Structural Optimization Of Tertiary Amine Oxide-drug Coniugates For Active Tumor Penetration

Transcytosis(namely endocytosis-intracellular transport-exocytosis)has been verified as an effective strategy to overcome physical barriers in the tumor tissue.This strategy enables nanomedicine to actively transport across various physiological barriers during the drug delivery process to obtain deep tumor penetration.Generally,nanomedicines need to be partially captured by the cells to take therapeutic effect and partially exocytosed to penetrate the tumor.This intracellular performance is beneficial for nanomedicine to strike the balance of drug tumor penetration and drug release and obtain superior antitumor activity.However,the relationship between nanomedicine’s intracellular capture as well as exocytosis and the structure of carriers still remains unknown.Our group previously found that poly(tertiary amine-oxide)(PTAO)could quickly launch transcytosis to achieve deep tumor penetration.Based on this,this thesis put forward the strategy to modulate subcellular distribution by adjusting the structure of PTAO to control the ratio of intracellular capture and exocytosis of nanomedicine,from which we can acquire the nanomedicine striking the balance of intracellular drug release and tumor penetration.The first part of this thesis investigated the effect of the hydrophilic/hydrophobic ratio of PTAO and the content of the TAO group on the transcytosis,and screened out the optimal one that could be partially delivered to lysosomes to release drugs and could be partially transported to Golgi apparatus to trigger transcytosis,and the first part also carried out biological evaluation of the screened one.Firstly,biocompatible poly(glutamic acid)(PGA)was synthesized via NCA ring-opening polymerization and conjugated with PTX at different ratios via GFLG peptide linker that is responsive to cathepsin B distributing in lysosomes.The rest empty branch chains of PGA were modified with TAO moiety.Finally,we developed OPGA-PTX at different hydrophobic/hydrophilic ratios.With the increase of PTX content(hydrophobic moiety),tumor cells could internalize the conjugate faster,and the conjugate tended to distribute more in lysosomes and Golgi apparatus.Then,we synthesized a series of OxPGA-PTX at the hydrophilic/hydrophobic ratio of 10:1 but with different content TAO group to investigate the effect of the TAO group’s content on the cellular performance of drug-conjugates.We found that the cellular uptake rate of drugconjugates and their distribution in lysosomes and Golgi apparatus increased with the increase of the TAO group’s proportion.Additionally,the differentiated cellular uptake behavior and subcellular distribution make it possible for the hydrophilic/hydrophobic ratio and TAO group to affect drug-conjugates’ transcytosis,exocytosis,and multiple tumor spheroid penetration.Finally,OPGA-PTX at the hydrophilic/hydrophobic ratio of 10:1 and with 100%content TAO group was selected as OPPX.Its biological properties such as blood circulation features,biodistribution,tumor penetrating ability and antitumor activity were systematically studied.This work firstly proposes a strategy to modulate drug-conjugate’ cellular uptake,subcellular distribution and transcytosis by changing the hydrophilic/hydrophobic ratios and TAO group’s proportion.Finally,we screened out the optimal drug-conjugate that could strike the balance of intracellular capture and transcytosis and has better antitumor activity.Carrier-free nanomedicines have the advantages of specific structures,high drugloading capacity as well as reproducible self-assembly.However,they always have poor tumor penetrating and subcellular targeting ability.Therefore,the second part of the thesis designed novel carrier-free prodrugs based on the TAO group to realize active tumor penetration and mitochondrial targeting We conjugated insoluble camptothecin(CPT)with the TAO group via the ROS responsive linker to obtain CPT-S-NO.CPTS-NO could self-assemble into nanoparticles with a diameter of 100 nm and could circulate long in the blood to accumulate in the tumor tissue followed by deep tumor penetration and mitochondrial targeting.Besides,CPT-S-NO could release CPT to trigger cell apoptosis under intracellular high-ROS level and acidic microenvironment.Finally,CPT-S-NO showed significantly enhanced therapeutic efficacy in MDA-MB231 and 4T1 tumor models.This work provides a new way to design carrier-free nanomedicine with the ability of active tumor penetration and mitochondrial targeting...