Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Strategies for Combatting the Formation of Fungal Biofilms on Biomaterials Surfaces (#41)

Javad Naderi 1 , Carla Giles 2 3 , Solmaz Saboohi 1 , Hans J Griesser 1 , Bryan R Coad 1 2
  1. Future Industries Institute, University of South Australia, Mawson Lakes, SA, Australia
  2. School of Agriculture, Food & Wine, University of Adelaide, Adelaide, SA, Australia
  3. Centre for Aquatic Animal Health and Vaccines, DPIPWE Tasmania, Launceston, TAS, Australia

Polymicrobial biofilms can be formed on surfaces by microbial colonisation of materials such as biomedical implant devices and are caused by bacterial or fungal species, or both kinds of microbes. In the last two decades, research has mostly been focused on bacterial infections and anti-bacterial surfaces. Although fungal infections related to biomaterials are increasing and threatening human lives, this field has received comparatively little interest. Attachment of fungal cells onto biomaterial surfaces is the first step for biofilm formation, hence, this initial attachment should be prevented.

One strategy to combat fungal biofilms is to prepare coatings with covalently bound, FDA-approved antifungal agents such as echinocandins and polyenes on the biomaterial surfaces, for long-lasting effects that are non-toxic to human cells. Using plasma polymer interlayers is a convenient strategy to functionalise surfaces with desired chemical groups allowing straightforward immobilisation of bioactive molecules on various solid surfaces. Results show echinocandins retain activity when covalently bound onto the surface which indicate they can disrupt the cell wall integrity of fungal cells. Also it has been found that these coatings can be reused several times while still maintaining efficiency against fungal cells. In contrast, polyenes do not have antifungal activity when are covalently attached onto the surface because surface attachment prevents them from reaching their cell membrane target.

A second strategy is to encapsulate and release low molecular weight antifungal molecules such as azoles. Loading fluconazole, from the approved class of azoles which are able to target cell membranes and intracellular parts of fungal cells, offers an avenue for creating coatings that can selectively deter fungal colonization while supporting mammalian cell attachment. As a carrier coating for releasing the drug, heptylamine plasma polymer is a good option for its simple deposition technique, good absorption of drug, and compatibility with innate immune cell function. Results of surface characterization techniques like XPS and TOF-SIMS and also microbiological assays will be discussed.