Amphiphilic poly (amino acid), block copolyer using the amphiphilic poly (amino acid), and complex including the amphiphilic poly (amino acid) or the block copolymer and nucleic acid

An amphiphilic poly(amino acid) represented by the following formula (1):

• wherein:
• R1 is a hydroxy group, an oxybenzyl group, an —O—R1a group, or an —NH—R1b group, wherein R1a and R1b are each independently an unsubstituted or substituted, linear or branched alkyl group having 1 to 12 carbon atoms;
• R2 is a hydrogen atom, an unsubstituted or substituted, linear or branched alkyl group having 1 to 12 carbon atoms, or an unsubstituted or substituted, linear or branched alkylcarbonyl group having 1 to 24 carbon atoms;
• R3a, R3b, R4a, and R4b are each independently a methylene group or an ethylene group;
• R5a and R5b are each independently —O— or —NH—;
• R6a and R6b are each independently an unsubstituted or substituted aliphatic hydrocarbon group having 7 to 12 carbon atoms that contains an alicycle;
• R7a and R7b are each independently:
• —NH—(CH2)p1—[NH—(CH2)q1—]r1NH2 (i);
• —NH—(CH2)p2—N[—(CH2)q2—NH2]2 (ii);
• —NH—(CH2)p3—N{[—(CH2)q3—NH2][—(CH2)q4—NH—]r2H} (iii);
• or
• —NH—(CH2)p4—N{—(CH2)q5—N[—(CH2)q6—NH2]2}2 (iv),
• wherein p1 to p4, q1 to q6, and r1 and r2 are each independently an integer of from 1 to 5;
• R8 is a side chain of an amino acid selected from the group consisting of ornithine, lysine, homolysine, arginine, homoarginine, and histidine;
• m is an integer of 9 or more;
• n is an integer of from 0 to m;
• x is an integer of from 2 to 300;
• y is an integer of from 0 to x;
• and
• z is an integer of from 0 to x,
• provided that y+z≤x and 11≤m+x≤400, and repeating units in formula (1) can be randomly arranged.