A collagen-based layered chronic wound biofilm model for testing antimicrobial wound products

Ida C Thaarup*, Mads Lichtenberg, Kim T H Nørgaard, Yijuan Xu, Jan Lorenzen, Trine R Thomsen, Thomas Bjarnsholt

*Corresponding author for this work
1 Citation (Scopus)

Abstract

A new in vitro chronic wound biofilm model was recently published, which provided a layered scaffold simulating mammalian tissue composition on which topical wound care products could be tested. In this paper, we updated the model even further to mimic the dynamic influx of nutrients from below as is the case in a chronic wound. The modified in vitro model was created using collagen instead of agar as the main matrix component and contained both Staphylococcus aureus and Pseudomonas aeruginosa. The model was cast in transwell inserts and then placed in wound simulating media, which allowed for an exchange of nutrients and waste products across a filter. Three potential wound care products and chlorhexidine digluconate 2% solution as a positive control were used to evaluate the model. The tested products were composed of hydrogels made from completely biodegradable starch microspheres carrying different active compounds. The compounds were applied topically and left for 2-4 days. Profiles of oxygen concentration and pH were measured to assess the effect of treatments on bacterial activity. Confocal microscope images were obtained of the models to visualise the existence of microcolonies. Results showed that the modified in vitro model maintained a stable number of the two bacterial species over 6 days. In untreated models, steep oxygen gradients developed and pH increased to >8.0. Hydrogels containing active compounds alleviated the high oxygen consumption and decreased pH drastically. Moreover, all three hydrogels reduced the colony forming units significantly and to a larger extent than the chlorhexidine control treatment. Overall, the modified model expressed several characteristics similar to in vivo chronic wounds.

Original languageEnglish
JournalWound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society
Volume31
Issue number4
Pages (from-to)500-515
Number of pages16
ISSN1067-1927
DOIs
Publication statusPublished - 2023

Keywords

  • biofilm
  • chronic wounds
  • in vitro
  • microenvironment

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