Spherical Nucleic Acids
Nucleic acids are found in nature in one-dimensional linear and even two-dimensional circular forms. In 1996, the Mirkin group prepared the first spherical forms of nucleic acids using a gold nanoparticle template and short strands of DNA (typically ~10-30mers). They found that this new form of matter has different properties and functions compared to DNA of other shapes as well as the same sequence of DNA not highly oriented on the particle surface at high density. The Mirkin group also found that the base-pairing interactions of the DNA on the surface could be utilized to organize the nanoparticles into hierarchical assemblies. This work and the resulting patents are foundational to the subsequent use of spherical nucleic acids (SNAs) in biodetection and nanotherapeutics as well as colloidal crystal engineering with DNA. SNAs act as programmable atom equivalents (PAEs) where the identities of the nanoparticle “atoms” are separated from the DNA “bonding elements”. Since 1996, the Mirkin group has synthesized and studied dozens of SNAs with different core and nucleic acid shell compositions.
Transmission electron microscopy (TEM) image of SNAs with gold cores (dark circles) and DNA shells (white rings); staining was used to enhance contrast.