DNA-directed assembly of multifunctional nanoparticle networks using metallic and bioinorganic building blocks

摘要

Oligonucleotide-modified nanoparticles of gold or protein-encapsulated iron oxide (ferritin) were prepared respectively by covalent or streptavidin/biotin coupling,and reversibly assembled into interlinked networks by a two-step process involving targeted DNA hybridisation.In the first step,a 3'-biotin-terminated 12-base single-strand oligonucleotide was bound to a streptavidin-biotinylated ferritin conjugate to produce an oligonucleotide-protein complex,which was then mixed with Au nanoparticles capped with a 5'-mercapto-terminated 12-base non-complementary single-strand oligonucleotide.Double-stranded crosslinks between the oligonucleotide-modified Au and ferritin building blocks were then induced by addition of a half-complementary 24-base single-strand target oligonucleotide.TEM studies revealed the presence of disordered networks often several micrometres in size that consisted of closely associated Au nanoparticles and iron oxide ferritin cores.Corresponding uv-vis spectra showed a reduction in the intensity of the oligonucleotide 260 nm absorbance band,consistent with base-pairing and duplex formation,and a small but distinct 7 nm red shift for the Au surface plasmon resonance band.Heating the aggregates to 70degC shifted the plasmon resonance peak back to an original value of 524 nm,and produced a marked increase in absorbance at 260 nm consistent with disassembly of the DNA duplex and solubilization of the Au nanoparticles.Thermal cycling of the Au-ferritin networks revealed a melting temperature for interparticle duplex hybridisation of 54degC,and indicated that the assembly process was reversible.