Complementary Approaches to Imaging Subcellular Lipid Architectures in Live Bacteria Using Phosphorescent Iridium Complexes and Raman Spectroscopy

Anna Maria Ranieri, Chiara Caporale, Valentina Fiorini, Alysia Hubbard, Paul Rigby, Stefano Stagni, Elizabeth Watkin, Mark I. Ogden, Mark J. Hackett, Massimiliano Massi

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Abstract

A family of three neutral iridium(III) tetrazolato complexes are investigated as bacterial imaging agents. The complexes offer a facile tuning of the emission colour from green (520 nm) to red (600 nm) in aqueous media, while keeping the excitation wavelength unchanged. The three complexes do not inhibit the bacterial growth of Bacillus Cereus, used as a model in this study, and exhibit extremely fast cellular uptake. After a minute incubation time, the nontoxic complexes show subcellular localisation in spherical structures identified as lipid vacuoles. Confocal Raman imaging has been exploited for the first time on live bacteria, to provide direct and label-free mapping of the lipid-enriched organelles within B. cereus, complementing the use of luminescent probes. Examination of the Raman spectra not only confirmed the presence of lipophilic inclusions in B. cereus but offered additional information about their chemical composition, suggesting that the lipid vacuoles may contain polyhydroxybutyrate (PHB).

Original languageEnglish
Pages (from-to)10566-10570
Number of pages6
JournalCHEMISTRY-A EUROPEAN JOURNAL
Volume25
Issue number45
DOIs
Publication statusPublished - 9 Aug 2019

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