Micro-targeting: high efficiency gene transfer using a novel approach for the acceleration of micro-projectiles.

We have constructed a novel micro-projectile accelerating system for efficient gene transfer into cells in situ that avoids binding DNA to micro-projectiles and keeps the DNA in solution. Further, instead of a macro-projectile (or the equivalent), it accelerates the particles in a Bernoulli air stream. The micro-targeting approach directs highly dispersed particles to sites with diameters as little as 0.15 mm, allowing precise aiming to restricted tissues. The system is physically flexible and should therefore be adaptable to different tissues and species. Transient expression of the Escherichia coli beta-glucuronidase gene in immature wheat embryo scutella was obtained at a frequency of up to 3% of the treated cells in the surface layer. In tobacco SR1, we achieved many transgenic plants, and the efficiency of stable transformation with the neomycin phosphotransferase (NPTII) gene was approximately 10(-3) per exposed cell.