Abstract
Fungal infections in humans, contamination of food and structural damage to buildings by fungi are associated with high costs for the general public. In addition, the increase in antifungal resistance towards conventional treatment raises the demand for new fungicidal methods. Here, we present the antifungal use of Photodynamic Inactivation (PDI) based on the natural photosensitizer curcumin and a water-soluble positively charged derivative thereof (SA-CUR 12a) against two different model organisms; Candida albicans grown in a liquid culture and photo treated with a 435 nm LED light followed by counting of the colony-forming units and photoinactivation of tissue-like hyphal spheres of Aspergillus niger (diameter ~5 mm) with subsequent monitoring of colony growth. Curcumin (50 µM, no incubation period, i.p.) supplemented with 10% or 0.5% DMSO as well as SA-CUR 12a (50 µM no i.p or 5 min i.p.) triggered a photoantifungal effect of >4 log units towards C. albicans. At 100 µM, SA-CUR 12a (0 min or 5 min i.p.) achieved a reduction of >6 log units. Colonies of A. niger shrunk significantly during PDI treatment. Photoinactivation with 50 µM or 100 µM curcumin (+0.5% DMSO) resulted in complete growth inhibition. PDI using 20, 50 or 100 µM SA-CUR 12a (with or without 10% DMSO) also showed a significant reduction in colony area compared to the control after 48 h, although less pronounced compared to curcumin. In summary, PDI using curcumin or SA-CUR 12a against C. albicans or A. niger is a promising alternative to currently used fungicides, with the advantage of being very unlikely to induce resistance.
Highlights
From the kingdom of fungi, about 600 species are known to be human pathogens, that can be potentially harmful to immunocompromised people (e.g., Candida spp. or Aspergillus spp.) [1]
Photodynamic Inactivation (PDI), known as Antimicrobial Photodynamic Therapy, is a method that was shown to be highly effective against bacteria [7,8,9,10,11,12]
Two different model organisms were selected for the investigation of the potential antifungal effect of PDI: Candida albicans (C. albicans) and Aspergillus niger (A. niger)
Summary
From the kingdom of fungi, about 600 species are known to be human pathogens, that can be potentially harmful to immunocompromised people (e.g., Candida spp. or Aspergillus spp.) [1]. As the number of immuno-deficient people increases due to the rising number of patients undergoing cancer therapy, organ recipients or people treated for human immunodeficiency virus, the risk of contracting a fungal infection increases [2,3,4]. Photodynamic Inactivation (PDI), known as Antimicrobial Photodynamic Therapy, is a method that was shown to be highly effective against bacteria [7,8,9,10,11,12]. Two different model organisms were selected for the investigation of the potential antifungal effect of PDI: Candida albicans (C. albicans) and Aspergillus niger (A. niger)
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