Original Synthesis of a Nucleolipid for Preparation of Vesicular Spherical Nucleic Acids

Abstract

Spherical nucleic acids (SNAs)—nanostructures, consisting of a nanoparticle core densely functionalized with a shell of short oligonucleotide strands—are a rapidly emerging class of nanoparticle-based therapeutics with unique properties and specific applications as drug and nucleic acid delivery and gene regulation materials. In this contribution, we report on the preparation of hollow SNA nanoconstructs by co-assembly of an originally synthesized nucleolipid—a hybrid biomacromolecule, composed of a lipidic residue, covalently linked to a DNA oligonucleotide strand—with other lipids. The nucleolipid was synthesized via a click chemistry approach employing initiator-free, UV light-induced thiol-ene coupling of appropriately functionalized intermediates, performed in mild conditions using a custom-made UV light-emitting device. The SNA nanoconstructs were of a vesicular structure consisting of a self-closed bilayer membrane in which the nucleolipid was intercalated via its lipid–mimetic residue. They were in the lower nanometer size range, moderately negatively charged, and were found to carry thousands of oligonucleotide strands per particle, corresponding to a grafting density comparable to that of other SNA structures. The surface density of the strands on the bilayer implied that they adopted an unextended conformation. We demonstrated that preformed vesicular structures could be successfully loaded with either hydrophilic or hydrophobic dyes.

Three-Dimensional Nucleic Acid Nanostructures Based on Self-Assembled Polymer-Oligonucleotide Conjugates of Comblike and Coil-Comb Chain Architectures

“…N s/p was given by the product of N agg and the average number of oligonucleotide strands conjugated to each polymer chain of the homopolymer, random and block copolymers. Typical values for reference SNAs − vary between 70 and 1200 strands per particle though considerably larger values have recently been reported. ,,, Consistent with their relatively large dimensions and comblike and coil-comb chain architectures of the conjugates comprising 5–8 oligonucleotide strands per polymer chain, N s/p values of the present aggregates are larger than those of reference SNAs. − N s/p went through a maximum for ssODNconjB apparently owing to the highest oligonucleotide content (8 strands per polymer chain). The aggregates exhibited moderately negative ζ potentials due to the negative charge of the grafted ssDNA strands, without any pronounced trend that could be associated with the variations of e.g., size, N agg , or N s/p .…”

“…Typical values for reference SNAs 44−47 vary between 70 and 1200 strands per particle though considerably larger values have recently been reported. 10,27,48,49 Consistent with their relatively large dimensions and comblike and coil-comb chain architectures of the conjugates comprising 5−8 oligonucleotide ρ, N agg , N s/p , and σ denote the density of the material within the particle, aggregation number, number of oligonucleotide strands per particle, and grafting density, respectively. The standard deviations are up to 4% for static and dynamic light scattering parameters and 3% for the ζ potential.…”

“…SNAs have been prepared with a variety of core materials including inorganic compositions (Au, Ag, Pt, SiO 2 , Fe 3 O 4 , quantum dots) as well as organic and polymeric compositions. ,− Although introducing great versatility in the chemistry, structure, and properties of the SNAs, the latter are yet underexplored. They can be obtained by self-assembly of amphiphilic conjugates, prepared from a synthetic polymer covalently linked to a short oligonucleotide strand, into core–shell type micelles.…”