Synthesis and structure-activity relationships of a series of increasingly hydrophobic cationic steroid lipofection reagents.
The use of cholesterol-based cationic lipids and the ability of glucocorticoids to reduce local inflammatory response to lipoplexes motivated an investigation of structure-activity relationships for cationic steroids. A one-step synthetic scheme using iminothiolane was developed to link spermine to the 21-OH position of steroids via an amidine linkage. Five steroids (cortisol, dexamethasone, corticosterone, 11-deoxycortisol, and 11-deoxycorticosterone) with increasing hydrophobicity of the parent steroid (Log P(ster) from 1.51 to 3.01) were conjugated with spermine, formulated with dioleoylphosphatidylethanolamine (DOPE) at DOPE : steroid mole ratios (R) of R = 0.5 to 2, and then complexed with 1 microg enhanced green fluorescent protein (EGFP) plasmid DNA at charge ratios (CR) = 2 to 24 amines per phosphate (0.5 to 6 steroids per phosphate). The resulting 105 different formulations of the cationic steroid series were used to lipofect bovine aortic endothelial cells. Transgene expression data at either 24 or 48 h post-lipofection for all formulations was collapsed onto master curves when plotted against a single empirical dimensionless parameter, the lipofection index (LI) = CR (Log P(liposome))(Log P(ster)/|DeltaLog P|) [R/(R + 1)] where DeltaLog P = Log P(DOPE)- Log P(ster) and Log P(liposome) is a mole-weighted average of the DOPE/cationic steroid liposome hydrophobicity. For 7 < LI < 29, the EGFP expression at 24 or 48 h post-lipofection increased linearly with LI (EGFP approximately 0 for LI < 7), but did not increase further for LI > 29, thus providing a predictive design rule based on Log P of the hydrophobic moiety of the cationic steroid lipid.
Gruneich
Jeffrey A
JA
Department of Bioengineering, Institute for Medicine and Engineering, 1024 Vagelos Research Laboratory, University of Pennsylvania, Philadelphia, PA 19104, USA.
Diamond
Scott L
SL
D000818:Animals; D001011:Aorta / Q000166:cytology; D002412:Cations; D002417:Cattle; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D007202:Indicators and Reagents; D008055:Lipids / Q000737:chemistry / Q000627:therapeutic use; D010714:Phosphatidylethanolamines / Q000737:chemistry; D021281:Quantitative Structure-Activity Relationship; D013096:Spermine / Q000737:chemistry; D013256:Steroids / Q000737:chemistry / Q000627:therapeutic use; D014162:Transfection / Q000379:methods* / Q000592:standards
C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D002412:Cations; D007202:Indicators and Reagents; D008055:Lipids; D010714:Phosphatidylethanolamines; D013256:Steroids; D013096:Spermine