Cell transfection, or the introduction of foreign DNA into a eukaryotic cell, is often accomplished using specially-developed transfection reagents. These reagents are either chemical or biological in nature.
One of the first, cheapest, and least reliable transfection reagents is chemical phosphate, administered as a combination of a calcium chloride solution with the desired DNA and a HEPES-buffered saline solution containing phosphate ions. The DNA is delivered when calcium phosphate precipitates and binds the DNA to the surface of the eukaryotic cell membrane. The cell absorbs the precipitate, and the DNA goes in with it. This is only one of a number of transfection reagents that work in similar ways.
Biological reagents can also be used for transfection. Dendrimers, highly-branched organic compounds, bind the foreign DNA to the cell to be infected in the same way as chemical reagents. Liposomes have proven to be an effective transfection reagent as well; instead of binding and being absorbed, liposomes fuse with the cell membrane, releasing the DNA they carry into the cell in the process.
Other methods of introducing DNA into a cell involve "gene guns," which shoot inert solid nanoparticles bound with the foreign DNA into the cell's nucleus; using viruses as carriers of desired DNA; and even direct microinjection of DNA into the nucleus.
Web Resources On Transfection Reagents
Cell Line Transfection Reagents
BioCompare: Transfection Reagents
Book Resources On Transfection Reagents
Synthetic DNA Delivery Systems by Luo & Saltzman (Editors)
Gene Transfer to Animal Cells by Richard M. Twyman