Hydrophilic MoSe2 Nanosheets as Effective Photothermal Therapy Agents and Their Application in Smart Devices

Advances in two-dimensional transition metal dichalcogenides-based sensors for environmental, food, and biomedical analysis: A review

Transition metal dichalcogenides (TMDCs) are versatile two-dimensional (2D) nanomaterials used in biosensing applications due to their excellent physical and chemical properties. Due to biomaterial target properties, biosensors' most significant challenge is improving their sensitivity and stability. In environmental analysis, TMDCs have demonstrated exceptional pollutant detection and removal capabilities. Their high surface area, tunable electronic properties, and chemical reactivity make them ideal for sensors and adsorbents targeting various contaminants, including heavy metals, organic pollutants, and emerging contaminants. Furthermore, their unique electronic and optical properties enable sensitive detection techniques, enhancing our ability to monitor and mitigate environmental pollution. In the food analysis, TMDCs-based nanomaterials have shown remarkable potential in ensuring food safety and quality. These nanomaterials exhibit high specificity and sensitivity for detecting contaminants, pathogens, and adulterants in various food matrices. Their integration into sensor platforms enables rapid and on-site analysis, reducing the reliance on centralized laboratories and facilitating timely interventions in the food supply chain. In biomedical studies, TMDCs-based nanomaterials have demonstrated significant strides in diagnostic and therapeutic applications. Their biocompatibility, surface functionalization versatility, and photothermal properties have paved the way for novel disease detection, drug delivery, and targeted therapy approaches. Moreover, TMDCs-based nanomaterials have shown promise in imaging modalities, providing enhanced contrast and resolution for various medical imaging techniques. This article provides a comprehensive overview of 2D TMDCs-based biosensors, emphasizing the growing demand for advanced sensing technologies in environmental, food, and biomedical analysis.

Magnetic two-dimensional nanocomposites for multimodal antitumor therapy: a recent review

Magnetic two-dimensional nanocomposites (M2D NCs) that synergistically combine magnetic nanomedicine and 2D nanomaterials have emerged in multimodal antitumor therapy, attracting great interest in materials science and biomedical engineering. This review provides a summary of the recent advances of M2D NCs and their multimodal antitumor applications. We first introduce the design and fabrication of M2D NCs, followed by discussing new types of M2D NCs that have been recently reported. Then, a detailed analysis and discussions about the different types of M2D NCs are presented based on the structural categories of 2D NMs, including 2D graphene, transition metal dichalcogenides (TMDs), transition metal carbides/nitrides/carbonitrides (MXenes), black phosphorus (BP), layered double hydroxides (LDHs), metal organic frameworks (MOFs), covalent organic frameworks (COFs) and other 2D nanomaterials. In particular, we focus on the synthesis strategies, magnetic or optical responsive performance, and the versatile antitumor applications, which include magnetic hyperthermia therapy (MHT), photothermal therapy (PTT), photodynamic therapy (PDT), drug delivery, immunotherapy and multimodal imaging. We conclude the review by proposing future developments with an emphasis on the mass production and biodegradation mechanism of the M2D NCs. This work is expected to provide a comprehensive overview to researchers and engineers who are interested in such a research field and promote the clinical translation of M2D NCs in practical applications.

2D nanocomposite materials for HER electrocatalysts - a review

Hydrogen energy has the potential to be a cost-effective and strong technology for brighter development. Hydrogen fuel production by water electrolyzers has attracted attention. 2D nanocomposites with distinctive properties have been extensively explored for various applications from hydrogen evolution reactions to improving the efficiency of water electrolyzer, which is the most eco-friendly, and high-performance for hydrogen production. Recently, typical 2D nanocomposites such as Metal-Free 2D, TMDs, Mxene, LDH, organic composites, and Heterostructure have recently been thoroughly researched for use in the HER. We discuss effective ways for increasing the HER efficiency of 2D catalysts in this paper, And the unique advantages and mechanisms for specific applications are highlighted. Several essential regulating strategies for developing 2D nanocomposite-based HER electrocatalysts are included such as interface engineering, defect engineering, heteroatom doping, strain & phase engineering, and hybridizing which improve HER kinetics, the electrical conductivity, accessibility to catalytic active sites, and reaction energy barrier can be optimized. Finally, the future prospects for 2D nanocomposites in HER are discussed, as well as a thorough overview of a variety of methodologies for designing 2D nanocomposites as HER electrocatalysts with excellent catalytic performance. We expect that this review will provide a thorough overview of 2D nanocatalysts for hydrogen production.

CoFeSe2 @DMSA@FA Nanocatalyst for Amplification of Oxidative Stress to Achieve Multimodal Tumor Therapy

Nanomedicine has significantly advanced precise tumor therapy, providing essential technical blessing for active drug accumulation, targeted consignment, and mitigation of noxious side effects. To enhance anti-tumor efficacy, the integration of multiple therapeutic modalities has garnered significant attention. Here, we designed an innovative CoFeSe2 @DMSA@FA nanocatalyst with Se vacancies (abbreviated as CFSDF), which exhibits synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT), leading to amplified tumor oxidative stress and enhanced photothermal effects. The multifunctional CFSDF nanocatalyst exhibits the remarkable ability to catalyze the Fenton reaction within the acidic tumor microenvironment, efficiently converting hydrogen peroxide (H2 O2 ) into highly harmful hydroxyl radicals (⋅OH). Moreover, the nanocatalyst effectively diminishes GSH levels and ameliorates intracellular oxidative stress. The incorporation of FA modification enables CFSDF to evade immune detection and selectively target tumor tissues. Numerous in vitro and in vivo investigations have consistently demonstrated that CFSDF optimizes its individual advantages and significantly enhances therapeutic efficiency through synergistic effects of multiple therapeutic modalities, offering a valuable and effective approach to cancer treatment.

