Quantum dots (QDs) are semiconductor nanoparticles with many favorable properties such as high brightness, broad excitation spectrum, narrow emission spectrum and high photostability. These characteristics have made them a popular choice for DNA biosensors. An emerging theme in QD-based biosensing is the use of multi-nanoparticle complexes. These complexes can form functional constructs, such as the molecular beacon, facilitating novel biosensing schemes. Vital to the assembly of these complexes is the formation of defined QD-ligand conjugates. This is a challenge due to the high surface area of nanoparticles, which results in a distribution of conjugates being formed even when incubated with one equivalent of the ligand. This presentation will discuss a novel method for the formation and purification of QD-DNA monoconjugates (i.e. 1 DNA per QD). Using magnetic beads, a protocol was developed and optimized to selectively isolate QD-DNA monoconjugates from a mixture. Monoconjugates can be prepared with nucleic acids as short as 19 bases and as long as 39 bases in length. The monoconjugates were isolated in less than 5 minutes with isolation efficiencies between 70-93 %, depending on the length of DNA used. Characterization of these monoconjugates using single-molecule fluorescence microscopy will be discussed. Finally, FRET based analysis was used to determine the analytical performance of the QD-DNA monoconjugates.

Magnetic beads for the isolation of monovalent quantum dot - nucleic acid conjugates

248th National Meeting (2014)

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