2D magnetic titanium carbide MXene for cancer theranostics

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.

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.

State-of-the-art: MXene structures in nano-oncology

Cancer nanomedicine has been investigated widely and boomed in the last two decades, resulting in designing nanostructures with biofunctionalization, giving rise to an "All-in-One" multifunctional platform. The development of rational design technology with extended functionalities brought interdisciplinary researchers to work continuously, aiming to find a prevent or effectively treat the deadly disease of the century. Thus, it led to some Food and Drug Administration (FDA)-approving nano-based formulations for cancer treatment and opening a vast area of promising discoveries by exploiting different nanomaterials. Two-dimensional (2D) materials have recently gained tremendous interest among scientists because of their outstanding structural, optical, electronic, thermal, and mechanical characteristics. Among various 2D nanomaterials, MXenes are a widely studied nanosystem because of their close similarity to graphene analogs. So, it is synthesized using multiple approaches and exploits their inherited properties. But in most cases, surface functionalization techniques are carried out for targeting, site-specific drug clearance, renal clearance, and biocompatible with healthy cells. Thus, fabricating a multimodal agent for mono or combined therapies is also an image-guided diagnostic agent. This review will explain the recent and emerging advancements of MXenes-based composites as a multifunctional theragnostic agent and discuss the possibilities of transferring laboratory research to clinical translation.

Two-dimensional-Ti3C2 magnetic nanocomposite for targeted cancer chemotherapy

Introduction: Cervical cancer is the leading cause of cancer-related death in women, so novel therapeutic approaches are needed to improve the effectiveness of current therapies or extend their activity. In recent decades, graphene analogs, such as Mxene, an emerging class of two-dimensional (2D) graphene analogs, have been drawing considerable attention based on their intrinsic physicochemical properties and performance as potential candidates for tumor therapy, particularly for therapeutic purposes. Here we explored the targeted drug delivery in cervical cancer in in vivo model. Mxene-based nanocarriers are not able to be precisely controlled in cancer treatment. Method: To solve this problem, the titanium carbide-magnetic core-shell nanocarrier (Ti₃C₂-Fe₃O₄@SiO₂-FA) is also developed to provide synergetic anticancer with magnetic controlling ability along with pH-responsive drug release. A xenograft model of the cervix was used to investigate the effects of Cisplatin alone, or in combination with Ti₃C₂@FA and Ti₃C₂@ Fe₃O₄@SiO₂-FA, on tumor growth following histological staining for evaluation of necrosis. Result and Discussion: A significant tumor-growth suppression effect is shown when the Ti₃C₂-Fe₃O₄@SiO₂-FA nanocarrier is magnetically controlled Cisplatin drug release. It reveals a synergistic therapeutic efficacy used in conjunction with pharmaceuticals (p < .001). According to the in vivo study, the Ti₃C₂@FA@Cisplatin nanocomposite exhibits less tumor growth than the drug alone or Ti₃C₂@FA@Cisplatin via increasing necrosis effect (p < .001). Through this study, Mxene nanosheets are expanded for biomedical applications, not only through the fabrication of biocompatible magnetic Mxene nanocomposite but also through the development of functionalization strategies that enable the magnetic Ti₃C₂ nanocomposite to load high levels of Cisplatin for cervical cancer treatment (242.5%). Hence, Ti₃C₂-Fe₃O₄@SiO₂-FA nanocarriers would be promising candidates to improve cancer treatment efficiency.

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.

Plasmon-enhanced photothermal properties of Au@Ti3C2Tx nanosheets for antibacterial applications

