Appilication Of Quantum Dots In Diagnosis, Treatment And Prevention Of Early Gastric Cancer

Gastric cancer(GC) is the fourth most common cancer and the second leading cause of cancer-related death worldwide. In China, the average death number due to GC is about 229 thousand each year, and early diagnosis of GC is less than 10%. It has been proved that, if the strategies of early diagnosis and intervention can be applied to GC, the poor prognosis and 5-year survival rates can be greatly improved.In order to meet the increasing requirements of life and health, modern medicine requires the establishment of new diagnostic methods with high sensitivity and high specificity for GC. However, the traditional organic dyes often failed to label tissues and cells for its low quantum yield, broad emission spectrum, photobleaching and other shortcomings. Compared with traditional organic reagents, quantum dots(QDs) have many inherent properties and have shown the promising potentials in many biological fields, including biochemistry, cell biology, molecular biology, analytical chemistry and other areas of research. In the last decade, with the developments of QDs surface chemistry and the discovery of bio-specific targets, QDs have been widely used in cell labeling, single molecule tracking, and cell tracing, visualized diagnosis and targeted therapy in vivo.In this paper, we chose the functionalized QDs as the research object, intensively investigated the spectral controllable synthesis, surface chemistry, biocompatibility, and stability of QDs. Furthermore, the primary applications of QDs in highly sensitive and specific labeling of GC cells in vitro, in vivo GC imaging with high resolution, the dentritic cell based GC vaccine in active targeted immunotherapy and immunoprophylaxis were investigated systematically, and a series of results were achieved, as follows:1. Firstly, we synthesized the CdSe/ZnS core-shell QDs in organic solvents at high temperature, designed and prepared amphiphilic polymer with alkyl dentate coordination bonds and carboxyl groups. Then, the amphiphilic polymer was used to transfer QDs from orgainc phase to inorganic phase by surface group interaction. Finally, we evaluated the characteristics of the phase transferred QDs, including the surface charge, carboxyl content, hydrated diameter, ionic and pH stability, cytotoxicity in vitro, etc. These data are very critical parameters of QDs in biomolecule labeling, cell imaging and tracing in vivo.2. We selected the aforementioned water-soluble CdSe/ZnS QDs as the standard material, and synthesized the BRCAA1-QDs and Her2-QDs fluorescent probes by chemical conjugation. The results confirmed that these probes can be used to label the GC cell of MGC-803 in vitro sensitively and specifically. In addition, the MGC-803 cells labeled with the 657 nm QDs can be effectively traced in GC model mice by in vivo imaging system. These results indicated that the QDs probes prepared in this study can be introduced to label the GC cells in single molecule level, and can be imaged with high resolution and sensitivity in vivo, showing great potential in diagnosis of early GC.3. We isolated the mononuclear cells from peripheral blood lymphocytes(PBL) of healthy human donors and induced the allogeneic dentritic cells(DCs) by cytokines in vitro. Based on the allogeneic DCs and MGC-803 cells, we prepared the fused GC vaccine cells(FCs) by polyethylene glycol(PEG) mediated fusion. Meanwhile, we synthesized CuInS2/ZnS QDs with emission wavelength in near infrared region(NIR), and functionalized the NIR-QDs with DSPE-PEG. In order to evaluate the effectiveness of immunotherapy and immunoprophylaxis of FCs, we vaccinated the C57BL/6 mouse with NIR-QDs probes labeled FCs and monitored the real-time distribution of the labeled cell in vivo. The results showed that the prepared FCs strongly manifested tumor antigen-specific CTL responses to a wide range of GC cell lines. Additionally, the immune memory research revealed that immunized with appropriate antigen carrier and effector cells(FC+CIKs) in tumor bearing mice can triggered and maintained the corresponding immune memory for a long period(at least 3 months). Efficacy comparison tests in tumor-free and tumor-bear mice demonstrated that the FCs vaccination have the appreciable effects on the occurrence, development, metastasis and prognosis of GC. Our results provide a new insight into the immunobiology of tumor-associated vaccines and offer the proof-of-principle of the application of DCs based vaccine in GC immunotherapy.4. In this part, we labeled induced pluripotent stem cells(iPSCs) with synthesized fluorescent magnetic nanopaticles(FMNPs) and selected the GC as the target in vivo. The interaction of FMNPs-labeled iPSCs and GC were investigated by various methods, including in vivo fluorescence and magnetic resonance imaging(MRI), and the hyperthermal effect coupled with the external magnetic field. The results confirmed that the FMNPs-labeled iPSCs can be an ideal biological agent in GC imaging and targeted hyperthermal treatment. These results are expected to be extended to clinical diagnostic and therapeutic applications of other tumors.