Asymmetric Functionalization of Gold Nanoparticles with Oligonucleotides

Abstract

Programmable assembly methods based upon the use of oligonucleotide-functionalized nanoparticles and sequence-specific assembly with complementary DNA have led to the development of a variety of fundamentally interesting materials and technologically significant detection systems. 1-3 The attractive feature of this approach to materials synthesis is that one can control the size, shape, and compositions of the individual nanoparticle building blocks as well as their spacing and periodicity within a macroscopic and, often times, polymeric structure through judicious choice of nanoparticle building block and DNA linkers. Most of the work in this area has focused on the use of isotropically functionalized particles since there are very few ways of selectively functionalizing different surface regions of an individual particle. However, if one could deliberately functionalize only one hemisphere or one distinct point on a particle in a general way, one could begin to introduce valency into such structures, thereby allowing greater control over the assembly process. 4A kinetic control approach, developed by Alivisatos and coworkers, allows one to functionalize nanoparticles with as few as one oligonucleotide per particle. 2b,5 This novel strategy introduces anisotropy into such particles and has enabled the assembly of dimer and trimer structures not attainable with the isotropically functionalized particles. Although this was an important step forward in nanoparticle functionalization, it has been limited to very small particles and typically leads to mixtures of products that must be separated by electrophoretic means. Here, we report a general strategy to functionalize a AuNP with two different types of oligonucleotides in a site-specific manner by using a magnetic sphere as a geometric restriction template (Scheme 1).Anisotropic functionalization of AuNPs was accomplished using a three-component assembly strategy (Scheme 1) consisting of the following: (1) magnetic microparticles (MMPs, 2.8 μm diameter polystyrene particles with iron oxide cores) functionalized with 3′thiol-terminated 30-mer oligonucleotides 1, (2) 3′-hydroxyl-modified "extension" oligonucleotides 2 that are complementary to half of the MMP oligonucleotides, and (3) AuNPs (13 nm, citrate-stabilized particles) densely functionalized with 3′-thiolated and 5′-phosphorylated 15-mer oligonucleotides 3 that are half-complementary to the other half of the MMP oligonucleotides. Standard methods were used to functionalize the MMPs and AuNPs with oligonucleotides (see Supporting Information). After combining the three components in the presence of a ligation buffer, they assembled to form complex 4 in which the oligonucleotide-modified MMP acts as a template to co-align the 3′-hydroxy group of the extension oligonucleotides with the 5′-phosphate group of the AuNP oligonucleotide. T4 DNA ligase was added to the reaction solution to catalyze the formation of a phosphodiester bond between the 3′-hydroxyl and the 5′-phosphate of the extension oligonucleotides ...

Colloids with valence and specific directional bonding

“…This approach is conceptually simple, yet challenging to realize. For example, so-called Janus particles with asymmetrically functionalized surfaces can be made, but normally have only a single patch [20][21][22] . Triblock Janus particles have also been fabricated by glancing-angle deposition and assembled into a kagome lattice, the 2-dimensional analogue of a diamond crystal 23 .…”

One-pot polymerase chain reaction with gold nanoparticles for rapid and ultrasensitive DNA detection

“…The clearly distinguishable color change facilitates a very simple sensor readout which can be performed by the naked eye. The use of controllable aggregation of Au NPs was pioneered by Mirkin et al, harnessing DNA hybridization to induce an assembly of particles modified with single-stranded DNA (ssDNA) [12,13]. PCR is a revolutionary technique in molecular biology and medical sciences, possessing both high sensitivity and high selectivity [14,15].…”

A systems approach towards the stoichiometry-controlled hetero-assembly of nanoparticles

“…Compared with these 'homo-coupling' nanoreactions, controlling stoichiometry in the 'cross-coupling' of NPs presents different and arguably greater challenges. It was only achieved through the brilliant design and pre-fabrication of NPs with anisotropic surface functionalities (for example, NP with a single DNA molecule) [17][18][19][20][21][22] .…”