Copper-Free Click Chemistry for Highly Luminescent Quantum Dot Conjugates: Application to in Vivo Metabolic Imaging

Abstract

Quantum dots (QD) are inorganic nanocrystals with outstanding optical properties, specially suited for biological imaging applications. Their attachment to biomolecules in mild aqueous conditions for the design of bioconjugates is therefore highly desirable. 1,3-dipolar [3 + 2] cycloaddition between azides and terminal alkynes ("click chemistry") could represent an attractive QD functionalization method. Unfortunately, the use of the popular Cu(I)-catalyzed version of this reaction is not applicable for achieving this goal, since the presence of copper dramatically alters the luminescence properties of QD dispersions. We demonstrate here that copper-free click chemistry, between strained cyclooctyne functionalized QD and azido-biomolecules, leads to highly luminescent conjugates. In addition, we show that QD-cyclooctyne can be used at previously unreported low concentration (250 nM) for imaging the incorporation of azido-modified sialic acid in cell membrane glycoproteins.

Quantum Dots in Bioanalysis: A Review of Applications across Various Platforms for Fluorescence Spectroscopy and Imaging

“…3xi; often called ''click chemistry''). 100,101 Both of these chemistries have commercially available ''chemical handles'' that can be used to modify amine-bearing QDs and biomolecules for subsequent ligation. 102 Alternative bioconjugation strategies based on self-assembly and specific recognition take advantage of highaffinity noncovalent interactions to assemble biomolecules of interest to QDs.…”

Tracking the Subcellular Fate of 20(S)-Hydroxycholesterol with Click Chemistry Reveals a Transport Pathway to the Golgi

“…fluorescence intensity of FP-tagged organelle markers was substantially diminished after the copper-catalyzed click reaction (50).…”

The potential of bioorthogonal chemistry for correlative light and electron microscopy: a call to arms

“…In the case of CLEM labelling, one difficulty with the modification of Qdots using 'classic' copper-catalysed Huisgen reaction (Fig. 1c) is fluorescence quenching [36]. Fluorescence quenching was circumvented by using either the strain-promoted [3+2]-cycloaddition reaction (Fig.…”

“…Fluorescence quenching was circumvented by using either the strain-promoted [3+2]-cycloaddition reaction (Fig. 1d) [36] or the tetrazine-norbornene inverse electron-demand Diels-Alder reaction (Fig. 1e) [37].…”