Hydrothermal-Assisted Synthesis and Stability of Multifunctional MXene Nanobipyramids: Structural, Chemical, and Optical Evolution

3D-bioprinting of MXenes: Developments, medical applications, challenges, and future roadmap

MXenes is a member of 2D transition metals carbides and nitrides with promising application prospects in energy storage, sensing, nanomedicine, tissue engineering, catalysis, and electronics. In the current era, MXenes have been widely applied in biomedical applications due to their unique rheological and electrochemical attributes. They have a larger surface area with more active sites, higher conductivity, lower cytotoxicity, and greater biocompatibility, making them highly suitable candidates for in-vivo biomedical applications. Due to recent advancemnets in MXenes 3D bioprinting, they are widely applied in regenerative medicine to combat challenges in suitable transplantation of tissues and organs. However, 3D bioprinting of MXenes has several complexities based on cell type, cytotoxicity, cell viability, and differentiation. To address these intricacies, surface modifications of MXene materials are done, which makes them highly fascinating for the 3D printing of tissues and organs. In the current review, we summarized recent progress in 3D bioprinting of MXene materials to construct scaffolds with desired rheological and biological properties, focusing on their potential applications in cancer phototherapy, tissue engineering, bone regeneration, and biosensing. We also discussed parameters affecting their biomedical applications and possible solutions by applying surface modifications. In addition, we addressed current challenges and future roadmaps for 3D bioprinting of MXene materials, such as generating high throughput 3D printed tissue constructs, drug delivery, drug discovery, and toxicology.

Innovative applications of MXenes in dialysis: enhancing filtration efficiency

MXenes, a family of two-dimensional transition metal carbides and nitrides, exhibit exceptional properties such as high electrical conductivity, large surface area, and chemical versatility, making them ideal candidates for various dialysis applications. One prominent application of MXenes lies in the efficient removal of toxic metals and harmful dyes from wastewater. Their unique structure allows for rapid adsorption and selective separation, significantly improving purification processes. MXenes show great promise in the therapeutic management of acute kidney injury, where their biocompatibility and ability to facilitate toxin removal can mitigate damage to renal tissues. In hemodialysis, MXenes can enhance membrane performance through improved permeability and selectivity, leading to more effective clearance of waste products. Despite the potential of MXene-based composites in dialysis applications, several challenges loom large on the horizon. The stability of MXenes in physiological environments is a critical concern, as they can undergo oxidation or degradation, which may compromise their functionality over time. The scalability of synthesis processes remains a significant barrier; producing high-quality MXene materials in sufficient quantities for clinical use is not yet fully realized. Moreover, ensuring biocompatibility is paramount, as any adverse reactions could lead to inflammation or other complications in patients. The integration of MXenes into existing dialysis systems requires meticulous engineering to maintain optimal filtration properties while avoiding clogging or fouling. The future of MXenes and their composites in dialysis presents a promising horizon, teeming with potential innovations. The development of hybrid materials that utilize MXenes alongside other nanomaterials can lead to multifunctional systems, capable of addressing multiple challenges faced in dialysis treatments. Advancements in fabrication techniques may allow for tailored porosity, enabling customized dialysis solutions for individual patients. Research into surface modifications and composites can enhance their stability and functionality, potentially overcoming current limitations. The purpose of this review is to provide a comprehensive understanding of the current landscape of MXenes in dialysis, highlighting their applications, challenges, and future directions. This review explores the diverse applications of MXenes in the field of dialysis, focusing on their roles in the removal of toxic metals and dyes, therapy for acute kidney injury, and hemodialysis enhancement.

Fabrication of a uniform quantum dot film with a high quantum yield

We present a method that uses viscosity-lowering materials to fabricate flexible polydimethylsiloxane-based quantum dot (QD) films with high quantum yield (QY) and improved uniformity. We found that the aggregation of individual QDs was prevented, and the QY improved simultaneously in films that contained surfactants. These films showed an improved absorption of approximately 27% in the near-UV and blue light regions, along with an improved photoluminescence of approximately 18%, indicating improved light conversion from the UV to the visible frequency region.

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.

