Cationic lipid having disulfide bond, lipid membrane structure including same, nucleic acid introduction agent and pharmaceutical composition containing any one of same, method for introducing nucleic acid into cell or target cell, and method for producing cellular pharmaceutical

A cationic lipid having a disulfide bond represented by the formula (1):

• wherein
• X is a nitrogen-containing aliphatic group containing one or more tertiary nitrogens,
• R1 is an aliphatic hydrocarbon group having not more than 8 carbon atoms,
• L1 is an ester bond, an amide bond, a carbamate bond, an N-alkylcarbamate bond, a carbonate bond or a urea bond,
• k is 0 or 1,
• Rx and Ry are each independently an alkylene group having 2-5 carbon atoms,
• L2 is an ester bond, an amide bond, a carbamate bond, a carbonate bond, an ether bond or a urea bond,
• R2 is an alkylene group having not more than 8 carbon atoms, or absent, and
• Y is a group which (i) contains one or more divalent groups derived from an aromatic compound optionally having a hetero atom, (ii) contains a group containing at least one selected from the group consisting of an ester bond and a carbonate bond on the aromatic ring of the divalent group, and (iii) contains at least one selected from the group consisting of an aliphatic hydrocarbon group having 10-37 carbon atoms, a liposoluble vitamin residue, and a residue of a sterol derivative.