Escort^™ III Transfection Reagent

The DNA needs to be good quality or it may cause the cells to lyse and/or they won't transfect efficiently.  Plasmid DNA prepared with a column-based DNA purification kit is suitable for transfections.  Sigma's GenElute™ Minprep, Midiprep and Maxiprep kits work well for DNA plasmid purification.  After preparing the DNA, confirm the OD A260:A280 ratio is greater than 1.6 for use in plasmid transfections.

Yes, we recommend cells are at a low passage when being  used for any application, including transfection.  The reason why depends on what type of cells they are.  Primary cells will undergo a finite number of divisions, and as they get closer to senesence they divide more slowly - both affecting their ability to take up DNA (transient transfection), and minimizing their abillity to incorporate the DNA into the genome (stable selection).Cultured common cell lines are often immortalized, and generally continue to aquire mutations, leading to a heterogenous population that may perform differently from cells of lower passage number - leading to results that are not reproducible.

Escort™ III is best for sensitive cells and primary cells, particularly PC-12 and Jurkat.Escort™ IV is excellent for mammalian cell lines, primary cells and insect cells.

The precipitate is likely excess lipid or EDTA and will probablly not affect transfection efficiency.  If your DNA plasmid is suspended in TE, be sure the concentration of EDTA is <0.3 mM, or suspend the DNA in sterile molecular biology grade water instead.

For most transfections, cells should be >70% confluency the day of transfection, and growing in mid-log phase.  Some transfection reagents are now designed to work with cells at low density, when required.

Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product.

Transfection efficiency is affected by many different things, including plasmid size and purity, media components present, transfection reagent selected, amount of DNA and transfection reagent used, cell density, etc.  Optimizing the protocol with respect to these concerns will allow you to achieve a higher transfection efficiency.  For many cell lines and transfection reagents, optimized protocols are already available.

When the DNA enters the nucleus of the cell, the plasmid is replicated by the cell machinery (transient transfection).  During this time, RNA is transcribed and protein translated until the plasmid DNA is lost after a few cell divisions.  This expression of the plasmid DNA, mRNA, and protein is transient (temporary).In some cases, the plasmid DNA is integrated into the host cell genome.  This is usually accompanied by forced expression using a selection antibiotic and sometimes a cloning step (to be sure all cells have the same integration site).  Once the DNA is stable, the cell line can be frozen and used to express protein for many years.  Clones may even be screened for those expressing the highest amount of protein.

There are many guides that help you select a transfection reagent.  In general, consider:The type of cell(s) you will transfectThe type of nucleic acid or protein you will introduce to the cellThe composition of your cell culture mediumThe need for stable or transient transfectionThe equipment you have availableThe other factors important to you - cost, protocol flexibility, ease of use, etc.

Calculating transfection efficiency is very useful when optimizing transfection protocols.  Transfection efficiency can be performed using a GFP-expressing plasmid.  After transfection, cells are stained with propidium iodide and counted.  The propidium iodide provides a count of the total cells in the population, and the GFP-expressing cells provide a count of the number of cells transfected.  The transfection efficiency (%) can then be calculated by:(# GFP-expressing cells / total cell #) * 100