The Study On Interfacial Properties And Interaction With Schistosoma Japonicum Cercariae Of Self-diffusion Pesticides

The self-diffusion pesticides (niclosamide derivatives) have good excellent bioactivityagainst cercariae, which have been invented by our group. But the interfacial properties ofself-diffusion pesticides at the air/water interface and the interaction mechanism betweenself-diffusion pesticides and Schistosoma japonicum cercariae are not very well studied. For thisreason, AFM technique is used to study the interfacial properties of self-diffusion pesticides at theair/water interface, combined with BAM and LB techniques in this thesis. And introduction of rareearth upconversion nanoparticles in the self-diffusion pesticides as fluorescent probes,fluorescence imaging technology is used to study the interaction mechanism betweenself-diffusion pesticides and Schistosoma japonicum cercariae. The main contents are as follows:(1) The interfacial properties of self-diffusion pesticides have been investigated by usingBAM, LB and AFM techniques at the air/water interface. The BAM experimental results showthat the self-diffusion pesticides (niclosamide derivatives)2a and2b can form self-diffusion filmat the air/water interface. The π–A isotherms show that compound2a (2b) could form stablemonolayers with a limiting molecular area of around1.1-2.5(1.6-6.5) nm2/molecular at theair/water interface when surface pressure less than35(48) mN/m. The monolayer of self-diffusionpesticides have been prepared by LB techniques and characterized by AFM. The AFMexperimental results show that thickness of monolayer films of compound2a (2b) are0.70(0.85)nm,0.99(1.07) nm and1.50(1.75) nm when the surface pressure are5,10,20mN/m, respectively.By varying the surface pressure, the nano-film morphologies could be modulated. The MTT assaydata show that self-diffusion pesticides2a and2b exhibit low cytotoxicity to HeLa cells. Theanti-cercarial activity experimental results show that the self-diffusion pesticides2a and2brepresented excellent bioactivity against cercariae.(2) The interaction mechanism between self-diffusion pesticides and Schistosoma japonicumcercariae has been studied by fluorescence imaging technology. Rare earth upconversionnanoparticles (UCs-OA) were synthesized by hydrothermal method. On this basis, theself-diffusion pesticides have been loaded to rare earth upconversion nanoparticles to preparedrug-loaded rare earth upconversion nanoparticles (UCs-Ni). The AFM and the TEM experimentalresults show that product sizes of UCs-OA and UCs-Ni particles are15-25nm. The MFSexperimental results show that UCs-OA and UCs-Ni have good conversion fluorescence. The cellfluorescence imaging experiments show that UCs-Ni is water-soluble and biocompatible. Thecercariae fluorescence imaging experiments show that UCs-Ni could penetrate into cercarial bodyand it can be transformed by the cercariae. These results indicate that self-diffusion pesticides candestroy the circulatory system of cercariae to lead the rapid death of cercariae.