Controlled Synthesis Of Hollow Vesicle-Like Nanomedicine And Their Applications In Tumor Theranostics

Early detection and treatment play a key role in improving the cancer treatment ratio and prolonging the survival of patients.The rapid development of nanotechnology provides an effective strategy for the early diagnosis and effective treatment of tumors.Ferroptosis,an iron-based cell death pathway,has recently attracted great attention owing to its effectiveness in killing cancer cells.Previous investigations in various countries focused on the iron-based nanomaterials to induce ferroptosis.After taken up by tumor cells,the iron-based nanomaterials can release iron ions and then take part in the Fenton reaction to upregulate the reactive oxygen species(ROS)level in cells,and finally causing cell death by ferroptosis.Recently,ferroptosis also can be induced by inhibiting the activity of glutathione peroxidase 4(GPX4)and increasing the level of cellular lipid peroxidation.In this paper,we first designed and synthesized arginine-rich manganese silicate nanobubbles(AMSNs),and charactered the structure of AMSNs by transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and energy-dispersive X-ray spectroscopy(EDX).The surface modification of Arg was characterized by ultraviolet spectrophotometer(UV-vis),infrared spectrometer(FTIR)and thermogravimetric analysis(TGA).The particle size and surface potential of the AMSNs were characterized by dynamic light scattering analyzer and zeta potential analyzer.These results showed that AMSNs were hollow manganese silicate nanobubbles.Each singal nanobubble had a particle size of about 6±1 nm and the surface modification by Arg indicated the successful synthesis of AMSNs.The stability and biodegradation behavior of AMSNs were further analyzed by TEM and inductively coupled plasma mass spectrometry(ICP-MS),and the result showed that AMSNs could degrade and release manganese ions at low pH and high GSH conditions.The selective uptake of tumor cells showed that the liver cancer cells Huh7 had higher uptake efficiency than normal liver cells L02,indicating that Arg on the surface of AMSNs can increase the uptake ratio of AMSNs by tumor cells.Further investigation of the cellular uptake pathway of AMSNs revealed that AMSNs were mainly endocytosed by endosomal/lysosomal pathways.The in vitro and in vivo T1-weighted magnetic resonance imaging(MRI)enhancement ability of AMSNs were examined by a magnetic resonance scanner.The results showed that the relaxation efficiency(r1)of AMSNs increased from 0.1573 mM-1 s-1(pH 7.4,GSH 0 mM)to 4.5865 mM-1 s-1(pH 5.0,GSH 10 mM).In vivo experimental results showed that the signal intensity at the tumor site was enhanced after the administration of AMSNs,indicating that AMSNs could be used as a good tumor microenvironment-responsive T1 MRI contrast agent.Advantages of the nanobubble structure of AMSNs were determined by comparing with solid manganese oxide nanoparticles(MnO)and the mechanism of the ferroptosis induced by AMSNs was also been investigated.The results showed that AMSNs had higher GSH depletion efficiency than MnO and AMSNs also exhibited higher cytotoxicity.The mechanism of how AMSNs causeing cell death was investigated by the addition of various inhibitors,and the results showed that AMSNs caused cell death mainly through the pathway of ferroptosis.Because AMSNs can efficiently consume GSH in cells,thereby inhibiting the activity of GPX4,increasing the level of intracellular lipid oxidation,and finally causing cell ferroptosis.The controlled drug release profile of AMSNs and anti-tumor effects in vitro and in vivo were further investigated.The drug loaded with doxorubicin(DOX)mainly by electrostatic interaction and coordinate bonds between the N atoms in DOX and the Mn atoms in the AMSNs.With the biodegradation of AMSNs under the tumor microenvironment,DOX can be released for targeted anti-tumor therapy.In vitro experiments had shown that AMSNs alone had good anti-tumor effects,while combined with DOX,a synergetic result could be further obtained.In vivo studies showed that compared with the PBS group and the DOX group,the AMSNs and AMSNs/DOX groups significantly inhibited tumor growth and reduced tumor volume,while AMSNs/DOX significantly reduced the heart and liver toxicity compared with free DOX.In addition,in vivo biosafety investigation results showed that AMSNs could be excreted by feces and urine,and would not accumulated in the body to produce long-term toxicity,indicating that AMSNs have good biosafety.The results in this paper showed that the AMSNs could efficiently deplete the GSH level in tumor cells,thereby inhibiting the activity of GPX4,increasing the level of lipid oxidation,and finally causing tumor cells death by ferroptosis.In addition,the degradation of AMSNs during the GSH depletion contributed to T1-weighted magnetic resonance imaging(MRI)enhancement as well as on-demand chemotherapeutic drug release for synergistic cancer therapy.The mechanism of ferroptosis caused by GSH depletion can provide new theoretical,experimental evidences and design ideas for future design and development of more tumor visualization therapeutic drugs.