Functionalized Anti-phagocytic Polydopamine Nanoparticles For Enhanced Tumor Imaging And Treatment Research

Purpose:Malignant tumors are a serious threat to human health,and the morbidity and mortality rates are increasing year by year.Its precise diagnosis and controllable treatment have become an urgent problem in clinical diagnosis and treatment.However,there are still many shortcomings in the current clinical diagnosis and treatment process,diagnostic sensitivity,and treatment effectiveness of cancer.Based on this,this experiment constructs a functionalized anti-phagocytic polydopamine nanoparticles that integrates immune escape,efficient imaging and chemotherapy,which expected to be applied to the precise diagnosis and treatment of malignant tumors,and to realize real-time monitoring of the effect of tumor chemotherapy under imaging guidance.Methods:In this experiment,the melanin-like polymer polydopamine was used as the template,and the magnetic resonance imaging component(Gd³⁺)and CD47 functional peptide SP were multifunctionally assembled,and loaded with chemotherapy drugs（DOX）,to prepare functionalized anti-phagocytic dopamine nanoparticles.Characterize it to clarify the in vitro imaging performance,drug loading and controlled release capabilities of the nano-diagnostic and therapeutic agent.Through CCK-8 test,in vitro anti-tumor cell activity test and cell uptake test to explore its cytotoxicity,anti-macrophage phagocytosis and tumor cell inhibitory effects.Establish subcutaneous transplantation tumor and lung metastases models.Use the MR imaging system to dynamically observe the enrichment of the nanoparticles in the tumor site,liver and spleen at the in vivo level,as well as the tumor treatment effect,to verify the actual efficacy of the nanoparticles in tumor MR imaging and chemotherapy.And monitor the body weight,blood routine and biochemical,metabolism quantitative analysis of tumor-bearing mice,and histological analysis,to explore the in vivo biodistribution,biosafety and biocompatibility of functionalized anti-phagocytic polydopamine nanoparticles.Results:（1）In this experiment,functionalized anti-phagocytic polydopamine nanoparticles（SP-DPG-DOX NPs）were successfully synthesized.The characterization results show that the particle size is uniform,the structure is stable,the surface potential is appropriate,and the dispersion is good.The relaxation rate test results show that SP-DPG-DOX NPs have a higher longitudinal relaxation time(r₁=16.5704 m M^-1·s^-1,r₂=15.79567 m M^-1·s^-1,r₂/r₁=0.9532),so it can be used for efficient MR T1 imaging.The results of drug loading experiments showed that the drug loading rate and encapsulation rate of doxorubicin（DOX）in SP-DPG-DOX NPs were 20.36%and 93.15%,respectively.The cumulative DOX release of SP-DPG-DOX NPs in the simulated tumor tissue environment in vitro was significantly higher than that in the simulated normal tissue environment,indicating that SP-DPG-DOX NPs have superior drug loading and controllable sustained release capabilities.（2）In vitro cytotoxicity experiments were performed on H22（mouse liver cancer cells）,RAW264.7（mouse mononuclear macrophage leukemia cells）,hep G2（human liver cancer cells）and HUVEC（human umbilical vein endothelial cells）by CCK-8 method confirmed that the functionalized anti-phagocytic polydopamine nanoparticles have low cytotoxicity.The results of the drug IC50 experiment showed that the median lethal concentration（IC50）of SP-DPG-DOX NPs was 4.67μg/m L,which was significantly lower than that of free DOX（8.29μg/m L）,proving that functionalized antiphagocytic polydopamine nanoparticles have a good anti-tumor effect in vitro.The uptake ability of SP-DPG-DOX NPs in RAW264.7 and H22 cell lines was observed by laser confocal scanning microscope,no red fluorescence representing DOX was observed in RAW264.7,confirming the important role of polypeptide SP in antiphagocytosis.（3）Successfully constructed mouse subcutaneous transplanted tumor and metastatic tumor models.The results of in vivo dynamic MR imaging verify the ability of SP-DPG NPs to image tumors.The T1 signal intensity at the tumor site increased significantly over time,and the signal reached its peak at 12 hours,and could continue to increase for 24 hours.The imaging effect was significantly better than that of nanoparticles without SP modification.The results of dynamic signal intensity of liver and spleen showed that the signal intensity of SP-DPG-DOX NPs in liver and spleen was lower than that of DPG-DOX NPs,which proved the inhibitory effect of polypeptide SP in the process of RES system clearance.The results of in vivo dynamic MR imaging of the lung metastasis model showed that the T1 signal intensity of the lung tumor reached the highest after 6 hours of drug application,which can clearly image the lung metastasis.（4）The relative tumor volume and MR imaging results of the experimental group（SP-DPG-DOX NPs）,experimental control group（DPG-DOX NPs group,DOX group）and blank control group（PBS）before and after subcutaneous transplantation tumor treatment,and the observation of the solid tumor images of each group of tumor-bearing mice after the treatment showed that the tumor volume of the SP-DPG-DOX NPs group was the smallest,indicating that the SP-DPG-DOX NPs has the best tumor suppression effect.（5）Quantitative analysis of in vivo metabolism and pharmacokinetic studies in tumor-bearing mice confirmed the in vivo distribution of functionalized anti-phagocytic polydopamine nanoparticles and the ability of blood circulation.Through mouse weight monitoring,blood routine and biochemical tests,and histopathological sections,it was confirmed that the functionalized anti-phagocytic polydopamine nanoparticles have good biosafety and biocompatibility.Conclusion:In this experiment,functionalized anti-phagocytic polydopamine nanoparticles（SP-DPG-DOX NPs）were successfully constructed,which not only have anti-phagocytic effect,but also have high MR T1 imaging ability and good tumor inhibition effect,providing an important scientific basis for the efficient diagnosis and treatment of malignant tumors,and a new method for real-time monitoring of tumor chemotherapy effects.