Supramolecular effects on the antifungal activity of cyclodextrin/di-n-decyldimethylammonium chloride mixtures Loïc Leclercq a , Quentin Lubart a , Anny Dewilde b , Jean-Marie Aubry a , Véronique Nardello-Rataj a,⇑ a Université Lille 1, EA Chimie Moléculaire et Formulation 4478, Equipe ‘‘Oxydation et Physico-chimie de la Formulation’’, Bât. C6, F-59655 Villeneuve d’Ascq Cedex, France b Institut de Microbiologie, Université Lille 2, Faculté de Médecine, CHRU Lille, Bd du Professeur Leclercq, F-59037 Lille Cedex, France article info Article history: Received 6 January 2012 Received in revised form 20 February 2012 Accepted 21 February 2012 Available online 1 March 2012 Keywords: Cyclodextrins Dialkyldimethylammonium cation Antifungal surfactant Supramolecular chemistry Host–guest chemistry abstract Candidiasis infections are growing problem worldwide especially for the immunocompromised individ- uals. 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-decyldimethylammoni- um cation and its cyclodextrin inclusion complexes. Depending on the type of cyclodextrin (a-, b- or c-CD), inclusion complexes can be as active as ammonium alone in terms of microorganism death (fun- gicidal activity). Moreover, with b-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 f-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. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Candida albicans is a commensal fungus which lives in the hu- man mouth and gastrointestinal tract. Under normal circum- stances, C. albicans lives in 80% of the human population with no harmful effects. Sometimes, C. albicans overgrowth results in oral and genital candidiasis (Ryan and Ray, 2010; d’Enfert and Hube, 2007). Candidiasis, also known as ‘‘thrush’’, is a common condition, usually easily cured. However, the treatment is much more difficult in immunocompromised individuals (AIDS, chemo- therapy, organ transplantation, etc.) and patients in intensive care units. In some case, Candidiasis results in septicemia. There- fore, C. albicans, which form biofilms on the surface of implant- able medical devices, emerged as important causes of mortality in these patients. To avoid nosocomial infections, hospitals have sanitation protocols (e.g. equipment sterilization, etc.). One of the most widely used biocidal agents to clean chirurgical instru- ments is a double-tailed cationic surfactant: the didecyldimethy- lammonium chloride, [DiC 10 ][Cl](Šuljagic ´, 2008; Russell et al., 1999), which exhibits an optimal activity in comparison with other dialkyldimethylammonium salts (Cybulski et al., 2008; Per- nak et al., 2006; Pernak and Feder-Kubis, 2005; Pernak and Chwała, 2003). However, the [DiC 10 ] cation is not used alone. Indeed, the formulation involves the use of other surfactants (e.g. polyethoxylated alcohols). In binary and multicomponent surfactant mixtures, there is a spontaneous self-aggregation which inhibits the biocidal activity due to the reduction of free [DiC 10 ] cations. To prevent this inhibition, cyclodextrins (CDs) can be used to form highly water-soluble complexes (Leclercq et al., 2010a,b, 2009, 2007, 2005; Leclercq and Schmitzer, 2008; Uekama et al., 1998; Funasaki et al., 2008; Jeulin et al., 2008; Kopecky ´ et al., 2004, 2002, 2001; Lehner et al., 1993). In- deed, naturally CDs are six, seven or eight-membered-1,4-linked cyclic oligomers of D-glucopyranose (a-, b- and c-CD) and are described as shallow truncated cones with an hydrophobic cavity (Uekama et al., 1998). Moreover, CDs are biocompatible and have already been used in a wide range of applications including food and pharmaceutical industries (Funasaki et al., 2008; Jeulin et al., 2008; Kopecky ´ et al., 2004, 2002, 2001; Lehner et al., 1993). However, depending on the complex structure, the bio- cidal activity can be switched: encapsulated biocides can be sig- nificantly more or less active than the biocides alone (Leclercq et al., 2010a,b; Schmidt et al., 1996; Simpson, 1992). Despite a large number of publications in this field, the delivery mecha- nism of encapsulated [DiC 10 ] cations remains unexplored. In this article, we report on the antifungal mechanism of various CD/ [DiC 10 ] aqueous mixtures based on in silico (molecular properties calculation and molecular dynamics) and in vitro analyses (anti- fungal activity against C. albicans, potentiometry and zetametry). 0928-0987/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ejps.2012.02.017 ⇑ Corresponding author. Tel.: +33 032 033 6369. E-mail address: veronique.rataj@univ-lille1.fr (V. Nardello-Rataj). European Journal of Pharmaceutical Sciences 46 (2012) 336–345 Contents lists available at SciVerse ScienceDirect European Journal of Pharmaceutical Sciences journal homepage: www.elsevier.com/locate/ejps