Microenvironment Restruction of Emerging 2D Materials and their Roles in Therapeutic and Diagnostic Nano-Bio-Platforms

Engineering advanced therapeutic and diagnostic nano-bio-platforms (NBPFs) have emerged as rapidly-developed pathways against a wide range of challenges in antitumor, antipathogen, tissue regeneration, bioimaging, and biosensing applications. Emerged 2D materials have attracted extensive scientific interest as fundamental building blocks or nanostructures among material scientists, chemists, biologists, and doctors due to their advantageous physicochemical and biological properties. This timely review provides a comprehensive summary of creating advanced NBPFs via emerging 2D materials (2D-NBPFs) with unique insights into the corresponding molecularly restructured microenvironments and biofunctionalities. First, it is focused on an up-to-date overview of the synthetic strategies for designing 2D-NBPFs with a cross-comparison of their advantages and disadvantages. After that, the recent key achievements are summarized in tuning the biofunctionalities of 2D-NBPFs via molecularly programmed microenvironments, including physiological stability, biocompatibility, bio-adhesiveness, specific binding to pathogens, broad-spectrum pathogen inhibitors, stimuli-responsive systems, and enzyme-mimetics. Moreover, the representative therapeutic and diagnostic applications of 2D-NBPFs are also discussed with detailed disclosure of their critical design principles and parameters. Finally, current challenges and future research directions are also discussed. Overall, this review will provide cutting-edge and multidisciplinary guidance for accelerating future developments and therapeutic/diagnostic applications of 2D-NBPFs.

Gum Arabic-mediated liquid exfoliation of transition metal dichalcogenides as photothermic anti-breast cancer candidates

Transition metal dichalcogenides (TMDs) have gained considerable attention for a broad range of applications, including cancer therapy. Production of TMD nanosheets using liquid exfoliation provides an inexpensive and facile route to achieve high yields. In this study, we developed TMD nanosheets using gum arabic as an exfoliating and stabilizing agent. Different types of TMDs, including MoS₂, WS₂, MoSe₂, and WSe₂ nanosheets, were produced using gum arabic and were characterized physicochemically. The developed gum arabic TMD nanosheets exhibited a remarkable photothermal absorption capacity in the near-infrared (NIR) region (808 nm and 1 W⋅cm^-2). The drug doxorubicin was loaded on the gum arabic-MoSe₂ nanosheets (Dox-G-MoSe₂), and the anticancer activity was evaluated using MDA-MB-231 cells and a water-soluble tetrazolium salt (WST-1) assay, live and dead cell assays, and flow cytometry. Dox-G-MoSe₂ significantly inhibited MDA-MB-231 cancer cell proliferation under the illumination ofan NIR laser at 808 nm. These results indicate that Dox-G-MoSe₂ is a potentially valuable biomaterial for breast cancer therapy.

Metal selenide nanomaterials for biomedical applications

Metal selenide nanomaterials have received enormous attention as they possess diverse compositions, microstructures, and properties. The combination of selenium with various metallic elements gives the metal selenide nanomaterials distinctive optoelectronic and magnetic properties, such as strong near-infrared absorption, excellent imaging properties, good stability, and long in vivo circulation. This makes metal selenide nanomaterials advantageous and promising for biomedical applications. This paper summarizes the research progress in the last five years in the controlled synthesis of metal selenide nanomaterials in different dimensions and with different compositions and structures. Then we discuss how surface modification and functionalization strategies are well-suited for biomedical fields, including tumor therapy, biosensing, and antibacterial biological applications. The future trends and issues of metal selenide nanomaterials in the biomedical field are also discussed.

Dual Glutathione Depletion Enhanced Enzyme Catalytic Activity for Hyperthermia Assisted Tumor Therapy on Semi-Metallic VSe2/Mn-CS

Semimetallic nanomaterials as photothermal agents for bioimaging and cancer therapy have attracted tremendous interest. However, the poor photothermal stability, low biocompatibility, and single component limit their therapeutic efficiency in cancer treatment. Here, manganese-doped VSe₂ semimetallic nanosheets were prepared and subsequently modified with chitosan (named VSe₂/Mn-CS NSs) for combined enzyme catalytic and photothermal therapy. VSe₂/Mn-CS NSs show high photothermal property with a photothermal conversion efficiency of 34.61% upon 808 nm near-infrared laser irradiation. In the tumor microenvironment, VSe₂/Mn-CS NSs can convert endogenous H₂O₂ into lethal hydroxyl radicals (•OH) to induce cancer cell apoptosis. The interaction between glutathione (GSH) and Se-Se bonds in VSe₂/Mn-CS NSs results in the depletion of GSH level, and the valence states transition of manganese ions is also beneficial for the GSH consumption. This dual depletion of GSH markedly enhances the peroxidase (POD) activity, leading to the high •OH production and the improved therapeutic effect. What is more, the T₁-weighted magnetic resonance and photoacoustic imaging endow VSe₂/Mn-CS NSs with the ability to guide and track the treatment process. Our study provides a research strategy for the application of semimetallic nanomaterials in cancer diagnosis and treatment.

