Fabrication Of The Novel Upconversion Nanoprobes For Imaging Analysis Of PH Or Hypoxia In Living Cells

Upconversion nanoparticles combined with lanthanide element have the remarkable ability to combine two or more low-energy photons and produce single high-energy photon through the anti-Stokes process,with a broad prospect of widespread use f-rom high resolution biological imaging to modern photovoltaic technologies.Compared to traditional fluorescent nano-labels(such as small organic molecule fluorescent dyes,quantum dots,etc.),UCNPs have several advantages such as excellent light stability,continuous emission capability and sharp multi-peak emission.In addition,light scattering from biological tissues is greatly reduced under near-infrared(NIR)excitation.The reduction of scattering of light stimulated by NIR also makes the penetration depth of the tissue much greater than that of the UV or visible light excitation.More importantly,these nanoparticles stimulated by a NIR light source eliminates background interference from fluorophores or probes belonging to nonspecific combination,making quantitative analysis of interactions among molecular in biological samples come true.However,due to the oleic acid coated on the surface of the upconvertion nanoparticles during application,they have poor water dispersibility and instability.Therefore,in order to make the upconversion nanoparticles further used,the surface of the particles should be modified by hydrophilic modification to transfer the upconversion nanoparticles into water.Therefore,we have combined previous research,innovated upconversion nanoparticles through different reaction mechanisms,and modified and characterized the surface of upconversion nanoparticles to make them have good biocompatibility and minimal cytotoxicity,which enables the detection of pH environment in vivo and the exploration of hypoxic environment in vitro and lays the foundation for further experimental research.The specific research is as follows:1.Functionalizing the construction of upconversion fluorescent nanoprobes substrate and detecting and imaging of pH in cellsPH regulates the function of many organelles and plays an important role in regulating many cell behaviors.To better monitor the change of pH in the cell,we have designed and studied new type of upconversion nanoparticles fluorescent probe.Firstly,according to the reports and documents,the upconversion nanoparticles with regular shape,uniform particle size and stably optical properties can be synthesized by(solvent)hydrothermal method.The synthetic samples are measured by characterization methods such as fluorescence spectroscopy and so on.Then,with some certain conditions controlled,mesoporous silica is encapsulated in the outer layer of the upconversion nanoparticles treated with an aminosilylation reagent,so that the surfaces of the upconversion nanoparticles are evenly filled with amino functional groups.Then,the synthesized pH-sensitive organic fluorescent small molecule probes are combined with the modified hydrophilic up-conversion nanoparticles.And the alkynyl mono-substituted ?-cyclodextrin is modified on the surface of the particle by click reaction to blocking the pores of mesoporous silica and form closed nanoparticles to prevent dye leaking.The fluorescence experiments in vitro demonstrate that our synthesized probes can respond well in different pH conditions.Finally,imaging of cells and tissues also further demonstrates the successful construction and use of our probes.2.Functionally converting upconversion fluorescent nanoprobe for the detection of hypoxic conditionsRapid cell division,exponential grovwth and insufficient blood supply produce oxygen gradients in solid tumors.Hypoxia often accompanies solid tumors in breast,colon,pancreatic,and prostate cancers.Due to a dense extracellular matrix and the development of early hypoxia,cancer is exacerbated.To better detect cancer,we also have synthesized new upconversion nanoparticles to detect the early hypoxia.Firstly,we have compounded even up-conversion nanoparticles by hydrothermal method.Upconversion nanoparticles coated by the oleic acid are converted to aqueous phase by coordination.The organic small molecule diazene-1,2-diylbis(4,1-phenylene)diacrylate is further linked to gold nanoparticles to achieve specific detection of hypoxic environments.Comparing fluorescence spectra in vitro under normal and hypoxic condition,we have validated the successful construction of our probes and laid the foundation for future tests in vivo by using cytotoxicity assays.