Protein-based Multifunctional Nanosystems For Tumor Treatment And Imaging

Cancer is one of the most important causes of death.The tranditional treatements such as surgical resection,chemotherapy and radiotherapy are still suffering from their unsatisfactory proformance in metasitic cancers.To address these issues,new anti-cancer theraputic strategies have been extensively explored.Nanotherapeutic systems have brought new opportunities for anti-cancer therapy.Proteins,especially those presented in human body,such as serum albumin,transferrin,etc.,have attracted much attention for construction of nanotherapeutic systems due to their natural advantages of good biocompatibility,biodegradability,high biosafety,and the feasibility for modification.In this thesis work,a series of protein-based multi-functional nanosystems were designed and prepared for tumor treatments and imaging.In Chapter 1,the applications and research status of protein-based nanomaterials in the field of tumor treatment and imaging are introduced,with the emphisis in tumor targeting modification.In Chapter 2,a facile strategy was used to construct aptamer-functionalized albumin-based nanoparticles for effective drug delivery.A hydrophobic chemotherapeutic drug,doxorubicin(DOX)was employed to trigger the self-assembly of bovine serum albumin(BSA)to from stable nanoparticles via hydrophobic interaction,and then a tumor targeting aptamer AS1411 was incorporated to the surface of DOX loaded BSA.Due to the specific recognition between AS1411 and its receptor over-expressed on tumor cells,the aptamer-modified nanoparticles show higher cellular uptake and stronger cell inhibitory efficacy against cancerous MCF-7 cells as compared with the nanoparticles without aptamer modification.In addition,DOX loaded aptamer-functionalized nanoparticles can induce more significant down-regulation of Bcl-2 and PCNA as well as up-regulation of p RB,PARP and Bax in MCF-7 cells compared with unmodified nanoparticles,indicating the aptamer modification can induce cell apoptosis more effectively.Besides,aptamer-modified nanoparticles exhibit a significantly improved capability in up-regulating p16,p21 and E-cadherin,and down-regulating Ep CAM,vimentin,Snail,MMP-9,CD44 and CD133,implying the favorable effects of drug delivery on the prevention of tumor progression and metastasis.In Chapter 3,a tumor targeting protein-based delivery system(DOX&ICG@BSA-KALA/Apt)was developed to efficiently integrate multimodal therapy with tumor imaging and realize synchronous PDT/PTT/chemotherapeutic functions.In the delivery system,a chemotherapeutic drug(doxorubicin,DOX)and an optotheranostic agent(indocyanine green,ICG)were co-loaded in bovine serum albumin(BSA)via hydrophobic interaction induced self-assembly to form stable DOX&ICG@BSA nanoparticles.After decoration of a surface layer composed of a tumor targeting aptamer AS1411 and a cell penetrating peptide KALA,the obtained DOX&ICG@BSA-KALA/Apt nanoparticles exhibit significantly improved multimodal cancer therapeutic efficiency due to the enhanced cancer cellular uptake mediated by AS1411 and KALA.In vitro and in vivo studies show the multimodal theranostic system can efficiently inhibit tumor growth.In addition,the near-infrared fluorescent/photothermal dual-mode imaging enables accurate visualization of the therapeutic action in tumor sites.In Chapter 4,In order to improve the efficiency and safety of photothermal therapy,a p H-responsive and tumor-targeting nanosystem(ND-630@Cu S/Tf)combined the noninvasive inhibition of fatty acid synthesis(FASyn)with photothermal therapy(PTT)was constructed.With transferrin(Tf)coated on the surface of hollow mesoporous Cu S loaded with an acetyl-Co A carboxylase(ACC)inhibitor(ND-630),the nanosystem can deliver ND-630 to tumor cells specifically.ND-630-mediated inhibition of FASyn can block cell membrane formation,enhance the sensitivity of tumor cells to the damage of Cu S mediated PTT,and inhibit cell resistance to PTT via prevention on cell membrane re-formation.Additionally,down-regulation of ACC dramatically reduces the expression of tumor progression related proteins such as CD44 and MMP-9 to inhibit tumor metastasis.In vitro and in vivo studies reveal that this strategy can efficiently aggravate membrane damage with FASyn inhibition to enhance PTT efficiency,thereby realizing effective inhibition of tumor growth and metastasis.In Chapter 5,to effectively amplify the oxidative damage mediated by chemodynamic therapy(CDT),a tumor targeting multifunctional theranostic system to synergize the inhibition of tumor cells metabolic recycling of ammonia,chemodynamic therapy and real-time H₂O₂ responsive magnetic resonance imaging(MRI)was prepared.A hydrophobic drug(ferrocene)and a GDH inhibitor(purpurin)were self-assembled with amphiphilic bovine serum albumin(BSA)via hydrophobic interactions to form nanosized BSA@Ferrocene-Purpurin(BFP)particles.Subsequently,tumor-targeting AS1411 was introduced to BFP nanoparticles to obtain AS1411-BSA@Ferrocene-Purpurin(ABFP)nanoparticles.The multifunctional theranostic system(ABFP)delivers the drugs specifically and efficiently to the tumor site due to the high affinity of AS1411 with nucleolin overexpressed in tumorous cells.The inhibition of GDH by purpurin effectively inhibits the activity of active oxygen scavenging enzyme glutathione peroxidase(GPx),down-regulates the expression of glutathione(GSH),and enhances the level of H₂O₂ in tumor cells to provide enough H₂O₂ substrate for Fenton reaction and to increase the production of·OH.Inhibited GPx and down-regulated GSH effectively suppress the oxidative stress response of tumor cells and to guarantee highly efficient·OH production for effective CDT.Meanwhile,Fe(III)ions produced by Fenton reaction can be used as a negative contrast medium of magnetic resonance imaging(MRI)to mediate H₂O₂-responsive MRI to precisely guide and monitor the synergistic therapy.In vitro and in vivo studies demonstrate that ABFP significantly enhances the effieiciency of CDT.