Dear Daniel Scotto D'Antuono , I would like propose you should contact Michael Laue who actually is Head of the division "Advanced light and electron microscopy" (ZBS 4) and National Consultant Laboratory for Diagnostic Electron Microscopy of Infectious Pathogens (www.rki.de/cl-em).

I am sure, Prof. Dr. Hans R. Gelderblom also would be willing to answer your important question on LAB as well as PERSONAL SAFETY when working with virus solutions / virus specimens in the EM-Lab.

They for sure are experts in the field of virus observation by TEM methods and the issues of lab safety - I recommend you to contact them.... .

IMHO it will depend on the virus classes you are confronted with or your lab is going to examine and willing to receive.

The second issue, UO2Ac vs. PTA, is an old one and might point to differences in better staining for some class of viruses

(NOTE all URL#s noted http I added an underscore character not to end up with the automatic link to RESEARCHGATE-ARTICLE DISPLAY....so if you want to arrive at the original source, after copying and pasting into your browser, delete the underscore character in between http _ and ://xyz... cf:

https_://www.ncbi.nlm.nih.gov/pmc/articles/PMC3650645/ :

A Fera et al. - ‎2012

https_://www.ncbi.nlm.nih.gov/pmc/articles/PMC3650645/ will be changed automatically to:

Article A Negative Stain for Electron Microscopic Tomography

pdf: Article A Negative Stain for Electron Microscopic Tomography

As regarding Use of UO2Ac - vs - PTA solutions:

PTA often is meant to be:

SODIUM (POTASSIUM) PHOSPHOTUNGSTATE (PTA) but also another "PTA" is used too for some reasons:

NEUTRAL PHOSPHOTUNGSTIC ACID,

not to confuse with SODIUM SILICOTUNGSTATE !

besides -naturally: URANYL ACETATE

The most useful Negative staining solutions (along with the former information you can find in:

https://www.researchgate.net/profile/Vitaly_Vodyanoy/post/Can_someone_provide_a_protocol_for_SEM_TEM_for_measuring_self_assembled_peptide/attachment/59d61de779197b807797c244/AS%3A273841710927872%401442300361300/download/neg_stain.pdf

I stop here for some reason....if I had more time for the moment, I could write much more about... (I lost < 30 mins real writing> time due to an unwanted and uncareful action on my PC-keyboard prior to writing a new version of what I wanted to tell or communicate....)

Also: find hopefully valuable information in the resulting Q/A's in ResaerchGate@:

https://www.researchgate.net/topic/Negative-Staining

It would be interesting to get feedback about the solution of your 'problem issues....'

Regards and best wishes, W.H. M.

From pure scientific point of view (to get the best possible results), of course, it is not necessary... But from regulations and safety reasons, no one can say you remotely, just ask your local biosafety officers or your supervisor.

Good luck!

Thank you both for your replies!