Mixed-surface, lipid-tethered quantum dots for targeting cells and tissues.
Quantum dots (QDs), with their variable luminescent properties, are rapidly transcending traditional labeling techniques in biological imaging and hold vast potential for biosensing applications. An obstacle in any biosensor development is targeted specificity. Here we report a facile procedure for creating QDs targeted to the cell membrane with the goal of cell-surface protease biosensing. This procedure generates water-soluble QDs with variable coverage of lipid functional groups. The resulting hydrophobicity is quantitatively controlled by the molar ratio of lipids per QD. Appropriate tuning of the hydrophobicity ensures solubility in common aqueous cell culture media, while providing affinity to the lipid bilayer of cell membranes. The reaction and exchange process was directly evaluated by measuring UV absorption spectra associated with dithiocarbamate formation. Cell membrane binding was assessed using flow cytometry and total internal reflection fluorescence imaging with live cells, and tissue affinity was measured using histochemical staining and fluorescence imaging of frozen tissue sections. Increases in cell and tissue binding were found to be regulated by both QD hydrophobicity and surface charge, underlying the importance of QD surface properties in the optimization of both luminescence and targeting capability.
Department of Chemical and Biological Engineering, Iowa State University, 2114 Sweeney Hall, Iowa 50011-2230, United States.
Yanjie
Y
Zhang
Amanda
A
Haage
Elizabeth M
EM
Whitley
Ian C
IC
Schneider
Aaron R
AR
Clapp
D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002462:Cell Membrane / Q000737:chemistry* / Q000201:enzymology; D003470:Culture Media; D005347:Fibroblasts / Q000737:chemistry* / Q000201:enzymology; D005453:Fluorescence; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry; D008055:Lipids / Q000737:chemistry; D049449:Luminescence; D051379:Mice; D057054:Molecular Imaging; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000378:metabolism; D045663:Quantum Dots; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D055672:Static Electricity; D013499:Surface Properties; D013859:Thiocarbamates / Q000737:chemistry; D014867:Water / Q000737:chemistry
D003470:Culture Media; D008051:Lipid Bilayers; D008055:Lipids; D013859:Thiocarbamates; D014867:Water; D010447:Peptide Hydrolases