Design and Synthesis of Fluorescent Probes for Selective Detection of Thiols
Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) are three major low molecular weight biothiols that perform and regulate crucial physiological processes including proteins folding, biological redox homeostasis, intracellular signal transduction and gene regulation. Alterations in plasma and intracellular thiols levels have been linked to various diseases including Alzheimer’s disease, cardiovascular diseases, cancer and skin lesions. Therefore, selective and quantitative detection of thiols may help in early diagnosis of such diseases, in understanding the roles of biothiols in their onset which may help in preventing onset of the same.
Design principle and outcome: Most biological thiols are not inherently fluorescent and therefore cannot be directly visualized via fluorescence spectroscopy. Hence, in my PhD, I devoted my efforts to development and application of selective fluorescent probes that enables indirect visualization and quantification of specific biothiols in a complex biological environment.
In the design a fluorophore is attached to suitable moiety (quencher) which selectively reacts with biothiols . This state is termed as “Fluorescence-Off” state of the probe. Reaction with thiol results in the strong fluorescence of the resultant species. One strategy of sensing involves thiol mediated cleavage of the quencher releasing free fluorophore. Alternately, chemical reaction of thiol with quencher leads to destruction of its quenching ability. In both processes formation of strong fluorescent product leads to “Fluorescence-On” state of the probe.
For developing fluorescent probes having better photophysical properties such as excitation and emission in visible region, good water solubility and improved cell permeability various fluorophores like NBD chloride, Iminocoumarin, Naphthaleimide, Chromenoquinolines, BODIPY and Fluorescein are used. Cell permeability, selectivity and sensitivity of these probes was demonstrated via cell imaging studies.
In the second part of this talk, I will discuss about my future research plans.