Studies Of Nanocatalysis And Cell Imaging Based On Fluorescence Technology

In this thesis,the small-molecule fluorescent probes,which can convert the weak fluorescent signal into a strong fluorescent signal after being stimulated,are used to monitor the chemical catalytic reaction process,the temporal and spatial distribution of metal ions in the organism and monitor the process of nano-graphene oxide-based drug delivery system to release drugs in cancer cells.The chemically catalyzed reaction process is complex,and often involves multiple steps and multiple intermediate products.Capturing the dynamic changes of intermediate products helps to clarify the catalytic reaction mechanism.Due to the low content and short life of intermediate products,it is difficult for conventional methods to monitor the production and conversion of intermediate products in real time.Similarly,the content of trace element zinc which is involved in life processes such as protein structure regulation and neural signal transmission is low,and its content is dynamically balanced in normal cells.Monitoring the spatiotemporal dynamic distribution of Zn²⁺in real-time can provide an important basis for regulating and maintaining the steady state of Zn²⁺in vivo.What is more,there is a dynamic change in drug release after the drug delivery system delivers the drugs to cancer cells.Fluorescent labeling technology can dynamically detect the delivery process and drug release kinetics of the drug delivery system in real time.Fluorescent probes which have high resolution,high sensitivity,and fast detection speed are very suitable for monitoring samples with low content,short life,and dynamic changes.Therefore,this paper uses fluorescent probes to study the catalytic process of gold nanocatalysts in real time and monitor the spatiotemporal distribution of zinc ions in Alzheimer's disease and the process of nano-graphene oxide-based drug delivery system to release drugs in cancer cells.Details as follows:1.Fluorescent chemical reaction was used to study the catalytic activity of Au NPs after enrichment and concentration.500 nm silanization-SiO₂ adsorbs 5 nm Au NPs through electrostatic interaction and self-assembles to form Au NPs@SiO₂ complex.This self-assembly method not only highly enriched Au NPs with small particle sizes,but also prevented Au NPs from agglomerating.We further studied the catalytic activity of Au NPs@SiO₂ complex by using fluorescent chemical reaction.The results showed that the catalytic activity of AuNPs@SiO₂ was greatly enhanced by increasing the local concentration of AuNPs,and the catalytic activity was 3 times higher than that of AuNPs at the same concentration.After 5 times of reuse,the catalytic conversion efficiency remained at about 80%.The Au NPs@SiO₂ composite could be preserved for one month with the same structure and catalytic activity.Moreover,by adjusting the molar ratio of SiO₂ and Au NPs,the assembly density of Au NPs at SiO₂ can be precisely regulated,and the catalytic activity of Au NPs@SiO₂ can also be changed precisely.2.Single-molecule fluorescence technology is used to study the photocatalytic reaction enhanced by local surface plasmon resonance?LSPR?in real time and dynamically.Plasma-mediated photocatalysis provides a new strategy for utilizing solar energy.Determining the rate-determining step and its activation energy in plasma-mediated photocatalysis can help us understand the role of hot carriers?hot electrons-holes?and help to rationally design catalysts with high photochemical conversion efficiency and catalytic performance.However,this is still a challenge due to the lack of high-temporal-resolution research tools capable of capturing intermediate products.Therefore,we used a single-molecule fluorescence method to study the photocatalytic reaction enhanced by local surface plasmon resonance?LSPR?in real time and dynamically.By introducing variable temperature as an independent parameter in the plasma photocatalysis,the activation energy of the cascade reaction step can be clearly identified,including the intermediate product generation process,product generation process,and product dissociation process,and it is found that the intermediate product generation process is rate-limiting step.Remarkably,the cause of plasmon enhanced catalysis performance was found to be its ability of lowering the activation energy of intermediates generation.This study gives new insight into the photo-chemical energy conversion pathways in plasmon enhanced photocatalysis and sheds light on designing high performance plasmonic catalysts.3.A fluorescent probe based on framework nucleic acid?FNA?was constructed to monitor the spatial and temporal distribution of Zn²⁺in Alzheimer's disease.Zinc is an essential element of human health.Elevated levels of zinc ions in the body often cause neurodegenerative diseases such as Alzheimer's disease?AD?.Monitoring the spatiotemporal distribution of zinc ions in the development of Alzheimer's disease in real-time and dynamically is important for understanding the role of zinc ions in the pathogenesis.Therefore,we designed and synthesized FNA-zinc ion fluorescent probes with fixed morphology and size.The FNA-Zn²⁺fluorescent probes can monitor the concentration change of Zn²⁺,and realize the accurate detection of endogenous zinc in cells.We further monitored the spatiotemporal distribution of zinc ions in AD cells with FNA-zinc ion fluorescent probes.We found that during the pathogenesis of AD,the concentration of Zn²⁺rose rapidly and A?aggregated.Eventually,both Zn²⁺content and A?aggregates tended to be stable,but were still 2-3 times higher than normal levels.Our method can accurately reflect the change of endogenous zinc content in cells,and provides new ideas and new methods for the diagnosis and treatment of Alzheimer's disease.4.Fluorescent labeling method was used to study the effect of nano-graphene oxide?NGO?drug delivery system?DDS?in response to glutathione?GSH?on tumor targeted therapy.A bioreduction-responsive nanographene oxide?NGO?based drug delivery system?DDS?for chemotherapy with a disulfide linker as a glutathione-responsive switch was designed and prepared in a facile way,which can only be activated to release original water-insoluble anticancer drugs in cancer cells.For better biocompatibility and more functionalization,this DDS was constructed through a promising platform?PEG-NGO-SH?,which was based on dual-functionalized NGO with six-armed poly?ethylene glycol?on the edge and thiol groups on the basal plane.This DDS was found to exhibit a suitable lateral size?180 nm?,high drug loading ratio?20 wt%?,selective release?90%in 10 mM GSH?,bioavailability and significant difference in cytotoxicity to normal?293T?and cancer?A549?cells.Thus,it was obviously verified that this bioreduction-responsive DDS triggered by GSH and its construction method using a disulfide linker as a switch on dual-functionalized NGO show potency toward tumor-targeted therapy.