A hybrid nanozymes in situ oxygen supply synergistic photothermal/chemotherapy of cancer management

Catalytic Nanoparticles in Biomedical Applications: Exploiting Advanced Nanozymes for Therapeutics and Diagnostics

Catalytic nanoparticles (CNPs) as heterogeneous catalyst reveals superior activity due to their physio-chemical features, such as high surface-to-volume ratio and unique optical, electric, and magnetic properties. The CNPs, based on their physio-chemical nature, can either increase the reactive oxygen species (ROS) level for tumor and antibacterial therapy or eliminate the ROS for cytoprotection, anti-inflammation, and anti-aging. In addition, the catalytic activity of nanozymes can specifically trigger a specific reaction accompanied by the optical feature change, presenting the feasibility of biosensor and bioimaging applications. Undoubtedly, CNPs play a pivotal role in pushing the evolution of technologies in medical and clinical fields, and advanced strategies and nanomaterials rely on the input of chemical experts to develop. Herein, a systematic and comprehensive review of the challenges and recent development of CNPs for biomedical applications is presented from the viewpoint of advanced nanomaterial with unique catalytic activity and additional functions. Furthermore, the biosafety issue of applying biodegradable and non-biodegradable nanozymes and future perspectives are critically discussed to guide a promising direction in developing span-new nanozymes and more intelligent strategies for overcoming the current clinical limitations.

Bioengineered Bacterial Membrane Vesicles with Multifunctional Nanoparticles as a Versatile Platform for Cancer Immunotherapy

Inducing immunogenic cell death (ICD) is a critical strategy for enhancing cancer immunotherapy. However, inefficient and risky ICD inducers along with a tumor hypoxia microenvironment seriously limit the immunotherapy efficacy. Non-specific delivery is also responsible for this inefficiency. In this work, we report a drug-free bacteria-derived outer membrane vesicle (OMV)-functionalized Fe₃O₄-MnO₂ (FMO) nanoplatform that realized neutrophil-mediated targeted delivery and photothermally enhanced cancer immunotherapy. In this system, modification of OMVs derived from Escherichia coli enhanced the accumulation of FMO NPs at the tumor tissue through neutrophil-mediated targeted delivery. The FMO NPs underwent reactive decomposition in the tumor site, generating manganese and iron ions that induced ICD and O₂ that regulated the tumor hypoxia environment. Moreover, OMVs are rich in pathogen-associated pattern molecules that can overcome the tumor immunosuppressive microenvironment and effectively activate immune cells, thereby enhancing specific immune responses. Photothermal therapy (PTT) caused by MnO₂ and Fe₃O₄ can not only indirectly stimulate systemic immunity by directly destroying tumor cells but also promote the enrichment of neutrophil-equipped nanoparticles by enhancing the inflammatory response at the tumor site. Finally, the proposed multi-modal treatment system with targeted delivery capability realized effective tumor immunotherapy to prevent tumor growth and recurrence.

Nanoceria: an innovative strategy for cancer treatment

Nanoceria or cerium oxide nanoparticles characterised by the co-existing of Ce³⁺ and Ce⁴⁺ that allows self-regenerative, redox-responsive dual-catalytic activities, have attracted interest as an innovative approach to treating cancer. Depending on surface characteristics and immediate environment, nanoceria exerts either anti- or pro-oxidative effects which regulate reactive oxygen species (ROS) levels in biological systems. Nanoceria mimics ROS-related enzymes that protect normal cells at physiological pH from oxidative stress and induce ROS production in the slightly acidic tumour microenvironment to trigger cancer cell death. Nanoceria as nanozymes also generates molecular oxygen that relieves tumour hypoxia, leading to tumour cell sensitisation to improve therapeutic outcomes of photodynamic (PDT), photothermal (PTT) and radiation (RT), targeted and chemotherapies. Nanoceria has been engineered as a nanocarrier to improve drug delivery or in combination with other drugs to produce synergistic anti-cancer effects. Despite reported preclinical successes, there are still knowledge gaps arising from the inadequate number of studies reporting findings based on physiologically relevant disease models that accurately represent the complexities of cancer. This review discusses the dual-catalytic activities of nanoceria responding to pH and oxygen tension gradient in tumour microenvironment, highlights the recent nanoceria-based platforms reported to be feasible direct and indirect anti-cancer agents with protective effects on healthy tissues, and finally addresses the challenges in clinical translation of nanoceria based therapeutics.

