There are several chemistries allowing conjugating antibodies to ASOs:
Click chemistry utilizes azide-alkyne cycloaddition reactions to synthesize Ab-ASO conjugates with high specificity and bioorthogonality. These conjugation methods enable site-specific conjugation.
Disulfide linker chemistries utilize cleavable linker molecules in reducing environments, enabling the controlled release of ASO in the intracellular space.
Hydrazone or oxime ligation utilizes aldehyde-modified oligonucleotides with hydrazine-functionalized antibodies.
Thiol-maleimide chemistries introduce thiol groups on either the ASO or antibody. Thiols react with a maleimide-modified partner molecule. Thiol-maleimide-based conjugation methods are efficient and widely used.
Please review: Bioconjugate Chemistry for Molecular Engineering