Design And Application Of PH Protective Y₁ Receptor Ligand Functionalized Nanoprobes

Cancer has become a major factor that threatens the human health worldwide.Its mortality rate is second to cardiovascular and cerebrovascular diseases.According to available statistics,there are 2.2 million new cases and 1.6 million deaths each year,and these have climbed at a rate of 20%in China during the past 20 years.With the rapid development of medical technology,the treatment of cancer has been greatly developed,but due to the complex mechanism of cancer pathogenesis and high degree of personalization,its treatment is still difficult.Therefore,finding efficient and safe diagnosis and treatment methods have always been one of the difficulties in cancer diagnosis and treatment.The ever-increasing advancements in nanotechnology have enabled more substantial research in the field of biomedicine for the development of nanocarrier systems for tumor diagnosis and treatment.Nanocarrier systems offer many advantages in the delivery of drugs and contrast agents,thus prolonging blood circulation time,reducing toxic and side effects,and achieving higher active ingredient accumulation rate in tumors.However,the current nano-delivery systems also face some difficulties,such as non-specific uptake by macrophages,premature drug release,lack of active targeting and low loading efficiency of co-loading drugs and contrast agents.To ameliorate these,this dissertation mainly focuses on the construction of Y₁ligand active-targeting nanoprobes and their application in tumor diagnosis and treatment.The main research contents are summarized as follows:(1)Nanoparticle-based drug delivery is extensively studied for tumor imaging and therapy;however,few nanoparticle-mediated therapies can improve cancer patients'survival in the clinic,due to intrinsic premature drug leakage,lack of active targeting to tumors,and responsive release.Here,we synthesized Y₁ receptor ligand[Asn⁶,Pro³⁴]-NPY(AP)-and self-peptide(SP)-based novel BPLP-WPU polymeric micelles,with excellent antiphagocytosis,pH responsiveness,and tumor targeting.Due to AP structural changes under different pH conditions,AP modification not only improves the stability of probes during storage and blood circulation,but also increases tumor targeting and drug release in the acidic tumor microenvironment.Moreover,the co-modifier SP reduces phagocytic clearance during blood circulation,minimizes the uptake of probes in the liver and kidney,and further enhances micelle retention in the tumors.The improved stability and retention of super-paramagnetic iron oxide nanoparticles(SPION)-or doxorubicin(DOX)-loaded micelles in the tumor sites generate excellent magnetic resonance signal and therapeutic effects in vivo with prolonged survival time.The double-modified nanoprobe improved imaging efficiency by 47%and achieved 100%survival of treated mice in 100 days.This study may pave the way for safer and more specific Y₁receptor overexpressed breast cancer diagnosis and treatment.(2)Zeolitic imidazole frameworks(ZIFs)are becoming notable nanosystems in the field of biomedicine,due to their unique properties of favorable biocompatibility,pH-responsive degradable structure and high drug loading.Compared with the increasing attention of ZIF-8 in cancer imaging and treatment,there is limited research about the bio-application of ZIF-90,especially its in vivo therapeutic efficacy and related toxicity.Here,we synthesized nano ZIF-90 through a fast self-assembling process.The synthesized nano ZIF-90 is about 75 nm with a negative zeta potential,providing better mitochondrion targetability,cell biocompatibility and in vivo survival rate than nano ZIF-8.To further explore the applicability of ZIF-90 in cancer treatment,the synthesized nano ZIF-90 was encapsulated with doxorubicin(DOX)and a facile post-modification was used to conjugate Y₁ receptor ligand[Asn⁶,Pro³⁴]-NPY(AP)on its surface.AP-ZIF-90@DOX nanoprobe significantly reduces premature DOX release at physiological pH,and triggers more effective and faster DOX release inside the tumor cells with dual responsiveness to high adenosine triphosphate(ATP)and low pH condition.Combined targeted delivery and dual responsive release of DOX significantly improves the therapeutic efficacy of AP-ZIF-90@DOX in MDA-MB-231tumor-bearing mouse,and results in 80%survival rate over 40 days post-treatment.At the given dosage,AP-ZIF-90@DOX offers excellent biocompatibility in vivo,resulting in minimal side effects on the liver and renal functions.Therefore,Y₁Rs ligand combines with nano ZIF-90 to provide a nanosystem of favorable biocompatibility and dual responsiveness that can be used as a promising nanoprobe for targeted triple negative breast cancer treatment in vivo.(3)ZIFs as smart drug delivery systems with tumor microenvironment-triggered release have attracted great attention for tumor diagnosis and therapy.However,the exploration of ZIFs in biomedicine still encounters many issues,such as inconvenient surface modification,fast drug release during blood circulation,undesired damage to major organs,and severe in vivo toxicity.To address the above issues,we developed an Mn-ZIF-90 nanoprobe that was functionalized with originally designed active-targeting and pH-responsive Y₁ receptor ligand[Asn²⁸,Pro³⁰,Trp³²]-NPY(25-36)for image-guided tumor therapy.After Y₁ receptor ligand modification,the Mn-ZIF-90 nanoprobe with high drug loading,enhanced blood circulation stability,and dual breast cancer cell membrane and mitochondria targetability,further favors specific microenvironment-triggered tumor therapy.Meanwhile,the nanoprobe showed considerable in vivo T₁-weighted magnetic resonance imaging contrast enhancement in the tumor site,and increased the survival period of treated mice from 26 days to 60 days.Interestingly,the nanoprobe with fast clean-up exhibited almost no obvious toxicity and damage to mice major organs,thereby showing strong promise as a potential candidate for image-guided tumor therapy.