Commercial Transfection Reagents

 DOSPA

A well-known cationic lipid is N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA). The structure of DOTMA is:

DOTMA by itself or in 1:1 combination with dioleoylphosphatidylethanolamine (DOPE) is formulated into liposomes using standard techniques. Felgner, et al. supra demonstrated that such liposomes provided efficient delivery of nucleic acids to some types of cells. A DOTMA:DOPE (1:1) formulation is sold under the trade name LIPOFECTIN (Life Technologies, Inc., Rockville, Md.). Another commercially available cationic lipid is 1,2-bis(oleoyloxy)-3-3-(trimethylammonia) propane (DOTAP), which differs from DOTMA only in that the oleoyl moieties are linked via ester, rather than ether bonds to the propylamine. A related group of compounds differ from DOTMA and DOTAP in that one of the methyl groups of the trimethylammonium group is replaced by a hydroxyethyl group. Compounds of this type are similar to the Rosenthal Inhibitor (RI) of phospholipase A (Rosenthal, A. F. and Geyer, R. P. (1960) J. Biol. Chem. 235:2202–2206) which has stearoyl esters linked to the propylamine core. The dioleoyl analogs of RI are commonly abbreviated as DORI-ether and DORI-ester, depending on the linkage of the fatty acid moieties to the propylamine core. The hydroxy group can be used as a site for further functionalization.
The dimyristyloxy analog of RI is known as DRMIE. A 1:1 (M/M) DMRIE:cholesterol formulation is sold under the tradename (Life Technologies, Inc., Rockville, Md.). The structure of DMRIE is:

http://52.1.104.161/eln/images/f/fb/DRMIE.png

Another class of compounds has been disclosed by Behr et al. (1989) Proc. Natl. Acad. Sci. USA 86:6982-6986; EPO publication 0 394 111 (Oct. 24, 1990), in which carboxyspermine has been conjugated to two types of lipids. The structure of 5-carboxyspermylglycine dioctadecylamide (DOGS) is:

The structure of dipalmitoylphosphatidylethanolamine 5-carboxyspermylamide (DPPES) is:

 

Figure US07479573-20090120-C00005
Both DOGS and DPPES have been used to coat plasmids, forming a lipid aggregate complex that provides efficient transfection. The compounds are claimed to be more efficient and less toxic than DOTMA for transfection of some cell lines. DOGS is available commercially as TRANSFECTAM™ (Promega, Madison, Wis.).

Another class of compounds has been also described in which carboxy spermine has been conjugated to lipids via an amide bond (Gebeyehu, G. et al., U.S. Pat. No. 5,334,761). These compounds are useful for an efficient delivery of nucleic acids into various cells and also are intermediates for making other such lipids. 2,3-di-oleyloxy-N-[2(spermine-carboxamido)ethyl]-N,N-dimethyl-l-propan-aminium (DOSP A) is available as a 3:1 (w/w) formulation with DOPE under the trade name LipofectAMINE (available from Life Technologies, Inc., Rockville, Md.). The structure of DOSPA is as follows:

 Figure US07479573-20090120-C00006
Lipid compounds with a spermine head group have also been described (Haces, A., et al., U.S. Pat. No. 5,674,908). These compounds are especially useful for delivery of nucleic acids into insect cells. A 1: 1.5 (M/M) formulation of tetramethyltetrapalmitylspermine (TM-TPS) to DOPE is commercially available under the tradename CellFECTIN (Life Technologies, Inc., Rockville, Md.). The structure of TM-TPS is shown below:

 Figure US07479573-20090120-C00007
A cationic cholesterol derivative () has been synthesized and formulated into liposomes in combination with DOPE. (Gao. X. and Huang, L. (1991) Biochim. Res. Cornrn. 179:280–285). The compound's structure is:

http://52.1.104.161/eln/images/8/8d/DC-Chol.png

Liposomes formulated with DC-Chol are said to provide more efficient transfection and lower toxicity than DOTMA-containing liposomes for some cell lines.
Lipopolylysine, formed by conjugating polylysine to DOPE, has been reported to be especially effective for transfection in the presence of serum, a condition likely to be encountered in vivo (Zhou, X. et al. (1991) Biochim. Biophys. Acta 1065: 8–14).