Provided herein are nanocapsules comprising a single ribonucleoprotein (RNP) complex as a core and an biodegradable crosslinked polymer shell that encapsulates the core, wherein the RNP complex comprises a Cas9 polypeptide and a guide RNA, and the biodegradable crosslinked polymer shell comprises polymerized monomers of imidazolyl acryloyl monomers, bisacryloyl disulfide monomers (a biodegradable cross-linker), optionally PEG acryloyl monomers, and either cationic acryloyl monomers, anionic acryloyl monomers, or both cationic and anionic acryloyl monomers (optionally in combination with non-ionic acryloyl monomers) as defined herein. Also provided are methods of making the nanocapsules, kits containing the nanocapsules and methods of delivering the encapsulated RNP to cells.