Hollow Ruthenium-based Nanocapsules With Multiple Drug Loading For Combination Therapy Of Ectopic And Orthotopic Colorectal Tumor Model

Colorectal cancer is the third most common cancer worldwide.With nearly 1.4 million new cases have been diagnosed in 2012,the morbidity remains a constant upward trend.In the past two decades,the biomedical applications of nanomaterials have been extensively studied,especially in the fields of drug delivery and bioimaging.With the rapid development of nanotechnology,multi-drug treatment,imaging and targeted therapy of nanoparticles?NPs?become possible,which provide new hope for clinical detection,prevention and treatment of cancer.In the field of oncology,nanomedicine has shown unique advantages over traditional drugs.The complex microenvironment of tumors is totally different from normal tissues.The abnormal structure increases the interstitial fluid pressure,resulting in uneven blood flow,hypoxia and acidic pH.Based on these unique characteristics,stimulation-responsive therapeutic NPs can be developed to utilize or regulate the physiological environment of tumors for anti-cancer applications.Facing various diseases in human life,kinds of nanocarriers?NCs?have been developed.On the one hand,they are used to solve the shortcomings of conventional drugs in clinical application,such as the inactivation of drugs during delivery and overhigh plasma drug concentration beyond the therapeutic range.On the other hand,they are also used to solve the delivery problem of hydrophobic drugs and realize intelligent?targeting,stimulation-responsive release?delivery.Because of the excellent magnetic,thermal,optical and electrical properties,inorganic NPs can be developed and used as drug carriers to deliver drugs to cancer tissues without damaging normal organs.Since most conventional anticancer drugs can not distinguish normal cells and cancer cells,one of the main problems in cancer treatment is the untargeted distribution of therapeutic agents throughout the body.Many widely used traditional chemotherapeutic drugs?e.g.paclitaxel and doxorubicin?have strong side effects,which can induce a variety of tumor resistance mutations,posing new challenges for cancer treatment.In addition,physical and biological barriers in vivo can influence the accumulation of NPs in tumors.Most NPs can be blocked by reticuloendothelial system?RES?before reaching tumor site,which not only reduces the accumulation of drugs,but also may damage the RES-rich organs.Compared with single modal imaging agents or therapeutic agents,properly designed and modified NPs are expected to achieve flexible,intelligent and safe multi-modal treatment.Besides,multi-modal diagnostic imaging can provide more comprehensive information about the tumor area.Therefore,building an effective and intelligent nano-platform for treatment and diagnosis,combining the ability of visualizing disease tissue monitoring,delivery dynamics and anticancer efficacy,making each part work together without impairing or interfering with other functions,will become the key strategy of personalized and precise medicine in the future.Based on the above research background,two kinds of multifunctional ruthenium-based nanocapsules were designed and synthesized in this article.The hollow structure can be used to co-load a variety of drugs.As responding to tumor microenvironment and external near-infrared stimulation,drug delivery and controlled targeting release at tumor sites can be achieved.In addition,combined with the synergistic approach of multi-modal treatment and diagnosis,we explored the combined therapeutic effect of two nanosystems in ectopic and orthotopic colorectal tumor models,which could provide a new strategy for future cancer treatment.This article consists of three chapters.In chapter 1,we briefly described nanoparticles based drug delivery systems and drug loading strategies of nanocarriers.And further we analyzed various nano-therapeutic approaches developed by tumor microenvironment.Finally,we highlighted the latest advances in cancer targeting nanomedicine and multimodal nano-theranostic.In chapter 2,we synthesized hollow mesoporous Ruthenium nanoparticles?HMRu NPs?using an improved soft-hard double-templating method.The nanocapsules were loaded with fluorescent ruthenium complex([Ru?bpy?₂?tip?]²⁺,RBT).Bispecific antibody?anti-CD16 and anti-CEA,SS-Fc?were further conjugated through the bifunctional polyethylene glycol?PEG?linker.HMRu@RBT-SS-Fc is a passive and active dual-targeting nanosystem.We first studied the photothermal properties,drug loading and controlled release of HMRu@RBT-SS-Fc.Secondly,we investigated cell uptake,tumor infiltration and NIR-sensitive cytotoxicity at 2D and 3D cell levels.Finally,the in vivo fluorescence imaging and therapeutic effect of HMRu@RBT-SS-Fc were studied in unilateral and bilateral heterotopic colorectal cancer models.As the experimental results shown,the functionalized nanocomposites can sensitively release drugs and effectively ablate tumors under NIR irradiation,in the meantime trigger immune response and exhibit good combined therapeutic effect.In chapter 3,we synthesized Ru@CeO₂ yolk@shell nanoparticles?Ru@CeO₂ YSNs?using a simple and non-toxic one-pot method?auto-redox reaction and WAC etching?.The surface of YSNs was modified with double-layer polyethylene glycol?DPEG?,which had a dynamic PEG shell to reduce protein adsorption and prolong blood circulation.In addition,fluorescent ruthenium complex?RBT?and resveratrol?Res?were co-loaded to form the microenvironment-responsive Ru@CeO₂-RBT/Res-DPEG nanosystem.Firstly,we investigated the elemental distribution of nanoparticles and the catalytic performance towards hydrogen peroxide.Secondly,we studied the ability of cancer cells killing and multicellular spheroids penetration.Finally,the hypoxic environment improvement and combined anti-tumor effect of Ru@CeO₂-RBT/Res-DPEG were evaluated in ectopic and orthotopic CT26 tumor-bearing mice.The biosafety assessment preliminarily confirmed the good biocompatibility of nanosystem.