Antibiotic-resistant bacterial strains have become an ever-increasing public concern due to their significant threats to health safety. Nanomaterial-based photothermal treatment has shown potential in antibacterial applications, but many nanomaterials exhibited limited photothermal activity that may compromise their antibacterial efficacies. Herein, we report a novel strategy based on efficient photothermal ablation and physical contact over a supported nanostructure by loading Au nanoparticles (NPs) on few-layered Ti₃C₂T_x nanosheets (NSs) for antibacterial treatment. Ti₃C₂T_x NSs are delaminated via etching and sonication, and act as a reductant for the in situ reduction of HAuCl₄·xH₂O, producing "naked" Au NPs without any stabilizers. Meanwhile, by adjusting the Au/Ti ratio, the size and loading of the Au NPs are finely regulated, thereby providing an ideal model of a surface-clean Au@Ti₃C₂T_x heterostructure for probing the composition-performance relationship. Upon irradiation with visible light, it exhibits synergistically enhanced photothermal conversion efficiency and stability, owing to the localized surface plasmonic resonance effect of Au NP and Au-NS interactions. Moreover, under visible light irradiation for 10 min, the Au@ Ti₃C₂T_x heterostructure exhibits excellent antibacterial activity for Gram-positive S. aureus and Gram-negative E. coli, and kills over 99% bacteria with a low dose of the nanomedicine suspension (50 μg mL^-1). The work demonstrates that the incorporation of transition metal carbides with plasmonic metal nanostructures is an effective strategy to enhance the photothermal antibacterial efficacy.

MXene-Based Composites as Nanozymes in Biomedicine: A Perspective

MXene-based nanozymes have garnered considerable attention because of their potential environmental and biomedical applications. These materials encompass alluring and manageable catalytic performances and physicochemical features, which make them suitable as (bio)sensors with high selectivity/sensitivity and efficiency. MXene-based structures with suitable electrical conductivity, biocompatibility, large surface area, optical/magnetic properties, and thermal/mechanical features can be applied in designing innovative nanozymes with area-dependent electrocatalytic performances. Despite the advances made, there is still a long way to deploy MXene-based nanozymes, especially in medical and healthcare applications; limitations pertaining the peroxidase-like activity and sensitivity/selectivity may restrict further practical applications of pristine MXenes. Thus, developing an efficient surface engineering tactic is still required to fabricate multifunctional MXene-based nanozymes with excellent activity. To obtain MXene-based nanozymes with unique physicochemical features and high stability, some crucial steps such as hybridization and modification ought to be performed. Notably, (nano)toxicological and long-term biosafety analyses along with clinical translation studies still need to be comprehensively addressed. Although very limited reports exist pertaining to the biomedical potentials of MXene-based nanozymes, the future explorations should transition toward the extensive research and detailed analyses to realize additional potentials of these structures in biomedicine with a focus on clinical and industrial aspects. In this perspective, therapeutic, diagnostic, and theranostic applications of MXene-based nanozymes are deliberated with a focus on future perspectives toward more successful clinical translational studies. The current state-of-the-art biomedical advances in the use of MXene-based nanozymes, as well as their developmental challenges and future prospects are also highlighted. In view of the fascinating properties of MXene-based nanozymes, these materials can open significant new opportunities in the future of bio- and nanomedicine.

Emerging theranostics to combat cancer: a perspective on metal-based nanomaterials

OBJECTIVE

Theranostics, encompassing diagnostics and therapeutics, has emerged as a critical component of cancer treatment. Metal-based theranostics is one such next-generation nanotechnology-based drug delivery system with a myriad of benefits in pre-clinical and clinical medication for the deadly diseases like cancer, where early detection can actually be life-saving.

SIGNIFICANCE

Metal theranostics have shown promising outcomes in terms of anticancer medication monitoring, targeted drug delivery, and simultaneous detection and treatment of early-stage cancer.

METHODS

For collection of literature data, different search engines including Google scholar, SciFinder, PubMed, ScienceDirect have been employed. With key words like, cancer, theranostics, metal nanoparticles relevant and appropriate data have been generated.

RESULTS

Noninvasive administration of the active drug is made possible by theranostics nanoparticulate systems' ability to aggregate at the tumor site and offer morphological and biochemical characteristics of the tumor site. The recent advancement of metal-based theranostics including metallic nanoparticles, metal oxides, metal sulfides, nanocomposites, etc. has been explored at length in this article.

CONCLUSION

The review highlights emerging applications in terms of molecular imaging, targeted therapy and different diagnostic approaches of metal theranostics. Possible challenges faced by nanotheranostics in terms of clinical immersion and toxicological aspects which need to be addressed at depth are also discussed at the end.