Self-powered sensing platform for monitoring uric acid in sweat using cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode with excellent supercapacitor and sensing behavior

The synthesis of cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode (Co-GQD-Ti3C2TX) is reported via self-assembly of Ti3C2TX nanosheets induced by protonated arginine-functionalized graphene quantum dot and subsequent reduction of cobalt (III). The resulting Co-GQD-Ti3C2TX shows good monolithic architecture, mechanical property, dispersibility and conductivity. The structure achieves excellent supercapacitor and sensing behavior. The self-charging supercapacitor produced by printing viscous Co-GQD-Ti3C2TX hydrogel on the back of flexible solar cell surface provides high specific capacitance (296 F g-1 at 1 A g-1), high-rate capacity (153 F g-1 at 20 A g-1), capacity retention (98.1% over 10,000-cycle) and energy density (29.6 W h kg-1 at 299.9 W kg-1). The electrochemical chip produced by printing Co-GQD-Ti3C2TX hydrogel on paper exhibits sensitive electrochemical response towards uric acid. The increase of uric acid between 0.01 and 800 μM causes a linear increase in differential pulse voltammetry signal with a detection limit of 0.0032 μM. The self-powered sensing platform integrating self-charging supercapacitor, electrochemical chip and micro electrochemical workstation was contentedly applied to monitoring uric acid in sweats and shows one broad application prospect in wearable electronic health monitoring device.

Emerging 2D Nanomaterials-Integrated Hydrogels: Advancements in Designing Theragenerative Materials for Bone Regeneration and Disease Therapy

This review highlights recent advancements in the synthesis, processing, properties, and applications of 2D-material integrated hydrogels, with a focus on their performance in bone-related applications. Various synthesis methods and types of 2D nanomaterials, including graphene, graphene oxide, transition metal dichalcogenides, black phosphorus, and MXene are discussed, along with strategies for their incorporation into hydrogel matrices. These composite hydrogels exhibit tunable mechanical properties, high surface area, strong near-infrared (NIR) photon absorption and controlled release capabilities, making them suitable for a range of regeneration and therapeutic applications. In cancer therapy, 2D-material-based hydrogels show promise for photothermal and photodynamic therapies, and drug delivery (chemotherapy). The photothermal properties of these materials enable selective tumor ablation upon NIR irradiation, while their high drug-loading capacity facilitates targeted and controlled release of chemotherapeutic agents. Additionally, 2D-materials -infused hydrogels exhibit potent antibacterial activity, making them effective against multidrug-resistant infections and disruption of biofilm generated on implant surface. Moreover, their synergistic therapy approach combines multiple treatment modalities such as photothermal, chemo, and immunotherapy to enhance therapeutic outcomes. In bio-imaging, these materials serve as versatile contrast agents and imaging probes, enabling their real-time monitoring during tumor imaging. Furthermore, in bone regeneration, most 2D-materials incorporated hydrogels promote osteogenesis and tissue regeneration, offering potential solutions for bone defects repair. Overall, the integration of 2D materials into hydrogels presents a promising platform for developing multifunctional theragenerative biomaterials.

Facile Synthesis of Novel Ti2C Nano Bipyramids for Photothermal and Photodynamic Therapy of Breast Cancer

Photo-responsive synergetic therapeutics achieved significant attraction in cancer theranostic due to the versatile characteristics of nanomaterials. There have been substantial efforts in developing the simplest nano-design with exceptional synergistic properties and multifunctionalities. In this work, biocompatible Ti2C MXene nano bipyramids (MNBPs) were synthesized by hydrothermal method with dual functionalities of photothermal and photodynamic therapies. The MNBPs shape was obtained from two-dimensional (2D) Ti2C nanosheets by controlling the temperature of the reaction mixture. The structure of these Ti2C MNBPs was characterized by a high-resolution transmission electron microscope, scanning electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. The Ti2C NBPs have shown exceptional photothermal properties with increased temperature to 72.3 °C under 808 nm laser irradiation. The designed nano bipyramids demonstrated excellent cellular uptake and biocompatibility. The Ti2C NBP has established a remarkable photothermal therapy (PTT) effect against 4T1 breast cancer cells. Moreover, Ti2C NBPs showed a profound response to UV light (6 mW/cm2) and produced reactive oxygen species, making them useful for photodynamic therapy (PDT). These in-vitro studies pave a new path to tune the properties of photo-responsive MXene nanosheets, indicating a potential use in biomedical applications.

