Use of Sulfonation Method to Determine DNA Contamination of Cell Cultured Monoclonal Antibodies Produced for Human Therapeutics

In the past few years, culture of transformed mammalian cells has been widely used to produce natural or recombinant molecules, as monoclonal antibodies (MAb) and cytokines. For therapeutic use, the cellular DNA level must be determined. A number of techniques have been developed to measure the DNA content, based on sequential extraction blotting and hybridization with a labeled DNA probe. The sulphonate marker has been recently introduced by PBS-Orgenics; it allows the determination of picograms (pg) quantities of purified DNA. However, it is not simple to measure in complex biological samples especially when a large amount of protein is present. In considering the following points: Precautions in handling the samples at different steps of preparation; Modifications of the original technique Concentration of samples expected at very low level, we are able to dose up to 2 pg of contaminant DNA per mg of MAb with a satisfactory reproducibility and reliability. This level is required not only to qualify fin...