alternatives to antibiotics, were tested for their biocompatibility and cytotoxicity with progenitor fibroblasts, these latter having the capability of releasing of growth factors for enhanced wound repair. A screening of the following candidates was performed: Methyglyoxal (MGO), Antimicrobial Peptide Dendrimers (AMPDs), Cannabidiol (CBD), Bacteriophages, and Propolis.
The delivery of the antimicrobials in combination with progenitor cells requires the use of a scaffold. Therefore, chitosan-derived foams, bacterial nanocellulose (BNCs) and electrospinned polyesther-co-amides (PEAs), developed by other Swiss groups as a collaborative and translational effort, were also tested for their biocompatibility with progenitor cells. Similarly, cell proliferation and CAM assays were used to determine the biocompatibility and the scaffold candidates. Cell adhesion on scaffolds was visualized by Giemsa stain.
We determined that each of the tested scaffolds provided a competitive potential for specific tissue engineering applications in burn care, when compared to other existing solutions. Applications encompasses new dermal substitutes, temporary first covers and biodegradable delivery systems for cultured keratinocyte autografts The tested biomaterials, besides being highly biocompatible and cost-effective, have tunable molecular structure and porosity, along with specific functionalities such as to control tensile strength, flexibility, permeability to gases. The results generated (TRL3) can be exploited to advance the technologies validated in the lab towards demonstration in a relevant environment (TRL5), i.e. initial in-vivo testing.
The second experimental work package consisted in determining the bacterial landscape over time of burn wounds and healthy skin in burned patients, by collecting the topical bandages in contact with burn lesions (Jelonet) and other dressings in contact with the patient wounds or healthy skin area. The hypothesis was that a post-injury shift in skin microbiota (bacterial communities) could promote the appearance of persistent pathogens and provoke skin graft failure. A clinical protocol was written and approved by the local state ethical committee (CER-VD) in order to collect both, dressings directly from burn patients at our hospital, as well as their medical data, in order to determine the wound microbiota by metagenomics. A specific protocol for extracting the DNA from dressings has been developed, as the fatty composition of Jelonet dressings impedes DNA extraction and downstream sequencing. In total, 15 patients were within the inclusions criteria, for which we have collected bandages and extracted DNA. Among 76 samples, only 13 samples had enough microbial DNA for sequencing, all the other samples had mainly host DNA. Microbiota composition was analyzed by sequencing of the V3 and V4 regions of the 16S rRNA gene. All samples had a significantly reduced alpha diversity. When looking at the abundances of each taxa, we observed considerable variability between the samples, and the important abundance of actinobacteria in some samples, which are soil bacteria, implying the plausible presence of contamination.