Promising Colloidal Rhenium Disulfide Nanosheets: Preparation and Applications for In Vivo Breast Cancer Therapy

Photothermal therapy (PTT) has become an important therapeutic strategy in the treatment of cancer. However, exploring novel photothermal nanomaterials with satisfactory biocompatibility, high photothermal conversion efficiency, and efficient theranostic outcomes, remains a major challenge for satisfying clinical application. In this study, poly-ethylene glycol modified rhenium disulfide (PEG-ReS₂) nanosheets are constructed by a simple-liquid phase exfoliation method. The PEG-ReS₂ nanosheets were demonstrated to have good solubility, good biocompatibility, low toxicity, and strong capability of accumulating near-infrared (NIR) photons. Under 808 nm laser irradiation, the PEG-ReS₂ nanosheets were found to have an excellent photothermal conversion efficiency (PTCE) of 42%. Moreover, the PEG-ReS₂ nanosheets were demonstrated to be ideal photothermal transduction agents (PTAs), which promoted rapid cancer cell death in vitro and efficiently ablated tumors in vivo. Interestingly, the potential utility of up-regulation or down-regulation of miRNAs was proposed to evaluate the therapeutic outcomes of PEG-ReS₂ nanosheets. The expression levels of a set of miRNAs in tumor-bearing mice were restored to normal levels after PTT therapy with PEG-ReS₂ nanosheets. Both down-regulation miRNAs (miR-125a-5p, miR-34a-5p, miR-132-3p, and miR-148b-3p) and up-regulation miRNAs (miR-133a-3p, miR-200c-5p, miR-9-3p, and miR-150-3p) were suggested to be important clinical biomarkers for evaluating therapeutic outcomes of breast cancer-related PTT. This work highlights the great significance of PEG-ReS₂ nanosheets as therapeutic nanoagents for cancer therapy.

Synergetic contribution of enriched selenium vacancies and out-of-plane ferroelectric polarization in AB-stacked MoSe2 nanosheets as efficient piezocatalysts for TC degradation

Novel MoSe2 piezocatalysts with surface selenium vacancies and out-of-plane ferroelectric polarization exhibit ultrafast degradation of the antibiotic tetracycline.

NIR -I and NIR-II irradiation tumor ablation using NbS2 nanosheets as the photothermal agent

Photothermal therapy has been considered a powerful means of cancer therapy due to its minimal invasiveness, effectiveness, and convenience. Although promising, the therapeutic effects are greatly limited as they rely on the photothermal agent (PTA). It is urgent to develop new PTAs with high photothermal conversion performance, especially under irradiation in the long-wavelength biowindows. Herein, a dual-biowindow-responsive PTA made of NbS₂-PVP nanosheets was fabricated to be used both in the first near-infrared (NIR-I) and the second near-infrared (NIR-II) biowindows. With excellent hydrophilicity and biocompatibility, the nanosheets could effectively convert the near-infrared (NIR) light into heat, showing prominent photothermal stability. The calculated photothermal conversion efficiencies reached 59.2% (under NIR-I excitation) and 69.1% (under NIR-II excitation), respectively, which are comparable to those of metallic PTAs. The NbS₂-PVP nanosheets had low cytotoxicity and could trigger strong photothermal treatment and cause cancer cell death upon irradiation by NIR-I or NIR-II light in vitro. Moreover, we have also demonstrated the highly efficient tissue ablation and tumor inhibition capability of NbS₂-PVP nanosheets in vivo. This work explores an effective PTA of two-dimensional nanomaterials in NIR-I and NIR-II biowindows and offers a reference for the design of new kinds of PTAs.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Spatially Controlled Preparation of Layered Metallic-Semiconducting Metal Chalcogenide Heterostructures

Spatially controlled preparation of heterostructures composed of layered materials is important in achieving interesting properties. Although vapor-phased deposition methods can prepare vertical and lateral heterostructures, liquid-phased methods, which can enable scalable production and further solution processes, have shown limited controllability. Herein, we demonstrate by using wet chemical methods that metallic Sn_0.5Mo_0.5S₂ nanosheets can be deposited epitaxially on the edges of semiconducting SnS₂ nanoplates to form SnS₂/Sn_0.5Mo_0.5S₂ lateral heterostructures or coated on both the edges and basal surfaces of SnS₂ to give SnS₂@Sn_0.5Mo_0.5S₂ core@shell heterostructures. They also showed good light-to-heat conversion ability due to the metallic property of Sn_0.5Mo_0.5S₂. In particular, the core@shell heterostructure showed a higher photothermal conversion efficiency than the lateral counterpart, largely due to its randomly oriented and polycrystalline Sn_0.5Mo_0.5S₂ layers with larger interfacing area for multiple internal light scattering.

