Bioactive inorganic nanomaterials for cancer theranostics.

Bioactive materials are a special class of biomaterials that can react in vivo to induce a biological response or regulate biological functions, thus achieving a better curative effect than traditional inert biomaterials. For cancer theranostics, compared with organic or polymer nanomaterials, inorganic nanomaterials possess unique physical and chemical properties, have stronger mechanical stability on the basis of maintaining certain bioactivity, and are easy to be compounded with various carriers (polymer carriers, biological carriers, etc.), so as to achieve specific antitumor efficacy. After entering the nanoscale, due to the nano-size effect, high specific surface area and special nanostructures, inorganic nanomaterials exhibit unique biological effects, which significantly influence the interaction with biological organisms. Therefore, the research and applications of bioactive inorganic nanomaterials in cancer theranostics have attracted wide attention. In this review, we mainly summarize the recent progress of bioactive inorganic nanomaterials in cancer theranostics, and also introduce the definition, synthesis and modification strategies of bioactive inorganic nanomaterials. Thereafter, the applications of bioactive inorganic nanomaterials in tumor imaging and antitumor therapy, including tumor microenvironment (TME) regulation, catalytic therapy, gas therapy, regulatory cell death and immunotherapy, are discussed. Finally, the biosafety and challenges of bioactive inorganic nanomaterials are also mentioned, and their future development opportunities are prospected. This review highlights the bioapplication of bioactive inorganic nanomaterials.

Degradable Vanadium Disulfide Nanostructures with Unique Optical and Magnetic Functions for Cancer Theranostics.

Multifunctional biodegradable inorganic theranostic nano-agents are of great interest to the field of nanomedicine. Upon lipid modification, VS2 nanosheets could be converted into ultra-small VS2 nanodots encapsulated inside polyethylene glycol (PEG) modified lipid micelles. Owing to paramagnetism, high near-infrared (NIR) absorbance, and chelator-free 99m Tc4+ labeling of VS2 , such VS2 @lipid-PEG nanoparticles could be used for T1-weighted magnetic resonance (MR), photoacoustic (PA),and single photon emission computed tomography (SPECT) tri-modal imaging guided photothermal ablation of tumors. Importantly, along with the gradual degradation of VS2 , our VS2 @lipid-PEG nanoparticles exhibit effective body excretion without appreciable toxicity. The unique advantages of VS2 nanostructures with highly integrated functionalities and biodegradable behaviors mean they are promising for applications in cancer theranostics.

Magnesium galvanic cells produce hydrogen and modulate the tumor microenvironment to inhibit cancer growth.

Hydrogen can be used as an anti-cancer treatment. However, the continuous generation of H2 molecules within the tumor is challenging. Magnesium (Mg) and its alloys have been extensively used in the clinic as implantable metals. Here we develop, by decorating platinum on the surface of Mg rods, a Mg-based galvanic cell (MgG), which allows the continuous generation of H2 in an aqueous environment due to galvanic-cell-accelerated water etching of Mg. By implanting MgG rods into a tumor, H2 molecules can be generated within the tumor, which induces mitochondrial dysfunction and intracellular redox homeostasis destruction. Meanwhile, the Mg(OH)2 residue can neutralize the acidic tumor microenvironment (TME). Such MgG rods with the micro-galvanic cell structure enable hydrogen therapy to inhibit the growth of tumors, including murine tumor models, patient-derived xenografts (PDX), as well as VX2 tumors in rabbits. Our research suggests that the galvanic cells for hydrogen therapy based on implantable metals may be a safe and effective cancer treatment.

Biodegradable Fe-Doped Vanadium Disulfide Theranostic Nanosheets for Enhanced Sonodynamic/Chemodynamic Therapy.

Sonodynamic therapy (SDT), a noninvasive and highly penetrating tumor therapy, which employs ultrasound and sonosensitizers, has attracted extensive attention because of its ability to treat deep tumors. However, many current sonosensitizers have drawbacks in phototoxicity and limited sonodynamic effect. Herein, as a novel kind of sonosensitizer, iron-doped vanadium disulfide nanosheets (Fe-VS2 NSs) are constructed by a high-temperature organic-solution method and further modified with polyethylene glycol (PEG). With Fe doping, the sonodynamic effect of Fe-VS2 NSs is greatly enhanced, owing to the prolonged electron-hole recombination time. Simultaneously, such Fe-VS2-PEG NSs as a good Fenton agent can be utilized for chemodynamic therapy (CDT) by using the endogenous H2O2 in the tumor microenvironment (TME). Moreover, the multivalent Fe and V elements in the Fe-VS2 NSs can consume glutathione to amplify the reactive oxygen species-induced oxidative stress by SDT and CDT. Utilizing the strong near-infrared optical absorbance and enhanced magnetic resonance (MR) contrast by Fe-VS2 NSs, photoacoustic/MR biomodal imaging reveals a high accumulation of Fe-VS2-PEG NSs in the tumor. The great tumor suppression effect is then achieved by the in vivo combined CDT&SDT treatment. Importantly, most of the injected Fe-VS2-PEG NSs can be gradually decomposed and excreted from the mice, making them as safe sonosensitizers for cancer treatment. Our work highlights a new type of biodegradable sonosensitizer with the ability of regulating TME for applications in cancer theranostics.