Improvement in Photoelectrochemical Water Splitting Performance of GaN-nanowire Photoanode Using MXene

The photoelectrochemical water splitting (PEC-WS) performance of a photoanode consisting of GaN nanowires (NWs) is significantly improved using a Ti3C2-MXene coating as an intermediate layer to promote carrier transfer toward the electrolyte. The maximum current density and applied-bias photon-to-current efficiency of the photoanode comprising GaN NWs coated with Ti3C2-MXene (MGNWs) are measured to be 34.24 mA/cm2 and 14.47% at 1.2 and 0.4 V versus a reversible hydrogen electrode (RHE), respectively. These values are much higher than those of the GaN-NW photoanode without Ti3C2-MXene (4.04 mA/cm2 and 1.95%) and also markedly exceed those of previously reported photoanodes. After 8 days of PEC-WS, the current density was measured to be 31.07 mA/cm2, which corresponds to 97.58% of that measured immediately after the reaction started. Based on the time dependence of the current density, the hydrogen evolution rate over the reaction time is calculated to be 0.58 mmol/cm2·h. The results confirm that the PEC-WS performance of the optimized MGNW photoanode is superior to and more stable than those of previously reported photoanodes.

Biocompatible and Oxidation-Resistant Ti3 C2 Tx MXene with Halogen-Free Surface Terminations

Surface chemistry influences not only physicochemical properties but also safety and applications of MXene nanomaterials. Fluorinated Ti3 C2 Tx MXene, synthesized using conventional HF-based etchants, raises concerns regarding harmful effects on electronics and toxicity to living organisms. In this study, well-delaminated halogen-free Ti3 C2 Tx flakes are synthesized using NaOH-based etching solution. The transversal surface plasmon mode of halogen-free Ti3 C2 Tx MXene (833 nm) confirmed red-shift compared to conventional Ti3 C2 Tx (752 nm), and the halogen-free Ti3 C2 Tx MXene has a different density of state by the high proportion of -O and -OH terminations. The synthesized halogen-free Ti3 C2 Tx exhibits a lower water contact angle (34.5°) and work function (3.6 eV) than those of fluorinated Ti3 C2 Tx (49.8° and 4.14 eV, respectively). The synthesized halogen-free Ti3 C2 Tx exhibits high biocompatibility with the living cells, as evidenced by no noticeable cytotoxicity, even at very high concentrations (2000 µg mL⁻1 ), at which fluorinated Ti3 C2 Tx caused ≈50% reduction in cell viability upon its oxidation. Additionally, the oxidation stability of halogen-free Ti3 C2 Tx is enhanced unexpectedly, which cumulatively provides a good rationale for pursuing the halogen-free routes for synthesizing MXene materials for their uses in biomedical and therapeutic applications.

Preclinical safety assessment of red emissive gold nanocluster conjugated crumpled MXene nanosheets: a dynamic duo for image-guided photothermal therapy

Red emissive gold nanoclusters have potential as biological fluorescent probes, but lack sufficient light-to-heat conversion efficiency for photothermal therapy (PTT). MXene nanomaterials, on the other hand, have shown promise in PTT due to their strong near-infrared absorption abilities, but their instability caused by restacking of the sheets can decrease their available surface area. One approach to address this issue is to design sheets with wrinkles or folds. However, the crumpled or 3D MXene materials reported in the literature are actually aggregates of multiple nanosheets rather than a single sheet that is folded. In this study, a modified method for crumpling a single MXene sheet and further conjugating it with red emissive gold nanoclusters and folic acid was developed. A detailed in vitro toxicity study was performed in various cell lines and cellular uptake in cancer cells was studied using AFM to understand its interaction at the nano-bio interface. The material also demonstrated excellent utility as a bioimaging and PTT agent in vitro, with its high fluorescence allowing bioimaging at a lower concentration of 12 μg mL^-1 and a photothermal conversion efficiency of 43.51%. In vitro analyses of the cell death mechanisms induced by PTT were conducted through studies of apoptosis, cell proliferation, and ROS production. In vivo acute toxicity tests were conducted on male and female Wistar rats through oral and intravenous administration (20 mg kg^-1 dose), and toxicity was evaluated using various measures including body weight, hematology, serum biochemistry, and H&E staining. The findings from these studies suggest that the MXene gold nanoconjugate could be useful in a range of biomedical applications, with no observed toxicity following either oral or intravenous administration.

