Biomimetic Tumor Microenvironment-responsive Drug- Loaded Nanoparticles For Tumor Precise Theranostics

Malignant tumors,as one of the most vicious killers in the world,it has seriously threatened the physical and mental health of human beings.Tumor microenvironment?TME?responsive nanocarriers integrate tumor targeting,diagnosis,and treatment,have overcome poor specificity,large side effects and incomplete treatment of traditional treatment methods?surgery,chemotherapy,and radiotherapy?,showing broad prospects for humans'vision of overcoming tumors.However,nanoscale drug-delivery systems?DDSs?prepared by conventional methods are unable to precisely mimic the complex interfaces present in nature,and ultimately cannot completely vitiate recognition as a foreign body and the subsequent immune response,which inevitably greatly reduced the therapeutic efficacy.In recent years,biomimetic approaches,especially cell membranes camouflaged DDSs,can effectively avoid being captured by the mononuclear phagocytic system and reticuloendothelial system due to their excellent biocompatibility and low immunogenicity,enabling the DDSs to circulate in the body for a long time and thus passive accumulate in tumor sites based on enhanced penetration and retention?EPR?effects.In addition,the chemotactic properties of some functional cells,for example,activated platelets can specifically adhere to damaged blood vessels and cancer cell membrane proteins;the chemokines secreted in tumor inflammatory sites can recruit leukocyte.By using these cell membranes to cloak DDSs have potential for active attacking lesion sites.Therefore,it is expected to use biomimetic approach to cloak TME-responsive drug carriers to construct intelligent theranostic nanoplatform for enhanced antitumor effect with high biocompatibility,as well as low immunogenicity.In this study,the Chapter 1 presented a brief literature overview on TME features as associated with TME-responsive DDSs,the current status,and the recent advances in designing biomimetic system for tumor targeted theranostics.Chapter 2-4 illustrated the main research contents are presented briefly as follows:?1?Platelet-membrane-biomimetic nanoparticles for targeted antitumor drug delivery.Aiming to construct low immunogenic and active targeted nano delivery,in this study,porous nanoparticles loaded with the anti-cancer drug bufalin?Bu?were prepared from a chitosan oligosaccharide?CS?-poly?lactic-co-glycolic acid??PLGA?copolymer.These were subsequently coated with platelet membrane?PLTM?to form PLTM-CS-pPLGA/Bu NPs.The PLTM-CS-pPLGA/Bu NPs bear a particle size of¹92 nm,and present the same surface proteins as the PLTM.Confocal microscopy and flow cytometry results revealed a greater uptake of PLTM-CS-pPLGA/Bu NPs than uncoated CS-pPLGA/Bu NPs,as a result of the targeted binding of P-selectin on the surface of the PLTM to the CD44 receptors of H22 hepatoma cells.While the drug-free carrier does not cause any death of H22 cells,the PLTM-coated NPs have greater toxicity than free bufalin.In vivo biodistribution studies in H22-tumor carrying mice revealed that the PLTM-CS-pPLGA NPs accumulated in the tumor,because of a combination of active targeting effect and the EPR effect.The PLTM-CS-pPLGA/Bu NPs led to more effective tumor growth inhibition over other bufalin formulations.These results indicate that the PLTM biomimetic nanoparticles are promising drug delivery systems for the targeted treatment of cancer.?2?Platelet membrane biomimetic bufalin-loaded hollow MnO₂ nanoparticles for MRI-guided chemo-chemodynamic combined therapy of cancer.Based on the low immunogenicity and active targeting of PLTM biomimetic cloaked NPs confirmed in chapter 2,in chapter 3,TME-responsive nanoparticles were designed for both diagnostic and combined treatment of tumor.As a tumor microenvironment?TME?responsive and biodegradable chemodynamic therapy?CDT?agent,manganese dioxide nanoparticles?MnO₂ NPs?have attracted considerable attention for tumor-targeted theranostics.However,the MnO2-based agent prepared in published studies exists limitations,such as uncontrolled self-growth rate,complex preparation processes,irregular particle morphologies.This section?Chapter 3?use the“green chemistry”strategy to prepare hollow MnO₂ NPs for precise tumor theranostics.PLTM biomimetic hollow MnO₂ nanoparticles were prepared and