Zwitterionic Brush-Engineered Molecular Spherical Nucleic Acids for Enhanced Intracellular Antisense Activity

Spherical nucleic acids (SNAs) enhance antisense oligonucleotide (ASO) uptake and nuclease resistance, but their activity is often constrained by inefficient intracellular trafficking. Here, we developed a zwitterionic brush-engineered molecular SNA (EmSNA) to improve ASO delivery. EmSNA was constructed by grafting poly(carboxybetaine) side chains onto a unimolecular ASO nanostructure, generating a compact, hydrated, near-neutral corona that modulated interfacial charge, oligonucleotide crowding, and intracellular processing. This architecture preserved rapid, sequence-specific hybridization while increasing duplex thermal stability and nuclease resistance. The zwitterionic brush further enhanced cellular uptake and reduced lysosomal sequestration, thereby improving antisense activity. Using a HER2-targeted ASO as a model cargo, EmSNA achieved stronger HER2 silencing in vitro and greater tumor growth inhibition in a xenograft model after local intratumoral administration, without overt systemic toxicity under the tested conditions. These findings establish zwitterionic brush engineering as an effective strategy to enhance functional SNA-based ASO delivery.