CdSe@CdS core-shell quantum dots as antifungal agents: significance of particle size and shell thickness

The exact role of the size and shell thickness of the core–shell nanoparticles on the antifungal property remains marginally known. Herein, a detail study of the antifungal property of the model core–shell quantum dots CdSe@CdS of size 2.4–3.9 nm, where the shell thickness was also varied from 0.2 to 0.7 nm, is presented. The core–shell structure exhibited tenfold enhancement in fluorescence compared to the core-only structure. Further, it was found that the CdSe particles (core-only) were most toxic towards Candida albicans cells, and the antifungal property was observed to be in the order CdSe > CdSe@CdS inferred from their MIC 90 values (25 and 150 μg/mL, respectively). Interestingly, larger particles showed a much lower MIC 90 value, which could be because of their higher shell thickness. The presence of CdS shell decreased the toxicity of CdSe due to the mitigating property of sulphur on Candida cells. The presence of sulfur decreased the toxic property of cadmium ions allowing for the higher shell thickness particles to be less toxic. While the core-only CdSe nanoparticles of the smallest size showed complete inhibition (100%) of fungus at a low concentration of 50 μg/mL, for the core–shell particles same was noticed at a much higher concentration of 200 μg/mL. Smaller QDs easily penetrated the fungal cells, thereby interacting more effectively with the cellular structure inducing cell damage. Results suggested that the cellular response was a distinct function of the physical size and shell thickness of these nanocrystals. Graphical Abstract