2D-ultrathin MXene/DOXjade platform for iron chelation chemo-photothermal therapy

Applications of pyroptosis activators in tumor immunotherapy

Contemporary progress in tumor immunotherapy has solidified its role as an effective approach in combating cancer. Nonetheless, the prevalent "immune cold" state within the tumor microenvironment poses a substantial barrier to its efficacy. Addressing this, pyroptosis-a gasdermin-mediated programmed cell death characterized by its inflammatory profile-emerges as a crucial mechanism. It catalyzes the release of vast quantities of pro-inflammatory cytokines and immunogens, potentially transforming immunosuppressive "cold" tumors into reactive "hot" ones. Herein, we will initially present an overview of pyroptosis as a distinct form of cell death, along with its molecular mechanisms. Subsequently, we will focus on introducing how pyroptosis activators are utilized in the field of tumor immunotherapy. Insights gained from applications of pyroptosis activators in tumor immunotherapy could lead to the development of safe and efficient pyroptosis activators, significantly enriching the arsenal for tumor immunotherapy.

Fabrication Methods, Structural, Surface Morphology and Biomedical Applications of MXene: A Review

Recently, two-dimensional (2-D) layered materials have revealed outstanding properties and play a crucial role for numerous advanced applications. The emerging transition metal carbides and nitrides, known as MXene with empirical formula Mn+1XnTx, have generated widespread attention and demonstrated impressive potential in various fields. The fabrication of 2-D novel MXene and its composites and their characterizations are applicable to vast applications in different areas such as energy storage, gas sensors, catalysis, and biomedical applications. In this review, the main focus is on the various synthesis methods, their properties, and biomedical applications. This review provides detailed illustrations of MXenes for many biomedical applications, including bioimaging, drug delivery, therapies, biosensors, tissue engineering, and antibacterial reagents. The challenges and future prospects were highlighted in a comprehensive manner, and the existing problems and potential for MXene-based biomaterials were analyzed with the goal of accelerating their use in the biomedical field.

MXene-based composites in smart wound healing and dressings

MXenes, a class of two-dimensional materials, exhibit considerable potential in wound healing and dressing applications due to their distinctive attributes, including biocompatibility, expansive specific surface area, hydrophilicity, excellent electrical conductivity, unique mechanical properties, facile surface functionalization, and tunable band gaps. These materials serve as a foundation for the development of advanced wound healing materials, offering multifunctional nanoplatforms with theranostic capabilities. Key advantages of MXene-based materials in wound healing and dressings encompass potent antibacterial properties, hemostatic potential, pro-proliferative attributes, photothermal effects, and facilitation of cell growth. So far, different types of MXene-based materials have been introduced with improved features for wound healing and dressing applications. This review covers the recent advancements in MXene-based wound healing and dressings, with a focus on their contributions to tissue regeneration, infection control, anti-inflammation, photothermal effects, and targeted therapeutic delivery. We also discussed the constraints and prospects for the future application of these nanocomposites in the context of wound healing/dressings.

Supramolecular 3 in 1: A Lubrication and Co-Delivery System for Synergistic Advanced Osteoarthritis Therapy

The complexity, heterogeneity, and drug resistance of diseases necessitate a shift in therapeutic paradigms from monotherapy to combination therapy, which could augment treatment efficiency. Effective treatment of advanced osteoarthritis (OA) requires addressing three key factors contributing to its deterioration: chronic joint inflammation, lubrication dysfunction, and cartilage-tissue degradation. Herein, we present a supramolecular nanomedicine of multifunctionality via molecular recognition and self-assembly. The employed macrocyclic carrier, zwitterion-modified cavitand (CV-2), not only accurately loads various drugs but also functions as a therapeutic agent with lubricating properties for the treatment of OA. Kartogenin (KGN), a drug for articular cartilage regeneration and protection, and flurbiprofen (FP), an anti-inflammatory agent, were coloaded onto CV-2 assembly, forming a supramolecular nanomedicine KGN&FP@CV-2. The three-in-one combination therapy of KGN&FP@CV-2 addresses the three pathological features for treating OA collectively, and thus provides long-term therapeutic benefits for OA through sustained drug release and intrinsic lubrication in vivo. The multifunctional integration of macrocyclic delivery and therapeutics provides a simple, flexible, and universal platform for the synergistic treatment of diseases involving multiple drugs.

