Crucial factors in biosynthesis of fluorescent CdSe quantum dots in Saccharomyces cerevisiae

Cadmium selenium (CdSe) quantum dots (QDs) were synthesized using Saccharomyces cerevisiae (ATCC9763) as a biomatrix cultured with 5 mmol L-1 Na2SeO3 and 1 mmol L-1 CdCl2. Five decisive factors in the biomanufacture of CdSe QDs in S. cerevisiae were investigated and optimized, including the time point of adding Na2SeO3, the optimal concentrations of selenite and cadmium, and the incubating duration of selenite and cadmium with yeast cells respectively. By exploiting two dependent metabolic pathways in an appropriate procedure, CdSe QDs were obtained simply with controllable particle size and tunable fluorescence emission. With the help of an effective extracting method, the maximum emission peaks of different isolated QDs had been further detected, with adjustable wavelengths ranging from 506 nm (green) to 562 nm (yellow). The following in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that the biocomposed CdSe QDs had much lower cytotoxicity compared with hydrothermally synthesized thioglycolic acid (TGA)-capped CdSe and TGA capped-CdTe. By the advantages of the operational protocol, these findings exhibited the potential of an uncomplicated biosynthetic method which is capable of producing easily detectable, environment-friendly and low toxic inorganic nanoparticles with easy access of raw materials.