Development of a new generation of bioengineered bandages

Periodic Reporting for period 1 - PHAS (Development of a new generation of bioengineered bandages)

Okres sprawozdawczy: 2019-05-01 do 2021-04-30

According to the World Health Organization, burn injuries implicate over 260,000 deaths each year and 11 million hospital consultations. Thus, burns remain among the common causes of trauma and death worldwide. Care management has improved over the last decade so that survival from the initial trauma has enhanced. However, subsequent infections due to exposed areas, have become a leading cause of morbidity and particularly in the case of severe skin damage. Furthermore, the rate of mortality in burn patients is three times higher in patients that are infected by pathogens. Such infections are particularly worrisome in the context of an increasing rise in the resistance of bacterial pathogens to antibiotic treatments, as resistance is among the top ten cause of death, implying an urgent need for the development of novel therapies.
With the support of the Marie Skłodowska-Curie program, the objective of the PHAS project was to improve patient healing, which in turn would reduce hospitalization duration and costs. Specifically, we investigated several formulations for developing a bioactive skin bandage which could cope with the burden of infections and enhance wound repair. In parallel, we implemented metagenomics techniques to identify the communities of microorganisms which may favor the advent of cutaneous infections.
In the frame of this action, promising antimicrobial candidates were identified and tested, showing good biocompatible properties for topical release, which could be used as alternative to antibiotics or Silver ions. Likewise, several formulations of bio-polymers were assessed and showed good biocompatible properties also, having thus the potential to be used as novel types of scaffolds to be combined with progenitor cells and our tested antimicrobials to form a novel anti-infective bio-bandage favoring the healing of burn wounds. The results generated in the frame of this action (TRL3) will be used for future investigations, to advance the technology formulated in the lab towards demonstration in a relevant environment (TRL5), i.e. in-vivo testing. The associated tissue engineering products to be further developed have the potential to affect many stakeholders, covering academic and business interests, physicians, and last but not least, the burn patients.

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.

For severely burned patients, treatment is associated with prolonged hospitalizations and rehabilitation, without mentioning the severe pain, emotional and physical strain that the burn trauma inflicts to the individual affected. Hospitalization is the main cost driver for any wound care, accounting for more than 50% of the total cost. As patients cannot be discharged until healing is well advanced, delays in wound closure have a significant cost impact on hospital stay and other associated resources within the health system. Nursing time is the second factor that outweighs the cost of materials at around 30% of the total care cost. Therefore, an implemented working solution preventing infections during wound care and regenerative tissue engineering as proposed in the PHAS project could drastically reduce the time of healing and the associated need for longer hospitalization.
Overall, the results of this action show promising potential with significant impacts of innovative combination of antimicrobials and biomaterials, nevertheless further investigations are required in order to advance the technologies.

Summary of the PHAS action

Periodic Reporting for period 1 - PHAS (Development of a new generation of bioengineered bandages)

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