Experimental determination of quantum dot size distributions, ligand packing densities, and bioconjugation using analytical ultracentrifugation.
Analytical ultracentrifugation (AUC) was used to characterize the size distribution and surface chemistry of quantum dots (QDs). AUC was found to be highly sensitive to nanocrystal size, resolving nanocrystal sizes that differ by a single lattice plane. Sedimentation velocity data were used to calculate the ligand packing density at the crystal surface for different sized nanocrystals. Dihydrolipoic acid poly(ethylene glycol) was found to bind between 66 and 60% of the surface cadmium atoms for CdSe nanocrystals in the 1.54-2.59 nm radius size regime. The surface ligand chemistry was found to affect QD sedimentation, with larger ligands decreasing the sedimentation rate through an increase in particle volume and increase in frictional coefficient. Finally, AUC was used to detect and analyze protein association to QDs. Addition of bovine serum albumin (BSA) to the QD sample resulted in a reduced sedimentation rate, which may be attributed to an associated frictional drag. We calculated that one to two BSA molecules bind per QD with an associated frictional ratio of 1.2.
Lees
Emma E
EE
School of Chemistry and Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia.
Gunzburg
Menachem J
MJ
Nguyen
Tich-Lam
TL
Howlett
Geoffrey J
GJ
Rothacker
Julie
J
Nice
Edouard C
EC
Clayton
Andrew H A
AH
Mulvaney
Paul
P
D008024:Ligands; D046529:Microscopy, Electron, Transmission; D011092:Polyethylene Glycols / Q000737:chemistry*; D045663:Quantum Dots; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D014461:Ultracentrifugation / Q000379:methods*
D008024:Ligands; D011092:Polyethylene Glycols; D008063:Thioctic Acid; C015144:dihydrolipoic acid