Design and Synthesis of Novel Thymoquinone-Zein Nanoparticles; Evaluation of the Inhibitory Effect on Candida albicans and Biofilm Formation in Vitro

Candida albicans (C. albicans) as a fungal pathogen is part of the normal flora of the human body, which could cause various infections in patients with defective immune systems. Nowadays, there is a need to design and synthesis new drug formulations to overcome drug resistance in this genus. Thymoquinone (TQ) is the main ingredient in Nigella sativa, which has considerable antifungal properties. The aim of this study was to investigate the inhibitory effects of thymoquinone-zein nanoparticles (TQ-ZNPs) on C. albicans.

In the current study, TQ was encapsulated in zein (as a biodegradable carrier) and polyethylene glycol (PEG). The antifungal activity of TQ-ZNPs against C. albicans (ATCC 10231; standard strain) and their inhibitory effects on biofilm formation were examined using standardized broth microdilution and MTT assays, respectively. The total oxidant status (TOS) of C. albicans was assessed using colorimetric method, and the toxic effect of nanoparticles on peripheral blood mononuclear cells (PBMCs) was evaluated by MTT assay.

The minimum inhibitory concentration (MIC) of TQ-ZNPs was significantly reduced compared to that of free TQ. MIC values of TQ-ZNPs and free TQ were determined to be 7.4 and 50 µg/mL, respectively. Biofilm formation was inhibited, and oxidant production by fungal cells was increased. The findings of this study showed that TQ-ZNPs had no toxic effect on PBMCs.

This study results revealed that the synthesized nanoparticles had a good antifungal activity without any toxicity. The results demonstrated the superior efficiency of TQ-ZNPs over free TQ. Hence, this structure could be used to load hydrophobic drugs. However, more studies are needed to evaluate the beneficial properties of TQ-ZNPs.