I'm trying to increase the contrast of OsO4 stained brain tissue for x-ray microtomography (a recent scan had very poor contrast). I was wondering if there is any literature precedent for getting denser OsO4 staining by first treating the tissue with an alkene that covalently links itself to biomolecules. My thought is that I could incubate my tissue in 3,4-epoxy-1-butene (or something similar) for a few hours, then lower the pH of the solution, facilitating covalent linkage of the alkenes to the sample's neurons. By coating the cells in alkenes, I would hope to subsequently get denser OsO4 staining and better x-ray contrast. If possible, I would greatly appreciate links to any similar protocols, related suggestions, etc. Thank you!