Long-term chemical biotransformation and pathways of Cd-based quantum dots in mice

Abstract

Cd-based quantum dots (QDs) have broad applications in biomedicine, electronics, and energy. Thus, their environmental and health risks have garnered attention owing to the toxicity of Cd. However, there is limited knowledge on the long-term chemical biotransformation and pathway of Cd-based QDs in mammals. Herein, the biodistribution and excretion of intravenously injected typical II-VI CdSe@ZnS core/shell QDs in mice, including the chemical transformation of Zn, Se, and Cd in their major organs, were systematically studied by synchrotron radiation-based X-ray fluorescence spectrometry and X-ray absorption spectroscopy. Our results showed the rapid breakdown of ZnS shells within 10 days after treatment, their transformation into Zn3(PO4)2-like species, and elimination via hepatobiliary route. Meanwhile, the CdSe core underwent an ultraslow degradation process by transformation into multiple species, which were primarily eliminated via the renal route. Therefore, this study provides a comprehensive understanding of the metabolism and elimination of CdSe@ZnS-QDs over one year.