Synthesis Of Napthalimide Derivative And Its Applications In Fluorescent Sensing

Galactosidase is a well-characterized enzyme that is widely used as a reporter to examine transcriptional regulation or to evaluate transfection efficiency. Detection of galactosidase activity offers potential insight into developmental biology, disease progression, and potentially personalized medicine.Fluorescence molecular probe have been widely used in the areas of biology, medicine, chemistry and environment, due to its simplicity, high sensitivity, specific selectivity, low detection limit, real-time and in-situ detection in vivo. Specially, ratiometric fluorescent probe allows the measurement of the changes of the fluorescent intensity at two wavelengths and provides a built-in correction for environment effects, such as instrumental efficiency, external environment conditions. Therefore, it can provide more accurate detection result and broader dynamic response rang that has attracted considerable attention.In this study, based on the mechanism of galactosidase catalysis reaction, we synthetized a new naphthalimide derivative NI-Gl as galactosidase substrate and used the change of intramolecular charge transfer before and after the enzyme-catalyzed reaction to achieve ratiometric detection for galactosidase.In the first part, the naphthalimide derivative NI-Gl with an galactosidase group at the 4th position of the naphthalic ring was successfully prepared from 4-bromo-1, 8-naphthalic anhydride. The chemical structure of NI-Gl was confirmed by 1H-NMR and ESI-MS, and its spectroscopic properties were investigated by UV-Vis absorption and fluorescence spetra. By comparing the spectroscopic properties of NI-Gl and NI-OH, which is substituted with hydroxyl group at the 4th position of the naphthalic ring,we found there is significant difference on UV-Vis absorption spetra and fluorescence spetra between NI-Gl and NI-OH.In the second part, the function of NI-Gl used in the galactosidase detection, including the change in UV-Vis absorption spetra and fluorescence spetra of NI-Gl in PBS( p H 7.4) buffered water before and after adding galactosidase,the influence of galactosidase inhibitor on the fluorescence spetra of the detection system and the comparison of the 1H-NMR spectrums of NI-Gl and purified reaction product from NI-Gl hydrolyzed by galactosidase were investigated experimentally. The results show that the cleavage of galactose group under catalysis of galactosidase transforms NI-Gl into NI-OH with change of intramolecular charge transfer results in the fluorescent ratiometric response. Furthermore, the detection limit of NI-Gl is 0.023U/L for the detecting of galactosidase.Currently the report about detecting galactosidase using ratiometric fluorescent probe was still relatively few. Our probe provides a new way to detect galactosidase.