Hi Amilcare, in addition to Calcein, here is a bunch of them:

http://www.lifetechnologies.com/search/global/searchAction.action?query=live+cell+membrane&resultPage=1&resultsPerPage=15&autocomplete=

But you might want to look into live cell dyes that can be fixed intracellularly by formaldehyde:

http://www.lifetechnologies.com/order/catalog/product/C2110?ICID=search-product

Hi Amilcare,

I think you can try Mitoracker red cmxros dye.

Best wishes

Susheel 

What would you like to detect more specificially in the cell? Or only to introduce it within the cell??

DAPI and IP

Thank you all.

I simply need a water-soluble dye to test delayed release from a hydrogel vector to be injected in specific tissue districts. all the dyes you indicated are good... the unknown is whether the dyes maintain their staining/fluorescent power over 4-5 days... anyway... I'm opting for well-known CellTracers or Evans Blue dye... thank you again.