A non-isotopic probe-hybridization assay for residual DNA in biopharmaceuticals

Although most biopharmaceuticals are highly purified, there is a theoretical concern that such recombinant products could be contaminated with oncogenic or bacterial DNA. A crucial part of the control of such biologicals is to ensure they do not contain more residual DNA than a safety limit suggested by the regulatory agency. Currently, the FDA has suggested a 100 pg per dose limit for residual DNA. DNA probes labeled with a radioisotope such as 32P have been commonly used in hybridization tests. Because of the radiation safety concern, we chose to develop a procedure for assessing DNA levels by either a dot or slot blot hybridization technique using a nonisotopic DNA probe and immuno-enzymatic detection. A minimum detectable limit (MDL) of < 10 pg DNA mg(-1) protein can be achieved. Method validation data demonstrated that the precision, reproducibility, and robustness of this approach are appropriate for quality control.