Ti3C2 (MXene), an advanced carrier system: role in photothermal, photoacoustic, enhanced drugs delivery and biological activity in cancer therapy

In the realm of healthcare and the advancing field of medical sciences, the development of efficient drug delivery systems become an immense promise to cure several diseases. Despite considerable advancements in drug delivery systems, numerous challenges persist, necessitating further enhancements to optimize patient outcomes. Smart nano-carriers, for instance, 2D sheets nano-carriers are the recently emerging nanosheets that may garner attention for targeted delivery of bioactive compounds, drugs, and genes to kill cancer cells. Within these advancements, Ti3C2TX-MXene, characterized as a two-dimensional transition metal carbide, has surfaced as a prominent intelligent nanocarrier within nanomedicine. Its noteworthy characteristics facilitated it as an ideal nanocarrier for cancer therapy. In recent advancements in drug delivery research, Ti3C2TX-MXene 2D nanocarriers have been designed to release drugs in response to specific stimuli, guided by distinct physicochemical  parameters. This review emphasized the multifaceted role of Ti3C2TX-MXene as a potential carrier for delivering poorly hydrophilic drugs to cancer cells, facilitated by various polymer coatings. Furthermore, beyond drug delivery, this smart nanocarrier demonstrates utility in photoacoustic imaging and photothermal therapy, further highlighting its significant role in cellular mechanisms.

Recent advances using MXenes in biomedical applications

An MXene is a novel two-dimensional transition metal carbide or nitride, with a typical formula of Mn+1XnTx (M = transition metals, X = carbon or nitrogen, and T = functional groups). MXenes have found wide application in biomedicine and biosensing, owing to their high biocompatibility, abundant reactive surface groups, good conductivity, and photothermal properties. Applications include photo- and electrochemical sensors, energy storage, and electronics. This review will highlight recent applications of MXene and MXene-derived materials in drug delivery, tissue engineering, antimicrobial activity, and biosensors (optical and electrochemical). We further elaborate on recent developments in utilizing MXenes for photothermal cancer therapy, and we explore multimodal treatments, including the integration of chemotherapeutic agents or magnetic nanoparticles for enhanced therapeutic efficacy. The high surface area and reactivity of MXenes provide an interface to respond to the changes in the environment, allowing MXene-based drug carriers to respond to changes in pH, reactive oxygen species (ROS), and electrical signals for controlled release applications. Furthermore, the conductivity of MXene enables it to provide electrical stimulation for cultured cells and endows it with photocatalytic capabilities that can be used in antibiotic applications. Wearable and in situ sensors incorporating MXenes are also included. Major challenges and future development directions of MXenes in biomedical applications are also discussed. The remarkable properties of MXenes will undoubtedly lead to their increasing use in the applications discussed here, as well as many others.

A multifunctional nano-hydroxyapatite/MXene scaffold for the photothermal/dynamic treatment of bone tumours and simultaneous tissue regeneration

After resection of bone tumour, the risk of cancer recurrence and numerous bone defects continues to threaten the health of patients. To overcome the challenge, we developed a novel multifunctional scaffold material consisting mainly of nano-hydroxyapatite particles (n-HA), MXene nanosheets and g-C3N4 to prevent tumour recurrence and promote bone formation. N-HA has the potential to restrict the growth of osteosarcoma cells, and the combination of MXene and g-C3N4 enables the scaffolds to produce photodynamic and photothermal effects simultaneously under near infrared (NIR) irradiation. Surprisingly, n-HA can further enhance the synergistic anti-tumour function of photodynamic and photothermal, and the scaffolds can eradicate osteosarcoma cells in only 10 min at a mild temperature of 45 ℃. Moreover, the scaffold exhibit exceptional cytocompatibility and possesses the capacity to induce osteogenic differentiation of bone marrow mesenchymal stem cells. Therefore, this multifunctional scaffold can not only inhibits the proliferation of bone tumour cells and rapidly eradicate bone tumour through NIR irradiation, but also enhances osteogenic activity. This promising measure can be used to treat tissue damage after bone tumour resection.

Superhydrophilicity Regulation of Carbon Nanotubes Boosting Electrochemical Biosensing for Real-time Monitoring of H2O2 Released from Living Cells

Dynamic and accurate monitoring of cell-released electroactive signaling biomolecules through electrochemical techniques has drawn significant research interest for clinical applications. Herein, the functionalized carbon nanotubes (f-CNTs) featuring with gradient surface wettability from hydrophobicity to hydrophilicity, and even to superhydrophilicity, were regulated by thermolysis of an ionic liquid for exploration of the dependence of surface wettability on electrochemical biosensing performance to a cell secretion model of hydrogen peroxide (H2O2). The superhydrophilic f-CNTs demonstrated boosting electrocatalytic reduction activity for H2O2. Additionally, the molecular dynamic (MD) simulations confirmed the more cumulative number density distribution of H2O2 molecules closer to the superhydrophilic surface (0.20 vs 0.37 nm), which would provide a faster diffusional channel compared with the hydrophobic surface. Thereafter, a superhydrophilic biosensing platform with a lower detectable limit reduced by 200 times (0.5 vs 100 μM) and a higher sensitivity over 56 times (0.112 vs 0.002 μA μM cm-2) than that of the hydrophobic one was achieved. Given its excellent cytocompatibility, the superhydrophilic f-CNTs was successfully applied to determine H2O2 released from HeLa cells which were maintained alive after a 30 min real-time monitoring test. The surface hydrophilicity regulation of electrode materials presents a facile approach for real-time monitoring of H2O2 released from living cells and would provide new insights for other electroactive signaling targets at the cellular level.

