Cationic lipid

Abstract

The present invention aims to provide a cationic lipid that can be used as a nucleic acid delivery carrier, a lipid membrane structure using a cationic lipid, a nucleic acid-introducing agent using a cationic lipid, and a method of achieving nucleic acid introduction by using a nucleic acid-introducing agent containing a cationic lipid. A lipid membrane structure containing a cationic lipid represented by the formula (1) wherein each symbol is as defined in the DESCRIPTION, is superior in the stability in blood and tumor accumulation property. A nucleic acid-introducing agent using the cationic lipid can achieve high nucleic acid delivery efficiency of nucleic acid to be delivered into the cytoplasm.

The invention claimed is: 
     
       1. A cationic lipid represented by the formula (1) 
       
         
           
           
               
               
           
         
         in the formula (1), R 1a  and R 1b  are each independently an alkylene group or oxydialkylene group having not more than 8 carbon atoms, 
         X a  and X b  are each independently an ester bond, an amide bond, a carbamate bond, or an ether bond, and 
         R 2a  and R 2b  are each independently a sterol residue, a liposoluble vitamin residue, or an aliphatic hydrocarbon group having 13-23 carbon atoms. 
       
     
     
       2. The cationic lipid according to  claim 1 , wherein R 1a  and R 1b  are each independently an alkylene group. 
     
     
       3. The cationic lipid according to  claim 1 , wherein X a  and X b  are ester bonds. 
     
     
       4. The cationic lipid according to  claim 1 , wherein R 2a  and R 2b  are each independently a liposoluble vitamin residue, or an aliphatic hydrocarbon group having 13-23 carbon atoms. 
     
     
       5. The cationic lipid according to  claim 1 , wherein R 2a  and R 2b  are each independently a liposoluble vitamin residue. 
     
     
       6. The cationic lipid according to  claim 1 , wherein R 2a  and R 2b  are each independently an aliphatic hydrocarbon group having 13-23 carbon atoms. 
     
     
       7. A lipid membrane structure comprising the cationic lipid according to  claim 1  as a membrane-constituting lipid. 
     
     
       8. A nucleic acid-introducing agent, which comprises the lipid membrane structure according to  claim 7 . 
     
     
       9. The nucleic acid-introducing agent according to  claim 8 , wherein an anti-inflammatory agent is encapsulated in the lipid membrane structure. 
     
     
       10. A method of delivering a nucleic acid into a cell, comprising contacting the nucleic acid-introducing agent according to  claim 8 , which encapsulates the nucleic acid, with the cell in vitro. 
     
     
       11. A method of introducing a nucleic acid into a cell, comprising administering the nucleic acid-introducing agent according to  claim 8 , which encapsulates the nucleic acid, to a living organism so that it will be delivered to the target cell.