The Study Of Optical And Electrochemical Sensing Methods Based On Acridone Derivatives

Acridine compounds form an important class of heterocycles containing nitrogen,including acridine orange,acridine ester,biacridine,acridone derivatives and so on.Acridone derivatives have good electron transport ability and strong fluorescence,these properties of acridone derivatives which attributable to their electron donor groups（N-R）,electron withdrawing groups（C=O）and their large ring conjugation system and rigid planar structure.Acridone derivatives also have exhibited bioactivities such as anticancer,antimicrobial,and antimalarial.At present,it has been widely used in the fields of medicine,photoelectric materials and other fields.Although acridone derivatives have been widely studied in the field of optical applications,the research and application of the ratio fluorescence and two-photon fluorescence are less.Meanwhile,the water-solubility of most acridone derivatives is poor,limiting their optical or electrochemical activity application.Therefore,several sensing methods of ratio fluorescence,two-photon fluorescence and electrochemistry based on commercialized or self-made acridone derivatives have been developed for the detection of ions,small molecules and biological macromolecules.These proposed sensing strategies are potential to provide a basis for the research expansion of acridone derivatives in the fields of photoelectric material,ion probe,biological two-photon probe and biological activity.This article includes four chapters.Chapter one:In this chapter,we developed a ratiometric fluorescence sensing method based on 2-aminoacridone for pH detection.The amino group of 2-amididone is protonated by H⁺in acidic conditions,and the protonated nitrogen atom conjugats with amididone structure to form the p-πconjugated structure,allowing the intramolecular charge transfer（ICT）.The fluorescence enhanced at the emission wavelength 420 nm,but weakened at 540 nm,showing the blue fluorescence.With the increase of pH value,it is easily deprotonation,the fluorescence weakened at the emission wavelength of 420 nm but enhanced at 540 nm,showing the yellow green fluorescence.Through the changes of fluorescence signals,this method is able to monitor the pH changes.The experimental results suggest a great linear relation between the logarithm of the fluorescence ratio(F₅₄₀/F₄₂₀)（F540 and F420 are fluorescence intensity in the emission wavelength of 540 nm and 420 nm）and the pH in the range of 2.0⁶.0.This method has also been applied to monitor intracellular pH changes of gastric cancer cells（SGC-7901）successfully by fluorescence imaging.And it is expected to provide a new method for the detection of intracellular pH under extreme-acidity conditions.Chapter two:In this chapter,we proposed a fluorescence sensing method based on 5,7-Dinitro-2-Sulfo-Acridone（DSA）and MnO₂ nanosheets（Nano-MnO₂）for the detection of glutathione（GSH）.The fluorescence of DSA was quenched due to DSA adsorption on Nano-MnO₂.Then,the redox reaction between GSH and Nano-MnO₂led to the digestion of the Nano-MnO₂ sheet,making DSA free and the quenched fluorescence recovered.Based on this principle,it can be used for detection of GSH.The experimental results show that the proposed sensing strategy realizes the detection of GSH in the linear range of 100⁷00μM with a detection limit of 4.0μM.Meanwhile,this method has been successfully applied to the fluorescence imaging of GSH in the cervical cancer cell（HeLa）.The proposed sensing strategy is expected to provide a new method for the detection of GSH in organisms.Chapter three:In this chapter,we developed a signal-on fluorescence sensing method based on 10-methyl-2-nitroacridone（MNA）for the detection of nitroreductase（NTR）.TheNTRcaneffectivelyreduceMNAto10-methyl-2-aminoacridone（MAA）in the presence of reduced nicotinamide adenine dinucleotide（NADH）as an electron donor,accompanied by a large fluorescence enhancement.The concentration of NTR is detected by the change of the fluorescence intensity.Under the optimum conditions,the proposed sensing strategy successfully measured NTR in the linear range of 0¹5μg/mL with a detection limit of 0.15μg/mL.The method was successfully applied to the detection of endogenous NTR in zebrafish,which was in agreement with the commercial fish nitro reductase kit.At the same time,we found that the generated MAA has the property of two-photon,and it can be applied to the two-photon fluorescence imaging of the endogenous NTR in zebrafish through femtosecond pulse laser technology.This proposed sensing strategy is potential to provide a new method for the detection of NTR in organisms.Chapter four:In this chapter,we developed an electrochemical sensing method based on the electrochemical behaviors of the interaction between 5,7-dinitro-2-sulfo-acridone（DSA）and bovine serum albumin（BSA）for the detection exosomal protein.DSA has excellent electrochemical activity on GCE with a couple reversible redox peaks.DSA bind with BSA to form an electrochemically non-active complex in pH 5.0 PB buffer,resulting the decrease of the equilibrium concentration of DSA.Additionally,the decrease of the peak current of DSA is proportional to the concentration of BSA in the linear range of 0.01⁰.10 mg/L with the detection limit of 0.002 mg/L.Meanwhile,this method is successfully applied to the detection of exosomal protein,and the detection result is in accordance with that of commercial protein quantitative reagent box method（BCA assay）.Therefore,it is expected to provide a new method for the detection of biological macromolecules such as protein in clinical biological samples.