DNA-directed Assembly Of Gold Nanoparticles With Varied Morphologies

Assembled gold nanoparticles with unique optical properties exhibit better optical and electronic properties than the original ones.In the middle of the twentieth Century,DNA was applied to construct nanostructures and nanodevices due to its well-established molecular-recognition and capability of programmable self-assembly.Since then,gold nanoparticles assembled with DNA have been extensively investigated.However,the three-dimensional assembly of DNA-directed gold nanoparticles with varied morphologies are limited.Thus,we further investigated the use of DNA strands to direct the assembly of gold nanoparticles to form more complex structures.Briefly,we employed single-stranded DNA and dual-modified DNA tetrahedron to direct the 3D assembly of gold nanoparticles.First,gold nanoparticles with diameter of 13 nm were synthesized through Turkevich's method and modified by thiol-modified DNA?SH-DNA?,which were analyzed by agarose gel electrophoresis and transmission electron microscope?TEM?.Moreover,Au nanorods and Au nanoprisms with different sizes were synthesized by seed-mediated growth.Then the DNA with complementray sequence?C-SH-DNA?of SH-DNA was used to modify gold nanorods and gold nanoprisms.Agarose gel electrophoresis showed that gold nanorods and gold nanoprisms were successfully modified.Due to the complementary sequences on gold nanoparticles,the nanospheres and nanorods were mixed and realized the assembly through DNA base pairing.Furthermore,gold nanorods,gold nanoprisms were tested to assemble together with DNA linker,but no controllable assembled nanostructures were observed under TEM.Thus,more endenvors may be put to realize the construction of well-defined nanostructures in future research.As we know,it is difficult to modified the gold nanoparticles with the single-stranded DNA in a controllable manner regarding the positions and numbers of DNA on the nanoparticle surface.To achieve the controlled assembly,we assembled different types of dual-modified DNA tetrahedrons,to encapsulate a modified 5 nm gold nanoparticle inside,which provides specific geometry on the spheric gold nanoparticles.In the experiment,we first designed and synthesized a central long strand DNA L3,medium strand M,short peripheral strand S.Meanwhile,we cyclized L3 and modified M strand for further assembly,which were purified by denaturing polyacrylamide gel electrophoresis analysis.Then DNA tetrahedra were assembled by a simple,one-pot process:the corresponding DNA strands were mixed in a Mg²⁺-containing buff er and slowly cooled from 95 to 25?over 48 h.Upon formation,polyacrylamide electrophoresis analysis?PAGE?showed that DNA tetrahedrons with specific moditications were successfully synthesized;Finally,gold nanoparticles were encapsulated in the well-defined DNA tetrahedron through DNA base pairing between DNA tails on polyhedra and SH-DNA on DNA-AuNPs.Meanwhile,DNA tetrahedron with gold nanoparticles was further conjugated to responsive polymer,through which the conjugates may be used for the assembly of more complex structures.