Anti-Cancer Polymeric Nanocarriers With High Drug Loading And Tumor-Selective Drug Delivery

Malignant tumors are currently the number one killer threatening human life.The recent development of nanomedicine has provided many new approaches for cancer treatment.Nanomedicines possess numerous advantages,such as prolonged blood circulation time,enhanced enrichment and retention at tumor sites,reduced toxic side effects,and selective,controlled drug release,etc.However,the intracellular delivery of small-molecule or protein therapeutics with high-efficiency encapsulation and tumor-specific release remains challenging.For instance,(1)the unsatisfied loading efficiency of small-molecule chemotherapeutics in nanocarriers due to the hydrophobic nature of most chemotherapeutics;(2)Chemotherapeutics usually differ greatly in physicochemical properties,as well as their pharmacokinetics and biological distribution.Therefore,it is challenging to achieve the combination of different drugs with high drug loading content and precise drug ratio;(3)Protein therapeutics are fragile in the body,and they differ greatly in molecular weight and isoelectric point.Therefore,developing a universal intracellular delivery system to achieve the efficient loading for different protein drugs is highly desired;(4)It is difficult to achieve precise and fixed-point release of the loaded therapeutics in the lesion tissue or cells,causing non-specific toxic side effects.To address the above-mentioned issues,this thesis aims to develop delivery systems for dual chemotherapeutics/proteins by introducing multiple interactions between polymer delivery vehicles and drug molecules,to achieve efficient,stable entrapment of chemical/protein therapeutics and selective release in tumor cells,significantly improving the drug's anti-tumor in vivo and in vivo efficacy.In Chapter 1,an overview of the status of conventional anticancer therapies(chemotherapy and protein-based therapy),nanomedicines,and responsive drug/protein delivery systems,was provided.In Chapter 2,the donor-acceptor coordination between the drugs and the polymeric nanocarriers was used to achieve the combination of ultra-high loading and precise ratio of dual chemotherapeutics for the cooperative treatment of cancer.In this strategy,an amphiphilic polymer micelle containing phenylboronic acid(PBA)in the hydrophobic block side-chains was designed.The PBA group in the polymer acted as an electron acceptor,which interacted with the amino group on doxorubicin(DOX)and irinotecan(IR)to form the donor-acceptor coordination,achieving the polymeric micelles with a diameter around 30-40 nm,high drug loading of DOX and IR(up to 50%),high encapsulation rate(>95%),and precise loading ratio.Upon being internalized,the high levels of intracellular reactive oxygen species(ROS,100 ?M H2O2)triggered the cleavage of the PBA segment,triggering the hydrophobic-to-hydrophilic transition of that segment,disassembly of polymeric micelles,and the fast,specific release of the loaded drugs.To this end,the dual drug-loaded polymeric micelles achieved excellent synergistic antitumor efficacy in a Lewis lung carcinoma mouse model with negligible systemic toxicity.In Chapter 3,nanocomposites formed by the phosphorylated protein prodrugs and guanidinated ?-helix cationic polypeptides(LPP)were constructed to achieve high-efficiency loading and intracellular delivery of protein drugs for anti-tumor therapy The protein's lysine residues were modified by PBA and ATP to obtain phosphorylated proteins and increase the negative charge density of proteins.The phosphorylated proteins and LPP self-assembled into a stable nanocomplex with a particle size of 100-200 nm through electrostatic and salt bridge interactions.The ?-helix structure and cationic nature of LPP promoted the efficient cellular uptake of proteins,as shown by the experiments where the cellular uptake efficiency of the loaded protein is 23 times higher than that of free protein.Under the stimulation of the acidic environment and high level of H2O2(100 ?M)in the tumor cells,the PBA and ATP were cleaved and the naive protein was released in situ.This strategy can achieve reversible modification and efficient LPP-mediated intracellular delivery for proteins with different molecular weights and isoelectric points(e.g.RNase,BSA,and Cytochrome C).Using RNase as a model protein,LPP-assisted phosphorylated prodrug exhibited excellent tumor-suppressive effects on the growth of mouse melanoma cells(B16F10)both in vivo and in vitro.In Chapter 4,a summary of this thesis and the prospects for future work was provided.