Construction Of Organosilicon Fluorescent Probes For Sensing Of Ions,pH And ClO~- In Living Organisms

Cancer diseases usually occur in association with alterations in biologically active molecules or parameters of the cellular physiological environment.Fluorescence imaging analysis techniques are favoured by researchers for its advantages such as high temporal and spatial resolution,availability for in vivo imaging analysis,excellent specificity and high sensitivity,and provide an important technical tool for life science analysis.Currently prepared fluorescent probes still suffer from undesirable biological toxicity,low sensitivity and poor stability,which greatly restricted their further application.However,silicone materials possess low biotoxicity,good biocompatibility,excellent stability to be suitable for bioimaging analysis.However,there are still large gaps regarding silicone materials in bioanalysis and strategies for the construction of polymeric fluorescent probes still need to be expanded.To solve the above problems,in this paper,three organosilicon functional platforms with different easy modifications were firstly constructed using dimethoxysiloxane,piperazinyl propyl methyl dimethoxysilane and（3-aminopropyl）trimethoxysilane as the structural units of organosilicon materials.Then,the organosilicon fluorescent probes with different molecular recognition functions were further constructed by functionalizing the main chain,side chain and terminal structures of the organosilicon functional platforms,respectively.In addition,optical properties and bioimaging studies were carried out on the organosilicon fluorescent probes with different molecular recognition functions.Ⅰ.The classical"hydrolytic condensation"method was applied to prepare vinyl POSS materials with multiple easy-to-modify sites.Subsequently,the borane functional modification of vinyl POSS was achieved by the“Friedel-Crafts”reaction,producing the caged organosilicon fluorescent probe PSI-A.Based on spectroscopic tests,the probe presented atypical blue fluorescence properties,photostability and low biotoxicity.The fluorescence was quenched by the coordination of PSI-A with Cu²⁺and Fe³⁺,and further restored to varying degrees by the differential coordination of amino acids/Cu²⁺and Fe³⁺with PSI-A/Cu²⁺and Fe³⁺after the addition of amino acids to the composite system.The probe was successfully used for fluorescence monitoring of Cu²⁺and Fe³⁺in cells,and imaging of amino acid/Cu²⁺and Fe³⁺interactions in zebrafish was also achieved.The above experimental results demonstrate the value of organosilicon materials for research and application in the field of bioimaging.Ⅱ.The chain-like polysiloxane molecular backbone was prepared from dimethylmethoxysiloxane,piperazinyl propyl methyl dimethoxysilane and（3-aminopropyl）trimethoxysilane.After modification of the polysiloxane side chain with a triphenylaminopyridine derivative with intramolecular charge-transfer mechanism,we prepared PA-1 with pH ratiometric response,which exhibited good targeting lysosomal function and achieved a ratiometric shift in fluorescence signal in response to H⁺changes in acidic environments by protonation of the pyridine structure in the side chain.The probe demonstrated favorable photostability during imaging,and excellent biocompatibility.The probe was utilised to successfully perform ratiometric imaging analysis of lysosomal pH changes during starvation-induced autophagy and chloroquine-inhibited autophagy,distinguishing pH changes during normal autophagy from abnormal autophagy.It provided a basis for further studies on the effect of pH changes in the play of autophagic processes.Ⅲ.A novel polysiloxane backbone was constructed via bonding perylene diimide to an aminopropyl bimodal head as a substrate.A new ratiometric fluorescent probe for polysiloxanes,PBN-1,was constructed through bonding of a naphthalene anhydride thioethyl derivative to the chain end of the main chain,which exhibited high selectivity,stability and low biotoxicity.Most notably,it achieved the ratiometric analysis of the fluorescence signal of the ClO^-/GSH redox fluctuation process,and enabled the analysis and detection of the redox imbalance to equilibrium process in cells and zebrafish through the ratiometric imaging channel,and the imaging performance was significantly better than the single-channel fluorescence imaging analysis changes.In addition,the probe PBN-1 was successfully evaluated for redox levels in zebrafish at different stages of growth and development.This suggested that organosilicon based fluorescent probes could be used as a potential tool for the detection of biologically active molecules,while the construction strategy provided new insights into the construction of ratiometric fluorescent probes.