Live cell organelles imaging is essential for understanding specific biochemical processes. Often, imaging of cell organelles, irrespective of pH-activable property, involves specific fluorescent probes having different scaffolds that are prepared separately by multistep synthesis. We introduce a modular one-step synthetic strategy using a common synthetic intermediate to develop new lysosomal, mitochondrial, and nucleus-targeting pH-activable fluorescent probes that are all based on a single boron dipyrromethane scaffold. In this structure organelle-relationship (SOR) framework, a common synthetic intermediate was prepared with amenable synthetic handle bromomethyl (-CH<sub>2</sub>Br). The bromomethyl functional group was converted into a specific functional group in a single step to target desired cell organelles such as nuclei, lysosomes, mitochondria. We show that the functional group transformation of the same scaffold influences cellular localization and specificity of pH-activable fluorescent probes in live primary microglial cells. To confirm the cell organelle targeting capabilities of pH-probes, we performed a series of confocal imaging and flow cytometry experiments in primary mouse microglial cells. The localization of the probes into the intracellular organelles was confirmed by co-staining with the commercially available standard dyes. All pH-activable probes show bright green fluorescence in the 500-535 nm range. Lysosomal probes were colocalized perfectly with standard LysoTracker dye. Interestingly, we observed that Mitochondrial targeting probes localize in both lysosomes and mitochondria and could be useful to investigate mitochondrial fusion with lysosomes in diseased conditions. Additionally, we also show that pH-activable probes were cell-permeable, non-toxic, and soluble in aqueous media. Furthermore, the synthetic intermediate and the probes with the free amine group can also be used for several bioconjugation reactions. This work aligns with our current research interest for cell-specific delivery of small molecules or biomolecules. The application of organelle-specific or cell-targeted delivery of molecules to control specific biochemical processes in disease-specific models will be explored in the future.

Structure-organelle-relationship (SOR) of pH-activable fluorescent probes for targeting live microglial cell organelles

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.