Design,Synthesis And Performance Study Of Molecular Probes Based On Fluorescent Sensor

When substance with fluorescent emission characteristic is affected by the surrounding environment(such as foreign chemistry,biological species,temperature or acidity,etc),its fluorescence emission performance(such as spectral and intensity,etc)changes,so as to achieve the characteristics of the surrounding environment or specific material identification,response and detection,which often referred to as fluorescence sensing.The rhodamine-type molecular probe is based on the change in the fluorophore structure to produce fluorescence emission.The spirolactam structures are nonfluorescent and colorless,whereas ring-opening of the corresponding spirolactam induced by target species gives rise to strong fluorescence emission and pink color.Fluorescent probe is designed to identify a variety of metal ionsbased on the reaction site of rhodamine derivative could combine with the rhodamine chromophore.On the basis of literature study,two novel rhodamine-based fluorescence enhanced molecular probes(RAi and RA2)were synthesized,which were both designed as comparative fluoroionophore and chromophore foroptical detection of Hg2+.Molecular structure of probe was charactered by 1H-NMR,FT-IR,EI-MS,UV-Vis.Photophysical properties of RA were measured by UV-Vis absorption spectrum and fluorescence spectrum.The results showed that both of the two probes RA1 and RA2 had specific responses to Hg2+.After adding mercury ions,the maximum absorption wavelength and the maximum fluorescence emission wavelength of RA2 were 556 nm and 580 nm respectively.The color changed from colorless to pink and emited bright orange light in the ultraviolet light.They exhibited high selectivity and sensitivity for Hg2+ over other commonly coexistent metal ions in CH3CN/H2O(1:1,v/v)solution.Test shows thathydroxy benzene of rich electron was more favorable for chelating with Hg2+ to form 1:1 complex,the fluorescence intensity reached the maximum afcter 50 min,binding constant was 1.72×104(mol/L)-1(R2=0.9904),detection range was 0.14-140 ?mol/L,detection limit was measured to be at least 0.14 ?mol/L,fluorescence quantum yield rose from 0.003 to 0.1458,enabling high selectivity and high sensitivity for Hg2+.In addition,two kinds of probes can be made into a portable test strip(2 cm × 5 cm)and a hydrogel block(radius 2 cm)by dipping method,which can produce obvious color change of Hg2+ in the environmental aqueous solution and realize the rapid detection of Hg2+.1,8-naphthalimide compounds are one of the important fluorescent dyes,which have high quantum yields and can be used as DNA-related biomarkers.1,8-naphthalene anhydride itself is not glowing.The formation of 1,8-naphthalimide structure can emit fluorescence in short wavelength range,but molar absorption coefficient is low and dye color is light.The introduction of electron-donating groups on the benzene ring of 1,8-naphthalimide resulted in a strong intramolecular push-pull electron system,which greatly increased the fluorescence quantum yield and emission wavelength of the dye.This feature makes it another candidate for fluorescent molecular probes.Cytochrome P450,one of the most important drug-metabolizing enzymes in humans.Isoform CYP1A is involved in the biotransformation of many endogenous and exogenous substances and plays a crucial role in the metabolic activation of procarcinogenic compounds to their ultimate carcinogens.At present,chemical probe-based assay is the most widely used approach for the evaluation of CYP activity although there are cross-reactions between the isoforms with high sequence homologies.The probe was designed on the basis of substrate preference of CYP1A and its high capacity for O-dealkylation,while 1,8-naphthalimide was selected as fluorophore because of its two-photon absorption properties.To achieve a highly selective probe for CYP1A,four kinds 1,8-naphthalimide derivatives were synthesized and used a panel of human CYP isoforms for selectivity screening to explore the potential structure-selectivity relationship:naphthalimide(MN)can easily enter the active chamber of CYP1A2 and CYP1A1,and the carboxyl group at the MN terminal can form hydrogen bonds with the partial amino acids on the CYP1A chain.After screening and optimization,we found that two ratiometric two-photon fluorescent probe NCMN and NEMN allowed for selective and sensitive detection of CYP1A.Naked-eye color change occurs after probe reacting with CYP1A,test system changed from blue to green with ultraviolet light.NCMN displayed better selectivity for CYP1A-catalyzed demethoxy.NEMN showed the largest UV absorption peak at 458 nm and the largest fluorescence emission peak at 552 nm.NEMN had better sensitivity for CYP1A(detection range 1.632-150 nmol/L,detection limit of 1.632 nmol/L),response time is short 10min.The results show that the probe NCMN and NEMN may be used for the selective sensitivity detection of CYP1A by the ratio fluorescence method.