A Review on Hydrogels with Photothermal Effect in Wound Healing and Bone Tissue Engineering

Photothermal treatment (PTT) is a promising strategy to deal with multidrug-resistant bacteria infection and promote tissue regeneration. Previous studies demonstrated that hyperthermia can effectively inhibit the growth of bacteria, whereas mild heat can promote cell proliferation, further accelerating wound healing and bone regeneration. Especially, hydrogels with photothermal properties could achieve remotely controlled drug release. In this review, we introduce a photothermal agent hybrid in hydrogels for a photothermal effect. We also summarize the potential mechanisms of photothermal hydrogels regarding antibacterial action, angiogenesis, and osteogenesis. Furthermore, recent developments in photothermal hydrogels in wound healing and bone regeneration applications are introduced. Finally, future application of photothermal hydrogels is discussed. Hydrogels with photothermal effects provide a new direction for wound healing and bone regeneration, and this review will give a reference for the tissue engineering.

Ultrathin Transition Metal Chalcogenide Nanosheets Synthesized via Topotactic Transformation for Effective Cancer Theranostics

Ultrathin transition metal chalcogenide (TMC) nanosheets with ultrahigh photothermal conversion efficiency (η) and excellent stability are strongly desired in the application of photothermal therapy (PTT). However, the current synthetic methods of ultrathin TMC nanosheets have issues in obtaining uniform morphology, good dispersion, and satisfactory PTT behavior. Herein, ultrathin nanosheets of CoFe-selenide (CFS) with a finely controlled structure were prepared via a topological structural transformation process from an ultrathin CoFe-layered double hydroxide (LDH) precursor, followed by surface modification with poly(ethylene glycol) (PEG). The as-prepared CFS-PEG nanosheets inherit the ultrathin morphology of CoFe-LDH and exhibit an outstanding photothermal performance with a η of 74.5%, which is the first rank level of reported two-dimensional (2D) TMC nanosheet materials. The CFS-PEG nanosheets possess a satisfactory photoacoustic (PA) imaging capability with an ultralow detection limit (5 ppm) and simultaneously superior T₂ magnetic resonance imaging (MRI) performance with a large transverse MR relaxivity value (r₂) of 347.7 mM^-1 s^-1. Moreover, in vitro and in vivo assays verify superior anticancer activity with a dramatic photoinduced cancer cell apoptosis and tumor ablation. Therefore, a successful paradigm is provided for rational design and preparation of ultrathin TMC nanosheets in this work, holding enormous potential in cancer theranostics.

Light-Responsive Inorganic Biomaterials for Biomedical Applications

Light-responsive inorganic biomaterials are an emerging class of materials used for developing noninvasive, noncontact, precise, and controllable medical devices in a wide range of biomedical applications, including photothermal therapy, photodynamic therapy, drug delivery, and regenerative medicine. Herein, a range of biomaterials is discussed, including carbon-based nanomaterials, gold nanoparticles, graphite carbon nitride, transition metal dichalcogenides, and up-conversion nanoparticles that are used in the design of light-responsive medical devices. The importance of these light-responsive biomaterials is explored to design light-guided nanovehicle, modulate cellular behavior, as well as regulate extracellular microenvironments. Additionally, future perspectives on the clinical use of light-responsive biomaterials are highlighted.

Photothermal augment stromal disrupting effects for enhanced Abraxane synergy chemotherapy in pancreatic cancer PDX mode

Cancer-associated fibroblasts (CAFs) are crucial for forming the desmoplastic stroma that is associated with chemoresistance in pancreatic ductal adenocarcinoma (PDAC). In the clinic, depleting dense stroma in PDAC tumor tissue is a promising chemotherapeutic strategy. In this study, we report that the local hyperthermia can reduce the number of CAFs in the PDAC PDX mouse mode, which further augments chemotherapeutic efficiency in the PDAC therapy. To achieve this goal, a photothermal-chemotherapeutic agent termed as Abraxane@MoSe₂ as a vehicle-saving theranostic probe is prepared by simply mixing an FDA-approved Abraxane and hydrophobic MoSe₂ nanosheets via electrostatic and hydrophobic interactions. After labeling with indocyanine green (ICG) dye on the Abraxane@MoSe₂, a relatively high fluorescence signal (near infrared second (NIR II)) in PDX tumors can be obtained, which can be precisely imaging-guide local photothermal-chemotherapy upon the 808 nm laser irradiation in vivo. Importantly, the synergy therapeutic efficiency in PDAC is enhanced by the photothermal effect reduction of the number of CAFs, which is confirmed viaα-SMA and vimentin immunofluorescence analysis. This combined therapeutic strategy may provide a new sight for PDAC therapy.

