Oolong tea extract as a substitute for uranyl acetate in staining of ultrathin sections based on examples of animal tissues for transmission electron microscopy.

Oolong tea extract (OTE) was assessed for its potential as an electron stain to substitute for uranyl acetate (UA) in transmission electron microscopy (TEM). A comparative analysis of the ultrastructures of biological specimens (i.e. compound eye and sciatic nerve tissue) stained by different methods (UA and 0.1% OTE) has been performed. Results revealed that there was no significant difference between the OTE double staining method and the traditional double staining method, except the contrast in the OTE method was slightly lower than the UA method. Nevertheless, the OTE method yielded better or equal details in collagen fibres, neurofilaments and basal lamina in the mammalian sciatic nerve samples, as well as in the microvilli between the cornea and crystalline cone of the insect compound eye. On the whole, it was suggested that OTE could potentially be used as a nonradioactive and hazard-free alternative to UA in TEM staining.