Construction And Application Of Nanodrug Delivery Systems By Utilizing The Tumor Hypoxic Microenvironment

With the deterioration of the global ecological environment and the aging of human society,the incidence and death rate of malignant tumors have shown an upward trend.As their special microenvironment,including hypoxia,the elevated interstitial hypertension,as well as high density of extracellular matrix,tumors are difficult to be cured.The clinical methods of tumor treatment include:surgical treatment,chemotherapy,phototherapy,radiotherapy,and immunetherapy.Among them,chemotherapy and phototherapy?including photodynamic therapy and photothermal therapy?are the most widely studied treatments in recent years.However,due to its low specificity for tumor,high toxicity and side effects of traditional chemotherapeutic drugs severely limit the clinical application of chemotherapy.Moreover,it is found that hypoxia in solid tumors induces tumor resistance to chemotherapeutic drugs and further reduces the effect of chemotherapy.Compared with chemotherapy,phototherapy has the characteristics of lower invasiveness,smaller wounds,no cumulative toxicity,and reusability.It has become an important means of adjuvant surgery in late-stage cancer.However,conventional photosensitizers consume oxygen during the PDT process,resulting in poor therapeutic effect in the hypoxic region of the tumor and aggravating the hypoxic environment,which causes to treatment failure,invasion and metastasis.Furthermore,the elevated interstitial hypertension,as well as high density of extracellular matrix act as a barrier to significantly impede transvascular permeability and intratumoral diffusion of nanomedicines and reduce the overall performance of treatments.Therefore,this dissertation revolves around the problems of“hypoxic resistance,low delivery efficiency,and limitations of monotherapy”encountered in chemotherapy and phototherapy.A series of nanodrug delivery systems are rationally designed to utilize chemotherapy and phototherapy for synergistic effect to solve the limitations of small molecule drugs and improve the system's anti-tumor activity.The main results are shown as follows:1.Prodrug-Embedded Angiogenic Vessel-Targeting Nanoparticle:A Positive Feedback Amplifier in Hypoxia-Induced Chemo-Photo TherapyThe tumor hypoxic environment usually results in the failure of photodynamic therapy.The previous method is to deliver oxygen to the hypoxic site and increase the oxygen pressure within the tumor,thereby reversing the resistance of hypoxia to photodynamic therapy.Contrary to the oxygen delivery method,this chapter uses the oxygen consumption of traditional photodynamic therapy,which greatly enhances the toxicity of the bioreductive drug tirapazamine.At the same time,hypoxic environment leads to angiogenesis,which is beneficial to the nanodrugs to target at tumors sites.Hence,we develop a small molecular drug delivery system,an angiogenesis vessel-targeting nanoparticle?TPC-GX1?,consist of photosensitizer,angiogenic vessel-targeting peptide,and bioreductive prodrug for a chemo-photo synergistic cancer therapy,with which anti-cancer effect is achieved first by PDT and immediately followed with hypoxia-activated cytotoxic free radicals.With targeting capability,the TPC-GX1 nanoparticle can effectively accumulate at the tumor site due to the promoted angiogenesis in response to PDT-induced hypoxia.The more nanoparticles delivered to the tumor tissue,the higher efficacy of PDT can be achieved,resulting in a more severe hypoxia and increased angiogenesis.Therefore,the prodrug embedded TPC-GX1functions as a positive feedback amplifier to open up a new research idea for the synergistic effect of photodynamic therapy and chemotherapy.2.Platinum???Compound-Based Polyprodrug Induced Hypoxia-Associated Synergistic ChemotherapyBesides oxygen consumption of traditional photodynamic therapy,platinum drugs also involved in the oxidative stress of cells by activating a family of enzymes named nicotinamide adenine dinucleotide phosphate oxidase?NOXs?for oxygen consumption.Based on the previous chapter,we replaced the method of consuming oxygen and developed a platinum???complex-based