Antifungal efficacy of Au@ carbon dots nanoconjugates against opportunistic fungal pathogen, Candida albicans.

In the current study, we have investigated the toxicological effect of a novel hydrophilic nanoconjugate gold@carbon dot (Au@CD) and carbon dots (CDs) on the opportunistic fungal pathogen, Candida albicans. A homogenous experimental analysis was conducted for determining the toxicity of Au@CDs nanoconjugates of five different sizes ranging from 22 ± 2 to 35 ± 3 nm prepared using the carbon dots of mean hydrodynamic radius 12 ± 1 nm. The smallest size of nanoconjugate was synthesized using 0.3 mg ml HAuCl precursor. Our study for the first time, conclusively establishes the size-dependent toxicity effect of these characterized nanoconjugates against the abovementioned fungal pathogen. The MIC value of smaller sized Au@CDs nanoconjugates, S1-S3 samples were 250, 500 and 500 μg ml, respectively, while nanoconjugates of R diameter greater than 30 nm (S4 and S5 samples) did not show any toxicity. The results thus demonstrate that alteration in composition (carbon vs Au@CDs) exhibits a profound effect on the susceptibility of Candida albicans cells. While a size-dependent toxicity was observed for the nanoconjugates, CDs were found to be quite toxic owing to their small size which facilitated their entry into the cells and challenged the biocompatibility of carbon allotropes.