A rapid method to monitor DNA precipitation onto microcarriers before particle bombardment

The binding or precipitation of DNA onto gold or tungsten microcarriers represents one of the most crucial steps for gene transfer via the particle bombardment process. We have developed a simple and rapid method to monitor DNA precipitation onto microcarriers before delivery to intact cells or tissues. Binding of DNA constructs to different microcarriers was evaluated with relative fluorescence values using a dedicated fluorometer. Significantly greater precipitation was detected using gold vs. tungsten microcarriers. Addition of glycerol resulted in a 46% increase in precipitation. A 42% difference in precipitation was observed using two different brands of polyproplyene tubes. Fluorescence values dropped 10-50% 3 hr after initial precipitation. Fluorescence values were correlated with the number of transient GUS transformants of rice (Oryza sativa, L.) cells. Precipitation with PEG gave higher fluorescent values and GUS transformants than a similar method without PEG. Results from these experiments indicate that fluorescence measurements are an effective and rapid method to monitor DNA precipitation for particle bombardment experiments.