Repeated use of qiagen columns in large-scale preparation of plasmid DNA

The preparation of large amounts of high-purity intact plasmid DNA is a significant expense in DNA vaccine research. In our laboratory, mice are typically each immunized by injection of 100 μg on four occasions, so that an experiment with 50 mice requires 20 mg DNA as a minimum. The Qiagen tip-10,000 (Giga) column is intended to deliver up to 10 mg of high copy-number plasmid DNA from Escherichia coli. We have found that by repeatedly regenerating the column and reapplying the flowthrough volume of DNA extract, we can readily obtain 2-4-fold increased yields, up to 40 mg, from the standard 2.5 L broth culture.