Direct attachment of oligonucleotides to quantum dot interfaces

A straightforward functionalization strategy for the direct attachment of single-stranded oligonucleotides (ssDNA) to quantum dot (qdot) interfaces is described. The approach takes advantage of a histidine-mediated phase transfer protocol that results in qdots with high colloidal stability in aqueous buffers. The weakly bound histidine encapsulation facilitates monolayer exchanged with both thiolated ssDNA and polyhistidine-tagged proteins. The successful biomodification at the qdot interface was probed by FRET analysis. The modest FRET efficiencies measured suggest the DNA to be in an extended conformation that is the result of high surface coverage that the direct attachment provides.