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Fluorescence intensity and intermittency as tools for following dopamine bioconjugate processing in living cells.

Khatchadourian R, Bachir A, Clarke SJ, Heyes CD, Wiseman PW, Nadeau JL - J. Biomed. Biotechnol. (2007)

Bottom Line: CdSe/ZnS quantum dots (QDs) conjugated to biomolecules that quench their fluorescence, particularly dopamine, have particular spectral properties that allow determination of the number of conjugates per particle, namely, photoenhancement and photobleaching.In this work, we quantify these properties on a single-particle and ensemble basis in order to evaluate their usefulness as a tool for indicating QD uptake, breakdown, and processing in living cells.This creates a general framework for the use of fluorescence quenching and intermittency to better understand nanoparticle-cell interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, McGill University, 3775 Rue University, 316 Lyman Duff Medical Building, Montréal, Canada.

ABSTRACT
CdSe/ZnS quantum dots (QDs) conjugated to biomolecules that quench their fluorescence, particularly dopamine, have particular spectral properties that allow determination of the number of conjugates per particle, namely, photoenhancement and photobleaching. In this work, we quantify these properties on a single-particle and ensemble basis in order to evaluate their usefulness as a tool for indicating QD uptake, breakdown, and processing in living cells. This creates a general framework for the use of fluorescence quenching and intermittency to better understand nanoparticle-cell interactions.

Show MeSH
Schematic of QD-dopamine conjugate preparation and mechanism of redox sensitivity.  (a) MSA-capped QD.  (b) Upon addition of dopamine (structure shown above arrow) and the zero-length cross-linker EDC, an amide bond is formed between the amine of dopamine and the carboxylate groups of MSA.  This schematic shows 100% linkage of dopamine to MSA termini; however, we show here that this ratio can be controlled. (c) Upon oxidation (“OX”), the catechol becomes a less-soluble quinone.
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fig1: Schematic of QD-dopamine conjugate preparation and mechanism of redox sensitivity. (a) MSA-capped QD. (b) Upon addition of dopamine (structure shown above arrow) and the zero-length cross-linker EDC, an amide bond is formed between the amine of dopamine and the carboxylate groups of MSA. This schematic shows 100% linkage of dopamine to MSA termini; however, we show here that this ratio can be controlled. (c) Upon oxidation (“OX”), the catechol becomes a less-soluble quinone.

Mentions: A quantitative understanding of the fate of conjugated QDs in biological systemsis therefore critical if these particles are to be used in in vitro diagnosticsor in vivo systems. Ourprevious work demonstrated that QD-dopamine conjugates (see Figure 1) can beused not only as static fluorescent labels, but also as sensors forintracellular redox processes such as endocytosis, lysosomal processing, andmitochondrial depolarization [5]. This is due to theelectron-donating properties of dopamine (DA), which permit this molecule toact as an electron shuttle between the nanoparticle and other molecules.


Fluorescence intensity and intermittency as tools for following dopamine bioconjugate processing in living cells.

Khatchadourian R, Bachir A, Clarke SJ, Heyes CD, Wiseman PW, Nadeau JL - J. Biomed. Biotechnol. (2007)

Schematic of QD-dopamine conjugate preparation and mechanism of redox sensitivity.  (a) MSA-capped QD.  (b) Upon addition of dopamine (structure shown above arrow) and the zero-length cross-linker EDC, an amide bond is formed between the amine of dopamine and the carboxylate groups of MSA.  This schematic shows 100% linkage of dopamine to MSA termini; however, we show here that this ratio can be controlled. (c) Upon oxidation (“OX”), the catechol becomes a less-soluble quinone.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2279208&req=5

fig1: Schematic of QD-dopamine conjugate preparation and mechanism of redox sensitivity. (a) MSA-capped QD. (b) Upon addition of dopamine (structure shown above arrow) and the zero-length cross-linker EDC, an amide bond is formed between the amine of dopamine and the carboxylate groups of MSA. This schematic shows 100% linkage of dopamine to MSA termini; however, we show here that this ratio can be controlled. (c) Upon oxidation (“OX”), the catechol becomes a less-soluble quinone.
Mentions: A quantitative understanding of the fate of conjugated QDs in biological systemsis therefore critical if these particles are to be used in in vitro diagnosticsor in vivo systems. Ourprevious work demonstrated that QD-dopamine conjugates (see Figure 1) can beused not only as static fluorescent labels, but also as sensors forintracellular redox processes such as endocytosis, lysosomal processing, andmitochondrial depolarization [5]. This is due to theelectron-donating properties of dopamine (DA), which permit this molecule toact as an electron shuttle between the nanoparticle and other molecules.

Bottom Line: CdSe/ZnS quantum dots (QDs) conjugated to biomolecules that quench their fluorescence, particularly dopamine, have particular spectral properties that allow determination of the number of conjugates per particle, namely, photoenhancement and photobleaching.In this work, we quantify these properties on a single-particle and ensemble basis in order to evaluate their usefulness as a tool for indicating QD uptake, breakdown, and processing in living cells.This creates a general framework for the use of fluorescence quenching and intermittency to better understand nanoparticle-cell interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, McGill University, 3775 Rue University, 316 Lyman Duff Medical Building, Montréal, Canada.

ABSTRACT
CdSe/ZnS quantum dots (QDs) conjugated to biomolecules that quench their fluorescence, particularly dopamine, have particular spectral properties that allow determination of the number of conjugates per particle, namely, photoenhancement and photobleaching. In this work, we quantify these properties on a single-particle and ensemble basis in order to evaluate their usefulness as a tool for indicating QD uptake, breakdown, and processing in living cells. This creates a general framework for the use of fluorescence quenching and intermittency to better understand nanoparticle-cell interactions.

Show MeSH