Studies On Improving Inner Filter Effect By Graphene Oxide And Imaging Mitochondria With Targetable Graphene Quantum Dot

Thiols play key roles in biological system.In order to detect GSH in living system,various organic probes have been developed based on colorimetric analysis methods.The visual colors can be observed by naked eys,and therefore no affiliated instruments are required,so colorimetric probe is simple and easy to used.However it’s low detection limits,insensitivity for target and short detection range constrain the full potential of its applications.Fluorescence inner filter effect(IFE)is introduced to improve it’s sensitivity and detection range by translate the absorbance of the absorber into the exponential changes in fluorescence of the fluorophore.In the approach,two dyes are employed,one absorbent,the other fluorescent,without covalent linking.However,the inner filter effects is too weak when compared with fluorescent sensor specially in complex biological samples,which is mainly attribute to that the distance between absorber and fluorophore is too far to effective convert absorption signal into fluorescence signal.In order to solve this problem,GO was introduced into this IFE system.GO can act like a 2D conjugated polyelectrolyte to react with positively charged organic molecules and aromatic compounds through electrostatic and π-π stacking cooperative interactions.Therefore,we introduce GO into IFE system to adsorb the absorber and fluorophore through electrostatic and π-πstacking cooperative interactions.The adsorption not only apparently quench the fluorescence intensity of background to improve the signal to noise ratio but also shorten the distance between both which avoid the interference from complex biological system.Mitochondria,the organelle found in almost all eukaryotic cells,play a vital role in the life and death of cells.The most prominent function of mitochondria is to produce ATP,the energy currency of the cell.The production of ATP involves a series of electron transport systems in the oxidation phosphorylation pathway,which is also found to associated with the generation of reactive oxygen(ROS).The production of ROS in mitochondria leads to the propagation of free radicals,damaging cells,and contributing to cell death,which is known as mitochondria-mediated apoptosis.So,mitochondrial imaging and tracking is meaningful for physiology,pathology and clinical medicine.However,commercially available mitochondria trackers suffer from poor photostability and high toxic to body.So it’s important to develop a new mitochondria tracker with superior photostability and low toxic.Based on the shortcoming above,this thesis was focused on the following two aspects works:(1)Graphene oxide as a signal amplifier in the thiols-selective fluorescent sensor based on the inner filter effect and detection in serum sample.In 10 mM HEPES buffer solution(50%ethanol,pH 7.4)the probe,CP,has good absorption peak in 536 nm which overlaps nicely with the excitation peak of Rhodamine 6G(R6G).The absorption peak disappeared with addition of GSH.Thus,a highly selective GSH fluorescent sensor has been designed based on the UV-Vis absorption of CP coupled with the use of R6G based on IFE.Since the changes in the absorbance of the absorber are translated into exponential changes in fluorescence of the fluorophore,the novelty of the present device is that the analytical signal is more sensitive over that of the absorptiometry or that of the using one single dye.In order to realize a practical fluorescent sensor,GO wad introduced into IFE system,which adsorb the absorber and fluorophore through electrostatic and π-π stacking cooperative interactions.The adsorption not only apparently quench the fluorescence intensity of background to improve the signal to noise ratio but also shorten the distance between both which avoid the interference from complex biological system.(2)Graphene quantum dots for specific mitochondrial imaging.Graphene quantum dots(GQDs)was prepared through a facile one-pot solvothermal method.Then,triphenylphosphonium(TPP)was linked with GQDs through covalent modification.Zeta potential,TEM,AFM,UV-Vis,EDX,and IR were used to characteristic all the products.Last,HeLa cell was employed as the model for imaging for mitochondria.Co-staining experiment with MitoTracker Red FM(MT),a commercially available mitochondria imaging agent,suggests that the observed fluorescence for GQDs-TPP is localized to the mitochondria of the living HeLa cells.