Use of polysaccharide derivative

A crosslinked structure, comprising:

• (a) a polysaccharide derivative in which a group represented by Formula (A) below is introduced into an acidic, basic or amphoteric polysaccharide;
• and
• (b) at least one of an amino group-containing polymer and an amino group-containing low-molecular-weight compound, which contain two or more primary amino groups, a hydrazide group, or an aminoxy group, and a group represented by Formula (x1) below, wherein
• the primary amino groups, the hydrazide group, or the aminoxy group contained in the amino group-containing polymer and the amino group-containing low-molecular-weight compound and the group represented by Formula (A) contained in the polysaccharide derivative are crosslinked by a covalent bond via a Schiff base:
• wherein in Formula (A), R1 represents a hydrogen atom or a C1-4 alkyl group,
• ring P is a phenyl ring or pyridine ring, and the phenyl ring or pyridine ring is optionally substituted with one or more substituents independently selected from among a halogen atom, —CF3, —NO2, a carboxyl group and —SO3H,
• Y represents a divalent group selected from the group consisting of —NH—, —C(═O)—, —S—, —O—, a C1-6 alkylene group, —(CH2CH2O)n—, and any combinations of these, and n is an integer from 1 to 9, and
• * represents a linkage with the polysaccharide,
• wherein in Formula (x1), k is an integer from 2 to 5,
• L5 is a single bond or a divalent group selected from the group consisting of —C(═O)—, —S—, —O—, an alkylene group, —(CH2CH2O)n—, and any combinations of these,
• n is an integer from 1 to 9, and
• * represents a linkage with the amino group-containing polymer or the amino group-containing low-molecular-weight compound.

A tissue adhesive material containing a polysaccharide derivative in which a group represented by Formula (A-2) below is introduced into a polysaccharide containing an amino group, wherein

• the group represented by Formula (A-2) is introduced into the polysaccharide by substituting a hydrogen atom of the amino group of the polysaccharide to form an amide bond, and
• the tissue adhesive material is in the form of a gel:
• wherein in Formula (A-2),
• R1 represents a hydrogen atom or a C1-4 alkyl group,
• ring P is a phenyl ring or pyridine ring, and the phenyl ring or pyridine ring is optionally substituted with one or more substituents independently selected from among a halogen atom, —CF3, —NO2, a carboxyl group and —SO3H,
• L2 is a single bond or represents a divalent group selected from the group consisting of —NH—, —S—, —O—, a C1-6 alkylene group, —(CH2CH2O)n—, and any combinations of these,
• n is an integer from 1 to 9, and
• * represents a linkage with the polysaccharide.