Smart polymeric micelles as nanocarriers for oligonucleotides and siRNA delivery.

The development of in vivo delivery systems for oligonucleotides and siRNA is strongly desired to achieve their clinical applications. Recently, polyplex micelles, which are formed through an electrostatic interaction between nucleic acid compounds (DNA and RNA) and poly(ethylene glycol) (PEG)-polycation block copolymers, have received much attention due to their nanometric-scaled size and excellent biocompatibility. Here, three types of newly engineered block copolymers were developed to construct polyplex micelles useful for oligonucleotides and siRNA delivery: (1) PEG-polycation diblock copolymers possessing diamine side-chain with distinctive pKa for siRNA encapsulation into polyplex micelles with high endosomal escaping ability, (2) Lactosylated PEG-(oligonucleotide or siRNA) conjugate through acid-labile beta-thiopropionate linkage to construct pH-sensitive PIC micelles, and (3) PEG-poly(methacrylic acid) block copolymer for the construction of organic/inorganic hybrid nanoparticles encapsulating siRNA.