Amino derivative of biotin that can be used as an intracellular label for cells, particularly neurons. It is used for neuronal tracing studies by visualizing neural architecture and for the identification of gap junction coupling. It is better soluble and non-toxic compared to other neuronal labels. It remains longer in cellsand can be fixed with formalin or glutaraldehyde. It can be detected using avidin or streptavidin systems with either chromogenic or fluorescence visualization methods.