Polyvalent oligonucleotide iron oxide nanoparticle "click" conjugates

Abstract

We have utilized the copper-catalyzed azide-alkyne reaction to form a dense monolayer of oligonucleotides on a superparamagnetic nanoparticle core. These particles exhibit the canonical properties of materials densely functionalized with DNA, which can be controlled by modulating the density of oligonucleotides on the surface of the particles. Furthermore, like their Au analogues, these particles can easily cross HeLa (cervical cancer) cell membranes without transfection agents due to their dense DNA shell. Importantly, this approach should be generalizable to other azide-functionalized particles.

Figure 1

(Top) Melting transitions for DNA-SPION aggregates (10 nm in diameter) at various salt concentrations: 0.15, 0.30, 0.50, and 0.70 M. (Bottom) A plot of T_m as a function of salt concentration. An example of the derivative of a melting curve for DNA-SPION conjugates with a FWHM of 2°C.

Figure 2

(Top) Melting transitions for DNA-SPION aggregates (10 nm in diameter) with various loadings. (Bottom) A plot of T_m as a function of DNA strands/particles. A plot of FWHM of melting transitions as a function of DNA strands/particle.

Figure 3

(Top) ICP analysis of SPIONs in HeLa cells shows that the monolayer of DNA on the surface of the nanoparticles greatly promotes cellular uptake. (Bottom) Fluorescence microscopy image of HeLa cells incubated with DNA-SPIONs for 24 h. The red channel is fluorescence associated with DNA-SPIONs labeled with Cy5, the green channel is fluorescence associated taxol-Alexa 488 specific for tubulin, and the blue channel is fluorescence associated with Hoechst 3342 specific for the nucleus. Scale bar is 20 μm.

Scheme 1

CuACC conjugation of oligonucleotides to superparamagnetic iron oxide nanoparticles: (Top) schematic and (Bottom) water-soluble tris-hydroxylpropyl triazolylamine ligand and complementary oligonucleotides.