The process of cell culturing was developed, in 1907, by Harrison while investigating the origin of nerve fibres [15]. Specifically, explanted pre-differentiated neural tissue from frog embryos was placed in a drop of lymph hanging from a sterile cover-slip, kept sealed and in a moist chamber. This method allowed tissue growth and differentiation to be continually observed [16]; demonstrating a means by which cells of interest could be maintained outside the body of origin and observed over time.
Substantial improvements have been made on the 2D cell culture technique initially developed by Harrison. Containers used for culturing have been developed which enable cells to be fed with ease and that allow more space for cell growth. Additionally, the traditional use of blood plasma as the only source of nutrition for the growing cells changed to the use of synthetic medium. There are many advantages including the fact that batches of synthetic medium can be made reproducibly; do not contain antigens which can cause allergic reactions; and are relatively cheap to produce. Antibiotics and anti-fungal agents have been developed that are suitable for cell cultures and thus help to prevent bacteria and fungi from infecting cultures. While these additives are not a substitute for good cell culture practice, they can be useful for maintenance of infection-free cells, if contam- ination is envisaged to be a problem.
Cells are typically grown as a monolayer on a flat surface, most commonly in culture flasks or sometimes in Petri-dishes with med- ium as a source of nutrition and at body temperature (378C). Medium is often supplemented with bovine serum and L-glutamine to aid cell growth. When reaching confluency, cells are sub-cultured so as to avoid complications from senescence or nutrient-exhaus- tion from medium. To sub-culture, cells are cleaved from the bottom of their culture dish (with trypsin and/or EDTA) and a quantity