A gas-driven gene gun for microprojectile methods of genetic engineering

A study has been made of a gas-driven gene gun which launches microprojectiles carrying foreign genetic material into living cells. The gene gun consists of a shock tube driver which generates pressure pulses that accelerate a membrane (macroprojectile) fitted across the end of the shock tube. The macroprojectile launches a cloud of high-speed microprojectiles on firing. The performance was studied in terms of the initial macroprojectile geometry and the pressure-time history on its surface. The pressure-time history was altered by varying the length of the shock tube. Direct measurements were made of the macroprojectile velocity and the penetration of microprojectiles into model cell systems. Under conditions of shock acceleration, good agreement was found between measured velocities and those predicted using one-dimensional gas dynamic theory. In terms of the terminal velocity of the macroprojectile, when the macroprojectile was initially planar, best results were obtained with the long shock tube (shock acceleration), but when the macroprojectile was initially domed convex upstream to increase acceleration distance, best results were obtained with the short shock tube (pressure pulse excitation). The difference between the performance of those two configurations was due to interaction of pressure loading mechanics and the structural properties of the macroprojectile as a consequence of its shape. Significant fractions of microprojectiles penetrated at least six cell layers at conditions consistent with a theoretical maximum macroprojectile velocity of 330 m s. Transient gene expression was achieved in target wheat suspension cells