Sequence-defined Digital Bottlebrush Polymers for Programmable Oligonucleotide Delivery.

Oligonucleotide therapeutics hold transformative potential, yet their clinical translation is hindered by delivery barriers, including rapid renal/hepatic clearance and poor organ specificity. Bottlebrush polymer conjugates have emerged as a promising vector to address these limitations, but conventional architectures with uniform backbones can only achieve an unmodifiable, rigid biodistribution profile. Here, we report a library of sequence-defined "digital" bottlebrush polymers, precisely engineered with controlled placements of chemical motifs that modify physicochemical properties─including lipids, cholesterol, and cationic groups─along a polyphosphodiester backbone. Systematic evaluation of the digital bottlebrush polymer library reveals distinct structure-property relationships and enables organ-biased systemic delivery to several traditionally difficult-to-reach tissues, including muscle and skin. In a mouse model of rheumatoid arthritis, a single dose of a spleen-homing polymer-conjugated antisense oligonucleotide targeting TNF-α significantly reduced arthritis severity and preserved animal body weight. These findings establish a versatile design framework for tailoring bottlebrush polymers to specific therapeutic applications.