Hypoxia-ameliorated photothermal manganese dioxide nanoplatform for reversing doxorubicin resistance

Drug resistance is a huge hurdle in tumor therapy. Tumor hypoxia contributes to chemotherapy resistance by inducing the hypoxia-inducible factor-1α (HIF-1α) pathway. To reduce tumor hypoxia, novel approaches have been devised, providing significant importance to reverse therapeutic resistance and improve the effectiveness of antitumor therapies. Herein, the nanosystem of bovine serum albumin (BSA)-templated manganese dioxide (MnO₂) nanoparticles (BSA/MnO₂ NPs) loaded with doxorubicin (DOX) (DOX-BSA/MnO₂ NPs) developed in our previous report was further explored for their physicochemical properties and capacity to reverse DOX resistance because of their excellent photothermal and tumor microenvironment (TME) response effects. The DOX-BSA/MnO₂ NPs showed good biocompatibility and hemocompatibility. Meanwhile, DOX-BSA/MnO₂ NPs could greatly affect DOX pharmacokinetic properties, with prolonged circulation time and reduced cardiotoxicity, besides enhancing accumulation at tumor sites. DOX-BSA/MnO₂ NPs can interact with H₂O₂ and H⁺ in TME to form oxygen and exhibit excellent photothermal effect to further alleviate hypoxia due to MnO₂, reversing DOX resistance by down-regulating HIF-1α expression and significantly improving the antitumor efficiency in DOX-resistant human breast carcinoma cell line (MCF-7/ADR) tumor model. The hypoxia-ameliorated photothermal MnO₂ platform is a promising strategy for revering DOX resistance.

Iridium Tungstate Nanozyme-Mediated Hypoxic Regulation and Anti-inflammation for Duplex Imaging Guided Photothermal Therapy of Metastatic Breast Tumors

Metastasis of breast cancer is key to poor prognosis and high mortality. However, the excess reactive oxygen species (ROS) and inflammatory response induced by photothermal therapy (PTT) further aggravate tumor metastasis. Meanwhile, the hypoxic tumor microenvironment promotes tumor cells to metastasize to distant organs. Herein, the intrinsic limitations of PTT for metastatic tumor have been addressed by fabricating polyethylene glycol modified iridium tungstate (IrWO_x-PEG) nanoparticles. The as-designed IrWO_x-PEG nanoparticles displayed good photothermal (PT) conversion ability for duplex photoacoustic/PT imaging guided PTT and multienzyme mimetic feature for broad-spectrum ROS scavenging. On the one hand, IrWO_x-PEG effectively removed excess ROS generated during PTT and reduced inflammation. On the other hand, owing to the catalase-like activity, it preferentially triggered the catalytic production of oxygen by decomposing ROS, leading to relieving of the hypoxic microenvironment. Hence, under bimodal imaging guidance, IrWO_x-PEG induced PTT completely eliminated in situ breast cancer in 4T1 tumor-bearing mice with no observable system toxicity, as well as further restricting tumor metastasis to other vital organs (lungs) by ROS scavenging, anti-inflammation, and regulating hypoxic microenvironment. We anticipate that this work will lead to new treatment strategies for other metastatic cancers.

Recent Trends in Composite Nanozymes and Their Pro-Oxidative Role in Therapeutics

Nanozymes are inorganic nanostructures whose enzyme mimic activities are increasingly explored in disease treatment, taking inspiration from natural enzymes. The catalytic ability of nanozymes to generate reactive oxygen species can be used for designing effective antimicrobials and antitumor therapeutics. In this context, composite nanozymes are advantageous, particularly because they integrate the properties of various nanomaterials to offer a single multifunctional platform combining photodynamic therapy (PDT), photothermal therapy (PTT), and chemodynamic therapy (CDT). Hence, recent years have witnessed great progress in engineering composite nanozymes for enhanced pro-oxidative activity that can be utilized in therapeutics. Therefore, the present review traverses over the newer strategies to design composite nanozymes as pro-oxidative therapeutics. It provides recent trends in the use of composite nanozymes as antibacterial, antibiofilm, and antitumor agents. This review also analyzes various challenges yet to be overcome by pro-oxidative composite nanozymes before being used in the field.

Oxygenic Enrichment in Hybrid Ruthenium Sulfide Nanoclusters for an Optimized Photothermal Effect

Transition-metal dichalcogenide (TMD)-based nanomaterials have been extensively explored for the photonic therapy. To the best of our knowledge, near-infrared (NIR) light is a requirement for the photothermal therapy (PTT) to achieve the feature of deep-tissue penetration, whereas no obvious absorption peaks existing in the NIR region for existing TMD nanomaterials limit their therapeutic efficacy. As one category of TMD nanomaterials, ruthenium sulfide-based nanomaterials have been less exploited in biomedical applications including tumor therapy so far. Here, we develop a facile biomineralization-assisted bottom-up strategy to synthesize oxygenic hybrid ruthenium sulfide nanoclusters (RuS_x NCs) by regulating the oxygen amounts and sulfur defects for the optimized PTT. By regulating the increasing initial molar ratios of Ru to S, RuS_x NCs with small sizes were endowed with increasing oxygen contents and sulfur defects, leading to the photothermal conversion efficiency (PCE) increasing from 32.8 to 41.9%, which were higher than that of most small-sized inorganic photothermal nanoagents. In contrast to commercial indocyanine green, these RuS_x NCs exhibited higher photostability under NIR laser irradiation. The high PCE and superior photostability allowed RuS_x NCs to effectively and completely ablate cancer cells. Thus, the proposed defect engineering strategy endows RuS_x NCs with an excellent photothermal effect for the PTT of tumors of living mice, which also proves the potential of further exploring the properties of RuS_x NCs for future biomedical applications.