Construction Of Magnetic Carbon Quantum Dots Probe And Its Application In Diagnosis And Treatment Of Tumors

The early diagnosis of cancer has attracted people’s attention. Molecular imaging detection is an important tool for the early diagnosis of cancer, which could provide more accurate and complete information for tumor diagnosis so as to achieve the purpose of early diagnosis and early treatment. Based on the multifunctional nanoparticle molecular imaging techniques have been achieved some progress in terms of sensitivity and specificity for tumor detection, such as quantum dots, fluorescence dye molecules and magnetic nanoparticles has been applied to the in vivo fluorescence imaging and magnetic resonance imaging. However, these probes are toxic and have poor stability and poor sensitivity, which greatly limit their application in vivo. Therefore, it is an urgent problem to construct a kind of multi-functional target probe which is simple, bio- friendly and imaging sensitive.Based on this, this paper used gadolinium chloride(GdCl3) with gadolinium Gd3+ ions doped into carbon CDs by microwave assisted method and the surface of CDs were modified with amino by PEI. We obtain the high quantum yield of gadolinium doped carbon quantum dots Gd-CDs, which emit bright green light under visible light irradiation and has high fluorescence intensity and stability of optical and well biological compatibility. Natural apoferritin(AFn) nanocages, an excellent drug delivery carrier, have its hollow structure with their pH-dependent unfolding–refolding process at pH 2.0 and 7.4. The chemotherapeutic drug DOX can be highly effective encapsulated into AFn cavity. Gd-CDs connected AFn package DOX as a fluorescence and magnetic probe. Folic acid was acted as a tumor target with the catalysts of EDC and NHS,which obtained the ability of tumor target. Gd-CDs/AFn(DOX)/FA specificly targeting the tumor cells and Tumor lesion tissue with folic acid mediated. Realising In vivo and in vitro dual mode(fluorescence / nuclear magnetic resonance) imaging and cell tracking for the early diagnosis and treatment of tumors.X ray photoelectron spectroscopy(XPS) technique was used to analyze the obtained Gd-CDs elements. The track changes of Gd elements show that Gd ion was doped into CDs.The particle size of Gd-CDs was about 6 nm observed by transmission electron microscope. The polydispersity index of Gd-CDs was 0.201 and the potential of Zeta was about 9.05 mV, which indicates that the surface of Gd-CDs was modified with amino. Fluorescence emission spectrum showed Gd-CDs have obviously up and down conversion luminescence properties. Gd-CDs/AFn(DOX)/FA was characterized by different methods. The average particle size of Gd-CDs/AFn(DOX)/FA was about 112 ± 3.5 nm and the potential was about-23.7 ± 2.1 mV. The results of encapsulation efficiency showed that encapsulation efficiency in ferritin cage was 86.6%.The release of DOX were determined by dialysis method respectively in pH 5.0 and pH 7.4 in vitro. The analysis results show that we can can control the release of composites by adjusting the pH value. Drug release rate was 79.2% in the acidic environment of pH5.0. Gd-CDs/AFn(DOX) /FA with gadolinium ion with the imaging capabilities of T1, MRI in vitro experiments indicated that Gd-CDs/AFn(DOX) /FA had obvious concentration dependence and presented whitening effect with the increase of concentration in the T1 field.Based on MCF-7 cell lines as the model cells in vitro, we study the cell cytotoxicity and its influencing factors of Gd-CDs/AFn(DOX) /FA. The cell cytotoxicity of Gd-CDs and Gd-CDs/AFn were studied by MTT. Results showed the cell survival rate of Gd-CDs and Gd-CDs/AFn were both above 85%. Gd-CDs/AFn have more cell survival rate compared withGd-CDs. Cell uptake experiments showed Gd-CDs could better markers load cell uptake of drug delivery system by observing Gd-CDs fluorescence.Gd-CDs/AFn. Gd-CDs/AFn(DOX) /FA had higher cellular uptake compared with Gd-CDs/AFn(DOX),which indicated drug delivery system Gd-CDs/AFn(DOX)/FA could quickly access to tumor cells. In vitro antitumor experiments showed that Gd-CDs/AFn(DOX)/FA could be concentrate on MCF-7 cells and penetrated cell membrane effectively, which can carry more DOX into cells. In acid environent, ferritin cage gradually dissociation and thus slowly release DOX resulting in apoptosis of MCF-7 cells, which ultimately inhibit the growth and proliferation of MCF-7 cells.The mouse ascites tumor cell line S180 was used as tumor mice model. Systematic studies in vivo showed that Gd-CDs/AFn(DOX) /FA have lower toxicity and trapped in the tumor tissue in the FA mediated. As for the acidic environment of tumor tissue, Gd-CDs/AFn(DOX)/FA released largely DOX from dissociated apoferritin nanocages, which a large number of drugs are more likely to stay at the tumor site. It induced apoptosis of tumor cells by means of inhibition of nucleic acid synthesed. Study on pharmacokinetics showed that Gd-CDs/AFn(DOX)/FA could prolong the residence time of DOX in vivo circulation. Drug distribution in various tissues showed that with folate targeted to the Gd-CDs/AFn(DOX) /FA drug more gathered at the site of the tumor, the results further proved that the constructed in the study of nano drug delivery in vivo magnetic targeting ability. And with folate targeted Gd-CDs/AFn(DOX) /FA make the drug more gathered in the tumor site, the results further prove that the target ability of nanoparticles. In addition, MRI in vivo experiments showed that the T1 signal intensity in tumor mice enhanced after injection of Gd-CDs/AFn(DOX) /FA, which indicated Gd-CDs/AFn(DOX) /FA can acted as contrast agents for magnetic resonance imaging.