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The cadmium-mercaptoacetic acid complex contributes to the genotoxicity of mercaptoacetic acid-coated CdSe-core quantum dots.

Tang W, Fan J, He Y, Huang B, Liu H, Pang D, Xie Z - Int J Nanomedicine (2012)

Bottom Line: Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes.However, the genotoxicity potential of QDs still remains unclear.The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Wuhan University, Wuhan, People's Republic of China.

ABSTRACT
Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA-QDs) were investigated. After incubation with different concentrations of MAA-QDs (0.043, 0.13, 0.4, 1.2, and 3.6 μmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA-QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd-MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles.

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Co-effect of Cd2+ and MAA on the configuration of plasmid DNA. (A) Electrophoresis in 1% agarose gel of pUC18 DNA (150 ng per sample) incubated with Cd2+ in the presence of increasing MAA concentrations for 12 hours at 4°C in the dark. Lane 1: pUC18 DNA only; lane 2: pUC18 DNA digested by Hind III; lanes 3–9: pUC18 DNA incubated with mixtures of Cd2+ (500 μmol/L) and 0, 5, 10, 15, 25, 35, 45 mmol/L MAA. (B) Scanning densitometry results of three replicate experiments for each sample, with the error bars representing the standard deviations.Abbreviations: OC, opened circular; CCC, covalently closed circular; MAA, mercaptoacetic acid.
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f4-ijn-7-2631: Co-effect of Cd2+ and MAA on the configuration of plasmid DNA. (A) Electrophoresis in 1% agarose gel of pUC18 DNA (150 ng per sample) incubated with Cd2+ in the presence of increasing MAA concentrations for 12 hours at 4°C in the dark. Lane 1: pUC18 DNA only; lane 2: pUC18 DNA digested by Hind III; lanes 3–9: pUC18 DNA incubated with mixtures of Cd2+ (500 μmol/L) and 0, 5, 10, 15, 25, 35, 45 mmol/L MAA. (B) Scanning densitometry results of three replicate experiments for each sample, with the error bars representing the standard deviations.Abbreviations: OC, opened circular; CCC, covalently closed circular; MAA, mercaptoacetic acid.

Mentions: In previous work, high levels of free cadmium (1.1 mmol/L) could be found in 0.25 mg/mL solutions of QDs because of the degradation of the QDs.10 DNA strand breaks, arising from the photogenerated free radicals or the generated surface oxide,22,23 have been reported; however, the direct interaction between DNA and the chemical composition of QDs currently remains unclear. To determine whether cadmium or MAA is capable of inducing damage to DNA, the effects of MAA, Cd2+ and the combination of both on DNA nicking were studied. Because incubations of plasmid DNA with 0.5, 5, 50, 500 μmol/L CdCl2 (lanes 3–6, Figure 3) at 4°C for 12 hours in the dark did not cause DNA nicking, it is evident that the DNA nicking caused by QDs in the dark was not due to cadmium. Additionally, when the DNA was incubated with increasing concentrations of MAA, the gel electrophoresis bands became smeared without the expected DNA nicking (lanes 8–10, Figure 3). However, a dose-dependent increase in DNA nicking was observed when 300 ng of the pUC18 plasmid DNA was incubated with mixtures of Cd2+ (0.5 mmol/L) and MAA (0, 5, 10, 15, 25, 35 mmol/L) at 4°C for 12 hours in the dark (lanes 3–8, Figure 4).


The cadmium-mercaptoacetic acid complex contributes to the genotoxicity of mercaptoacetic acid-coated CdSe-core quantum dots.

Tang W, Fan J, He Y, Huang B, Liu H, Pang D, Xie Z - Int J Nanomedicine (2012)

Co-effect of Cd2+ and MAA on the configuration of plasmid DNA. (A) Electrophoresis in 1% agarose gel of pUC18 DNA (150 ng per sample) incubated with Cd2+ in the presence of increasing MAA concentrations for 12 hours at 4°C in the dark. Lane 1: pUC18 DNA only; lane 2: pUC18 DNA digested by Hind III; lanes 3–9: pUC18 DNA incubated with mixtures of Cd2+ (500 μmol/L) and 0, 5, 10, 15, 25, 35, 45 mmol/L MAA. (B) Scanning densitometry results of three replicate experiments for each sample, with the error bars representing the standard deviations.Abbreviations: OC, opened circular; CCC, covalently closed circular; MAA, mercaptoacetic acid.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368512&req=5

f4-ijn-7-2631: Co-effect of Cd2+ and MAA on the configuration of plasmid DNA. (A) Electrophoresis in 1% agarose gel of pUC18 DNA (150 ng per sample) incubated with Cd2+ in the presence of increasing MAA concentrations for 12 hours at 4°C in the dark. Lane 1: pUC18 DNA only; lane 2: pUC18 DNA digested by Hind III; lanes 3–9: pUC18 DNA incubated with mixtures of Cd2+ (500 μmol/L) and 0, 5, 10, 15, 25, 35, 45 mmol/L MAA. (B) Scanning densitometry results of three replicate experiments for each sample, with the error bars representing the standard deviations.Abbreviations: OC, opened circular; CCC, covalently closed circular; MAA, mercaptoacetic acid.
Mentions: In previous work, high levels of free cadmium (1.1 mmol/L) could be found in 0.25 mg/mL solutions of QDs because of the degradation of the QDs.10 DNA strand breaks, arising from the photogenerated free radicals or the generated surface oxide,22,23 have been reported; however, the direct interaction between DNA and the chemical composition of QDs currently remains unclear. To determine whether cadmium or MAA is capable of inducing damage to DNA, the effects of MAA, Cd2+ and the combination of both on DNA nicking were studied. Because incubations of plasmid DNA with 0.5, 5, 50, 500 μmol/L CdCl2 (lanes 3–6, Figure 3) at 4°C for 12 hours in the dark did not cause DNA nicking, it is evident that the DNA nicking caused by QDs in the dark was not due to cadmium. Additionally, when the DNA was incubated with increasing concentrations of MAA, the gel electrophoresis bands became smeared without the expected DNA nicking (lanes 8–10, Figure 3). However, a dose-dependent increase in DNA nicking was observed when 300 ng of the pUC18 plasmid DNA was incubated with mixtures of Cd2+ (0.5 mmol/L) and MAA (0, 5, 10, 15, 25, 35 mmol/L) at 4°C for 12 hours in the dark (lanes 3–8, Figure 4).

Bottom Line: Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes.However, the genotoxicity potential of QDs still remains unclear.The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Wuhan University, Wuhan, People's Republic of China.

ABSTRACT
Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA-QDs) were investigated. After incubation with different concentrations of MAA-QDs (0.043, 0.13, 0.4, 1.2, and 3.6 μmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA-QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd-MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles.

Show MeSH
Related in: MedlinePlus