Enhancement of MXene optical properties towards medical applications via metal oxide incorporation

MXenes have garnered research attention in the field of biomedical applications due to their unique properties, such as a large surface area, low toxicity, biocompatibility, and stability. Their optical behavior makes them versatile for a wide range of biomedical applications, from diagnostics to therapeutics. Nonetheless, MXenes have some minor limitations, including issues with restacking, susceptibility to oxidation, and a non-semiconducting nature. These limitations have prompted researchers to explore the incorporation of metal oxides into MXene structures. Metal oxides possess advantageous properties such as a high surface area, biocompatibility, intriguing redox behavior, catalytic activity, semiconducting properties, and enhanced stability. Incorporating metal oxides into MXenes can significantly improve their conductivity, surface area, and mechanical strength. In this review, we emphasize the importance of incorporating metal oxides into MXenes for light-influenced biomedical applications. We also provide insights into various preparation methods for incorporating metal oxides into MXene structures. Furthermore, we discuss how the incorporation of metal oxides enhances the optical behavior of MXenes. Finally, we offer a glimpse into the future potential of metal oxide-incorporated MXenes for diverse biomedical applications.

Multifunctional MXene-Based Bioactive Materials for Integrated Regeneration Therapy

The reconstruction engineering of tissue defects accompanied by major diseases including cancer, infection, and inflammation is one of the important challenges in clinical medicine. The development of innovative tissue engineering strategies such as multifunctional bioactive materials presents a great potential to overcome the challenge of disease-impaired tissue regeneration. As the major representative of two-dimensional nanomaterials, MXenes have shown multifunctional physicochemical properties and have been diffusely studied as multimodal nanoplatforms in the field of biomedicine. This review summarized the recent advances in the multifunctional properties of MXenes and integrated regeneration-therapy applications of MXene-based biomaterials, including tissue regeneration-tumor therapy, tissue regeneration-infection therapy, and tissue regeneration-inflammation therapy. MXenes have been recognized as good candidates for promoting tissue regeneration and treating diseases through photothermal therapy, regulating cell behavior, and drug and gene delivery. The current challenges and future perspectives of MXene-based biomaterials in integrated regeneration-therapy are also discussed well in this review. In summary, MXene-based biomaterials have shown promising potential for integrated tissue regeneration and disease treatment due to their favorable physicochemical properties and bioactive functions. However, there are still many obstacles and challenges that must be addressed for the regeneration-therapy applications of MXene-based biomaterials, including understanding the bioactive mechanism, ensuring long-term biosafety, and improving their targeting therapy capacity.

Mxene-Based Supramolecular Composite Hydrogels for Antioxidant and Photothermal Antibacterial Activities

Bacterial infections and oxidative damage caused by various reactive oxygen species (ROS) pose a significant threat to human health. It is highly desirable to find an ideal biomaterial system with broad spectrum antibacterial and antioxidant capabilities. A new supramolecular antibacterial and antioxidant composite hydrogel made of chiral L-phenylalanine-derivative (LPFEG) as matrix and Mxene (Ti3 C2 Tx ) as filler material is presented. The noncovalent interactions (H-bonding and π-π interactions) in between LPFEG and Mxene and the inversion of LPFEG chirality are verified by Fourier transform infrared and circular dichroism spectroscopy. The composite hydrogels show improved mechanical properties revealed by rheological analysis. The composite hydrogel system exhibits photothermal conversion efficiency (40.79%), which enables effective photothermal broad-spectrum antibacterial activities against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Furthermore, the Mxene also enables the composite hydrogel to exhibit excellent antioxidant activity by efficiently scavenging free radicals like DPPH•, ABTS•+, and •OH. These results indicate that the Mxene-based chiral supramolecular composite hydrogel, with improved rheological, antibacterial, and antioxidant properties has a great potential for biomedical applications.

