Highly fluorescent azine stain for the detection of ferric ions in Mucorales

Essential metals for life such as iron, zinc, copper, nickel and manganese play a pivotal role in the conflict between infecting microbes and their hosts. Mucormycosis is a potentially life threatening systemic fungal infection caused by members that belong to the order Mucorales which primarily affects immunosuppressed patients. Rapid diagnosis and subsequent initiation of therapy is imperative due to the fulminant nature of the infection. Clinical evidences indicate the ability of these mucoralean organisms to obtain iron from the host as a major virulence attribute. This study is an attempt to develop a novel iron dependent staining technique for the detection of filamentous Mucorales treated with ferric ion. Fluorescence sensors are one of the most powerful tools for detecting metal ions in biological systems. This study reports the fluorescent behavior of a metal-binding indicator 4,4'-[hydrazinediylidene dimethanylylidene]di(benzene-1,3-diol) (CS2) with specific optical responses on exposure to Fe³⁺ ions at two studied pH. Interestingly, the azine chemosensor CS2, displayed fluorescence quenching in presence of Fe³⁺ at pH 5.5, whereas retained its fluorescence specifically in Fe³⁺ solution at pH 7.4. The preliminary results indicate that pH sensitive CS2 can be a component of choice in the fluorescent stain for fungi like Mucorales in the research and diagnostic purposes.