Researches On Biomacromolecule Functionalization Upconversion Nanoprobes For Biosensing And Bioimaging

Due to the internal abundant electronic energy level,the upconversion nanoparticles(UCNPs)have high energy band emission,long fluorescence lifetime,excellent photostability,and multiple emission bands from ultraviolet(UV)to infrared(IR),which have attracted widespread attention.And UCNPs have been extensively used in background-free biosensing and biological imaging,light-triggered drug delivery,solar cells and super-resolution imaging.However,UCNPs do not have a recognition unit,they cannot detect analytes with high selectivity.Therefore,in this paper,we select different biological macromolecules as energy receptors and analyte recognition units of UCNPs,and design a novel near-infrared(NIR)sensing platform based on UCNPs,using the luminescence of UCNPs(UCL)to realize the biological imaging research of analyte.The informations are as follows: Chapter 1.OverviewThis chapter first briefly introduces the properties of UCL,UCNPs and synthesis.The focus is on surface functionalization based on UCNPs,selection of energy acceptors,and applications in biosensing and imaging.Finally,the research content and significance of this thesis are explained.Chapter 2.Rational modulation of the luminescence of upconversion nanomaterials with phycocyanin for the sensing and imaging of myeloperoxidase during an inflammatory process.In this work,we developed a novel luminescent nanoprobe(PC-UCNPs)based on upconversion nanoparticles(UCNPs)conjugated with phycocyanin(PC),which could detect the fluctuation of myeloperoxidase(MPO).By grafting PC onto the surface of UCNPs through amidation reaction,UCL is quenched by PC via energy transfer.Due to the specific recognition by PC,PC-UCNPs nanoprobe can be used for sensitive evaluation the bioactivity of MPO.PC-UCNPs nanoprobe has been successfully applied for the bioimaging of MPO in living cells and during the inflammatory process by taking an acute liver injury mouse as a model.Chapter 3.Acetal derivatized dextran modified upconversion for imaging lysosomal pH during AutophagyIn this work,we have developed a new NIR lysosomal pH probe based on UCNPs(Ac-DEX@UCNPs).First,we synthesized UCNPs by thermal decomposition,and modified dextran(DEX)to obtain acetal derivatized dextran(Ac-DEX).Ac-DEX and UCNPs are combined through the ligand exchange strategy,and UCL is quenched due to the aggregation-induced quenching effect(ACQ).Under acidic pH conditions,AcDEX is hydrolyzed to DEX,ACQ is weakened and UCL is restored.Therefore,AcDEX@UCNPs has a highly sensitive and highly selective fluorescence response to pH changes under acidic conditions.Cell imaging data shows that Ac-DEX@UCNPs can monitor the pH changes of lysosomes during autophagy with excellent photostability and low cytotoxicity.