Cell Recognition, Imaging, Diagnosis And Treatment Based On Silver Nanoparticles

Silver nanoparticles, as a kind of noble metal nanoparticels, have gained significant interest due to their remarkable optical, electrical and antimicrobial properties. The surface of silver nanoparticles is allowing for facile functionalization with various stabilizing agents, biomolecules and chemotherapeutic agents. Their most distinguishable properties are their enhanced optical performance (light absorption and scattering) and cytotoxicity, and these two properties could be used in cell imaging and therapy. Most of the studies assumed that the properties of silver nanoparticles depend on their size, shape and surface coating. Herein, in the works of this thesis, we mainly synthesized silver nanoparticles with different size and shape, and functionalized them with stabilizing and targeting molecules for cell recognition, imaging, diagnosis and treatment.We fabricated a multifunctional theragnostic agent Ag-Sgc8-FAM for apoptosis-based cancer therapy and fluorescence-enhanced cell imaging. For cancer therapy, aptamers Sgc8 and TD05 acted as recognizing molecules to bind CCRF-CEM and Ramos cells specifically. It was found that aptamer-silver conjugates (Ag-Sgc8, Ag-TDO5) could be internalized into cells by receptor-mediated endocytosis, inducing specific apoptosis of CCRF-CEM and Ramos cells. The apoptosis of cells depended on the concentration of aptamer-silver conjugates, as well as the incubation time between cells and aptamer-silver conjugates. The apoptotic effects on CCRF-CEM and Ramos cells were different. Annexin V/PI staining, AO/PI staining, MTT assays and ROS (Reactive oxygen species) detection demonstrated the specific apoptosis of CCRF-CEM and Ramos cells. For fluorescence-enhanced cell imaging, Ag-Sgc8-FAM was prepared. Compared to Sgc8-FAM molecules, Ag-Sgc8-FAM was an excellent imaging agent as numerous Sgc8-FAM molecules were enriched on the surface of AgNPs for multiple binding with CCRF-CEM cells and signal amplification. Moreover, AgNPs could increase the fluorescence intensity of FAM by metal-enhanced fluorescence (MEF) effect. Therefore, aptamer-silver conjugates can be potential theragnostic agents for inducing specific apoptosis of cells and achieving cells imaging in real time.We report on a silver decahedral nanoparticles (AgioNPs)-based FRET (Fluorescence Resonance Energy Transfer) sensor for target cell imaging. Fluorophores-functionalized aptamers (Sgc8-FITC) were bound with AgioNPs via the SH group on the aptamer_to form Agio-Sgc8-FITC. Then, quencher-carrying strands (BHQ-1) were hybridized with Sgc8-FITC to form Ag10NPs-based FRET sensor (Agio-Sgc8-F/Q). The sensor interacted with membrane protein tyrosine kinase-7 (PTK-7) on CCRF-CEM cells membrane to attain fluorescence imaging of CCRF-CEM cells. The addition of CCRF-CEM cells resulted in many sensors binding with cells membrane and the displacement of BHQ-1, thus disrupting the FRET effect and the enhanced fluorescence intensity of FITC. It was found that Ag10NPs largely enhanced the fluorescence intensity of FITC. The results also showed that the AgioNPs-based FRET sensor (Agio-Sgc8-F/Q) was not only superior to bare FRET sensor (Sgc8-F/Q) and sensor Ag-Sgc8-F/Q, but also highly sensitive and specific for CCRF-CEM cells imaging.