Bio-Rad Helios® Gene Gun System - Manual (Page 9)

Preparation of the gold/DNA tubes used in the Gene Gun requires an area approximate-
ly 1 m 2 for the Tubing Prep Station, for manipulating the tubing, precipitating the DNA onto
the gold, and processing the tubing into cartridges. Additionally, the Tubing Prep Station
requires an electrical outlet and a tank of pressurized nitrogen for evaporating the ethanol from
the DNA-coated gold particles from the inner surface of the tubing.
User Supplied Components
Helium Supply
Only helium gas is to be used with the Helios Gene Gun. The low atomic weight of heli-
um results in maximum gas expansion when the high pressure helium is released through the
valve opening and enters the cartridge at atmospheric pressure. Thus, sufficient acceleration
of the DNA-coated microcarriers is generated for penetration of the target cell membrane.
Compressed helium of grade 4.5 (99.995%) or higher should be used; lower grades may
contain contaminating material which can obstruct gas flow within the Helios Gene Gun as
well as contaminate the biological sample. A helium tank pressurized to 2,600 psi [approxi-
mately 5 ft (1.7 m) high, 291 cu ft standard in the United States] is recommended, although
a smaller tank [~2.5 ft (~0.8 m) high] may be used. Follow all safety instructions provided by
the helium supplier for helium tank installation.
The helium pressure regulator (supplied) has a CGA 580 female fitting (standard in the United
States) for attachment to the user-supplied helium tank. An adaptor to this fitting may be required
outside of the United States. Contact your local Bio-Rad office for information on the helium pres-
sure regulator adaptor requirements in your location. The regulator supplied with the Helios Gene
Gun is the only one that should be used with this instrument because of its three safety features: (1)
a self-venting valve that permits decreasing the pressure in the Helios Gene Gun System in the
event of battery failure or when it is necessary to reduce the pressure during an experiment; (2) an
over-pressure relief valve that prevents the helium pressure in the Helios Gene Gun System from
being adjusted above 700 psi ± 10%; and (3) a check valve that shuts off pressure if the helium hose
is disconnected while the system is still pressurized (Note: a check valve is also present at the
female connector of the helium hose where it connects to the Gene Gun to shut off pressure to the
gun if it is disconnected while the system is still pressurized.) Refer to Section 4.2 for proper use
of the helium regulator and to Section 5.4 for a description on shutting down the Gene Gun System.
A user supplied 10" or 12" (~25 cm) adjustable wrench or a 1 1/8" open end wrench is
required for attachment of the helium regulator to the helium tank.
Nitrogen Supply
Compressed nitrogen of grade 4.8 (99.998%) or higher is required for cartridge prepara-
tion using the Tubing Prep Station. Nitrogen is used for this purpose because it is relatively
inexpensive and provides a water-free atmosphere for evaporating the ethanol from the
DNA/gold sample inside the tubing. As with the helium tank, the nitrogen tank should be
properly secured on a floor stand or with a strap for safety.
A nitrogen regulator must be attached to the tank. A single stage regulator with an output gauge
that registers a maximum of 30 psi is recommended since an output pressure of no more than
1–2 psi is needed to produce the 0.4 liters per minute (LPM) flow rate necessary for using the Tubing
Prep Station. A regulator especially designed for this use, including a self-venting valve, an over-
pressure relief valve, and a hose barb for attaching the nitrogen hose is available from Bio-Rad
(catalog number 165-2425). Other regulators which are adjustable to give a low pressure output
may also be used. Manufacturers of regulators include Victor and Matheson; examples of regula-
tors which may be used include Victor Model No. SR250A-580 and Matheson Model No. 3537-580.
Large scientific supply houses (e.g., VWR, Fisher, CMS, etc.) are also good sources for regulators.
The nitrogen line provided for use with the Cartridge Prep Unit is 3/16" diameter Tygon tubing.
5