Studies On Mesoporous Carbon Nanospheres For Doxorubicin Delivery System

Doxorubicin (DOX) is a first-line anticancer drug and commonly applied in the treatments of acute and chronic leukemia and malignant lymphoma, breast cancer and other solid tumors. However, the nonselective destruction to normal cells has greatly limited its application. Construction of delivery system is of great importance in enhancing the efficacy and reducing the side effect of anti-cancer drugs.In order to achieve the aim, a highly effectively transmembrane delivery vehicle based on PEGylated oxidated mesoporous carbon nanospheres (oMCN@PEG) was successfully constructed in a facile strategy in our study. As expected, the oMCN@PEG will be a promising carrier with high drug-loading capacity and effective delivery of DOX molecules into tumour cells, consequently able to kill them in low dose and with significantly reduced side effects.This study included five chapters:(1) The establishment of the methodology of DOX. (2) Preparation and characterization of MCN-based Drug Delivery System for DOX. (3) In vitro antitumour studies of oMCN@DOX@PEG nanoparticles. (4) Pharmacokinetic of oMCN@DOX@PEG. (5) In vivo antitumour. studies of oMCN@DOX@PEG nanoparticles.First, we establish the U.V-Vis method to determine the DOX contents. The results showed that in the range of 0.39～50 μg/mL, DOX concentrations had a good correlation (r2=0.9994). The liner regression equation was A=0.0126c+0.1133. The linearity, precision, recovery, specificity and stability were required.Then we synthesized nanosized MCNs through a low-concentration hydrothermal treatment. In order to improve the hydrophilicity, we intended to introduce hrdrophilic groups onto the surface of MCNs by hydrogen perodider solution. After loading with DOX, the oMCN@DOX were subsequently wrapped up by DSPE-mPEG2000 with hydrophobic segments absorbed on the surface of the oMCNs and hydrophilic parts as the outer layers. The FTIR and’H-NMR spectra were collected to conform that hydrophilic groups and polyethylene glycol were successfully introduced to the MCNs. The morphology and mesostructure of nanoparticles were characterized with TEM. The mesostructured was characterized by the small-angel X-ray scattering (SAXS) and N2 sorbtion analysis. Dynamic light scattering (DLS) experiments were performed to measure the particle size distribution and surface potential. The Raman spectra show a structure of graphite with defects of MCNs. The pH-controlled drug loading and release were also achieved. Our results showed that oMCNs have a high loading capacity of DOX and the amount of DOX releasing from oMCN@DOX@PEG is pH-dependent. In acid medium, about 42% of total DOX was released over 72 h. By contrast, only about 8.7% DOX was released over 120 h.We further investigated the transmembrane delivery and intracellular release process of oMCN@DOX@PEG by fluorescent images. The results imply that oMCN@PEG can be used as transmembrane delivery vehicles for intracellular release of drugs. The biocompatibility of the synthesized oMCN@PEG was further measured by the Cell Counting Kit-8 (CCK-8) assays. No obvious growth inhibition was found which indicated that oMCN@PEG are very biocompatibility in vitro. The cytotoxicity of oMCN@DOX@PEG was both dose- and time-dependent. Results of apoptosis of LLC cells reveal that oMCN@DOX@PEG induce Annexin V+ /PI+ apotosis of LLC cells via dose-dependent manner.Then pharmacokinetic parameters of free DOX, oMCN@DOX and oMCN@DOX@PEG nanoparticles were calculated using non-compartmental model. Results showed that oMCN@DOX@PEG significantly extended plasma half-life (t1/2), reduced clearance (CL) and improved bioavailability of DOX.Finally in order to demostrate the anti-tumour effect of the delivery system in vivo, free DOX, oMCN@DOX@PEG and saline were adminstrated into LLC tumour bearing C57BL/6N mice by injecting via tail vein. Our results showed that oMCN@DOX@PEG tended to accumulate in tumour tissue and lung, exhibiting efficient growth inhibition and anti-metastasis effect.In conclusion, in this study a drug delivery system based on PEGylated oxidated mesoporous carbon nanospheres (oMCN@PEG) have been successfully fabricated in a facile strategy. Such a nano-platform integrates the advantages of well-defined morphology, suitable diameter, excellent hydrophilicity, good biocompatibility and high payload of anticancer drugs. The drug system (oMCN@DOX@PEG) exhibits excellent stability under neutral pH conditions, but dramatically releases DOX at reduced pH conditions. This nanoparticle could efficiently penetrate the membrane of tumour cells and subsequently release drugs in the acidic microenvironment of intracellular lysosomes and endosomes. oMCN@DOX@PEG could efficiently inhibit the growth of cancer cells both in vitro and in vivo. Specially, oMCN@DOX@PEG exihibited significantly antimetastasis effect in advanced maligant cancer which improve the survival time of the tumor-bearing mice.