Degradable Molybdenum Oxide Nanosheets with Rapid Clearance and Efficient Tumor Homing Capabilities as a Therapeutic Nanoplatform

Defect engineering to tailor structure-activity relationship in biodegradable nanozymes for tumor therapy by dual-channel death strategies

Pursuing biodegradable nanozymes capable of equipping structure-activity relationship provides new perspectives for tumor-specific therapy. A rapidly degradable nanozymes can address biosecurity concerns. However, it may also reduce the functional stability required for sustaining therapeutic activity. Herein, the defect engineering strategy is employed to fabricate Pt-doping MoOx (PMO) redox nanozymes with rapidly degradable characteristics, and then the PLGA-assembled PMO (PLGA@PMO) by microfluidics chip can settle the conflict between sustaining therapeutic activity and rapid degradability. Density functional theory describes that Pt-doping enables PMO nanozymes to exhibit an excellent multienzyme-mimicking catalytic activity originating from synergistic catalysis center construction with the interaction of Pt substitution and oxygen vacancy defects. The peroxidase- (POD), oxidase- (OXD), glutathione peroxidase- (GSH-Px), and catalase- (CAT) mimicking activities can induce robust ROS output and endogenous glutathione depletion under tumor microenvironment (TME) response, thereby causing ferroptosis in tumor cells by the accumulation of lipid peroxide and inactivation of glutathione peroxidase 4. Due to the activated surface plasmon resonance effect, the PMO nanozymes can cause hyperthermia-induced apoptosis through 1064 nm laser irradiation, and augment multienzyme-mimicking catalytic activity. This work represents a potential biological application for the development of therapeutic strategy for dual-channel death via hyperthermia-augmented enzyme-mimicking nanocatalytic therapy.

Oxygen-Deficient Molybdenum Oxide Nanosensitizers for Ultrasound-Enhanced Cancer Metalloimmunotherapy

Oxygen-deficient molybdenum oxide (MoO_X ) nanomaterials are prepared as novel nanosensitizers and TME-stimulants for ultrasound (US)-enhanced cancer metalloimmunotherapy. After PEGylation, MoO_X -PEG exhibits efficient capability for US-triggered reactive oxygen species (ROS) generation and glutathione (GSH) depletion. Under US irradiation, MoO_X -PEG generates a massive amount of ROS to induce cancer cell damage and immunogenic cell death (ICD), which can effectively suppress tumor growth. More importantly, MoO_X -PEG itself further stimulates the maturation of dendritic cells (DCs) and triggeres the activation of the cGAS-STING pathway to enhance the immunological effect. Due to the robust ICD induced by SDT and efficient DC maturation stimulated by MoO_X -PEG, the combination treatment of MoO_X -triggered SDT and aCTLA-4 further amplifies antitumor therapy, inhibits cancer metastases, and elicits robust immune responses to effectively defeat abscopal tumors.

Mo2 C-Derived Polyoxometalate for NIR-II Photoacoustic Imaging-Guided Chemodynamic/Photothermal Synergistic Therapy

To overcome the current limitations of chemodynamic therapy (CDT), a Mo₂ C-derived polyoxometalate (POM) is readily synthesized as a new CDT agent. It permits synergistic chemodynamic and photothermal therapy operating in the second near-infrared (NIR-II) biological transparent window for deep tissue penetration. POM aggregated in an acidic tumor micro-environment (TME) whereby enables specific tumor targeting. In addition to the strong ability to produce singlet oxygen (¹ O₂ ) presumably via Russell mechanism, its excellent photothermal conversion enhances the CDT effect, offers additional tumor ablation modality, and permits NIR-II photoacoustic imaging. Benefitting from the reversible redox property of molybdenum, the theranostics based on POM can escape from the antioxidant defense system. Moreover, combining the specific responsiveness to TME and localized laser irradiation, side-effects shall be largely avoided.

Highly stable molybdenum dioxide nanoparticles with strong plasmon resonance are promising in photothermal cancer therapy

Photothermal therapy (PTT) is one of promising cancer therapy with high efficiency and minimal invasiveness. Exploiting of perfect PTT agent is vital to improve the therapy. In this study, a new type of bow tie-like molybdenum dioxide (MoO₂) nanoparticles was successfully synthesized. These nanobow-ties had strong localized surface plasmon resonance (SPR) effect from visible to near infrared regions, and exhibited ultrahigh chemical stability. They could not only withstand high temperature heating without oxidation, but also resist the corrosion of strong acid and alkali. Meanwhile, the MoO₂ nanoparticles were highly stable in protein-containing biological medium, though they partly degraded in PBS solution. Both in vivo and in vitro experiments indicated that they exhibited inappreciable toxicity. Under illumination of near infrared laser, they showed excellent PTT effect, as revealed by significant inhibition of cancer cell viability in vitro and efficient destruction in tumor tissue growth in vivo. These MoO₂ nanoparticles possessed highly chemical stability and low toxicity with high PTT efficiency, thus promising them high potential as nanoagent in cancer treatment.

Plasmonic titanium nitride nanoparticles for in vivo photoacoustic tomography imaging and photothermal cancer therapy

Titanium nitride, an alternative plasmonic material to gold with unique physiochemical properties, has been widely used in microelectronics, biomedical devices and food-contact applications. However, its potential application in the area of biomedicine has not been effectively explored. With the spectral match of their plasmon resonance band and the biological transparency window as well as good biocompatibility, titanium nitride nanoparticles (TiN NPs) are promising photoabsorbing agents for photothermal therapy (PTT) and photoacoustic imaging. Nevertheless, the photothermal performance of TiN NPs has not been investigated until now. Here, we presented the investigation of employing TiN NPs as photoabsorbing agents for in vivo photoacoustic tomography (PAT) imaging-guided photothermal cancer therapy. Our experimental results showed that TiN NPs could strongly absorb the NIR light and provided up to 48% photothermal conversion efficiency. After PEGylation, the resultant nanoparticles demonstrated improved physiological stability and extensive blood retention. Following intravenously administration, they could simultaneously enhance the photoacoustic signals of the tumor region and destroy tumors in the tumor-bearing mouse model by taking advantage of the photothermal effect of the TiN NPs. Our findings highlighted the great potential of plasmonic TiN NPs in detection and treatment of cancer.