Hybrid nanoarchitectonics of molybdenum dioxide (MoO2) and doxorubicin (DOX) for synergistic chemo-photothermal-based breast carcinoma therapy

Cancer has emerged as one of the severe ailments due to the uncontrolled proliferation rate of cells, accounting for millions of deaths annually. Despite the availability of various treatment strategies, including surgical interventions, radiation, and chemotherapy, tremendous advancements in the past two decades of research have evidenced the generation of different nanotherapeutic designs toward providing synergistic therapy. In this study, we demonstrate the assembly of a versatile nanoplatform based on the hyaluronic acid (HA)-coated molybdenum dioxide (MoO₂) assemblies to act against breast carcinoma. The hydrothermal approach-assisted MoO₂ constructs are immobilized with doxorubicin (DOX) molecules on the surface. Further, these MoO₂-DOX hybrids are encapsulated with the HA polymeric framework. Furthermore, the versatile nanocomposites of HA-coated MoO₂-DOX hybrids are systematically characterized using various characterization techniques, and explored biocompatibility in the mouse fibroblasts (L929 cell line), as well as synergistic photothermal (808-nm laser irradiation for 10 min, 1 W/cm²) and chemotherapeutic properties against breast carcinoma (4T1 cells). Finally, the mechanistic views concerning the apoptosis rate are explored using the JC-1 assay to measure the intracellular mitochondrial membrane potential (MMP) levels. In conclusion, these findings indicated excellent photothermal and chemotherapeutic efficacies, exploring the enormous potential of MoO₂ composites against breast cancer.

Roles of MXenes in biomedical applications: recent developments and prospects

....With the development of nanomedical technology, the application of various novel nanomaterials in the biomedical field has been greatly developed in recent years. MXenes, which are new inorganic nanomaterials with ultrathin atomic thickness, consist of layered transition metal carbides and nitrides or carbonitrides and have the general structural formula M_n+1X_nT_x (n = 1-3). Based on the unique structural features of MXenes, such as ultrathin atomic thickness and high specific surface area, and their excellent physicochemical properties, such as high photothermal conversion efficiency and antibacterial properties, MXenes have been widely applied in the biomedical field. This review systematically summarizes the application of MXene-based materials in biomedicine. The first section is a brief summary of their synthesis methods and surface modification strategies, which is followed by a focused overview and analysis of MXenes applications in biosensors, diagnosis, therapy, antibacterial agents, and implants, among other areas. We also review two popular research areas: wearable devices and immunotherapy. Finally, the difficulties and research progress in the clinical translation of MXene-based materials in biomedical applications are briefly discussed.

Covalent organic framework nanomedicines: Biocompatibility for advanced nanocarriers and cancer theranostics applications

Nanomedicines for drug delivery and imaging-guided cancer therapy is a rapidly growing research area. The unique properties of nanomedicines have a massive potential in solving longstanding challenges of existing cancer drugs, such as poor localization at the tumor site, high drug doses and toxicity, recurrence, and poor immune response. However, inadequate biocompatibility restricts their potential in clinical translation. Therefore, advanced nanomaterials with high biocompatibility and enhanced therapeutic efficiency are highly desired to fast-track the clinical translation of nanomedicines. Intrinsic properties of nanoscale covalent organic frameworks (nCOFs), such as suitable size, modular pore geometry and porosity, and straightforward post-synthetic modification via simple organic transformations, make them incredibly attractive for future nanomedicines. The ability of COFs to disintegrate in a slightly acidic tumor microenvironment also gives them a competitive advantage in targeted delivery. This review summarizes recently published applications of COFs in drug delivery, photo-immuno therapy, sonodynamic therapy, photothermal therapy, chemotherapy, pyroptosis, and combination therapy. Herein we mainly focused on modifications of COFs to enhance their biocompatibility, efficacy and potential clinical translation. This review will provide the fundamental knowledge in designing biocompatible nCOFs-based nanomedicines and will help in the rapid development of cancer drug carriers and theranostics.

The design of small-molecule prodrugs and activatable phototherapeutics for cancer therapy

Cancer remains as one of the most significant health problems, with approximately 19 million people diagnosed worldwide each year. Chemotherapy is a routinely used method to treat cancer patients. However, current treatment options lack the appropriate selectivity for cancer cells, are prone to resistance mechanisms, and are plagued with dose-limiting toxicities. As such, researchers have devoted their attention to developing prodrug-based strategies that have the potential to overcome these limitations. This tutorial review highlights recently developed prodrug strategies for cancer therapy. Prodrug examples that provide an integrated diagnostic (fluorescent, photoacoustic, and magnetic resonance imaging) response, which are referred to as theranostics, are also discussed. Owing to the non-invasive nature of light (and X-rays), we have discussed external excitation prodrug strategies as well as examples of activatable photosensitizers that enhance the precision of photodynamic therapy/photothermal therapy. Activatable photosensitizers/photothermal agents can be seen as analogous to prodrugs, with their phototherapeutic properties at a specific wavelength activated in the presence of disease-related biomarkers. We discuss each design strategy and illustrate the importance of targeting biomarkers specific to the tumour microenvironment and biomarkers that are known to be overexpressed within cancer cells. Moreover, we discuss the advantages of each approach and highlight their inherent limitations. We hope in doing so, the reader will appreciate the current challenges and available opportunities in the field and inspire subsequent generations to pursue this crucial area of cancer research.

