Characterization of the adsorption of oligonucleotides on mercaptopropionic acid-coated CdSe/ZnS quantum dots using fluorescence resonance energy transfer
There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Semiconductor quantum dots (QDs) coated with thioalkyl acid ligands are often used
as probes and reporters for nucleic acid sensing, or protein sensing using aptamers,
and are also potential vectors for gene delivery. In such applications, the interactions
that potentially lead to the adsorption of oligonucleotides onto the surface of colloidal
QDs are an important consideration. To explore such interactions, fluorescence resonance
energy transfer (FRET) between QDs and oligonucleotides labeled with a fluorescent
dye was used to identify and characterize a set of conditions that favor strong adsorption
on 3-mercaptopropionic acid (MPA)-coated CdSe/ZnS QDs. Adsorption curves and competitive
binding experiments were used to determine that the order of affinity for nucleobase
adsorption was dC>dA≥dG≫dT. The length of the oligonucleotide sequence was also important,
with an 80-mer sequence adsorbing more strongly than its 20-mer analog. Adsorption
decreased with increasing pH and corresponded to the ionization of the carboxylic
acid groups of the MPA ligands. Increased ionic strength partially offsets ligand
ionization and increased the extent of adsorption. The interaction between QDs and
oligonucleotides was labile, with increases in adsorption at lower concentrations
of oligonucleotide and with an increasing number of oligonucleotides per QD. The results
were consistent with a hydrogen-bonding model for adsorption, where neutral thioalkyl
acid ligands interact favorably with nucleobases and ionized ligands resist adsorption.