Doug,
You did not mention exactly what you were trying
to image in/on the cells. Cells that have been
developed to grow in suspension have been
selected for this ability and they do not
generally have the ECM/integrin/cytoskeletal
network that provides surface adhesion. Then, of
course, someone may have simply given you some
freshly trypsinized cells resulting in the same
problem, namely the lack of surface adhesion
molecules. In any case, if the cells do not have
to be imaged live, cells can be gently pelleted
and washed a couple of times with iso-osmotic PBS
to eliminate extraneous proteins from growth
medium.
After a couple of rinses the cells can be
suspended then fixed with the usual reagents say
2% paraformaldehyde in PBS. After 30 minutes to
an hour the cells will usually be sufficiently
permeabilized to allow labeling with Ab
fluorophore conjugates, etc. Conventional
labeling on coverslips or slides is easily
adapted to perform in suspension using gentle
pelleting and resuspension for rinsing cells.
As for mounting in something that is ~
physiological, I like to use a solution of 50%
glycerol plus PBS. The glycerol viscosity helps
keep cells from moving around (more glycerol
helps, too), and because of the lower dielectric
constant, the electrostatic binding to coverslips
or slides treated with polylysine also helps with
adhesion (must have M.W.„ 300 kDa).
Even better would be to make some aminopropyl
silane treated slides and coverslips. Polylysine
can come off the glass and wrap cells together in
the extreme. The aminopropyl silane treatment
creates covalently bound positively charged
surfaces that won't come off (the amino group can
become oxidized but takes a very long time).
Although I have not tried this with live cells,
aminopropyl glass would be first thing I'd try.
However, there is a potential problem with using
anything that creates a very large electrostatic
field in that this could have a strong effect on
the PM causing channels to open/close, local
lipid rearrangement (lipid flip-flop), and
generally altered kinetics of membrane
transporters and receptors. Cell Tak as Nathan
suggested could prove advantageous for live
cells; however, some of the same problems could
apply in that anything you do to cells that are
without the capacity to adhere are likely to
experience significant perturbation in their cell
surfaces.
Further, I also have a concern about Cell Tak in
that its crosslinking capacity (->adhesive
ability) depends to a large extent on its
polyphenolic moieties that generate free
radicals. In theory, this can lead to activated
oxygen species then oxidative damage to the cell
plasma membrane. I am curious if anyone has ever
tested Cell Tak to evaluate damage that it might
cause to cells. This could show up as an
increased permeability to Ca++. There must be
lots of Cell Tak experts out there. Any thoughts?
Mario
>Last week I had some users bring in suspension
>cells for me to image with our confocal. Darn
>things were moving so much that it was difficult
>to get two colors to line up using sequential
>scanning. Apparently these are non-adherent
>cells, so growing them on a coverslip is not an
>option. Any suggestions? What they gave me was
>a drop of cells in culture media, we put it
>between a slide and coverslip.
>
>Doug
>
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>Douglas W. Cromey, M.S. - Assistant Scientific Investigator
>Dept. of Cell Biology & Anatomy, University of Arizona
>1501 N. Campbell Ave, Tucson, AZ 85724-5044 USA
>
>office: AHSC 4212 email: [log in to unmask]
>voice: 520-626-2824 fax: 520-626-2097
>
>http://swehsc.pharmacy.arizona.edu/exppath/
>Home of: "Microscopy and Imaging Resources on the WWW"
>
--
________________________________________________________________________________
Mario M. Moronne, Ph.D.
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