Mechanical stimuli-driven cancer therapeutics

Mechanical stimulation utilizing deep tissue-penetrating and focusable energy sources, such as ultrasound and magnetic fields, is regarded as an emerging patient-friendly and effective therapeutic strategy to overcome the limitations of conventional cancer therapies based on fundamental external stimuli such as light, heat, electricity, radiation, or microwaves. Recent efforts have suggested that mechanical stimuli-driven cancer therapy (henceforth referred to as "mechanical cancer therapy") could provide a direct therapeutic effect and intelligent control to augment other anti-cancer systems as a synergistic combinational cancer treatment. This review article highlights the latest advances in mechanical cancer therapy to present a novel perspective on the fundamental principles of ultrasound- and magnetic field-mediated mechanical forces, including compression, tension, shear force, and torque, that can be generated in a cellular microenvironment using mechanical stimuli-activated functional materials. Additionally, this article will shed light on mechanical cancer therapy and inspire future research to pursue the development of ultrasound- and magnetic-field-activated materials and their applications in this field.

Cellular and molecular basis of therapeutic approaches to breast cancer

In recent decades, there has been a significant amount of research into breast cancer, with some important breakthroughs in the treatment of both primary and metastatic breast cancers. It's a well-known fact that treating breast cancer is still a challenging endeavour even though physicians have a fantastic toolset of the latest treatment options at their disposal. Due to limitations of current clinical treatment options, traditional chemotherapeutic drugs, and surgical options are still required to address this condition. In recent years, there have been several developments resulting in a wide range of treatment options. This review article discusses the cellular and molecular foundation of chemotherapeutic drugs, endocrine system-based treatments, biological therapies, gene therapy, and innovative techniques for treating breast cancer.

Functional two-dimensional MXenes as cancer theranostic agents

Recently, MXenes, as a kind of two-dimensional (2D) layered materials with exceptional performance, have become the research hotspots owing to their unique structural, electronic, and chemical properties. They have potential applications in electrochemical storage, photocatalysis, and biosensors. Furthermore, they have certain characteristics such as large surface area, favorable biocompatibility, and ideal mechanical properties, which can expand their applications in biomedical fields, especially in cancer therapy. To date, several researchers have explored the applications of MXenes in tumor elimination, which exhibited other fantastic properties of those 2D MXenes, such as efficient in vivo photothermal ablation, low phototoxicity, high biocompatibility, etc. In this review, the structures, properties, modifications, and preparation methods are introduced respectively. More importantly, the multifunctional platforms for cancer therapy based on MXenes nanosheets (NSs) are reviewed in detail, including single-modality and combined-modality cancer therapy. Finally, the prospects and challenges of MXenes are prospected and discussed. STATEMENT OF SIGNIFICANCE: In this review, the structures, properties, modifications, and preparation methods of MXenes nanomaterials are introduced, respectively. In addition, the preparation conditions and morphological characterizations of some common MXenes for therapeutic platforms are also summarized. More importantly, the practical applications of MXenes-based nanosheets are reviewed in detail, including drug delivery, biosensing, bioimaging, and multifunctional tumor therapy platforms. Finally, the future prospects and challenges of MXenes are prospected and discussed.

From Low to No O2-Dependent Hypoxia Photodynamic Therapy (hPDT): A New Perspective

