Synthesis of CdSSe quantum dots in a protozoa Tetrahymena pyriformis.

Quantum dots (QDs) are recognized as the excellent fluorescence and photochemical materials to be applied in bioimaging, biomedical, and solar cell fields. Biosynthesized QDs (bio-QDs) have attracted attention due to their simple, eco-friendly, and excellent biocompatible traits. Moreover, bio-QDs could not be replaced by chemically fabricated QDs in many fields. Bio-QDs synthesized by different microorganisms have diverse characteristics. In this work, the biosynthesis of QDs by Tetrahymena pyriformis, a typical protozoa in aquatic environments, was achieved for the first time. The synthesized materials by T. pyriformis emitted yellow fluorescence and had an average diameter of 8.27 ± 0.77 nm. Spectral characterization results demonstrated that the synthesized QDs were CdSSe. Meanwhile, the fluorescence intensities of the synthesized bio-QDs showed a linear relationship with Cd dosage ranging from 20 to 80 μM. The fluorescence enhancement of the synthesized QDs was highly selective to Cd compared to other metal ions. The bio-QDs were demonstrated to have a great potential to be applied for Cd detection. This work provides valuable information about the transformation of heavy metal ions in protozoan and is useful to accelerate the applications of the synthesized QDs.