CHOgro® Expression System Enables Broad Scalability, 1000-fold. Human IgG1 was produced by transient transfection with the TransIT-PRO® Transfection Reagent and 1 µg plasmid DNA per milliliter of culture at a 1:1 reagent:DNA ratio. Cells were transfected at a density of 2 x 106 cells/ml in CHOgro® Expression Medium on an orbital shaker at the following volumes/culture vessels: 2.5 ml/non-tissue culture treated 6-well dish, 25 ml/125 ml Thomson flask, 100 ml/250 ml Thomson flask, 500 ml/1.6 L Thomson flask, 2500 ml/5 L Thomson flask. At twenty-four hours post-transfection all cultures were moved to 32°C for the remainder of the experiment. Antibody levels were analyzed from day 7 clarified supernatants using a human IgG ELISA (Zeptometrix). All values are normalized to the 25 ml volume sample and error bars represent the standard error of the mean of triplicate technical replicates.