Single-stranded nucleic acid molecule for regulating expression of gene having delivering function

An isolated molecule for inhibiting expression of a target gene, wherein the molecule has a delivery function and comprises, in the following order, a 5′-side region (Xc), a linker region (Lx), an inner region (Z), a linker region (Ly) and a 3′-side region (Yc) which regions are linked together, wherein

• the inner region (Z) is constituted by linkage of an inner 5′-side region (X) and an inner 3′-side region (Y),
• the 5′-side region (Xc), the inner 5′-side region (X), the inner 3′-side region (Y) and the 3′ side region (Yc) are each composed of a nucleotide residue or a nucleotide sequence,
• the 5′-side region (Xc) is complementary to the inner 5′-side region (X),
• the 3′-side region (Yc) is complementary to the inner 3′-side region (Y),
• at least one of the inner region (Z), the 5′-side region (Xc) and the 3′-side region (Yc) comprises an expression inhibitory sequence that inhibits expression of a target gene,
• the linker region (Lx) is linked to the 3′-end of the 5′-side region (Xc) and the 5′-end of the inner 5′-side region (X),
• the linker region (Ly) is linked to the 3′-end of the inner 3′-side region (Y) and the 5′-end of the 3′-side region (Yc),
• the linker region (Lx) and the linker region (Ly) are each composed of a nucleotide or non-nucleotide residue or a sequence of at least one nucleotide and non-nucleotide residues, wherein at least one selected from the group consisting of the linker region (Lx) and the linker region (Ly) comprises a lysine residue in such a manner that (i) the 5′-side region (Xc) and the inner 5′-side region (X) or (ii) the inner 3′-side region (Y) and the 3′-side region (Yc) are linked together via the lysine residue,
• a bio-related substance is covalently bound to the molecule via the lysine residue, and
• the bio-related substance is at least one selected from the group consisting of a peptide, polyethylene glycol (PEG), a polyamine, a fluorescence molecule, biotin, an intercalator molecule, a sugar, a water-soluble vitamin, a metal chelating agent, and a cross-linking agent.