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

Liu N, Mu Y, Chen Y, Sun H, Han S, Wang M, Wang H, Li Y, Xu Q, Huang P, Sun Z - Part Fibre Toxicol (2013)

Bottom Line: The Cd:Te ratio in the blood did not vary significantly within the first hour compared with intact CdTe/ZnS aqQDs.Sharp time-dependent increases in the Cd:Te ratio were found in liver tissues.In vitro, QDs are chemically stable and do not elicit the same biological responses or consequences as they do in vivo.

View Article: PubMed Central - HTML - PubMed

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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PLQY transformation of CdTe/ZnS aqQDs in situ (pH 8.3) for periods up to 80 days.
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Figure 2: PLQY transformation of CdTe/ZnS aqQDs in situ (pH 8.3) for periods up to 80 days.

Mentions: The stability data for the CdTe/ZnS aqQDs in vitro are shown in Figure 2 and Table 1. Figure 2 illustrates that in the first 20 days, the PLQYs of CdTe/ZnS aqQDs in situ were not significantly different (ranging from 70.3 to 72.3%). The PLQYs gradually decreased over the next 20 days, and the values had dropped to 43.8% of their original values 80 days later. Table 1 shows that the maximal emission (652 nm) of CdTe/ZnS aqQDs was not altered by dialyses lasting up to 3 d in pH 7.4 buffered solutions, but dialysis rapidly reduced the relative fluorescence intensity after 6 h (from 271.0 to 144.1). After 3 d, only 55.2 remained. In the filtrate, the concentrations of Cd, Te, and Zn gradually increased with time, but Cd:Te ratios did not vary significantly (the molar ratio of Cd and Te in CdTe/ZnS aqQDs used in this study was 3:1). Zn:Cd ratios were not significantly different (the molar ratio of Zn and Cd in CdTe/ZnS aqQDs used in this study was 1:1) in the first 6 h, but at the 24 h, 2 and 3 d time-points, the ratios had become slightly elevated (from 1.13:1 to 1.26:1).


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

Liu N, Mu Y, Chen Y, Sun H, Han S, Wang M, Wang H, Li Y, Xu Q, Huang P, Sun Z - Part Fibre Toxicol (2013)

PLQY transformation of CdTe/ZnS aqQDs in situ (pH 8.3) for periods up to 80 days.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750282&req=5

Figure 2: PLQY transformation of CdTe/ZnS aqQDs in situ (pH 8.3) for periods up to 80 days.
Mentions: The stability data for the CdTe/ZnS aqQDs in vitro are shown in Figure 2 and Table 1. Figure 2 illustrates that in the first 20 days, the PLQYs of CdTe/ZnS aqQDs in situ were not significantly different (ranging from 70.3 to 72.3%). The PLQYs gradually decreased over the next 20 days, and the values had dropped to 43.8% of their original values 80 days later. Table 1 shows that the maximal emission (652 nm) of CdTe/ZnS aqQDs was not altered by dialyses lasting up to 3 d in pH 7.4 buffered solutions, but dialysis rapidly reduced the relative fluorescence intensity after 6 h (from 271.0 to 144.1). After 3 d, only 55.2 remained. In the filtrate, the concentrations of Cd, Te, and Zn gradually increased with time, but Cd:Te ratios did not vary significantly (the molar ratio of Cd and Te in CdTe/ZnS aqQDs used in this study was 3:1). Zn:Cd ratios were not significantly different (the molar ratio of Zn and Cd in CdTe/ZnS aqQDs used in this study was 1:1) in the first 6 h, but at the 24 h, 2 and 3 d time-points, the ratios had become slightly elevated (from 1.13:1 to 1.26:1).

Bottom Line: The Cd:Te ratio in the blood did not vary significantly within the first hour compared with intact CdTe/ZnS aqQDs.Sharp time-dependent increases in the Cd:Te ratio were found in liver tissues.In vitro, QDs are chemically stable and do not elicit the same biological responses or consequences as they do in vivo.

View Article: PubMed Central - HTML - PubMed

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.

Show MeSH
Related in: MedlinePlus