Assembly of amphiphilic nucleic acid-polymer conjugates into complex superaggregates: Preparation, properties, and in vitro performance

Abstract

Nucleic acid-polymer conjugates (NAPCs) are obtained by click coupling reactions of appropriately functionalized oligonucleotides with synthetic polymer chains of different chemical nature, composition, and properties, namely, polyethers such as poly(ethoxyethyl glycidyl ether) and polyesters such as poly(ε-caprolactone). The resulting NAPCs are amphiphilic and form stable aggregates in aqueous solution. The aggregates are thoroughly investigated by a variety of techniques – static, dynamic, and electrophoretic light scattering, transmission electron microscopy, and atomic force microscopy. The size and molar masses of the particles as well as other parameters such as aggregation number and number of oligonucleotide strands per particle are significantly larger than those, reported for metal-free spherical nucleic acids. Formation of superaggregates of smaller individual micelles or non-micellar assemblies by hydrophobic interactions between the synthetic polymer chains and “sticky” interactions between oligonucleotides such as base pairing, π-stacking, hydrogen bonding is anticipated. The “sticky” interactions are counterbalanced by repulsion between the negatively charged oligonucleotide strands thus providing colloidal stability of the structures. The surface density of the oligonucleotide strands in the shell implies that the latter are in a random coil (mushroom) conformation rather than in a fully extended, brush regime. The hallmark properties of the prototypical spherical nucleic acids – non-toxicity and biocompatibility, increased cellular uptake without the need of transfection agents, enhanced nuclease stability – are also exhibited by the novel constructs despite of the differences in size, morphology, and structure.