polyprodrug delivery system?polyprodrug@TPZ?.After in situ polymerizing the platinum???compound-based prodrug monomer?PPM?and2-methacryloyloxy ethyl phosphorylcholine?MPC?,TPZ was loaded by Pt???polyprodrug nanogel.Upon the tumor microenvironment,the polyprodrug can be reduced to cisplatin that activated NOXs to trigger an O₂ consumption and ROS production.Immediately the exaggerated hypoxia further activated TPZ to form highly cytotoxic radicals.With the rational designed nanosized architecture,the polyprodrug@TPZ exhibited the advantages of sustained drug release,long-term circulation,and preferable tumor accumulation for a combinational chemodrug treatment in vitro and in vivo.This work utilize chemotherapeutic drugs to modulate the tumor cell microenvironment,improving the therapeutic effect of TPZ.Thus the synergistic chemotherapy effect between two chemotherapeutic drugs significantly enhancing the tumor treatment effect of the system.3.Platinum???Compound-Based Two-in-One Polyprodrug for A Synergistic Chemo-Photodynamic TherapyDespite great advances have been achieved by the oxygen consumption of photodynamic therapy or chemotherapy in combination with bioreductive drugs,there are still several major problems with this synergistic therapy.First,solid tumor have a hypoxic microenvironment,resulting in poor effect of photodynamic therapy and chemotherapy.Second,the method of oxygen consumption will aggravate the hypoxic microenvironment and induce angiogenesis,it is easy to cause treatment failure,tumor invasion and metastasis.Third,most of the bioreductive drugs need to be physically loaded,which easily leads to problems such as leakage of drugs during delivery process and increased systemic toxicity.Therefore,based on the Pt???monomer?PPM?and Pt???polyprodrug nanogels?polyPPM?synthesized in the previous chapter,we found that they can in situ generate the highly toxic cisplatin as chemotherapeutics and high level of ROS in an O₂-independent manner to enhance the PDT efficacy under light irradiation for“two-in-one”combination of photodynamic therapy and chemotherapy.The high level of ROS was induced simultaneously without the consumption of endogenous oxygen for overcoming hypoxic resistance.Moreover,the expression of multidrug resistance-associated protein 1?MRP1?was inhibited by ROS to reduce the efflux of drug.Through a nanostructure design,the as-synthesized polyprodrug exhibited the properties of sustained drug release,long-term circulation,and preferable tumor accumulation.In all,O₂-independent photo-chemo therapy using this polyprodrug resulted in a remarkably suppressed tumor growth in mice bearing both A549and A549R cancer cells.4.Gold Nanorods Polydrug Nanogels for A Synergistic Chemo-Photothermal TherapyBesides the resistance by tumor hypoxia,the elevated interstitial hypertension,as well as high density of extracellular matrix acts as a barrier to significantly impede transvascular permeability and intratumoral diffusion of nanomedicines and reduce the overall performance of treatments.Enhancing the drug accumulation into the hypoxic region of the tumor may help overcome the hypoxic resistance of the tumor.Due to their tunable surface plasmon and photothermal effects,gold nanorods?GNRs?have proven to be promising in a wide range of biomedical applications and ideally suited for theranostic and thermo-chemotherapeutic applications.Based on the advantages of platinum???prodrugs monomer and gold rods,we develop a"two-in-one"polymer nanogel coated gold nanorods drug delivery system?GNR@polydrug?for the chemotherapeutic-photothermal synergistic tumor therapy.After in situ copolymerizing with Pt???bis-urethan ethyl methacrylate prodrug monomer?PPM?and2-methacryloyloxyethyl phosphorylcholine?MPC?monomer onto gold nanorod,the systemic toxicity of the GNR@polydrug is significantly reduced.An enhanced blood circulation can be confirmed by pharmacokinetics and photoacoustic imaging.NIR laser irradiation was applied on the tumor site following its intravenous administration to mice tumor models significantly enhanced their accumulation in tumor,providing a prerequisite for efficient cancer treatment which almost completely inhibited tumor growth.