Folin-Ciocalteu Assay Inspired Polyoxometalate Nanoclusters as a Renal Clearable Agent for Non-Inflammatory Photothermal Cancer Therapy

Similar to translated thermal ablative techniques in clinic, the occurrence of cellular necrosis during tumor photothermal therapy (PTT) would induce inflammatory responses that are detrimental to therapeutic outcomes. Inspired by the well-known colorimetric Folin-Ciocalteu assay, monodispersed and renal-clearable tungsten (W)-based polyoxometalate nanoclusters (W-POM NCs, average diameter of around 2.0 nm) were successfully obtained here through a facile redox reaction with natural gallic acid in alkaline aqueous solution. Apart from excellent stability in the form of freeze-dried powder, the as-prepared W-POM NCs occupied considerable biocompatibility toward normal cells/tissues both in vitro and in vivo, since no obvious toxicities were observed by treating female Balb/c mice with concentrated W-POM NCs during the 30 day post-treatment period. More importantly, W-POM NCs exhibited not only considerable near-infrared (NIR) light absorption (coloration effect originated from the existence of electron-trapped W⁵⁺) for efficient PTT but also impressive anti-inflammatory ability (eliminating inflammation-related reactive oxygen species by the oxidation of W⁵⁺ into W⁶⁺ state) to achieve better therapeutic outcomes. Thus, our study pioneers the application of POMs for non-inflammatory PTT with expected safety and efficiency.

Responsive functionalized MoSe2 nanosystem for highly efficient synergistic therapy of breast cancer

The photothermal/photodynamic synergistic therapy is a promising tumor treatment, but developing nanosystems that achieve synchronous photothermal/photodynamic functions is still quite challenging. Here, we use a simple method to synthesize molybdenum selenide nanoparticles (MoSe₂ NPs) with a photothermal effect as a carrier, and load a photosensitizer ICG to form a nanosystem (MoSe₂@ICG-PDA-HA)with dual photothermal/photodynamic functions under near-infrared irradiation. In addition, the surface modification of the nanosystem with acid-responsive release polydopamine (PDA) and tumor-targeted hyaluronic acid (HA) enhanced the stability of the photosensitizer ICG and the accumulation of ICG at tumor sites. The multicellular sphere assay simulated solid tumors and demonstrated that MoSe₂@ICG-PDA-HA could significantly inhibit the 4T1 cell growth. The anti-tumor experiments in tumor-bearing mice showed that MoSe₂@ICG-PDA-HA not only significantly inhibited the growth of 4T1 subcutaneous tumors, but also inhibited their metastasis. This study presented a nanosystem that could improve the photostability of optical materials and enhance the photothermal/photodynamic synergy effect, providing a new idea for finding a way to effectively treat breast cancer.

Surface modification engineering of two-dimensional titanium carbide for efficient synergistic multitherapy of breast cancer

A nanocomposite drug delivery system (Ti₃C₂@Met@CP) can be used for the synergistic treatment of tumors through photothermal/photodynamic/chemotherapy and can also inhibit tumor recurrence and metastasis by activating the immune system.

MWCNT-mediated combinatorial photothermal ablation and chemo-immunotherapy strategy for the treatment of melanoma

DOX and CpG loaded MWCNT with NIR irradiation could destroy tumor cells by photothermal and chemotherapy and release tumor-associated antigens, thus generating melanoma specific immune response to achieve synergistic therapeutic effect.

Accelerating the peroxidase-like activity of MoSe2 nanosheets at physiological pH by dextran modification

One-pot synthesis of dextran-modified MoSe₂ nanosheets with peroxidase-like activity at physiological pH for bio-sensing.

Functionalized Hybridization of 2D Nanomaterials

The discovery of graphene and subsequent verification of its unique properties have aroused great research interest to exploit diversified graphene-analogous 2D nanomaterials with fascinating physicochemical properties. Through either physical or chemical doping, linkage, adsorption, and hybridization with other functional species into or onto them, more novel/improved properties are readily created to extend/expand their functionalities and further achieve great performance. Here, various functionalized hybridizations by using different types of 2D nanomaterials are overviewed systematically with emphasis on their interaction formats (e.g., in-plane or inter plane), synergistic properties, and enhanced applications. As the most intensely investigated 2D materials in the post-graphene era, transition metal dichalcogenide nanosheets are comprehensively investigated through their element doping, physical/chemical functionalization, and nanohybridization. Meanwhile, representative hybrids with more types of nanosheets are also presented to understand their unique surface structures and address the special requirements for better applications. More excitingly, the van der Waals heterostructures of diverse 2D materials are specifically summarized to add more functionality or flexibility into 2D material systems. Finally, the current research status and faced challenges are discussed properly and several perspectives are elaborately given to accelerate the rational fabrication of varied and talented 2D hybrids.

Biomedical and bioimaging applications of 2D pnictogens and transition metal dichalcogenides

Multifunctional platforms will play a key role and gain more prominence in the field of personalized healthcare worldwide in the near future due to the ever-increasing number of patients suffering from cancer. Along with the development of efficient techniques for cancer treatment, a considerable effort should be devoted toward the exploration of an emerging class of materials with unique properties that might be beneficial in this context. Currently, 2D post-carbon materials, such as pnictogens (phosphorene, antimonene), transition metal dichalcogenides, and boron nitride, have become popular due to their efficient photothermal behavior, drug-loading capability, and low toxicity. This review underlines the recent progresses made in the abovementioned 2D materials for photothermal/photodynamic cancer therapies and their applicability in bioimaging applications.

