First-generation transfection reagents
These reagents are generally based on monocationic lipids with a quaternary ammonium ion. They do not feature buffering properties and therefore do not offer the option of endosome buffering, which explains their lower efficiency compared to modern reagents. In addition, serum inhibition is reported for many of these transfection reagents with the exception of DOTAP.
A further feature of these reagents is a generally conventional transfection sequence providing for cell seeding and growth prior to the actual transfection and for change of medium after transfection. As a rule the proportion of DNA to lipids must be optimized carefully to ensure satisfactory results.