In Situ Raman Imaging Of Cell Surface Sialic Acids

Cancer has been a great threat for human health and is one of the important causes of human death. It has great practical significance to reduce the threat of cancer to human beings by early diagnosis and treatment. Glycans on cell surface are important parts of the cell, which play crucial roles in many important physiological processes including cell communication, immune response, signal transduction and tumour metastasis. The changes of the structure and expression of glycans on cell surface are closely related to the cellular states and have a close relationship with the occurrence of disease, such as cancer, inflammation and nervous system diseases.Surface-enhanced Raman scattering (SERS) imaging has emerged as an novel tool for glycan detection because of its advantages of high sensitivity, non-destructive and non-invasive features and fingerprinting capability on chemical structures. In this dissertation, we combined materials science, chemical biology, cytology and the technology of Raman spectroscopy, designed a single core-multi satellites nanostructure to produce a sensitive surface-enhanced Raman scattering (SERS) signal for imaging detection of glycans on living cells. The work of this thesis is as follow:Among the common monosaccharide blocks that constitute glycan chains, sialic acids (SAs), generally occupy the termini of these glycan chains, and are widely expressed on higher eukaryote cell surface and take part in diverse biological processes. The overexpression of SAs has been proven to correlate with several disease states such as cardiovascular, neurological diseases and cancer. Therefore, the in situ visualization of global SAs on living cells shows great importance for dynamic tracking of altered sialyltransferase expression closely associated with tumor malignancy, elucidation of the SA-regulated biological functions, and developing of novel diagnostic and therapeutic approaches. In this work, a novel Au nanoflower (AuNF) based probe was designed as a bridge to recognize the target cell surface SAs and assemble poly(N-acetylneuraminic acid) (PSA) modified Au nanoparticles (AuNPs), which formed a single core-multi satellites nanostructure for global imaging of SAs on living cells with the sensitized SERS effect.