Multifunctional fluorescent leucomalachite green derivatives for chemodosimetric detection of Fe3+, specific imaging of lipid droplets and intracellular pH monitoring

Three multifunctional leucomalachite green derivatives namely, BDPMBD, BInMBD and InMBD having fluorogenic substituents on one of the phenyl ring have been synthesized and their properties were evaluated. They exhibited multifunctional properties such as selective detection of Fe3+, specific staining of lipid droplets and as fluorescent probes for monitoring intracellular pH variations in microorganisms. Fe3+-mediated oxidation of these molecules to the corresponding malachite green derivatives altered their absorption and emission behaviour and these changes allowed the selective detection of Fe3+. The limits of detection (LOD) were estimated as 0.281 µM, 5.8 µM and 4.6 µM, respectively for BDPMBD, BInMBD, and InMBD. The cellular uptake of these molecules was then studied in yeast, HeLa and DLD (human colon adenocarcinoma) cells. They showed efficient internalization and localization primarily in the lipid droplets, which was confirmed via co-staining with lipid droplet specific dye Nile red. Since these compounds showed pH-dependent emission switching, they were also used for monitoring intracellular pH variations in yeast, gram-positive and gram-negative bacteria.