Compact and Stable Quantum Dots with Positive, Negative, or Zwitterionic Surface: Specific Cell Interactions and Non‐Specific Adsorptions by the Surface Charges

Abstract

A new type of quantum dot (QD) ligand chemistry is introduced that can provide positive, negative, or zwitterionic surface QDs. CdSe/CdZnS coreshell QDs are decorated with ligands, and the non-specifi c and specifi c interactions of the QDs through their surface charge are investigated with the focus on cellular adsorptions and endocytosis. Zwitterionic QDs are compact with a ligand hydrodynamic thickness of less than 2 nm, they are colloidally very stable over a broad pH range and even in saturated NaCl solution, and they show minimal non-specifi c adsorptions. Positive and negative QDs show a very different behavior for cellular adsorption and subsequent incorporation, suggesting mostly energy-independent pathways for positive QDs and exclusively adenosine triphosphate (ATP)-dependent pathways for negative QDs. The zwitterionic QD surface ligands can also be used in conjunction with other functional groups, which allows simple conjugations for highly specifi c targeting whereas retaining the advantages of a zwitterionic QD surface. This QD surface chemistry can provide highly specifi c and very sensitive imaging with very low background level. Using the mixed QD surface ligand system, we demonstrated streptavidin and antibody QD conjugates that show a signal-to-noise ratio that is over 4000 times higher than the unconjugated mixture, which was used as a control case. The QD chemistry reported herein can be easily extended to other functional groups, such as alkynes, azides, or other amines, and can be further used in many future applications, including single-QD level experiments, sensitive assays, or in vivo applications using anti-fouling QD probes. FULL PAPERwww.afm-journal.de www.MaterialsViews.com

Multivalent Glycosylation of Fluorescent Gold Nanoclusters Promotes Increased Human Dendritic Cell Targeting via Multiple Endocytic Pathways

“…Thioctic-zwitterion (Zw, M ~412 g.mol-1) was synthesized following the protocol described elsewhere 40,53 . Phalloidin (Sigma) and 1 µg/ml Hoechst 33258 (Sigma), respectively.…”

Zwitterion functionalized gold nanoclusters for multimodal near infrared fluorescence and photoacoustic imaging

“…We choose the ligand Zw (Figure 1(a)) to produce gold particles of different sizes because this molecule was shown to strongly improve the colloidal stability of particle 33 and also to obtain Au NCs exhibiting one the highest fluorescence intensity reported so far. 28,30,34 Molar ratio Au:ligand has been modified during the synthesis in order to play both on the final metal core size and on the ligand coverage.…”

Mixed-surface, lipid-tethered quantum dots for targeting cells and tissues

“…This is noteworthy and indicates that QD surface charge not only regulates solubility, but impacts binding affinity as well. [33] While we do not know how the enhancement would depend on charge for QDs with a net positive charge, generating QDs with charges near zero could increase the enhancement to ~3-fold. long timescale event, and individual QD diffusion, a short timescale event, impact the overall movement of punctae in images.…”