Nanobiomaterials: from 0D to 3D for tumor therapy and tissue regeneration

Nanobiomaterials have attracted tremendous attention in the biomedical field. Especially in the past few years, a large number of low dimensional nanobiomaterials, including 0D nanostructures, 1D nanotubes and 2D nanosheets, were employed for tumor therapy due to their optically triggered tumor therapy effects and drug loading capacities. However, these low dimensional nanobiomaterials cannot support cell adhesion and possess poor tissue regeneration ability, thus they are not suitable for application in regenerative medicine. Three dimensional (3D) nanofiber scaffolds have attracted extensive attention in tissue regeneration, including bone, skin, nerve and cardiac tissues, due to their similar extracellular matrix structures. Additionally, many 3D scaffolds displayed bone and cartilage regeneration abilities. Therefore, to obtain materials with both tumor therapy and tissue regeneration abilities, it is meaningful and necessary to develop 3D nanobiomaterials with multifunctions. In this review, we systematically review the research progress of nanobiomaterials with varied dimensional structures including 0D, 1D, 2D and 3D, as well as evolutional functions from single tumor therapy to simultaneous tumor therapy and tissue regeneration. This review may pave the way for developing an interdisciplinary research of nanobiomaterials in combination of tumor therapy and regenerative medicine.

A green luminescent MoS2-CdTe hybrid nanostructure synthesized through surface charge interaction

During the last few years, intensive research has been carried out on the synthesis of different hybrid nanostructures mostly using hydrothermal and solvothermal techniques. But the fabrication of the hybrid nanostructure through surface charge interaction of the individual components is comparatively less explored. Here in this work, a hybrid nanostructure based on MoS₂ and CdTe quantum dots is synthesized through a simple surface charge interaction process using the negative surface charge of the excess sulfide ions (S^2-) present at the edge of the MoS₂ QDs and positively charged CdTe QDs where the positive surface charge was induced in CdTe by using a cysteamine ligand in acidic medium. In the photoluminescence (PL) emission spectrum, a new peak is observed which is different from those of both of the individual components. Interestingly, with increasing the concentration of CdTe QDs during the preparation of the hybrid nano-structure, the peak of hybrid QDs is gradually blue shifted towards the emission of MoS₂ QDs. The maximum blue shift occurs up to 1 : 1 (v/v) ratio of MoS₂ : CdTe as in this concentration ratio all S^2- ions are neutralized by -NH₃ ⁺. This new emission occurs from a newly generated hybrid energy level. The energy level positions of the two different QDs along with the hybrid ones are estimated via cyclic voltammetry and absorption experiments.

Synthetic Techniques and Functionalization Approaches of 2D Transition Metal Dichalcogenides

As typical graphene analogues, two-dimensional (2D) transition-metal dichalcogenides (TMDs), including MoS2, WS2, etc., have attracted increasing research interest due to their semiconducting characteristics, sizable bandgap, large surface area, and outstanding performance in various applications such as electronics/optoelectronics, sensing, catalysis, and energy storage. For the widespread exploration of TMD nanosheets in fundamental studies and promising applications, a rapid pace of progress has recently been achieved in developing methodologies for reliable and scale-up production of atomically thin TMD nanosheets. In this chapter, we will present a comprehensive overview of different synthetic techniques of 2D TMDs and evaluate their relative merits and demerits. Particularly, the design principle, fabrication mechanism, typical process and special conditions will be emphasized to understand or follow the effective methods for obtaining required TMD nanosheets in single and few layers. Based on these synthetic techniques, further functionalization of TMD nanosheets with ligands and other nanocomponents are also discussed for gaining some specific properties. Based on our knowledge, we finally propose some possible challenges and potential opportunities in the exploitation of TMD nanosheets for novel applications.

Portable Colorimetric Detection of Mercury(II) Based on a Non-Noble Metal Nanozyme with Tunable Activity

The nanozyme-based strategy is currently one of the frontiers in the detection of toxic heavy metal ions. However, the utilization of noble metal free nanozymes to construct an economically and environmentally sustainable methodology remains largely unknown. Here, chitosan-functionalized molybdenum(IV) selenide nanosheets (CS-MoSe₂ NS), greenly synthesized by an ionic liquid-assisted grinding method, were exploited for the colorimetric sensing of mercury ions (Hg²⁺). The sensing principle was based on the activating effect of Hg²⁺ on CS-MoSe₂ NS nanozyme activities, triggered by the in situ reduction of chitosan-captured Hg²⁺ ions on a MoSe₂ NS surface. Using 3,3',5,5'-tetramethylbenzidine (TMB) as a colorimetric indicator, the concentrations of activator-like Hg²⁺ ions could be quantitatively and selectively monitored, reaching a limit of detection of 3.5 nM with the ultraviolet-visible spectrophotometer. In addition, the integration system of CS-MoSe₂ NS with a smartphone achieved a portable detection limit as low as 8.4 nM Hg²⁺ within 15 min and showed high specificity and anti-interfering ability over other ions and great practicability in real water and serum samples. The eco-friendly properties of such sensing system were also confirmed. This work emphasizes the rational portable assembly of biocompatible nanozymes like CS-MoSe₂ NS for the field detection of Hg²⁺ in food, biological, and environmental samples.

Recent advances of stimuli-responsive systems based on transition metal dichalcogenides for smart cancer therapy

A comprehensive overview of the development of stimuli-responsive TMDC-based nanoplatforms for “smart” cancer therapy is presented to demonstrate a more intelligent and better controllable therapeutic strategy.

