I'm reading an article in the current issue of Analog magazine, where
they're talking about gene repacement therapy.  After touching on viral
delivery agents and stuff like that,  we get to this part:

"Then there are some methods just slightly more...forceful."

"John Sanford may be the rootinest tootinest genetic researcher either
side of the Mississippi.  In 1983,  while human geneticists were tricking
cells into taking up DNA,  Sanford was blasting it in with a .22-caliber
air rifle.  The cell walls of plants form a rigid,  nearly impenetrable
barrier.  With the help of two engineers at Cornell's Nanofabrication
Facility he invented a device that shoots microscopic particles of tungsten
coated with DNA.  The gun,  fit with a metal barrier at the end of the
barrel,  fires a plastic bullet.  The barrier is coated on the outside with
tungsten/DNA particles.  The impace sends the tungsten particles flying --
right through the plant's cell walls,  carrying the DNA along with the
ride.  Sandford's invention,  now marketed by DuPont,  is known as a 'gene
gun'.  Many types of gene guns have been developed.  Some are powered by
compressed air,  some use an ammunition-like cartridge with gunpowder. 
Some models use a disk rather than a bullet for a projectile,  or gold
instead of tungsten for the carrier beads.  The agriculture industry has
used the gene gun to develop many of our common strains of wheat and
soybeans."

"Human geneticists have only recently discovered the gene gun. 
Frustrated by fussy viral vectors that don't work and sometimes kill their
hosts,  researchers in the dermatology branch of the National Cancer
Institute have locked and loaded,  and are now firing DNA-coated gold beads
into skin cancers. The method offers a way around the drawbacks and dangers
of viral gene therapy,  as long as you don't mind the drawbacks and dangers
of live gunpowder."

---