Spherical nucleic acid

Spherical nucleic acids (SNAs) – defined as structures that are an arrangement of densely packed, highly oriented nucleic acids in a spherical geometry – were first introduced in 1996 by the Mirkin group at Northwestern University. The arrangement and orientation of one-dimensional linear nucleic acids within this three-dimensional framework results in new chemical, biological, and physical properties in the use of nucleic acids for intracellular gene regulation (though this is disputed ), molecular diagnostics, and materials synthesis applications. Spherical nucleic acids (SNAs) – defined as structures that are an arrangement of densely packed, highly oriented nucleic acids in a spherical geometry – were first introduced in 1996 by the Mirkin group at Northwestern University. The arrangement and orientation of one-dimensional linear nucleic acids within this three-dimensional framework results in new chemical, biological, and physical properties in the use of nucleic acids for intracellular gene regulation (though this is disputed ), molecular diagnostics, and materials synthesis applications. The first SNA consisted of 3’ alkanethiol-terminated, single-stranded oligonucleotides (short DNA sequences) covalently attached to the surface of spherical gold nanoparticles. A dense nucleic acid loading was achieved through a series of salt additions, in which positively charged counterions were used to reduce electrostatic repulsion between adjacent negatively charged DNA strands and thereby enable more efficient DNA packing onto the nanoparticle surface.