Effect Of Renal-clearable Gold Nanomaterials On The Growth Of Mouse Breast Tumors

The vigorous development of nanomaterials in biomedical field has provided a variety of research ideas for cancer treatment.Among these medical nanomaterials,gold nanoparticles（AuNPs）have been widely favored by researchers due to their unique photochemical properties and good biocompatibility.Besides,the renal-clearable 2 nm AuNPs have a long blood circulation time and high tumor targeting efficiency.They can accumulate in the tumor area through the EPR effect（high permeability and long retention effect）and can minimize their non-specific accumulation in the reticuloendothelial system（RES）such as the liver and spleen.In this thesis,the effect of renal-clearable gold nanomaterials on the growth of mouse breast tumors was studied.On the one hand,this renal-clearable AuNPs can be used as a drug carrier to deliver anticancer drugs to tumor sites through endosomal escape and acid-sensitive release,thereby effectively inhibiting the growth of mouse breast tumors.On the other hand,from the perspective of safety,we explored the promoting effect of renal-clearable AuNPs on the growth of mouse breast tumors,and systematically studied the effect of the injection dose on its growth.The main contents are as follows:1.We have developed and characterized a p H-sensitive gold nanocarrier drug-controlled release system,DOX-PDPH-AuNPs,with endosomal escape function and high renal clearance efficiency.Doxorubicin（DOX）,a therapeutic agent,was modified with p H-sensitive hydrazone linker PDPH and attached to renal-clearable 2nm glutathione-modified AuNPs（GS-AuNPs）.Under the weakly acidic conditions of the endosome,PDPH would be cleaved,allowing DOX to be released from GS-AuNPs and reach the tumor area to exert its efficacy.It could be seen from in vitro release experiments that Au-DOX-PDPH was relatively stable under physiological p H conditions and DOX was released in a p H-and time-dependent manner under acidic conditions.The endosomal escape behavior of DOX was successfully observed in fluorescence imaging experiments.Au-DOX-PDPH had certain toxicity to mouse breast cancer 4T1 cells and showed good anti-tumor effect in mouse breast tumor model.These results clearly indicate that Au-DOX-PDPH,which can be activated in the tumor microenvironment,can successfully deliver DOX to tumor sites and inhibit tumor growth,which is expected to be used in cancer treatment.2.We investigated the effects of renal-clearable 2 nm GS-AuNPs and PEG-AuNPs on the growth of mouse breast tumors.Compared with pure GSH and PEG,the total antioxidant capacity of GS-AuNPs and PEG-AuNPs was significantly improved,and they showed concentration-dependent scavenging effects on Superoxide anion（O₂·^-）and free radicals.These AuNPs had basically no toxic effects on mouse breast cancer 4T1 cells,showing good biocompatibility.Tail vein injection of GSH,PEG and GS-AuNPs to tumor-bearing mice could effectively promote the accelerated growth of breast tumors.Among them,continuous injection of PEG had the most obvious effect while injection of PEG-AuNPs had almost no promoting effect on the growth of mouse breast tumors.The results of ICP-OES analysis showed that the accumulation of GS-AuNPs and PEG-AuNPs in the tumor site was greatly increased,while retaining low RES organ uptake and high renal clearance efficiency.These results suggest that tail vein injection of GS-AuNPs can promote the accelerated growth of mouse breast tumors,while injection of PEG-AuNPs does not have such a promotion effect,and the possibility of insufficient dose cannot be ruled out.3.We studied the effects of renal-clearable 2 nm GS-AuNPs and PEG-AuNPs at different doses on the growth of mouse breast tumors.When the injection dose of GS-AuNPs was 2.25-45mg/kg,the higher the dose,the more obvious the effect of accelerating the growth of mouse breast tumors.When the injection dose of GS-AuNPs was 45-900 mg/kg,the tail vein injection of GS-AuNPs could accelerate the growth of mouse breast tumors,but also damaged the heart,liver and other major organs of mice,so the promotion effect was not as good as the low-dose group.These damages were well documented by HE staining.In contrast,high-dose PEG-AuNPs had a more significant growth promoting effect than low-dose PEG-AuNPs,possibly because PEG-AuNPs did not alter the redox environment in the tumor region.The results of HE staining and Ki-67 staining showed that the tumor tissues of the mice in the low-dose GS-AuNPs group and the high-dose PEG-AuNPs group had pseudo-adenoid structures,indicating the active growth of tumor cells.In addition,most of the tumor cells had left the proliferation stage and entered the non-proliferation stage of G₀phase,differentiation or death.These results indicate that the tail vein injection of renal-clearable AuNPs can promote the accelerated growth of mouse breast tumors in a dose-dependent manner.