Fast, Efficient, and Stable Conjugation of Multiple DNA Strands on Colloidal Quantum Dots

A novel method for covalent conjugation of DNA to polymer coated quantum dots (QDs) is investigated in detail. This method is fast and efficient: up to 12 DNA strands can be covalently conjugated per QD in optimized reaction conditions. The QD-DNA conjugates can be purified using size exclusion chromatography and the QDs retain high quantum yield and excellent stability after DNA coupling. We explored single-stranded and double-stranded DNA coupling, as well as various lengths. We show that the DNA coupling is most efficient for short (Is mer) single-stranded DNA. The DNA coupling has been performed on QDs emitting at four different wavelengths, as well as on gold nanoparticles, suggesting that this technique can be generalized to a wide range of nanoparticles.