The inorganic dye
ammoniated , also known as ruthenium oxychloride ruthenium red, is used in histology to stain aldehyde fixed mucopolysaccharides.
Ruthenium red (RR) has also been used as a pharmacological tool to study specific cellular mechanisms. Selectivity is a significant issue in such studies as RR is known to interact with many proteins.
These include mammalian ion channels (  CatSper1, TASK, RyR1, RyR2, RyR3, TRPM6, TRPM8, TRPV1, TRPV2, TRPV3, TRPV4, TRPV5, TRPV6, TRPA1, mCa1, mCa2, CALHM1  )  TRPP3, a plant ion channel,  Ca, 2+-ATPase mitochondrial Ca, 2+ uniporter  tubulin, myosin light-chain phosphatase, and Ca 2+ binding proteins such as calmodulin. Ruthenium red displays nanomolar potency against several of its binding partners (e.g. TRPV4, ryanodine receptors,...). For example, it is a potent inhibitor of intracellular calcium release by ryanodine receptors (Kd ~20 nM). As a TRPA1 blocker, it assists in reducing the airway inflammation caused by  pepper spray.
RR has been used on plant material since 1890 for staining
pectins, mucilages, and gums. RR is a stereoselective stain for pectic acid, insofar as the staining site occurs between each monomer unit and the next adjacent neighbor.
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Journal of Ultrastructure Research Volume 60, Issue 2, August 1977, Pages 135–139