EM, cell preparation: to coat or not to coat slide with collagen - electron microscopy (Jul/11/2006 )

I am doing SEM for the first time and had monolayer MDCK grown on glass cover slips, which were coated with collagen.

The cells were fine after fixation (overnight with glutaldehyde), but were soon detaching as sheets upon rinsing/osmium treatment. The problem worsen at subsequent steps. Could it be that collagen coating is susceptible to osmium treatment, such that cells were peeled off together with detaching collagen coat?

Thanks for any input.

perhaps rinsing too hashly caused detarchment, rather than Os treatment did.