Design, Synthesis And Cell Application Of FRET-based Fluorescent PH Chemosensor

pH is a measure of the acidity or basicity of an aqueous solution. The pH of blood is usually slightly basic with pH from7.35to7.45in medicine, if pH comes up fluctuating, it is pathology phenomenon. In chemistry, many chemical reaction can only take place in specific pH condition. Intimate connections between the cell functions with intracellular pH means that precise measurement of intracellular pH can provide critical information for studying physiological and pathological processes. Compared to other pHj measurement methods such as NMR, fluorescence spectroscopy has advantages with respect to spatial and temporal observation of pHi changes. Moreover, fluorescence techniques have high sensitivities, they tend to be operationally simple, and they are in most cases nondestructive to cells.Lysosomes are described as the stomach of the cell. Lysosomes can digest excess or worn-out organelles, food particles, and engulf viruses or bacteria. A significant part of the clinically approved drugs are lipophilic weak bases with lysosomotropic properties. This explaines many pharmacological properties of these drugs.The fluorescence measurement by an increase of the fluorescence intensity can be influenced by many factors, such as the localization of the probe, changes of environment around the probe (pH, polarity, temperatur). To reduce the influence of such factors, FRET-based ratiometric measurement in utilized, simultaneous recording of the fluorescence intensities at two wavelengths and calculation of their ratio. They can achieve large pseudo-stokes shift, meanwhile with fluorescent ratiometic change. Since the emission spectrum of naphthalimide and the excitation spectrum of rhodamine B have substantial overlap, it meets the happen condition of FRET.both of fluorophores provide a good platform for designing FRET-based Chemosensor.we design and synthesize three FRET-Based pH Chemosensor, RN1, RN2, and RN3. They can detect H+with high selectivity, the reactions of the probes with H+is Reversibility. They have very low Cytotoxicity. They can image the intracellular pH change and locate lysosome.Through introducing1,4-displace trizole and changing the link way of two fluorophores. Enchancing FRET system FRET efficiency. FRET efficiency of RN3is72%, So far, FRET efficiency of RN3is the highest in naphthalimide-rhodamine FRET system.