Amphiphilic Polymeric Micelle Spherical Nucleic Acids (SNAs) as Drug Delivery Vehicles

This work describes the synthesis and characterization of a new class of spherical nucleic acid (SNA) derived from amphiphilic polymeric micelles (APM-SNA) for the delivery of hydrophobic drugs. Core structures are assembled from amphiphilic copolymers comprising a hydrophobic block (made from hydroxypropyl methacrylate and methacrylates bearing n-butyl, benzyl, or n-hexyl side chains) and a hydrophilic polyethylene glycol block terminated with an azide group. Alkyne-modified oligonucleotides are conjugated to the polymer cores via click chemistry to form APM-SNAs. Cellular uptake of APM-SNAs is dependent on oligonucleotide density, increasing up to 10-fold at the highest densities. Moreover, higher-density APM-SNAs induce up to a six-fold increase in immune activation compared to linear DNA. Increasing the hydrophobicity and pi-pi stacking interactions of the polymer core with benzyl methacrylate enhances cellular uptake relative to APM-SNAs constructed with the least hydrophobic (n-butyl methacrylate) monomers. Additionally, benzyl APM-SNAs show superior drug encapsulation efficiency (67 vs 41%) and extended-release profiles (half-life of 27.8 vs 7.4 h) for the STAT3 inhibitor WP1066 compared to n-butyl APM-SNAs. Oligonucleotide sequence influences the extent of cellular uptake in Caki-1 cells; T20-SNAs exhibit ∼40% greater uptake compared to CpG and G-quadruplex sequences after 24 h. These structure-dependent properties lead to a 40% improvement in WP1066 potency when delivered via T20 benzyl APM-SNAs, reducing the drug's EC₅₀ from 6.18 to 3.54 μM. Collectively, these results demonstrate that increasing the hydrophobicity of the APM-SNA core and the interactions between the core and the drug enhance drug encapsulation efficiency, prolong release kinetics, and improve therapeutic efficacy.