Bio-Rad Helios® Gene Gun System - Manual (Page 38)

Another variable parameter, DNA loading rate (DLR), is determined by varying the con-
centration of DNA precipitated on to the gold particles. Table 3 shows DNA dosage results
for transfection of CHO cells using the method described in Section 6.2. Secretion of murine
granulocyte macrophage colony stimulating factor (mGM-CSF) was greater at higher DNA
dosages. Similar results have been found for several in vivo and in vitro systems, with max-
imal expression observed for 1–5 µg DNA/mg gold particles. At dosages above ~5 µg/mg, the
DNA and gold can form a single clump which is unsuitable for cartridge preparation.
Table 3. Effect of DNA concentration on mGM-CSF expression
in CHO cells
a
Expression c
DNA loading rate b (ng/10 6 cells)
2.5 515
0.25 239
0.025 25
0.0025 0.9
a CHO cells were transfected as suspension cultures using the Accell Gene Gun.
b Irrelevant plasmid DNA was added to each preparation to bring the total amount of DNA precipitated constant.
c mGM-CSF in the media was assayed 24 hours post-bombardment by ELISA as described by Mahvi et al. (1996).
7.2 Parameters for in vitro Delivery
The following conditions have been found to be effective for transformation of mam-
malian cell lines. However, each laboratory should determine the optimum parameters for
their particular application. (See previous section.)
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