Hi Rolands,

I work with spores, but from bacteria. What I am doing is using wet chemistry combined with dry chemistry. So, I first fix bacterial spores with a solution of glutaraldehyde + para-formaldehyde in caco buffer, then I wash with caco buffer and then I fix with osmium tetroxide, then wash again with caco buffer followed with dehydration with increasing concentrations of ethanol. After that you may do critical point if needed. Then you apply a gold coat, by sputtering your sample mounted in the SEM stub.

You can find several protocols in the internet, however my experience says that you mus adjust the osmium concentrations and time to your samples. I have samples that need 1 hr with 2% osmium and others 30 min with 1% osmium is enough. The osmium step is critical to have a good image. If this is not well tuned the image will be ruined.

Good luck.