Construction Of Nanomedicine Based On Carbon Dots And Its Application In Tumor Therapy

The effective aggregation and deep tissue penetration of drugs in tumor sites are the key to the effect of tumor treatment.Poor drug resistance and side effects of chemotherapy will eventually lead to drug resistance in vivo.Thus,the nano drug delivery system developed in recent years had the effect of enhancing penetration and retention.It could passively target the tumor site,or actively target the tumor blood vessels and cells through the targeted modification of materials,which promoted the enrichment of drugs in the tumor site to a certain extent.However,both free drugs and nano drugs were still difficult to diffuse or penetrate in the tumor.The drug concentration in the tumor tissue was too low to completely eradicate all tumor cells,which was very easy to relapse and metastasis.Therefore,promoting the deep penetration of nano drugs in the tumor site was the key problem to be solved to improve the effect of tumor treatment.It is well known that small size nanoparticles had strong tumor tissue permeability due to their fast diffusion rate.As a kind of ultra-small particle size nanoparticles,Carbon dots（CDs）not only had good biocompatibility,stable structure and easy surface modification,but also had good fluorescence imaging and photothermal conversion ability to effectively kill tumorcells through photothermal therapy（PTT）.In order to explore the tissue permeability of CDs,three kinds of ultra-small size nanomedicine based on CDs were designed and synthesized,and their killing effect and mechanism on tumor irradiated by the second biological near-infrared（NIR II）were deeply studied.（1）The penetration efficiency of near-infrared light is an important factor affecting the PTT of tumors in vivo.In order to explore the tumor tissue permeability of CDs,nitrogen and sulfur co-doped CDs with NIR II PTT capacity were synthesized in one step by solvothermal method.The high tissue permeability of NIR II and the deep tissue permeability of CDs were used to realize the PTT of tumors.Based on the characterization of the physical and chemical properties of CDs,the fluorescence and photoacoustic imaging abilities of CDs in vivo and in vitro were evaluated.Then,the permeability of CDs in vivo and in vitro was evaluated in 3D tumor spheres and tumor tissues.Furthermore,the killing effects of NIR I and NIR II on tumors were evaluated at the level of cells and 3D tumor spheres.Besides,the ability of tumor PTT under NIR II irradiation was investigated in tumor tissues in vivo.The killing effects of NIR I and NIR II on tumors were also evaluated at the level of cells and 3D tumor spheres.Finally,the ability of tumor PTT under NIR II irradiation was studied in tumor tissues in vivo.The results showed that the diameter of CDs was 3-5 nm,with fluorescence in visible light region and photoacoustic imaging ability under 808 nm excitation in vivo and in vitro.The enrichment of CDs could be mostly accumulated in the tumor tissue at 8 h after the injection of CDs into the tail vein of tumor bearing mice.Moreover,after injection of CDs into 3D tumor ball and paracanceroued injection of 2 mg/m L of PCD into MCF-7 tumor-bearing mice for several hours,,CDs could penetrate into tumor ball and tumor tissue with the extension of time.Under the irradiation of NIR II 1064 nm laser,the photothermal conversion efficiency could reach 77.25%,and the photothermal stability kept good.Combined with the high tissue permeability of CDs,the efficient tumor killing effect in vivo and in vitro would be achieved.（2）Near infrared photothermal could not only kill tumor cells efficiently,but also promote bone formation of osteoblasts in vitro and in vivo when it is 3-5℃higher than normal body temperature.In order to explore the effect of PTT on tumor cells and bone cells in the vicious spiral microenvironment of cancer bone metastasis,a carbon targeting nano drug（CDs-ZOL）with bone targeting and photothermal effect under NIR II laser irradiation was designed and synthesized.The effect of photothermal therapy on bone cancer cells in the treatment of breast cancer bone metastases was studied.Based on the characterization of CDs-ZOL,the effects of CDs-ZOL on NIR activity,invasion and migration of breast cancer cells under NIR II irradiation were studied at the cell level.Then,the effect of CDs-ZOL on the bone microenvironment of the vicious cycle of tumor cells-osteoblast-osteoclasts under NIR II laser irradiation was investigated at the sub-tissue level of 3D tumor spheres co-cultured with rat skull slices.Finally,the nude mouse model of breast cancer bone metastases was established to further evaluate the therapeutic effect of CDs-ZOL on bone metastases in nude mice under NIR II irradiation.The results showed that the particle size of CDs-ZOL was 8 nm and could specifically target bone tissue.Under 1064 nm laser irradiation,CDs-ZOL could efficiently kill tumor cells in vitro and inhibited the formation of osteoclast like cells and bone resorption.Moreover,CDs-ZOL could also promote the proliferation,differentiation and mineralization of osteoblasts and bone marrow mesenchymal stem.At the sub-tissue level of tumor cell,osteoblast and osteoclast co-culture,the bone resorption of CDs-ZOL on bone slices was weakened and the bone formation was enhanced under NIR II irradiation.At the same time,the tumor tissues of nude mice injected with CDs-ZOL after treatment with NIR II for 4 weeks were significantly reduced,and no obvious osteolysis was observed,thus achieving effective treatment for breast cancer bone metastases.（3）Near infrared photothermal and high H₂O₂ level of tumor tissue provide more suitable reaction conditions and sufficient reaction substrates for single atom catalytic chemokinetic therapy（CDT）.In order to further explore the permeability of CDs in large tumor tissues,the Fe monatomic nanoenzyme based on CDs（CDs-Fe）was synthesized in one step by pre-coordination solvothermal method.The killing effect of ultra-small CDs-Fe on large tumor under the high tissue penetration of NIR II,PTT and CDT were studied.Based on the characterization of physical and chemical properties of CDs-Fe,the ability of CDs-Fe to catalyze H₂O₂ to produce hydroxyl radicals（·OH）in vitro and its influencing factors were firstly studied.Then the tumor permeability of CDs-Fe was detected on 200 mm³ tumor tissue.Moreover,we investigated the effects of CDs-Fe with NIR II on MDA-MB-231activity,reactive oxygen species production,intracellular localization,invasion and migration in breast cancer cells at cellular level.Finally,the therapeutic effect of NIR II PTT combined with chemokinetic therapy on large volume tumors was evaluated in nude mouse model.The results showed that the particle size of CDs-Fe was 8 nm.Spherical aberration electron microscope and synchrotron radiation confirmed that Fe in CDs-Fe existedin the form of atomic dispersion in Fe-N₄ configuration.Within a certain range,with lower p H value,higher temperature and H₂O₂ concentration,CDs-Fe had stronger catalytic activity and more（·OH）were produced.After injecting CDs-Fe into the tumor tissue with the size of 200 mm³,with the extension of time,CDs-Fe could penetrate the whole tumor tissue after 8 hours and remain unchanged for 24 h.Under 1064 nm laser irradiation,CDs-Fe could produce a large number of reactive oxygen species in MDA-MB-231 cells,followed by inducing apoptosis and inhibiting cell invasion and migration.At the same time,the tumor tissue of nude mice injected with CDs-Fe through tail vein decreased significantly after treatment under NIR II irradiation,and the survival time of nude mice was significantly prolonged.Compared with PTT and CDT alone,the combination of PTT and CDT mediated by NIR II could achieve efficient treatment of large-volume tumors.These results provided basic research data for the design and development of ultra-small particle nano drugs based on CDs for the treatment of tumors and tumor bone metastasis.