| The Guava ViaCount assay provides cell counts and viability
data quickly and easily for a variety of mammalian cell lines, both suspension
and adherent. However, the Guava ViaCount reagent is incompatible
with some non-mammalian cell lines, in particular, insect cells, which are
becoming increasingly important for the expression of transfected proteins.
The Guava ViaCount Flex reagent was developed to address the
special needs of non-mammalian cell lines. Guava ViaCount Flex was
optimized and validated using Sf9 insect cells that were adapted to suspension
culture in serum-free medium. Results from the ViaCount Flex
assay on the Guava Personal Cell Analysis (PCATM) system were compared
to cell counts and viability results obtained using trypan blue and a hemacytometer.
Good correspondence for cell count and viability results was
seen for the two methods over a broad range of cell densities (about 104
to 6 x 105 cells/mL) and culture conditions (about 65% - 90%). Assay
results were highly reproducible, with % CV for replicate total cell counts
from three different operators ranging from 5% - 14% for the Guava Via-
Count assay vs. 16% - 41% for hemacytometer counting. The % CV for
replicate viability measurements of Sf9 cultures from three (3) different
operators was 2% - 4% for the Guava ViaCount assay vs. 6% - 14% for
hemacytometer counting of trypan blue-stained cells. Instrument-to-instrument
precision was <5% CV for cell counts and <2% CV for viability
measurements. Cell counts were linear over a broad range of concentrations
(104 to >5 x 105 cells/mL). The viability of Sf9 cells was unchanged for at
least 45 minutes after staining with Guava ViaCount Flex reagent. |