Synthesis and degradation mechanism of renally excretable gold core-shell nanoparticles for combined photothermal and photodynamic therapy

Photothermal therapy (PTT) has emerged as a very potent therapeutic approach in the treatment of tumors. Gold nanoparticles have gained considerable scientific interest as a photosensitizer due to their absorbance in the near-infrared regions. However, their biodegradation and excretion from the body is a challenge. Various biodegradable systems consisting of liposomes and polymers have been synthesized, but their precise manufacturing and decomposition mechanisms have not yet been explored. Using zein nanoparticles as a template, we have fabricated a glutathione-functionalized gold core shell type of formulation. The scalability of the one-step seedless gold coating process is also reported. The synthesis procedure of these tunable nanoparticles is understood with TEM. The thermal degradation of the material under the physiological conditions is thoroughly examined using UV and TEM. In vitro PTT effectiveness on breast cancer cells is assessed after an extensive in vitro toxicity research. The mechanism of cell death is studied using ROS and cell cycle analysis. The material exhibited good efficacy as a PTT agent in mice and showed non-toxicity up to 14 days. The renal clearance study of the material in mice shows its disintegration into renal clearable minute gold seeds. All the findings suggest biodegradable glutathione-functionalized gold core-shell nanoparticles as potential photothermal cancer treatment agents.

MXene-based electrochemical sensors for detection of environmental pollutants: A comprehensive review

Since the discovery of MXenes at Drexel University in the United States in 2011, there has been extensive research regarding various applications of MXenes including environmental remediation. MXenes with a general formula of M_n+1X_nT_x are a class of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides with unique chemical and physical characteristics as nanomaterials. MXenes feature characteristics such as high conductivity, hydrophobicity, and large specific surface areas that are attracting attention from researchers in many fields including environmental water engineering such as desalination and wastewater treatment as well as designing and building efficient sensors to detect hazardous pollutants in water. In this study, we review recent developments in MXene-based nanocomposites for electrochemical (bio) sensing with a particular focus on the detection of hazardous pollutants, such as organic components, pesticides, nitrite, and heavy metals. Integration of these 2D materials in electrochemical enzyme-based and affinity-based biosensors for environmental pollutants is also discussed. In addition, a summary of the key challenges and future remarks are presented. Although this field is relatively new, future research on biosensors of MXene-based nanocomposites need to exploit the remarkable properties of these 2D materials.

Ti3C2 MXene with pillared structure for hybrid magnesium-lithium batteries cathode material with long cycle life and high rate capability

Cationic surfactants (CS) pillared Ti₃C₂ composites (Ti₃C₂/CS) were prepared by a facile electrostatic assembly method, which have large interlayer spacing and slight N-doping. In hybrid magnesium-lithium batteries (HMLBs), the Ti₃C₂/CS composites exhibit excellent performance by utilizing both Li⁺ and Mg²⁺ as charge carriers. Among these composites, the Ti₃C₂/CTAB (CTC) electrode displays a reversible capacity of 115.9 and 60 mAh g^-1 in APC/LiCl (APCL) and APC electrolytes at 0.1 A g^-1, and it also exhibits excellent high rate performance and ultralong cycle performance. It is verified that CS is vital to significantly improve the diffusion kinetics of Mg²⁺ on the electrode surface. The CS can act as the conductive "bridge" which connects different Ti₃C₂ layers and the interlayer pillar which expands the interlayer distance. In addition, the N element in CS is effective in neutralizing electronegativity and enhancing electrical conductivity for the CTC electrode. The electrode design strategy can adapt to the synthesis of cathode materials with high rate capability in HMLBs.