these were investigated for delivery of bufalin.Additionally,these nanoparticles,in response to the tumor microenvironment,showed rapid drug release and generated the hydroxyl radicals?HO·?by the Fenton-like reaction between Mn²⁺and endogenous H₂O₂ for use in MRI-guided anti-tumor activity.Firstly,poly?lactic-co-glycolic acid??PLGA?nanoparticles were used to reduce KMnO₄ to HMnO₂ nanoparticles after acetone etching.After bufalin loading,these NPs were biomimetically cloaked with PLTM to form PLTM-Bu@HMnO₂ NPs.In vitro release profiles showed that the NPs responded to acid pH and glutathione?GSH?to induce decomposition of HMnO₂,resulting in rapid release of bufalin and yielding the MRI contrast agent Mn²⁺.In vivo MRI studies revealed an obvious T1 contrast enhancement at the tumor site because of a combination of the EPR and active targeting effects.The PLTM-HMnO₂ NPs led to effective inhibition of tumor growth,attributing to Fenton-like Mn²⁺conversion of endogenous H₂O₂ in the tumor to highly toxic HO·and this anti-tumor efficacy was enhanced when combined with chemotherapy.These results indicate that the PLTM biomimetic HMnO₂ nanoparticles are promising drug delivery systems for MRI-monitoring and enhanced targeted treatment of tumors.?3?Her2-antagonistic affibody mediated cisplatin-loaded nanoparticles for tumor enhanced chemo-radiotherapyRadiation therapy?RT?,a local treatment,has become one of the most routine and feasible therapeutic modalities of malignant tumors.However,the RT therapeutic efficacy is largely limited due to the common existed hypoxic environment of solid tumors.The destroyed DNA by RT tend to self-repair under hypoxia,and thus rendering RT resistance.RT sensitization by increasing the oxygen content of solid tumors is an effective way to improve antitumor efficacy.MnO₂,besides the triple effects described in Chapters 3,another excellent effect is to catalyze the decomposition of endogenous H₂O₂ in tumors to produce O₂ to relieve tumor hypoxia,ultimately achieve RT sensitization.First,excellent biocompatible mesoporous polydopamine nanoparticles?mPDA NPs?were prepared by the nanoemulsion assembly method.After loading Pt,a thin MnO₂ layer grew on the peripheral surface of Pt@mPDA NPs by the in-situ reduction of KMnO₄ and then a biomimetic PDA layer was polymerized on the surface of the MnO₂ layer to improve the overall biocompatibility,as well as provide a chemically reactive surface for further functional modification.A human epidermal growth factor receptor 2?Her2?targeting affibody(Z_Her2)yielded by genetic engineering was then linked to the peripheral PDA layer,giving the NPs active targeting.The gel electrophoresis results determined the successful yield of Z_Her2.A series of physical and chemical characterizations confirmed that the sandwich-like structure of Pt@mPDA/MnO₂/PDA-Z_Her2 NPs was successfully prepared.These NPs were biodegradable under simulated TME and simultaneously achieved drug accelerated release.Cell uptake experiments demonstrated that Z_Her2endows NPs targeted bind to Her2-positive SKOV-3 cells?human ovarian cancer cell?.In vivo MRI studies revealed an obvious T1 contrast enhancement at the SKOV-3 tumor site.Immunofluorescence analysis showed that the presence of MnO₂ significantly reduced the expression of hypoxia-inducible factor-1??HIF-1??,and Cy5.5 fluorescently labeled carrier had a high affinity to Her2.Chemotherapy results verified that Pt@mPDA/MnO₂/PDA-Z_Her2 NPs have a strong targeted antitumor efficacy.Under X-Ray irradiation,the Pt@mPDA/MnO₂/PDA-Z_Her2 NPs can relieve tumor hypoxia,and thus exhibited the highest tumor grow inhibition effect.Furthermore,these NPs possess high biocompatibility with low risk of off-target toxicity.In summary,the nanocarriers constructed in this chapter integrate Her2 targeting,RT sensitization,combined therapy,and diagnosis,providing a new idea for sensitized tumor RT.In conclusion,in this work,we constructed biomimetic TME-responsive nanoplatform with low immunogenicity,active tumor targeting for tumor theranositics.This system integrates chemotherapy,chemodynamic therapy,enhanced radiotherapy,and has achieved considerable results in the accurate diagnosis and treatment of malignant tumors,which provides a new idea to guide clinical transformation by reducing systemic side effects,improving the anti-tumor efficacy.