Protein-enclosing polymeric micelle

A block copolymer represented by the following formula (1):

• wherein R1 and R2 each independently represent a hydrogen atom, or a linear or branched alkyl group containing 1 to 12 carbon atoms,
• R3 represents a group represented by the following formula (Ia) or (Ib):
• L1 represents a group represented by the following formula (11):
• —(CH2)p1—NH— (11),
• wherein p1 represents an integer of 1 to 6,
• m1 represents an integer of 0 to 500 and m2 represents an integer greater than 0 up to 500, provided that the sum of m1 and m2 represents an integer of 10 to 500,
• m3, m4 and m5 each independently represent an integer of 1 to 5,
• n represents an integer of 0 to 500, and
• the symbol “/” means that (m1+m2) units of the respective monomer units shown on the left and right sides of this symbol may be in any sequence.