Transfection is a process of introducing exogenous nucleic acids into cells, both in vitro and in vivo. In order to perform transfection, lipids in the form of liposomes, micelles, and other similar compounds are used. These structures merge with the cellular plasma membrane and deliver the cargo molecules to the inside of the cell. Lipids are typically suitable for the introduction of biologically active substances into many types of eukaryotic cells, such as proteins, DNA, RNA, peptides, and ribosomes.
Cationic lipid reagents typically exhibit low efficiency in serum based culture media or when antibiotics are used in cell cultures. Polymer based reagents are particularly helpful in transfecting cells that exhibit low efficiency when transfected using lipid based reagents. When used at optimal concentrations, these reagents exhibit low toxicity. Polymer based transfection reagents can be used to transfect suspension cultures, primary cells, a variety of eukaryotic cell lines and adherent cells. Many natural and synthetic cationic polymer based transfection reagents are now commercially available.
Commonly used cationic polymers are histones, poly-L-lysine, polyamidoamine dendrimers, and protamine. Structurally, cationic polymer molecules may either be linear or highly branched. Cationic polymer based transfection reagents promote high transfection efficiency by condensing DNA. Exogenous DNA forms complexes with cationic polymer molecules resulting in a DNA/polymer complex taken up by host cells via endocytosis. The reagents, specifically designed to be biocompatible, enhance stability and promote successful release of engulfed genetic material from endosomes.
These new polymer-based transfection reagents consist of biodegradable and slightly hydrophobic polymers such as polyethylenimine. They are used as efficient non-viral delivery mechanisms to transfer exogenous genetic material into cells in culture. Life scientists use these systems to study structural and functional details of cells and cell organelles. Some polymer based transfection reagents have been specifically developed to aid the uptake of plasmids in serum free culture media.
Polymer based transfection reagents can cause cytotoxicity and need to be optimized for specific cell type transfections. Early experiments with cationic polymers showed that short side chain polymers had poor transfection ability but were better at intranuclear transcription and formed stable low charged small complexes with nucleic acids. On the other hand, long chain polymers exhibited better transfection efficiency but formed less stable complexes with a high positive charge. Recent experiments demonstrate that cationic polymers rich in imidazole show improved transfection efficiency with lower toxicity.
Commercial Polymer-based Transfection Reagents
Developing a custom transfection reagent for a particular experiment can be time-consuming and costly; the large amounts of testing and optimization can lay off an experiment for considerable time. Fortunately, many companies have pre-optimized polymer-based transfection reagents for a variety of cell lines. These reagents have been tested for efficiency, and can save time during research.
Scientists at research facilities such as Altogen Labs have worked to optimize polymeric transfection reagents across multiple cell lines. They can create a specific reagent for cell lines that are otherwise difficult to transfect. Knowledge of cell internalization and endocytosis are helpful in designing the optimal transfection protocol.