Supramolecular effects on the antifungal activity of cyclodextrin/di-n-decyldimethylammonium chloride mixtures

Candidiasis infections are growing problem worldwide especially for the immunocompromised individuals. Di-n-decyldimethylammonium chloride is one of the most common antifungal agents used to clean medical devices. The current study examines the antifungal mechanism of di-n-decyldimethylammonium cation and its cyclodextrin inclusion complexes. Depending on the type of cyclodextrin (α-, β- or γ-CD), inclusion complexes can be as active as ammonium alone in terms of microorganism death (fungicidal activity). Moreover, with β-CD inclusion complexes, synergism is observed against fungus growth (fungistatic activity). Based on molecular dynamics, we propose a mechanism supported by cell number, selective electrode and ζ-potential measurements as a function of time. The mechanism involves four steps: (i) the positively-charged complex diffuses through the solution, (ii) it adsorbs onto the fungus membrane surface by electrostatic interaction, (iii) then it dissociates and the ammonium inserts in the microorganism membrane, and (iv) the change of the cell surface charge induces cell lysis.