The advent of photochemical techniques has revolutionized the landscape of biology and medical sciences. Especially appealing in this context is photodynamic therapy (PDT), which is a photon-initiated treatment modality that uses cytotoxic reactive oxygen species (ROS) to kill malignant cells. In the past decade, PDT has risen to the forefront of cancer therapy. Its optical control enables noninvasive and spatiotemporal manipulation of the treatment process, and its photoactive nature allows unique patterns to avoid drug resistance to conventional chemotherapeutics. However, despite the impressive advances in this field, achieving widespread clinical adoption of PDT remains difficult. A major concern is that in the hostile tumor microenvironment, tumor cells are hypoxic, which hinders ROS generation during PDT action. To overcome this "Achilles' heel", current strategies focus primarily on the improvement of the intratumoral O₂ perfusion, while clinical trials suggest that O₂ enrichment may promote cancer cell proliferation and metastasis, thereby making FDA approval and clinical transformation of these paradigms challenging.In an effort to improve hypoxia photodynamic therapy (hPDT) in the clinic, we have explored "low to no O₂-dependent" photochemical approaches over the years to combat hypoxia-induced resistance. In this Account, we present our contributions to this theme during the past 5 years, beginning with low O₂-dependent approaches (e.g., type I superoxide radical (O₂^•-) generator, photodynamic O₂-economizer, mitochondrial respiration inhibition, cellular self-protective pathway modulation, etc.) and progressing to O₂-independent strategies (e.g., autoadaptive PDT/PTT complementary therapy, O₂-independent artificial photoredox catalysis in cells). These studies have attracted tremendous attention. Particularly in the pioneering work of 2018, we presented the first demonstration that the O₂^•--mediated partial O₂-recyclability mechanism can overcome PDT resistance ( J. Am. Chem. Soc. 2018, 140, 14851-14859). This launched an era of renewed interest in type I PDT, resulting in a plethora of new O₂^•- photogenerators developed by many groups around the world. Moreover, with the discovery of O₂-independent photoredox reactions in living cells, artificial photoredox catalysis has emerged as a new field connecting photochemistry and biomedicine, stimulating the development of next-generation phototherapeutic tools ( J. Am. Chem. Soc. 2022, 144, 163-173). Our recent work also disclosed that "photoredox catalysis in cells" might be a general mechanism of action of PDT ( Proc. Natl. Acad. Sci. U.S.A. 2022, 119, e2210504119). These emergent concepts, molecular designs, photochemical mechanisms, and applications in cancer diagnosis and therapeutics, as well as pros and cons, are discussed in depth in this Account. It is expected that our contributions to date will be of general use to researchers and inspire future efforts to identify more promising hPDT approaches that better meet the clinical needs of cancer therapy.

Advanced MXene-Based Micro- and Nanosystems for Targeted Drug Delivery in Cancer Therapy

MXenes with unique mechanical, optical, electronic, and thermal properties along with a specific large surface area for surface functionalization/modification, high electrical conductivity, magnetic properties, biocompatibility, and low toxicity have been explored as attractive candidates for the targeted delivery of drugs in cancer therapy. These two-dimensional materials have garnered much attention in the field of cancer therapy since they have shown suitable photothermal effects, biocompatibility, and luminescence properties. However, outstanding challenging issues regarding their pharmacokinetics, biosafety, targeting properties, optimized functionalization, synthesis/reaction conditions, and clinical translational studies still need to be addressed. Herein, recent advances and upcoming challenges in the design of advanced targeted drug delivery micro- and nanosystems in cancer therapy using MXenes have been discussed to motivate researchers to further investigate this field of science.

Cancer therapeutics based on diverse energy sources

Light-based phototherapy has been developed for cancer treatment owing to its non-invasiveness and spatiotemporal control. Despite the unique merits of phototherapy, one critical disadvantage of light is its limited penetration depth, which restricts its application in cancer treatment. Although many researchers have developed various strategies to deliver light into deep-seated tumors with two-photon and near-infrared light irradiation, phototherapy encounters the peculiar limitations of light. In addition, high oxygen dependency is another limitation of photodynamic therapy to treat hypoxic tumors. To overcome the drawbacks of conventional treatments, various energy sources have been developed for cancer treatment. Generally, most energy sources, such as ultrasound, chemiluminescence, radiation, microwave, electricity, and magnetic field, are relatively free from the restraint of penetration depth. Combining other strategies or therapies with other energy-source-based therapies improves the strength and compensates for the weakness. This tutorial review focuses on recent advances in the diverse energy sources utilized in cancer treatment and their future perspectives.

Photoredox catalysis may be a general mechanism in photodynamic therapy

Elucidating the underlying photochemical mechanisms of action (MoA) of photodynamic therapy (PDT) may allow its efficacy to be improved and could set the stage for the development of new classes of PDT photosensitizers. Here, we provide evidence that "photoredox catalysis in cells," wherein key electron transport pathways are disrupted, could constitute a general MoA associated with PDT. Taking the cellular electron donor nicotinamide adenine dinucleotide as an example, we have found that well-known photosensitizers, such as Rose Bengal, BODIPY, phenoselenazinium, phthalocyanine, and porphyrin derivatives, are able to catalyze its conversion to NAD+. This MoA stands in contrast to conventional type I and type II photoactivation mechanisms involving electron and energy transfer, respectively. A newly designed molecular targeting photocatalyst (termed CatER) was designed to test the utility of this mechanism-based approach to photosensitizer development. Photoexcitation of CatER induces cell pyroptosis via the caspase 3/GSDME pathway. Specific epidermal growth factor receptor positive cancer cell recognition, high signal-to-background ratio tumor imaging (SBRTI = 12.2), and good tumor growth inhibition (TGI = 77.1%) are all hallmarks of CatER. CatER thus constitutes an effective near-infrared pyroptotic cell death photo-inducer. We believe the present results will provide the foundation for the synthesis of yet-improved phototherapeutic agents that incorporate photocatalytic chemistry into their molecular design.

