Bio-Rad PDS-1000 / He™ and Hepta™ Systems - Manual (Page 34)

Table 5.1. Cell Types, Settings, and Conditions
Target Helium
Cell Growth Cell Vacuum Distance Pressure Particle
Type Phase Density Osmoticum (inches Hg) (cm) (psi) Size
Bacteria Late log 10 8 –10 9 per 0.75 M sorbitol 29 6 1,100 M5
to early 100 mm tungsten
stationary plate
Yeast Early 10 8 –10 9 per 0.75 M sorbitol 28 6 1,300 0.6 µ
stationary 100 mm and 0.75 M gold
plate manitol
Algae Log 10 8 –10 9 per 29 6 1,300 0.6 µ
100 mm gold
plate
Plant
• embryos –
10 explants None 28 6 1,300 1.0 µ
per 100 mm gold
plate
• callus or Log 0.75 ml None 28 9 1,100 1.0 µ
cell culture packed cell gold
volume
Subcellular Mid-log 5 x 10 7 per None 28 6 1,300 0.6 µ
Organelles 100 mm gold
plate
Animal
• tissue
Log 50–80% None 15 3 1,100 1.6 µ
culture confluent gold
on 35 mm
plates
• tissue 1 hr–4 days400 µm None 25 9 1,100 1.6 µ
sections post- sections gold
excision
5.2 Vacuum Level in Bombardment Chamber
The vacuum in the bombardment chamber reduces the frictional drag of the microcarri-
ers as they are accelerated toward the target cells. The unit should be connected to a vacuum
system (see previous section) that can evacuate the bombardment chamber to 28–29 inches
Hg in less than 30 seconds. This level of vacuum is useful for most plant and microbial
cells/tissues. Mammalian cells/tissue should be bombarded at approximately 15 inches Hg.
Helium gas enters the evacuated bombardment chamber once the rupture disk bursts. The
use of low molecular weight helium minimizes the deceleration of the microcarriers as they
pass through helium and also reduces the force of the gas shock wave that hits the target cells.
This reduced impact will help minimize target tissue damage.
5.3 Helium Pressure / Rupture Disk Selection
Each of the nine different rupture disks available ruptures at a specific pressure, ranging in
rating from 450 to 2,200 psi. The rupture pressure determines the power of the shock wave
entering the bombardment chamber. Increasing helium pressure will increase particle acceler-
ation and subsequent target tissue penetration by the DNA-coated microcarriers. Since the
shock wave or resulting acoustic wave may cause damage to the target cells or tissue, use the
lowest helium pressure used that gives high transformation efficiency.
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