Synthesis and Characterization of Small Molecule Fluorescent Probes for Zinc-Sensing in Cellular Systems

Zinc is an essential trace element in the human body, playing vital roles in numerous physiological processes. Aberrant zinc homeostasis has been implicated in various pathologies, including cancer and neurodegenerative disorders. However, current zinc-detecting probes often suffer from limitations such as cytotoxicity or insufficient spatiotemporal resolution. This study reports the design, synthesis, and characterization of two novel imine-based organic fluorescent probes, referred to as Compound 1 and Compound 2, for zinc detection. The probes were synthesized via standard organic methods and characterized using 1H-NMR, UV-Vis, and fluorescence spectroscopy and mass spectrometry. Both compounds demonstrated high selectivity for zinc ions, exhibiting a fluorescence “turn-on” response through a photoinduced electron transfer (PET) mechanism. Spectroscopic and spectrometric analysis of the compounds confirmed product purity, and fluorescence emission spectra revealed a significant increase in intensity upon zinc binding. Compound 2 also exhibited a measurable shift in absorbance peak in the presence of zinc. These findings suggest that compounds 1 and 2 hold promise as effective tools for high-resolution, low-toxicity zinc imaging in biological systems, potentially advancing the study of diseases associated with zinc dysregulation.

Hello. My name is Daewa Zaheer, and as a chemistry major planning to go into the field of healthcare, I was interested in working on a project that could use chemistry to advance the field of medicine. For that reason, under Dr. Dilek in the Department of Chemistry and Biochemistry and with the help of Ab, a grad student mentoring my project, I decided to research the Synthesis and Characterization of Small Molecule Fluorescent Probes for Zinc-Sensing in Cellular Systems. What that means is that I worked on developing molecules that would go into cells and light up, or fluoresce, under ultraviolet light after binding to zinc. Why zinc, you may ask? As the second most abundant element in the body, zinc is incredibly important to our health and plays significant catalytic, structural, and physiological roles. That means that zinc levels that are abnormal may indicate varying diseases, particularly cancers and neurodegenerative disorders, like Alzheimer’s. A major reason that we are not entirely sure of the role that zinc plays is due to a lack of tools we can use to study zinc in cellular systems without interfering with the cell itself, and that is where my research comes in. My research involved designing molecules that could “probe” cells and study zinc with high spatial and temporal fidelity with minimal toxicity to cells, meaning that it would be potentially useful in medical diagnostics. A chemical probe refers to a small-molecule ligand that binds to specific biological targets for study in a system. The probes involved in this research were imine-based fluorophores sensitive to zinc, meaning that zinc binding would cause the molecules to fluoresce through photoinduced electron transfer. Photoinduced electron transfer refers to electrons entering a state of excitation upon binding to the target, or zinc in this case, before returning to ground state. This return to ground state is what causes a fluorescence emission. Two probes were designed, compound 1 and compound 2, and after organically synthesizing the molecules, we characterized the molecules through H-NMR, C-NMR, UV-Vis, and fluorescence spectroscopy alongside mass spectrometry to ensure that we had truly created the two molecules. The characterization revealed that the molecules were successfully created and able to fluoresce upon zinc binding through photoinduced electron transfer, as shown in the images on the bottom left. This indicates that our research is verifiable and reproducible and can be used for the purpose of further study and refinement in finding out where the puzzle pieces click when it comes to zinc in our bodies. Thank you.