Physically-triggered nanosystems based on two-dimensional materials for cancer theranostics

There is an increasing demand to develop effective methods for treating malignant diseases to improve healthcare in our society. Stimuli-responsive nanosystems, which can respond to internal or external stimuli are promising in cancer therapy and diagnosis due to their functionality and versatility. As a newly emerging class of nanomaterials, two-dimensional (2D) nanomaterials have attracted huge interest in many different fields including biomedicine due to their unique physical and chemical properties. In the past decade, stimuli-responsive nanosystems based on 2D nanomaterials have been widely studied, showing promising applications in cancer therapy and diagnosis, including phototherapies, magnetic therapy, drug and gene delivery, and non-invasive imaging. Here, we will focus our attention on the state-of-the-art of physically-triggered nanosystems based on graphene and two-dimensional nanomaterials for cancer therapy and diagnosis. The physical triggers include light, temperature, magnetic and electric fields.

Tungsten disulfide-based nanocomposites for photothermal therapy

Nanostructures of transition-metal dichalcogenides (TMDC) have raised scientific interest in the last few decades. Tungsten disulfide (WS₂) nanotubes and nanoparticles are among the most extensively studied members in this group, and are used for, e.g., polymer reinforcement, lubrication and electronic devices. Their biocompatibility and low toxicity make them suitable for medical and biological applications. One potential application is photothermal therapy (PTT), a method for the targeted treatment of cancer, in which a light-responsive material is irradiated with a laser in the near-infrared range. In the current article we present WS₂ nanotubes functionalized with previously reported ceric ammonium nitrate-maghemite (CAN-mag) nanoparticles, used for PTT. Functionalization of the nanotubes with CAN-mag nanoparticles resulted in a magnetic nanocomposite. When tested in vitro with two types of cancer cells, the functionalized nanotubes showed a better PTT activity compared to non-functionalized nanotubes, as well as reduced aggregation and the ability to add a second-step functionality. This ability is demonstrated here with two polymers grafted onto the nanocomposite surface, and other functionalities could be additional cancer therapy agents for achieving increased therapeutic activity.

Biocompatible carbon-doped MoSe2 nanoparticles as a highly efficient targeted agent for human renal cell carcinoma

MoSe₂ is a typical transition-metal dichalcogenide material, and many researches have been focused on using its property of near infrared strong absorption for laser mediated photothermal cancer treatment. However, the anti-canter effect of MoSe₂ and its possible mechanism in renal cell carcinoma (RCC) is still unclear. RCC has high incidence of metastasis, which is known as one of the most lethal malignancies in the urological system. This study revealed that the carbon-doped MoSe₂ particles can obviously inhibit proliferation for 786-O and ACHN cells. Meanwhile, the carbon-doped MoSe₂ nanoparticles have little impact on the viability of KH-2 cells in vitro. The mechanism analysis revealed that the carbon-doped MoSe₂ particles have hydrogen bond effect in aqueous solution, and the particle aggregation effect caused the KH-2 cells to have high viability. The carbon-doped MoSe₂ nanoparticles with minimal toxicity may be a potential therapeutic candidate against RCC.

HK-2 cells have weak cellular uptake efficiency leading to high viability with carbon-doped MoSe₂ nanoparticles.

Reduced graphene oxide (rGO) hybridized hydrogel as a near-infrared (NIR)/pH dual-responsive platform for combined chemo-photothermal therapy

For personalized cancer treatment, developing smart biomaterials with multiple biological functions is indispensable in nanomedicine fields. In this work, we developed a highly efficient near-infrared- (NIR-) and pH-responsive carboxymethyl chitosan-functionalized reduced graphene oxide/aldehyde functionalized poly (ethylene glycol) (CMC-rGO/CHO-PEG) hydrogel, which exhibits outstanding delivery performance of antitumor drug, doxorubicin hydrochloride (DOX). CMC was functionalized on the GO nanosheets via a controllable approach in order to achieve strong NIR absorption property and good distribution of rGO. The intercalation effect of CMC-rGO complex improved rGO distribution in the 3D hydrogel, contributing to the enhanced photothermal performance of CMC-rGO/CHO-PEG hydrogel. Furthermore, potential utilization of these CMC-rGO/CHO-PEG hydrogel for drug loading was studied, which provided pH-sensitive release of DOX payload. Particularly, DOX could be released in a more efficient way under acidic environment (pH = 6.5) than that under physiological environment (pH = 7.4). Therefore, this rGO hybridized PEG hydrogel holds strategic potential as a novel drug release platform for combined chem-photothermal therapy.

Hybrid MoSe2-indocyanine green nanosheets as a highly efficient phototheranostic agent for photoacoustic imaging guided photothermal cancer therapy

