A GAS-DRIVEN GENE GUN FOR MICROPROJECTILE METHODS OF GENETIC-ENGINEERING

A study has been made of a gas-driven gene gun which launches micropro jectiles carrying foreign genetic material into living cells. The gene gun consists of a shock tube driver which generates pressure pulses t hat accelerate a membrane (macroprojectile) fitted across the end of t he shock tube. The macroprojectile launches a cloud of high-speed micr oprojectiles on firing. The performance was studied in terms of the in itial macroprojectile geometry and the pressure-time history on its su rface. The pressure-time history was altered by varying the length of the shock tube. Direct measurements were made of the macroprojectile v elocity and the penetration of microprojectiles into model cell system s. Under conditions of shock acceleration, good agreement was found be tween measured velocities and those predicted using one-dimensional ga s dynamic theory. In terms of the terminal velocity of the macroprojec tile, 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 accele ration 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 m echanics and the structural properties of the macroprojectile as a con sequence of its shape. Significant fractions of microprojectiles penet rated at least six cell layers at conditions consistent with a theoret ical maximum macroprojectile velocity of 380 m s-1. Transient gene exp ression was achieved in target wheat suspension cells.