The Construction Of PH Hypersensitive Vectors Targeting Tumor Microenvironment Is Integrated With The Diagnosis And Treatment Of Tumors

Due to the high incidence and high mortality rate of tumors,high-precision diagnosis and treatment of tumors have always been the focus of research in the field of contemporary medicine.High-precision diagnosis and treatment rely on high-precision targeted methods.However,the existing active targeting that relies on molecular recognition which is limited in the applicable population,and the passive targeting that relies on the high permeability of tumor blood vessels cannot achieve satisfactory results in clinical practice due to tumor heterogeneity,high intratumor pressure,high density,and other reasons.According to a further understanding of the Warburg effect of tumor cell metabolism and the high-density tissue structure of tumors,it is found that solid tumors widely have a weak acid microenvironment,which provides new research ideas for tumor targeting.However,the pH range of the tumor microenvironment is relatively narrow,between 6.5～6.8,and it is close to the pH value of the physiological environment（7.35～7.45）,so the preparation can remain stable in the physiological environment,and the rapid phase change pH-sensitive delivery system in tumor tissue is more difficult.In order to solve this problem,a sulfonamide monomer with a suitable dissociation constant was selected,and PCL-b-p SA,an amphiphilic anionic pH-sensitive polymer with phase transition in a weak acid（pH=6.5～6.8）environment and stable in the physiological environment was prepared by active radical polymerization and an integrated delivery system for diagnosis and treatment targeting the tumor acid microenvironment was constructed.In view of the application potential of superparamagnetic nanomaterials in tumor magnetic resonance imaging（MRI）,magnetothermal therapy（MH）,and chemodynamic therapy（CDT）,we used the self-assembly of superparamagnetic nanoparticles and PCL-b-p SA to construct this integrated delivery system,that is,nanomagnetic fluids targeted by the tumor acid microenvironment.In the next research,we will study and verify the application potential of this nanomagnetic fluid in tumor hypersensitivity MRI and tumor MH and CDT synergistic therapy.According to the above research content,the paper mainly contains the following four chapters.In the first chapter,this paper mainly introduces the research background of this paper and summarizes the research purpose and research content of this paper.In this paper,the shortcomings of active and passive targeting of existing tumors are discussed,and then according to the difference between the local microenvironment of tumors at the tissue level and normal tissues,the potential of using tumor acid microenvironment to improve tumor targeting in the delivery system is proposed.This chapter then classifies pH-sensitive delivery systems according to the properties of polymers,provides an overview of cationic pH-sensitive polymers and anionic pH-sensitive polymers,and focuses on pH-sensitive polymers targeted by the tumor acid microenvironment.Since the research purpose of this paper is to construct a delivery system for integrated diagnosis and treatment,this chapter briefly introduces the current research status of integrated tumor diagnosis and treatment carriers and classifies them according to the similarities and differences between diagnostic agents and therapeutic agents.On this basis,in view of the multiple roles of superparamagnetic nanomaterials in tumor diagnosis and treatment,we also introduce their application status in MRI,MH,and CDT.Based on the above research background,at the end of this chapter,we put forward the research objective of this paper:to construct nano-magnetic fluids that respond to tumor microenvironment for the integration of tumor-targeted diagnosis and treatment and briefly introduce the specific research content of nano-magnetic fluids in tumor diagnosis and treatment.The second chapter mainly prepares nanomagnetic fluids that respond to the tumor microenvironment and studies their application potential in tumor MRI.In this chapter,PCL-b-p SA,an amphiphilic anionic pH-sensitive polymer with a phase transition pH of about 6.7,was prepared by reversible addition-break chain transfer polymerization（RAFT）.Then,we prepared Mn Fe₂O₄,a hydrophobic superparamagnetic nanoparticle with a particle size of 8～10 nm,by high-temperature precursor decomposition.Using the self-assembly between amphiphilic polymers and hydrophobic nanoparticles,we successfully prepared nanomagnetic fluids that respond to the tumor acid microenvironment and verified their responsiveness to the tumor acid microenvironment,that is,high stability in the physiological environment（pH=7.35～7.45）and rapid agglomeration in the weak acid microenvironment（pH=6.5～6.8）.Since the agglomeration of superparamagnetic nanoparticles can effectively prolong the transverse relaxation rate（r₂）of surrounding water molecules,the nanomagnetic fluids prepared in this chapter have shown MRI contrast enhancement of weak acid response in vitro studies.In further in vivo studies,the tumor microenvironment-responsive nanofluids can significantly enhance the T₂ imaging contrast of mice’s micro-in situ breast cancer compared with non-weak acid-responsive nanomagnetic fluids,demonstrating its potential in tumor-targeted diagnosis.The third chapter mainly prepares three nano-magnetic fluids that respond to weak acids in tumors,explores the properties of magnetocalotherapy heating and reactive oxygen generation,and screens the nano-magnetic fluids with the best properties for application in vitro cell experiments in the next chapter.Based on the amphiphilic pH-sensitive polymer PCL-b-p SA and superparamagnetic nanoparticle Mn Fe₂O₄synthesized in the previous chapter,another superparamagnetic nanoparticle Fe₃O₄ was first synthesized by high-temperature precursor decomposition,and two superparamagnetic nanoparticles and PCL-b-p SA were self-assembled according to different compositions,and three nanomagnetic fluids targeting the tumor microenvironment were successfully prepared,namely:（1）Fe₃O₄ nanofluids with weak acid response,（2）Mn Fe₂O₄ nanofluids with weak acid response,and（3）（Fe₃O₄ and Mn Fe₂O₄,w/w=1/1）mixed nanomagnetic fluids with weak acid response.Through the investigation of the physical and chemical properties,thermotheric therapy temperature rise,and reactive oxygen generation capacity of the three tumor weak acid response nano-magnetic fluids,it is found that the weakly acid-responsive Mn Fe₂O₄ nano-magnetic fluids have the highest heating efficiency under alternating magnetic fields under tumor microenvironmental conditions,and generate·OH has the strongest ability and is preferred for MH-CDT synergistic therapy research.The fourth chapter mainly focuses on the nano-magnetic fluids targeting the microenvironment as combination therapy agents selected in the above chapter and investigates the mechanism of action of combination therapy with magnetocaloric and chemical kinetics,the effect of pH on combination therapy,and the in vitro anti-tumor effect of simulating tumor microenvironment at the cellular level.This chapter first investigates the efficacy of magnetocalotherapy of magnetofluid materials and determines the parameters of magnetocalotherapy in vitro cell experiments.Since different groups of cell uptake,intracellular iron content determination and ROS generation were investigated,it was proved that the mechanism of action of MH-CDT combination therapy was to more effectively phagocytose magnetic fluids under the action of magnetothermal therapy,thereby amplifying the effect of CDT therapy.And under the tumor microenvironment condition of pH 6.5,due to the aggregation of magnetic fluids,the magnetic fluids entering the cells increase to achieve better CDT effect.In cell experiments that further mimic the microenvironmental conditions of tumor tissue,this magnetocori amplification of chemical kinetics has a more significant effect in cells,accelerates the apoptosis process,and proves that it has the effect of combined magnetocalotherapy and chemokinetic therapy.