Substrates for Cell Growth
Many types of vertebrate cells require support for their growth in vitro. Otherwise they will not grow properly. Such cells are called anchorage dependent cells. Therefore, a large number of substrates which may be either adhesive (e.g. plastic, glass, palladium, metallic surfaces, etc.) or nonadhesive (e.g. agar, agarose, etc.) are used.

Glass
It is the most commonly used substrate. It can be easily washed and readily sterilized. It is optically clear to allow microscopic observation of cultures. Glass made of alum-borosilicate (e.g. Pyrex) is preferred to soda-lime glass. Soda-lime glass releases alkali into the medium. Soda-lime glass can be detoxified by boiling in weak acid, before use. Repeated use of substrates reduces cell attachment. It is regained by treating with 1 mM magnesium acetate for several hours. Slides, test tubes and flasks, used as substrates must be washed with non­toxic detergent.

Palladium
Palladium deposited on agarose is used as a substrate for growth of fibroblasts and glia.

Modification of Substrate Surface
The efficiency of the cultured cells through increased cell attachment can be enhanced by treating the surface of the substrate with purified fibronectin or collagen. The chemical is poured onto the surface of the dish, excess chemical drained, and then dried and sterilized using UV light.

The surface of the substrate is also treated with a monolayer of special types of cells. This layer is called feeder layer, since it feeds the growing cells. The cells used as feeder layer are glial cells, normal foetal intestine, mouse embryo, fibroblasts, etc. The feeder layer is used for the growth of neurons, epithelium of breast and coelom, and production of transgenic animals.