Disulfide Cross-linked And Tumor-targeted Nanomedicines Based On Hyaluronic Acid-polytyrosine For Efficient Suppression Of Primary And Metastatic Tumors

Cancers are persisting as a grand challenge in global health,among which the metastasis of malignant tumors at distal sites causes the main death.Currently,many nanomedicines based on chemical anticancer agents have been advanced into the clinic or clinical trials,and show largely decreased side effects and enhanced anti-tumor effect.However,these nanomedicines still encounter several challenges including inefficient loading,short circulation time,poor tumor selectivity,and slow drug release at tumor sites,which compromises their suppression of primary and metastatic tumors.In Chapter one,we briefly introduce current status and clinical treatment strategies on varying tumors,summarize advanced nanocarriers recently developed for the treatment of primary and metastatic tumors,and especially highlight the strategies on the construction of cross-linked and stimuli-responsive nanocarriers.In Chapter two,we have designed and prepared disulfide cross-linked and tumor-targeted nanocarriers(CHTNP)for high and robust loading of docetaxel(DTX)to achieve efficient inhibition of primary and metastatic 4T1 breast cancer.CHTNP is prepared by self-assembly of hyaluronic acid-g-polytyrosine-lipoic acid(HA-g-PTyr-LA)in aqueous phase,followed by disulfide cross-linking with catalytic amount of dithiothreonol(DTT).CHTNP can efficiently encapsulate DTX through hydrophobic interactions and π-π stacking,and the drug loading content(DLC)is up to 7.8 wt.%.DTX-loaded CHTNP(DTX-CHTNP)has small sizes(60-100 nm),and the sizes increase with elevating degree of substitution of polytyrosine(PTyr).Under physiological conditions,DTX-CHTNP displays high stability and can prevent drug leakage.In the presence of 10 mM GSH,89.4%of DTX has been observed to release from DTX-CHTNP within 24 h.Cell experiments shows that DTX-CHTNP can inhibit the growth,migration and invasion of 4T1 cells.DTX-CHTNP is stable during blood circulation,and has an elimination half-life of 5.75 h,which is about 2.7 and 7.7 times longer than that of uncross-linked counterparts(DTX-HTNP)and free DTX,respectively.In vivo anti-tumor experiments shows that DTX-CHTNP can effectively inhibit the growth of primary 4T1 breast cancer,and even significantly suppress the metastasis of 4T1 tumor in the lung.These nanocarriers with superior features of natural components,facile construction,high stability,tumor-targetability and bioresponsivity,hold great potential of fabricating different nanomedicines to treat primary and metastatic tumors.In Chapter three,CHTNP developed in chapter two has been employed to achieve efficient encapsulation and hepatoma cell-targeted delivery of Lenvatinib(Len).The results show that CHTNP can efficiently encapsulate Len,and the loading efficiency is up to 53.4%when the theoretical load content was 20 wt.%.Len-loaded CHTNP(Len-CHTNP)displays small sizes of around 85 nm,and the sizes show little change with varying drug loading contents of 6.0-10.9 wt.%.Under physiological conditions,Len-CHTNP exhibits superb stability against high-volume dilution and serum.In the presence of 10 mM GSH,around 93.8%of Len was observed to release from CHTNP within 48 h.Flow cytometry assay displays that CHTNP can be efficiently internalized in CD44 positive SMMC-7721 and HepG2 hepatoma cells,and the cellular uptake is significantly inhibited by pre-treating the cells with free HA.MTT assays shows that Len-CHTNP can effectively inhibit the growth of SMMC-7721 cells with an IC50 of 5.2μg/mL,which is far less than free Len(8.5 μg/mL).Similarly,Len-CHTNP displays higher cytotoxicity in HepG2 cells in comparison with free drug(IC50:8.6 μg/mL vs.11.2 μg/mL)Len-CHTNP at drug concentration of 10 μg/mL induces obvious cell apoptosis in SMMC-7721,and the apoptosis rate is around 5.0 times of free Len.The remarkable apoptosis caused by Len-CHTNP can be attributed to the higher cellular uptake,which causes more efficient inhibition of the signal transduction pathways of FGFR,RET,PDGFRa,and KIT.Thus,Len-CHTNP is emerged as a promising nanomedicine for efficient chemotherapy of hepatoma.In Chapter four,we summarize the results of the thesis and propose the future work.