Enhancing the Stability and Immunomodulatory Activity of Liposomal Spherical Nucleic Acids through Lipid‐Tail DNA Modifications

Abstract

Liposomal spherical nucleic acids (LSNAs) are an attractive therapeutic platform for gene regulation and immunomodulation due to their biocompatibility, chemically tunable structures, and ability to enter cells rapidly without the need for ancillary transfection agents. Such structures consist of small (<100 nm) liposomal cores functionalized with a dense, highly oriented nucleic acid shell, both of which are key components in facilitating their biological activity. Here, the properties of LSNAs synthesized using conventional methods, anchoring cholesterol terminated oligonucleotides into a liposomal core, are compared to LSNAs made by directly modifying the surface of a liposomal core containing azide-functionalized lipids with dibenzocyclooctyl-terminated oligonucleotides. The surface densities of the oligonucleotides are measured for both types of LSNAs, with the lipid-modified structures having approximately twice the oligonucleotide surface coverage. The stabilities and cellular uptake properties of these structures are also evaluated. The higher density, lipid-functionalized structures are markedly more stable than conventional cholesterol-based structures in the presence of other unmodified liposomes and serum proteins as evidenced by fluorescence assays. Significantly, this new form of LSNA exhibits more rapid cellular uptake and increased sequence-specific toll-like receptor activation in immune reporter cell lines, making it a promising candidate for immunotherapy.

PLGA Spherical Nucleic Acids

“…The release profiles of the nucleic acid shell for all three PLGA‐SNAs are similar, exhibiting half‐lives of more than 2 h with K obs ranging from 7.4 × 10 −5 to 8.8 × 10 −5 s −1 (Figure C, Table ). These K obs values suggest that PLGA‐SNAs are nearly 100‐fold more stable than the most clinically advanced liposomal SNAs and three times more stable than the lipid‐tail SNAs ( K obs = 7.9 × 10 −3 s −1 and 2.8 × 10 −4 s −1 for liposomal SNA and lipid‐tail LSNAs, respectively) . The increased stability of the PLGA‐SNAs are likely due to the covalent bond utilized to immobilize the nucleic acids on the NPs and the intrinsically higher stability of polymer NPs (as compared with liposomes).…”

Rational vaccinology with spherical nucleic acids

“…The structural features of SNA H that drive the enhancement of codelivery are (i) the linkage of antigen to CpG by chemical conjugation and nucleic acid hybridization and (ii) the enhancement of cellular uptake of oligonucleotides by the SNA architecture. SNA H is not susceptible to erosion in codelivery through the mechanisms likely responsible for the separation of antigen and CpG in SNAs E and A (i.e., leakage of peptide through liposome membranes, desorption of antigen-functionalized oligonucleotides from liposomes) (30).…”

Progress toward Understanding the Interactions between DNA Nanostructures and the Cell

“…Serum stability is another structural parameter of cellular uptake. In 2018, Meckes et al prepared two versions of liposome‐cored SNAs by anchoring DNA oligonucleotides to the lipid bilayer via cholsterol molecules or hexadecyl chains . By using a Förster resonance energy transfer (FRET)‐based assay, the authors showed that hexadecyl‐based SNAs have a >20‐fold longer half‐life in serum‐containing medium than cholesterol‐based SNAs, with dissociation rates of 2.8 × 10 −4 and 7.9 × 10 −3 s −1 , respectively.…”