Preparation Of Folic Acid-Conjugated Gold Nanoclusters And Its Application Of Bioimaging

In recent years, with the development of the social economy and technology, people's living environment and habits are changed, and the tumor has become the primary problem to human's health. Faced with this harsh reality, it is important to propose an effective fluorescent probes which can accurately locate the tumor's location and size, or effectively release the drug into the cell. Then the cure rate of the tumor will be increased and the treatment can be achieved without the hazard of surgery. In addition, a highly efficient imaging method which can make living cells and tissues visualize, and reduce the death rate of cancer is also of great significance. Fluorescence imaging is one of the most advanced technology in recent years which can achieve visualization image of non-invasive and non-destructive testing in vivo. It has been proved to be superior to the conventional chemotherapy, and has got more and more attention in the field of biological medicine prediction, detection, diagnosis and treatment of other major diseases.In this paper, firstly, we introduced a variety of luminescent materials containing organic fluorescent dyes, semiconductor quantum dots, nano-materials and precious metals, and their preparation programs. By comparing the light-emitting materials, we selected gold nanoclusters(AuNCs). AuNCs has been extensively studied due to its ultra-small size, good colloidal stability and biocompatibility, simple synthesis and other outstanding features. Then, we introduced the AuNCs briefly and recommended the existing methods of preparation of AuNCs. And we also had a brief introduction of the prospect of AuNCs.Then, we synthesize gold nanoclusters(BSA-AuNCs) with bovine serum albumin(BSA) as a template, and listed its characterization data. In order to further improve the targeting characterization, we opted for a functional group for the surface modification of gold nanoclusters. Because folate receptors exist in the surface of many types of cancer cells, folic acid(FA) is an important cancer-specific labeled ligand. Folic acid is conjugated by covalent derivative of ?-carboxy of folic acid, and can maintain a high affinity of folate receptor. FA can be subjected into cells by the function of folate receptor-mediated endocytosis, and by moving a number of organelles the materials could be released into cytoplasm. Later, unconnected folate receptor may be recycled to the cell surface to transport more materials combined with folate ligand. Hence folate receptor could be used as targeting goals of folic acid compounds and accomplish the imaging and treatment of tumor with folic acid receptor overexpression. Therefore, we choose the folic acid as a functional group. We modified gold nanoclusters with functional folic acid(AuNCs-FA) ligand, and the characterization was completed by TEM, UV, fluorescence, FTIR and other methods. Finally, in order to investigate the biological imaging and tumor targeting ability of BSA-AuNCs and AuNCs-FA, we tested its cytotoxicity, cell uptake and in vivo imaging abilities. The results showed the low toxicity of BSA-AuNCs and AuNCs-FA and the good application of AuNCs-FA in terms of tumor targeting.