Phototheranostic technology based on photoacoustic imaging (PAI) and photothermal therapy (PTT) is emerging as a powerful tool for tumor theranostic applications. For effective tumor eradication, a novel PAI/PTT theranostic nanoagent with an excellent optical absorption and photothermal capability is highly desired. Herein, we present a new PAI/PTT nanohybrid named sMoSe2-ICG NSs by covalently conjugating aminated indocyanine green (ICG) onto a single layer of molybdenum selenide nanosheets (sMoSe2 NSs). We first validate the sMoSe2-ICG NS agent for the PAI and PTT effect in vitro and then use it for highly-sensitive PAI guided highly efficient tumor PTT in vivo. The sMoSe2-ICG NS hybrid possesses several advantages for PAI/PTT applications: (1) the sMoSe2-ICG NSs have strong absorbance in the broad near-infrared (NIR) region, enabling a highly efficient PAI/PTT theranostic effect and the selection of the most widely used excitation wavelength of 808 nm for PTT; (2) the photothermal ability of ICG in sMoSe2-ICG NSs is augmented due to ICG aggregation induced fluorescence quenching and the re-absorbance of ICG fluorescence by sMoSe2 NSs, which further enhances the PAI/PTT theranostic effect. (3) The characteristic absorption peak of sMoSe2-ICG NSs is red-shifted compared to free ICG, resulting in a higher PAI signal-to-noise ratio (SNR) in vivo. Thus, combined with the good stability, high biocompatibility and minimal toxicity properties, the obtained sMoSe2-ICG NSs hybrid has bright prospects for use in future PAI/PTT clinical applications.

Ti2C3Tx nanosheets as photothermal agents for near-infrared responsive hydrogels

Poly(N-isopropylacrylamide) (PNIPAM) is broadly applicable in many fields due to its temperature-induced phase transition property. Herein, a facile method to incorporate exfoliated Ti2C3Tx nanosheets in the PNIPAM network is reported. Due to compatibility, stability and photothermal properties of the incorporated Ti2C3Tx nanosheets, the obtained MXene/PNIPAM composite hydrogel shows excellent photothermal properties, expanding the pure thermal-responsive property of the PNIPAM hydrogel. Based on the smart composite hydrogel, remote light-control of the microfluidic pipeline is also demonstrated.

Hierarchical MoSe2 nanoflowers as novel nanocarriers for NIR-light-mediated synergistic photo-thermal/dynamic and chemo-therapy

The construction of nanoplatforms that integrate multiple therapies has attracted much attention in the field of cancer treatment. Herein, selenide molybdenum (MoSe2) nanoflowers were synthesized as nanocarriers capable of delivering NIR-mediated synergetic photothermal therapy (PTT), photodynamic therapy (PDT), and drug release. All of the MoSe2 nanoflowers (150-180 nm) are made up of many thin nanosheets of about 3-4 layers of MoSe2. With the novel hierarchical nanostructure and small band gap (1.24 eV), the as-synthesized MoSe2 nanoflowers possess strong near-infrared (NIR) absorption and high photothermal conversion efficiency (61.8%). In addition, they also exhibit NIR-stimulated ˙OH generation and this is the first time that MoSe2 nanostructures have been used as a PDT agent. The mechanism was investigated, which revealed that a sufficient number of photo-excited electrons and high O2 and H+ concentrations facilitate ˙OH production. After PEGylation, MoSe2@PEG exhibits high Dox-loading capacity due to electrostatic and π-π stacking interactions. After drug loading, the resulting MoSe2@PEG-Dox system exhibits acid/photothermal-triggered drug release. The synergistic effect of chemotherapy, PTT and PDT further induces superior cancer cell apoptosis and improved antitumor effectiveness.

Ultrathin Polypyrrole Nanosheets via Space-Confined Synthesis for Efficient Photothermal Therapy in the Second Near-Infrared Window

Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650-950 nm). However, PTAs for photothermal therapy in the second NIR window (1000-1350 nm) are still rare. Here, it is shown that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g^-1 cm^-1 at 1064 nm and can be used as an efficient PTA in the second NIR window. This unique optical property is attributed to the formation of bipolaron bands in highly doped PPy nanosheets. The measured prominent photothermal conversion efficiency could achieve 64.6%, surpassing previous PTAs that are active in the second NIR window. Both in vitro and in vivo studies reveal that these ultrathin PPy nanosheets possess good biocompatibility and notable tumor ablation ability in the second NIR window. Our study highlights the potential of ultrathin two-dimensional polymers with unique optical properties in biomedical applications.

2D transition metal dichalcogenide nanosheets for photo/thermo-based tumor imaging and therapy

Two-dimensional (2D) graphene-like nanomaterials show wide applications in the fields of nanodevices, sensors, energy materials, catalysis, drug delivery, bioimaging, and tissue engineering. Recently, many studies have been focused on the synthesis and application of 2D transition metal dichalcogenide (TMD) nanosheets for various biomedical applications. In particular, 2D TMD nanosheets exhibit great advantages for tumor imaging and therapy compared to some traditional nanomaterials due to their high specific surface area, good biocompatibility, easy modification, and ultrahigh light and heat conversion efficiency. In this review, we summarize the recent advances in the synthesis, modification, and photo/thermo-based tumor imaging and therapy of 2D TMD nanosheets. The important studies on tumor bioimaging with TMD nanosheets, such as X-ray computed tomography, magnetic resonance imaging, and photoacoustic imaging, are demonstrated and discussed. In another section, the physical photothermal and photodynamic therapies as well as the pharmacological therapy of tumors with TMD nanosheet-based nanohybrids are introduced. It is expected that this work will be valuable for readers to understand the synthesis and modification of TMD nanosheets to design novel 2D functional nanomaterials for photo/thermo-based tumor imaging and therapy in one aspect, and in another aspect will extend the applications of TMD-based nanomaterials in materials science, analytical science, electrocatalysis, tissue engineering, and others.