A new assay system for quality control testing of a chemically defined medium

Abstract

Mouse NCTC clone 929 L (L-929) cells were propagated continuously over 2 yr in protein-free Eagles's minimal essential medium (EMEM). The cells designated L-929-WS were used for quality-control testing of protein-free EMEM as a model for more general medium quality tests. The parameter for the suggested quality control assay was the growth-promoting activity of the medium for L-929-WS cells. As an example of quality tests we assayed the growth promoting activity of EMEM exposed to various conditions of storage time and temperature. We established the sensitivity of the new assay by comparing it to the original cells L-929 grown in EMEM supplemented with 10% fetal bovine serum (FBS). The assay system using L-929-WS cells propagated continuously in protein-free medium proved to be much more sensitive. The sensitivity, however, was abolished by the addition of FBS in a concentration as low as 1% to a culture medium.