| The tumor microenvironment plays a vital role in the initiation,maintenance and metastasis of tumorigenesis.In the process of tumor progression,on the one hand,the cells proliferate rapidly,the structure of the new blood vessels is abnormal,and the oxygen content is reduced,which causes the tumor cells to change the metabolic mode,activate drug resistance genes,and inhibit the antitumor effect of the drug.On the other hand,the tumor external matrix composed of fibroblasts,immune cells,and endothelial cells together forms the tumor tissue barrier,which prevents the drug from entering the deep layer of the tumor.This uneven distribution of the drug in the tumor is important for tumor metastasis and drug resistance.the reason.Nano-drug delivery system plays an important role in tumor treatment due to its synergistic and attenuating characteristics.The complex tumor microenvironment seriously hinders the effectiveness of the nano-drug delivery system.After in-depth investigation,it was found that after the nano-carriers enter the tumor through the tumor blood vessels,they will be trapped by the dense tissue barrier around the blood vessels and difficult to enter the tumor.At the same time,the hypoxic microenvironment in the tumor will change the metabolism of tumor cells,reduce the uptake of nano drug carriers and increase the efflux effect,making it difficult for drugs to enter the cell to play a role.The effect of these physiological and pathological barriers on tumor treatment The impact is significant.In order to overcome the problem of hypoxia and drug resistance of tumors,the design of multifunctional nanocarriers for the improvement of hypoxia in tumors and the promotion of drug efficacy has become a new research hotspot.Nano-drug carriers entering deep into the tumor need to have good diffusion and penetration capabilities,while improving internal hypoxia to promote cell uptake of the drug.The bionics of the principles of structure and function of graduate students has broad application prospects in the design of nano drug delivery systems.As the most common type of red blood cells in mammals,red blood cells are responsible for transporting oxygen tobody tissues.They release oxygen quickly in areas of low oxygen,but are relatively stable in areas of high oxygen.Inspired by the discoid structure of red blood cells and the function of oxygen carriers,and reviewing a large amount of literature,we designed a bionic nano red blood cell drug carrier.The red cell membrane-coated disc nano-carriers penetrated deeply in tumors and quickly released oxygen in a hypoxic environment.It shows unique advantages in reducing hypoxia and increasing the antitumor effect of drugs.In the second chapter of this paper,a series of physical and chemical characterizations of disc-shaped hollow silica nanocarriers(PDRs)wrapped around red blood cell membranes were performed.First,disc-shaped silica nanoparticles with hollow structures were synthesized by the template method.Perfluorohexane(PFH)and the model drug doxorubicin(DOX)were loaded into the interior of the hollow disc-shaped nanoparticles through physical adsorption.The erythrocyte membrane was wrapped on a disk-shaped nanocarrier under the ice bath probe ultrasound condition to prepare PDRs.Its particle size is 131.7±8.6 nm,zeta potential is-16.8±3.4 m V,and it is observed as a disk with a hollow structure under a frozen transmission electron microscope.The red blood cell membrane is tightly wrapped on the surface of the silica support.The protein on the surface of the red blood cell membrane remained intact,indicating that there was no loss of protein during the preparation process.Chapter 3 focuses on the performance of PDRs in vitro,exploring the penetrating ability of PDRs in vitro,and the oxygen release behavior of PDRs after PFH loading.Through in vitro observation with multi-particle tracking technology,it was found that PDRs showed the fastest diffusion ability in simulated tumor stroma,and the range of motion was better than that of the spherical control group.The mean mean square displacement(MSD)value was calculated.The diffusion speed of PDRs was4.2 times that of PSRs,which indicates that the disc-like shape promotes the motion penetrating ability in the nano-particle network structure.The log effective diffusivity(Log Deff)distribution further confirms the motion penetrability of PDRs.The oxygen content of PDRs was found to be 3.1 and 4.8 times that of the PSRs and PRRs groups,respectively.More importantly,PDR is rapidly released at low oxygen partial pressures and slowly released at high oxygen partial pressures.Cell experiments found that PDRs improved the cell’s hypoxia state and promoted cell uptake.The results showed that PDRs reduced the cell’s hypoxia by 65.3%,and the uptake rate was also 4.3 times higher than that of spherical nanocarriers.We also cultured 3D tumor spheroids using a mixture of Bx PC-3 and HPSC cell lines rich in ECM structure.After 2 hours of incubation,the penetration depth of PDRs reached about 90 μm,while the penetration depth of other nanocarriers was less than 20 μm,which further demonstrated the excellent penetration and diffusion ability of PDRs.The investigation of the safety of nanoparticles found that nanocarriers in the concentration range of 0.1-5 mg did not produce significant cytotoxicity to cells,which indicated that PDRs had good biological safety,and it was found that the way of uptake of PDRs by cells was linked The albumin-mediated endocytosis pathway is predominant,supplemented by the actin-mediated cellular uptake pathway.In Chapter 4,we explore the ability of nanocarriers to penetrate tumor mesenchyme,improve hypoxia,and pharmacodynamics in animals.It was found that PDRs can penetrate the tumor blood vessel wall and gradually penetrate into the tumor.The depth of penetration of the tumor blood vessels reaches 500 μm and into the depth of solid tumors,while other groups have only 100–200 μm.On the other hand,after the injection of PDRs,the oxygenated hemoglobin signal in the tumor increased significantly under photoacoustic imaging,indicating that PDR not only effectively penetrates into the tumor,but also rapidly releases oxygen in the hypoxic area.Hypoxic immunofluorescence staining showed that the hypoxic positive area in the tumor decreased from 72.5% to 5.2%,and the cell cycle change in the tumor was significantly promoted.Using subcutaneous tumor nude mice as a model,PDRs-DOX showed excellent tumor suppressive effect,and the average tumor weight was lowerthan that of the control group.The results of H & E staining showed that the PDRs-DOX group had a significant killing effect on tumors and no obvious damage to organs.In this paper,our synthetic PDRs can achieve hypoxia improvement in deep tumor areas and significantly improve the therapeutic effect of chemical drugs.Using natural red blood cells as a biomimetic template,firstly PDRs synthesized on the surface coated with red blood cell membranes retain the antigens and functions of red blood cells,which can effectively avoid rapid clearance in the blood circulation and extend the half-life of the carrier in vivo.More importantly,the unique disc-shaped structure consistent with red blood cells has better exercise ability,which allows it to efficiently penetrate into the hypoxic area deep inside the tumor in the tumor matrix;on the other hand,the disc has a larger The specific surface area can quickly release oxygen in the hypoxic area,and effective hypoxia improvement increases the sensitivity of tumor cells to the drug and enhances the killing effect of the drug.In this work,the erythrocyte-like nano-drug carrier developed from the perspective of biomimetics has achieved deep hypoxia improvement and enhanced anti-tumor effect of the drug,providing guidance for the further design of anti-tumor drug carrier strategies. |
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