Candida albicans is the most common polymorphic opportunistic fungal pathogen, possessing the unique ability to switch from unicellular yeast form to filamentous form characterized either by pseudohyphae or true hyphae [1]. Hyphal development in C. albicans requires several hyphae-specific genes. Hyphal wall protein 1 (Hwp1) is known to be a typical hyphal-associated cell surface protein, which leads to hyphal growth and biofilm development in the first stage. Agglutinin-like sequence (Als) 1 and Als3 proteins (encoded by ALS gene family) interact with the Hwp1 to mediate cell–cell and cell-surface adhesion [2,3]. However, the yeast-to-hyphal transition is essential for the pathogenesis of C. albicans [4]. A mounting body of mutation studies reinforced that C. albicans mutants locked in either the yeast or hyphal form displayed reduced virulence [4,5].

The therapeutic options of antifungal agents are mostly restricted polyenes, azoles, echinocandins, and flucytosine. The utility of these treatment options is limited by the increased development of resistance, toxicity and drug interactions [6]. The urgent need includes development of new strategies to combat the threat of infections. In order to resolve this scientifc problem, therapies with metallic nanoparticles have been developed to overcome these limitations. In addition, photodynamic therapy has attracted attention in the antimicrobial areas.

Magnetic iron oxide nanoparticles (Fe3O4; denoted as MION), a cubic inverse spinel crystal structure exhibit unique magnetic and electric properties based on the transfer of electrons between the Fe2+ and Fe3+ ions in the octahedral sites [7]. Some reports have documented a promising impact of diverse biomedical applications due to their chemical stability, high magnetic susceptibility, high saturation magnetization, biocompatibility, innocuousness, and inexpensiveness [7,8,9]. The antifungal properties to impede the yeast cell growth and biofilm formation in C. albicans have been revealed [10,11].

Over many centuries, phototherapy was widely used in ancient Greece, Egypt, and India for treatment of skin diseases. Antimicrobial photodynamic therapy is an effective medical tool due to the expanding versatility of photosensitizers and the many possibilities to combine with other antimicrobial treatments [12], [13], [14]. Therefore, the present study was consciously aimed to explore the inhibitory efficacy of MION alone and combined with visible light against C. albicans. We have also investigated the expression changes of hyphae-specific genes HWP1 and ALS1 with MION alone and combined with visible light in order to assess their potential use in molecular targeting in C. albicans.