Most normal untransformed cells survive and proliferate to produce 'primary culture' when attached to a substrate, but these cells need to be obtained by disaggregation. The disaggregated cells can also grow in suspension to produce the primary culture. Disaggregation is achieved by anyone of the following three methods:

(i) physical disruption,

(ii) enzymatic digestion and

(iii) treatment with chelating agents.

Physical disruption, which may involve cutting the tissue into pieces, is often combined with other methods, but chick embryo suspension may also be obtained by expressing (squeezing) the embryo through the nozzle of a syringe. Of the many enzymes that are used for disaggregation, trypsin and pronase are the most commonly used.

Other enzymes used successfully include collagenase, elastase, mucase, pancreatin, pappain, etc. Similarly, tissues like epithelium (which needs Ca + + and Mg + + ions for its integrity) can be treated with chelating agents, such as citrate and ethylene diamine tetra acetic acid (EDTA). Chelating agents are mainly used for production of cell suspensions from established cultures of epithelial type.