A QSAR-modeling perspective on cationic transfection lipids. 1. Predicting efficiency and understanding mechanisms.
BACKGROUND
As gene therapy using viral vectors involves clinical risks, limited DNA-carrying capacity, and manufacturing problems, non-viral vectors, including cationic lipids, have been investigated. Unfortunately, these agents have significantly lower transfectional ability and, due to the complexity of the transfectional pathway, no general schemes exist for correlating cationic lipid chemistry with transfectional efficacy.


METHODS
Quantitative structure-activity relationship (QSAR) analyses were carried out on sets of routinely used, experimental, and unsuccessful cationic lipid vectors taken from the literature. This approach described the amphipathic character, basicity, headgroup size, lipophilicity and shape of cationic lipids using numerical parameters. Compounds were plotted onto various parameter diagrams, and correlations were sought between numerical parameters and transfectional efficiency.


RESULTS
Transfectionally effective cationic lipids fell into restricted zones in various parameter spaces, indicating that amphipathic character, lipid shape and lipophilicity were generally significant factors, whilst basicity and headgroup size were only important for certain compounds. The data supported the general significance of membrane mixing followed by induction of membrane curvature, and the more limited role of osmotic shock, as mechanisms of membrane disruption. QSAR descriptions of effective lipids permitted detailed chemical guidelines for optimizing cationic lipid structure to be given. Limitations of the approach and models are discussed.


CONCLUSIONS
QSAR modeling indicated that induction of membrane curvature and osmotic shock are important mechanisms for membrane disruption by cationic lipids. The models also allowed specification of chemically detailed guidelines for selection or design of optimal cationic lipids.
Horobin
Richard W
RW
Division of Neuroscience and Biomedical Systems, West Medical Building, Institute of Biomedical and Life Sciences, Glasgow University, Glasgow, Scotland, UK. richardwhorobin@omn.net
Weissig
Volkmar
V
D002412:Cations / Q000737:chemistry; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D008055:Lipids / Q000737:chemistry*; D008563:Membrane Lipids / Q000378:metabolism; D008956:Models, Chemical; D021281:Quantitative Structure-Activity Relationship; D014162:Transfection / Q000379:methods*
D002412:Cations; D008055:Lipids; D008563:Membrane Lipids