Abstract: There are provided an anionic polymer, a polyion complex, and a ternary polymer composite, each of which is stable in a biological environment and is capable of realizing small RNA delivery without causing any undesired immune response. An anionic polymer according to an embodiment of the invention includes: a main chain which includes repeating units having carboxyl groups; and a side chain which is linked with part of the carboxyl groups in the main chain and is represented by the following formula: -A-B—X where: A represents a residue having one or more aminoethyl bonds; B represents an in vivo cleavable bond; and X represents a small RNA. A polyion complex according to an embodiment of the invention includes the anionic polymer as described above and a cationic polymer. A ternary polymer composite according to an embodiment of the invention includes the polyion complex as described above and a charge conversional polymer.

Abstract: The present invention relates to a block copolymer containing an uncharged hydrophilic polymer chain block and a cationic polyamino acid chain block, wherein the hydrophilic polymer chain block is covalently bound to one end of the main chain of the polyamino acid chain block, and the hydrophobic group is covalently bound to the side chains of not less than 10% and not greater than 70% of amino acid repeating units in the polyamino acid chain block. This block copolymer forms a stable aggregate with siRNA, a small-molecule nucleic acid, under a physiological condition.

Abstract: There are provided an anionic polymer, a polyion complex, and a ternary polymer composite, each of which is stable in a biological environment and is capable of realizing small RNA delivery without causing any undesired immune response. An anionic polymer according to an embodiment of the invention includes: a main chain which includes repeating units having carboxyl groups; and a side chain which is linked with part of the carboxyl groups in the main chain and is represented by the following formula: -A-B—X where : A represents a residue having one or more aminoethyl bonds; B represents an in vivo cleavable bond; and X represents a small RNA. A polyion complex according to an embodiment of the invention includes the anionic polymer as described above and a cationic polymer. A ternary polymer composite according to an embodiment of the invention includes the polyion complex as described above and a charge conversional polymer.

Abstract: The present invention relates to a block copolymer containing an uncharged hydrophilic polymer chain block and a cationic polyamino acid chain block, wherein the hydrophilic polymer chain block is covalently bound to one end of the main chain of the polyamino acid chain block, and the hydrophobic group is covalently bound to the side chains of not less than 10% and not greater than 70% of amino acid repeating units in the polyamino acid chain block. This block copolymer forms a stable aggregate with siRNA, a small-molecule nucleic acid, under a physiological condition.