Magnetofluorescent Nanoprobes Construction And Application In Human Lung Cancer Theragnosis

As a malignant tumor with the highest morbidityandmortality in China, lung cancer has been given rising attentions along with environmental deterioration. Development of comprehensive and reliabletechnique for early diagnosis is the key to conquer lung cancer. Noninvasive molecular imaging with multimodality has been considered as an effective tool for early diagnosis, due to the fact that no single imaging modality possesses all ideal traits of being quantitative and real-time, and provides both high resolution and sensitivity. In this dissertation, we synthesized graphene quantum dots (GQDs) and mesoporous silica nanosperes (MSNs), and used them as vehicles to develop a series of multi-functional probes which integrated the advantages of high resolution magnetic resonance imaging (MRI) with high sensitive fluorescent imaging (FI). The fabricated probes showed the ability to selectively image human lung cancer A549 in vitro and in vivo, as well as effectively transport anti-cancer drugs to target cells.The main contents are shown as follows:1. The principle of magnetic resonance imaging and fluorescent iamging were outlined. The development graphene and mesoporous silica spheres based multi-model imaging was introduced. On the basis of the above review we put forward our design ideas and research topics.2. Graphene quantum dots (GQDs) with controllable fluorescent emission were prepared by two steps of reactions:carbon based materials were oxidized in acid, and then cut into small pieces of GQDs by microwave-assistedhydrothermal method. The prepared GQDs werewater dispersable and showed no apparent in vitro toxicity. The quantum yield of highly green and yellow emission GQDs has reached to 48%. GQDs with controllable size were further delivered into cancer cells and used as fluorescent probes in FI.3. Using PEG-diamine as a bridge, a multi-model probe was fabricated by linking MRI contrast agentGd-DOTA and targeting molecularhyaluronic acid (HA) to the synthesized GQDs through amide condensation reactions. The fabricated probe could selectively accumulate in lung cancer A549 cellsby a receptor-mediatedprocess, and be used as vehicles to deliver anti-cancer drug Adriamycin. Because of the high longitudinal relaxation rate (75.6 mM-1·s-1) and auto-fluorescence from GQDs, this probe could light A549 cells in MRI and FI. Moreover, anti-cancer drug was released and reacted with nucleic acid, induced the apoptosis of cancer cells. The nano-construct combines the advantages of label-free fluorescence, high sensitivity, biocompatibility, and in vivostability. The results demonstrate great potential of such multifunctional nano-constructs for real-time dual-modality imaging duringtargeted therapy.4. Two types of water-insoluble texphyrins (TP), gadolinium-texphyrins (Gd-TP) and lutetium-texphyrins (Lu-TP), were synthesized and loaded onto RGD-functionalized graphene quantum dots via π-π stacking. The obtained complex could be used as a MRI-FI multi-model probe for photodynamic therapy (PDT). Compared with conventional PDT, our method demonstrated better therapy efficiency for deeper tissue, because a laser with longer wavelength was applied to active the photosensitizerLu-TP (λ= 765 nm). Furthermore, reactive oxygen species resultedfrom the reaction between redox active drug Gd-TP and cellular reducing metabolites led cancer cells more impressionable to photodynamic therapy (PDT) from Lu-TP.Our results showed 3 min irradiation with low power density (50 mW/cm2) could induce apoptosis and dead of human lung cancer AS49 cells. Cancer cells were lighted in CLSM because the overlap of fluorescence from GQDs and drugs resulted in strong fluorescence.The longitudinal relaxation rate of the designed probe was determined to be 8.51 mM/s, which is almost two times larger than commercial used MRI contrast agent Gd-DTPA. In vivo results showed the designed probe couldgenerate MRI contrast of tumor tissue. All results demonstrate great potential of such multi-functional probe for MRI-FI guided PDT.5. A pH-triggered molecular probe was desinged and fabricated for 19F magnetic resonace imaging (MRI) and fluorescent imaging of hunman lung cancer A549 cells.19F contrast agent was stuffed in FITC-doped mesoporous silica nanosperes (FMSNs) by anchoring gold nanoperticles (AuNPs) on the pore outlet of FMSNs via an acid-cleavable hydrazone linkage. After selective endocytosis, the acidic surroundings in A549 cells induced the cleavable of hydrazone linkage, resulting in the opening of AuNPs gate. Thus,19F contrast agent was released and A549 cells were lighted in 19F MRI. Meanwhile, fluorescence from the doped FICT ensured the successful and selective delivery of the designed probe to A549 cells. Our comprehensive experiments also demonstrated that the biocompatibility, durability, high internalizing efficiency and pore architecture justify the Au-FMSNs an ideal high-sensitive and high-specific vector of 19F MRI and FI for human lung cancer A549 cells.