Construction And Application Of Sensor Based On Upconversion Fluorescence

With the advantages of low cost,high sensitivity,long-distance luminescence,less sampling,and easy operation,fluorescence sensors have become a hot spot in the frontier research field,and have many important applications in the fields of life science,environmental science,and material science.As a new type of fluorescence sensor,the upconversion fluorescence sensor has the advantages of no background fluorescence interference and strong penetration of deep tissue.They have been widely used in the field of sensing detection in recent years.In this paper,a series of upconversion fluorescence sensors were constructed based on the F（?）rster resonance energy transfer（FRET）effect and fluorescence inner filter effect,respectively.The up-conversion luminescence sensors were applied to detect lactate dehydrogenase activity and hydrogen peroxide concentration in cells.The performance of the corresponding upconversion fluorescence sensors is systematically studied.In addition,an upconversion fluorescence sensor based on the cooperative upconversion fluorescence effect is constructed with an upconversion fluorescence metal-organic framework matrix to realize the optical sensing of relative humidity.The main results are as follows:（1）An upconversion fluorescence sensor for enzyme activity was constructed based on the FRET effectLactate dehydrogenase activity is a distinguishing characteristic of cancer cells from normal cells.Medical studies believe that high activity of lactate dehydrogenase may be the cause of cancer cell metastasis,invasion,invasion,and deterioration in living organisms.Therefore,the development of an upconversion fluorescence sensor to evaluate the efficacy of lactate dehydrogenase inhibitor drugs will be useful to accelerate the development of anti-cancer drugs from lactate dehydrogenase inhibitors.An organic-inorganic hybrid upconversion fluorescence sensor was designed and developed to evaluate the efficacy of LDH inhibitors on cancer cells by the change of red light emission intensity of upconversion fluorescence.The sensor is composed of two components:a tailed manganese doped upconversion fluorescence nanoparticles,which can generate bright upconversion fluorescence in the red region when excited by near-infrared light;and a Nile blue derivative for detecting lactate dehydrogenase activity,which can absorb the upconversion red light generated by manganese doped upconversion fluorescence nanoparticles via FRET.The cytotoxicity of the sensor in living cells（He La,A549,and Ges-1）was investigated by using the CCK-8 assay,which showed that HNFS possesses excellent biocompatibility.After the sensor was co-incubated with the three types of cells above,the mean fluorescence intensities of corresponding confocal images in vitro can illustrate the efficacy of lactate dehydrogenase inhibitors to different cancer cells and distinguish healthy cells（Ges-1）from cancer cells（A549 and He La）.Therefore,the systematic study of the organo-inorganic hybrid upconversion fluorescence sensor in vitro does encourage the potential applications of evaluating the lactate dehydrogenase inhibitors’efficacy in cancer cells.（2）An upconversion fluorescence sensor for hydrogen peroxide was constructed based on the fluorescence inner filter effectAn upconversion fluorescence sensor responsive to hydrogen peroxide was designed and developed.Lanthanide-doped upconversion nanoparticles were synthesized by the thermal coprecipitation method.After modification with an electron-donating ligand,silver ions were coated in situ on the surface of lanthanide-doped upconversion nanoparticles by photogenerated electron reduction under the irradiation of ultraviolet light.The core-shell structure of lanthanide-doped upconversion fluorescence nanoparticles with the silver metal surface is formed.The designed upconversion fluorescence sensor with good responsiveness to hydrogen peroxide was obtained by modifying the surface of core-shell nanoparticles with sulfhydryl group polyethylene glycol.The sensor is constructed based on the fluorescence inner filter effect,using lanthanide-doped upconversion fluorescence material as an energy donor and coated silver metal as an energy acceptor.The cytotoxicity of the sensor to Hep G2 cell lines was verified by the CCK-8 assay,and the results showed that the sensor had good biocompatibility.After the sensor was coincubated with Hep G2 cells,confocal images were analyzed in vitro,and the results showed that LDN@Ag-PEG could realize the sensing of endogenous hydrogen peroxide in cells.Therefore,the results of the sensor in vitro system show that the upconversion fluorescence sensor can be used to evaluate the level of intracellular hydrogen peroxide concentration.（3）An upconversion fluorescence sensor for humidity based on lanthanide-doped metal-organic frameworksLanthanide-doped metal-organic frameworks（named Y/Yb/Er-BTC-MOF）were synthesized by the solvothermal method.The obtained Y/Yb/Er-BTC-MOF shows the cooperative upconversion fluorescence of Yb³⁺and upconversion fluorescence of Er³⁺(Yb³⁺-sensitized)irradiated by a continuous wave 980 nm laser.It possesses two fluorescence centers,in which Yb³⁺forms emission at 500 nm through the cooperative fluorescence effect,and Er³⁺achieves 660 nm emission through excited state absorption and successive energy transfer from Yb³⁺.In order to explore the potential application of this unique fluorescence phenomenon in relative humidity sensors,the relative humidity responsiveness of Y/Yb/Er-BTC-MOF was investigated by measuring the intensity changes of upconversion fluorescence in different relative humidity environments,and a relative humidity ratio meter upconversion fluorescence sensor was constructed.The results show that the response of Y/Yb/Er-BTC-MOF to relative humidity presents a linear relationship in the range of 11～95%.The cycle stability of Y/Yb/Er-BTC-MOF responses to relative humidity was investigated with the intensity changes of upconversion fluorescence,and the recovery ratio was more than 93%each time.Therefore,the Y/Yb/Er-BTC-MOF is a humidity-sensitive material with great potential for applications such as humidity sensors...