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Comparative Study
. 2013 Aug 6:10:37.
doi: 10.1186/1743-8977-10-37.

Degradation of aqueous synthesized CdTe/ZnS quantum dots in mice: differential blood kinetics and biodistribution of cadmium and tellurium

Na Liu, Ying Mu, Yi Chen, Hubo Sun, Sihai Han, Mengmeng Wang, Hui Wang, Yanbo Li, Qian Xu, Peili Huang, Zhiwei Sun
Comparative Study

Degradation of aqueous synthesized CdTe/ZnS quantum dots in mice: differential blood kinetics and biodistribution of cadmium and tellurium

Na Liu et al. Part Fibre Toxicol. .

Abstract

Background: Quantum dots (QDs) have been used as novel fluorescent nanoprobes for various bioapplications. The degradation of QDs, and consequent release of free cadmium ions, have been suggested to be the causes of their overall toxicity. However, in contrast to sufficient investigations regarding the biological fate of QDs, a paucity of studies have reported their chemical fate in vivo. Therefore, the overall aim of our study was to understand the chemical fate of QDs in vivo and explore analytical techniques or methods that could be used to define the chemical fate of QDs in vivo.

Methods: Male ICR mice were administered a single intravenous dose (0.2 μmol/kg) of aqueous synthesized CdTe/ZnS aqQDs. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to simultaneously measure the concentrations of cadmium (Cd) and tellurium (Te) in the blood and tissues over the course of a 28 day period. We compared the blood kinetic parameters and biodistributions of Cd and Te, and used the molar ratio of Cd:Te as a marker for QDs degradation.

Results: Cd and Te display different blood kinetics and biodistribution profiles. The Cd:Te ratio in the blood did not vary significantly within the first hour compared with intact CdTe/ZnS aqQDs. The Cd:Te ratio decreased gradually over time from the 6 h time point on. Cd accumulated in the liver, kidneys, and spleen. Te was distributed primarily to the kidneys. Sharp time-dependent increases in the Cd:Te ratio were found in liver tissues.

Conclusions: QDs can undergo degradation in vivo. In vitro, QDs are chemically stable and do not elicit the same biological responses or consequences as they do in vivo. Our methods might provide valuable information regarding the degradation of QDs in vivo and may enable the design and development of QDs for biological and biomedical applications.

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Figures

Figure 1
Figure 1
Characteristics of CdTe/ZnS aqQDs: (A) AFM image, (B) absorption and emission spectra. The average size was 19.3 ± 2.2 nm in diameter. The maximal emission was observed at approximately 652 nm following excitation at 350 nm.
Figure 2
Figure 2
PLQY transformation of CdTe/ZnS aqQDs in situ (pH 8.3) for periods up to 80 days.
Figure 3
Figure 3
Bio-distribution of Cd (A) and Te (B) in mice exposed to CdTe/ZnS aqQDs. ICR mice were injected via tail vein with CdTe/ZnS aqQDs (0.2 μmol/kg). Serial sacrifices were carried out at 15 min, 1 h, 6 h, 24 h, 3 d, 7 d, 14 d, and 28 d after dosing. Several organs/tissues, including heart, liver, spleen, lungs, kidneys, and brain were isolated to determine concentrations of Cd and Te with ICP-MS. The mean values of the control were deducted as the baseline (Additional file 2: Table S2). All data are represented as the mean ± SD, n = 6.
See this image and copyright information in PMC

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