High Drug-Loading Nanomedicines for Tumor Chemo-Photo Combination Therapy: Advances and Perspectives

The combination of phototherapy and chemotherapy (chemo−photo combination therapy) is an excellent attempt for tumor treatment. The key requirement of this technology is the high drug-loading nanomedicines, which can load either chemotherapy drugs or phototherapy agents at the same nanomedicines and simultaneously deliver them to tumors, and play a multimode therapeutic role for tumor treatment. These nanomedicines have high drug-loading efficiency (>30%) and good tumor combination therapeutic effect with important clinical application potential. Although there are many reports of high drug-loading nanomedicines for tumor therapy at present, systematic analyses on those nanomedicines remain lacking and a comprehensive review is urgently needed. In this review, we systematically analyze the current status of developed high drug-loading nanomedicines for tumor chemo−photo combination therapy and summarize their types, methods, drug-loading properties, in vitro and in vivo applications. The shortcomings of the existing high drug-loading nanomedicines for tumor chemo−photo combination therapy and the possible prospective development direction are also discussed. We hope to attract more attention for researchers in different academic fields, provide new insights into the research of tumor therapy and drug delivery system and develop these nanomedicines as the useful tool for tumor chemo−photo combination therapy in the future.

Immunosonodynamic Therapy Designed with Activatable Sonosensitizer and Immune Stimulant Imiquimod

Sonodynamic therapy (SDT) has garnered extensive attention as a noninvasive treatment for deep tumors. Furthermore, imiquimod (R837), an FDA-approved toll-like receptor 7 agonist, is commonly used in clinical settings as an immune adjuvant. We prepared an activatable sonodynamic sensitizer platform (MR) based on glutathione-sensitive disulfide bonds linking Leu-MB, the reduced form of methylene blue (MB), and R837 to achieve efficient combinatory SDT and immunotherapy for tumors without harming normal tissues. We also used the amphiphilic polymer C₁₈PMH-PEG to create self-assembled MB-R837-PEG (MRP) nanoparticles for immunosonodynamic therapy (iSDT). iSDT is a cancer treatment that combines activatable SDT and immunotherapy. Our iSDT demonstrated an excellent sonodynamic effect only at the tumor site, demonstrating high specificity in killing tumor cells when compared to SDT reported in the literature. The iSDT improves its tumor-killing effect by inducing an immune response, which is accomplished by secreted immune adjuvants in the tumor site. MRP was selectively activated by glutathione in the tumor microenvironment to release MB and R837, exhibiting excellent antitumor sonodynamic and immune responses. In addition, when combined with an α-PD-L1 antibody for immune checkpoint blockade, this therapy effectively inhibited tumor metastasis. Furthermore, mice treated with iSDT and α-PD-L1 antibody did not develop tumors even after tumor reinoculation, indicating that long-term immune memory was achieved. The concept of sonodynamic sensitizer preparation as a next-generation iSDT based on a noninvasive synergistic therapeutic modality applicable in the near future is presented in this study.

Photocatalytic Superoxide Radical Generator that Induces Pyroptosis in Cancer Cells

Pyroptosis, a newly characterized form of immunogenic cell death, is attracting increasing attention as a promising approach to cancer immunotherapy. However, biocompatible strategies to activate pyroptosis remain rare. Here, we show that a photocatalytic superoxide radical (O₂^-•) generator, NI-TA, triggers pyroptosis in cancer cells. NI-TA was designed to take advantage of an intramolecular triplet-ground state splitting energy modulation approach. Detailed studies revealed that the pyroptosis triggered by NI-TA under conditions of photoexcitation proceeds through a caspase-3/gasdermin E (GSDME) pathway rather than via canonical processes involving caspase-1/gasdermin-D (GSDMD). NI-TA was found to function via a partial-O₂-recycling mode of action and to trigger cell pyroptosis and provide for effective cancer cell ablation even under conditions of hypoxia (≤2% O₂). In the case of T47D 3D multicellular spheroids, good antitumor efficiency and stemness inhibition are achieved. This work highlights how photocatalytic chemistry may be leveraged to develop effective pyroptosis-inducing agents.

Advances of MXenes; Perspectives on Biomedical Research

The last decade witnessed the emergence of a new family of 2D transition metal carbides and nitrides named MXenes, which quickly gained momentum due to their exceptional electrical, mechanical, optical, and tunable functionalities. These outstanding properties also rendered them attractive materials for biomedical and biosensing applications, including drug delivery systems, antimicrobial applications, tissue engineering, sensor probes, auxiliary agents for photothermal therapy and hyperthermia applications, etc. The hydrophilic nature of MXenes with rich surface functional groups is advantageous for biomedical applications over hydrophobic nanoparticles that may require complicated surface modifications. As an emerging 2D material with numerous phases and endless possible combinations with other 2D materials, 1D materials, nanoparticles, macromolecules, polymers, etc., MXenes opened a vast terra incognita for diverse biomedical applications. Recently, MXene research picked up the pace and resulted in a flood of literature reports with significant advancements in the biomedical field. In this context, this review will discuss the recent advancements, design principles, and working mechanisms of some interesting MXene-based biomedical applications. It also includes major progress, as well as key challenges of various types of MXenes and functional MXenes in conjugation with drug molecules, metallic nanoparticles, polymeric substrates, and other macromolecules. Finally, the future possibilities and challenges of this magnificent material are discussed in detail.

