Zwitterionic Biocompatible Quantum Dots for Wide pH Stability and Weak Nonspecific Binding to Cells

Applications of water-soluble quantum dots (QDs) in the life sciences are limited by their poor colloidal stability in physiological media and nonspecific interaction with biomatter, particularly cell membranes. We have studied colloidal stability and nonspecific interactions with living cells for z...

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Bibliographic Details
Published in:ACS nano 2009-09, Vol.3 (9), p.2573-2580
Main Authors: Breus, Vladimir V, Heyes, Colin D, Tron, Kyrylo, Nienhaus, G. Ulrich
Format: Article
Language:English
Subjects:
Adsorption
Animals
Biocompatible Materials - chemistry
Biocompatible Materials - metabolism
Cell Line, Tumor
Fatty Acids - chemistry
Fatty Acids - metabolism
Humans
Hydrogen-Ion Concentration
Microscopy, Fluorescence
Monocytes - metabolism
Penicillamine - chemistry
Penicillamine - metabolism
Quantum Dots
Solubility
Sulfhydryl Compounds - chemistry
Sulfhydryl Compounds - metabolism
Water - chemistry
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Summary:Applications of water-soluble quantum dots (QDs) in the life sciences are limited by their poor colloidal stability in physiological media and nonspecific interaction with biomatter, particularly cell membranes. We have studied colloidal stability and nonspecific interactions with living cells for zwitterionic d-penicillamine-coated QDs (DPA-QDs) and the traditionally used carboxylated 11-mercaptoundecanoic acid-coated QDs (MUA-QDs) and found clear advantages of DPA-QDs. In single molecule fluorescence experiments, DPA-QDs showed no aggregation over the physiologically relevant pH range of 5−9, whereas MUA-QDs showed significant aggregation below pH 9. Upon exposure to living Mono Mac 6 cells, DPA-QDs, which possess overall charge-neutral surfaces, exhibited weak interactions with the cell membrane and were easily removed by flushing with buffer. By contrast, the highly charged MUA-QDs strongly associated with the cells and could not be removed even by extensive rinsing with buffer solution. DPA-QDs exhibit a high chemical stability even in strongly oxidizing conditions, in contrast to cysteine-coated QDs reported earlier. This beneficial property may arise from reduced interactions between DPA ligands due to steric effects of the methyl groups on their β-carbon atoms.
ISSN:1936-0851
1936-086X
DOI:10.1021/nn900600w