Thermal Properties of MXenes and Relevant Applications

The properties and applications of MXenes (a family of layered transition metal carbides, nitrides, and carbonitrides) have aroused enormous research interests for a decade since the successful synthesis of few-layer transition metal carbides in 2011. Though MXenes, as the building blocks, have already been applied in various fields (such as wearable electronics) owing to the distinctive optical, mechanical and electrical properties, their thermal stability and intrinsic thermal properties were less thoroughly investigated compared to other characteristics in early reports. The pioneering theoretical prediction of the thermoelectric nature of MXenes was performed in 2013 while the first experiment-based report concerning the degradation behavior of the 2D structure at elevated temperatures in a controlled atmosphere was published in 2015, followed by numerous discoveries regarding the thermal properties of MXenes. Herein, after a brief description of the synthesis, this Review summarized the latest insights into the thermal stability and thermophysical properties of MXenes, and further associated these unique properties with relevant applications by multiple examples. Finally, current hurdles and challenges in this field were provided along with some advices on potential research directions in the future.

Artificial Nonenzymatic Antioxidant MXene Nanosheet-Anchored Injectable Hydrogel as a Mild Photothermal-Controlled Oxygen Release Platform for Diabetic Wound Healing

Hypoxia, excessive reactive oxygen species (ROS), impaired angiogenesis, lasting inflammation, and bacterial infection, are key problems impeding diabetic wound healing. Particularly, controllable oxygen release and ROS scavenging capacities are critical during the wound healing process. Here, an injectable hydrogel based on hyaluronic acid-graft-dopamine (HA-DA) and polydopamine (PDA) coated Ti₃C₂ MXene nanosheets is developed catalytically cross-linked by an oxyhemoglobin/hydrogen (HbO₂/H₂O₂) system combined with mild photothermal stimulation for diabetic wound healing. HbO₂ not only acts as a horseradish peroxidase-like to catalyze the hydrogel formation but also as an oxygen carrier to controllably release oxygen when activated by the mild heat produced from near-infrared (NIR) irradiation. Specifically, HbO₂ can provide oxygen repeatedly by binding oxygen in the air when the NIR is off. The stable photoresponsive heating behavior of MXene ensures the repeatable oxygen release. Additionally, artificial nonenzymatic antioxidant MXene nanosheets are proposed to scavenge excessive reactive nitrogen species and ROS including H₂O₂, O₂^•-, and ^•OH, keeping the intracellular redox homeostasis and alleviating oxidative stress, and eradicate bacteria to avoid infection. The antioxidant and antibacterial abilities of MXene are further improved by PDA coating, which also promotes the MXene nanosheets cross-linking into the network of the hydrogel. HA-DA molecules endow the hydrogel with the capacity to regulate macrophage polarization from M1 to M2 to achieve anti-inflammation. More importantly, the MXene-anchored hydrogel with multifunctions including tissue adhesion, self-healing, injectability, and hemostasis, combined with mild photothermal stimulation, greatly promotes human umbilical vein endothelial cell proliferation and migration and notably facilitates infected diabetic wound healing.

Next-Generation Intelligent MXene-Based Electrochemical Aptasensors for Point-of-Care Cancer Diagnostics

Delayed diagnosis of cancer using conventional diagnostic modalities needs to be addressed to reduce the mortality rate of cancer. Recently, 2D nanomaterial-enabled advanced biosensors have shown potential towards the early diagnosis of cancer. The high surface area, surface functional groups availability, and excellent electrical conductivity of MXene make it the 2D material of choice for the fabrication of advanced electrochemical biosensors for disease diagnostics. MXene-enabled electrochemical aptasensors have shown great promise for the detection of cancer biomarkers with a femtomolar limit of detection. Additionally, the stability, ease of synthesis, good reproducibility, and high specificity offered by MXene-enabled aptasensors hold promise to be the mainstream diagnostic approach. In this review, the design and fabrication of MXene-based electrochemical aptasensors for the detection of cancer biomarkers have been discussed. Besides, various synthetic processes and useful properties of MXenes which can be tuned and optimized easily and efficiently to fabricate sensitive biosensors have been elucidated. Further, futuristic sensing applications along with challenges will be deliberated herein.