MXenes in Cancer Nanotheranostics

MXenes encompass attractive properties such as a large surface area, unique chemical structures, stability, elastic mechanical strength, excellent electrical conductivity, hydrophilicity, and ease of surface functionalization/modifications, which make them one of the broadly explored two-dimensional materials in the world. MXene-based micro- and nanocomposites/systems with special optical, mechanical, electronic, and excellent targeting/selectivity features have been explored for cancer nanotheranostics. These materials exhibit great diagnostic and therapeutic potential and offer opportunities for cancer photoacoustic imaging along with photodynamic and photothermal therapy. They can be applied to targeted anticancer drug delivery while being deployed for the imaging/diagnosis of tumors/cancers and malignancies. MXene-based systems functionalized with suitable biocompatible or bioactive agents have suitable cellular uptake features with transferring potential from vascular endothelial cells and specific localization, high stability, and auto-fluorescence benefits at different emission-excitation wavelengths, permitting post-transport examination and tracking. The surface engineering of MXenes can improve their biocompatibility, targeting, bioavailability, and biodegradability along with their optical, mechanical, and electrochemical features to develop multifunctional systems with cancer theranostic applications. However, challenges still persist in terms of their environmentally benign fabrication, up-scalability, functionality improvement, optimization conditions, surface functionalization, biocompatibility, biodegradability, clinical translational studies, and pharmacokinetics. This manuscript delineates the recent advancements, opportunities, and important challenges pertaining to the cancer nanotheranostic potential of MXenes and their derivatives.

Application of MXene in the diagnosis and treatment of breast cancer: A critical overview

Breast cancer is the second most common cancer worldwide. Prognosis and timely treatment can reduce the illness or improve it. The use of nanomaterials leads to timely diagnosis and effective treatment. MXenes are a 2D material with a unique composition of attributes, containing significant electrical conductance, high optical characteristics, mechanical consistency, and excellent optical properties. Current advances and insights show that MXene is far more promising in biotechnology applications than current nanobiotechnology systems. MXenes have various applications in biotechnology and biomedicine, such as drug delivery/loading, biosensor, cancer treatment, and bioimaging programs due to their high surface area, excellent biocompatibility, and physicochemical properties. Surface modifications MXenes are not only biocompatible but also have multifunctional properties, such as aiming ligands for preferential agglomeration at the tumor sites for photothermal treatment. Studies have shown that these nanostructures, detection, and breast cancer therapy are more acceptable than present nanosystems in in vivo and in vitro. This review article aims to investigate the structure of MXene, its various synthesis methods, its application to cancer diagnosis, cytotoxicity, biodegradability, and cancer treatment by the photothermal process (in-vivo and in-vitro).

Antitumor Applications of Photothermal Agents and Photothermal Synergistic Therapies

As a new tumor treatment strategy, photothermal therapy (PTT) has the advantages of accuracy, ease of administration, a high efficiency and low side effects. Photothermal transduction agents (PTAs) are the key factor which play an important role in PTT. The mechanism of PTT is discussed in detail. The photothermal conversion efficiency (PCE) can be improved by increasing the light absorption and reducing the light scattering of photothermal conversion agents. Additionally, non-radiative relaxation path attenuation can also promote energy conversion to obtain a higher value in terms of PCE. The structure and photothermal characteristics of various kinds of PTAs (metal materials, carbon-based nanomaterials, two-dimensional nanomaterials, and organic materials) were compared and analyzed. This paper reviews the antitumor applications of photothermal synergistic therapies, including PTT combined with immunotherapy, chemotherapy, and photodynamic therapy. This review proposes that these PTAs promote the development of photothermal synergistic therapies and have a great potential in the application of tumor treatment.

MXene-Assisted Ablation of Cells with a Pulsed Near-Infrared Laser

Innovative therapies are urgently needed to combat cancer. Thermal ablation of tumor cells is a promising minimally invasive treatment option. Infrared light can penetrate human tissues and reach superficial malignancies. MXenes are a class of 2D materials that consist of carbides/nitrides of transition metals. The transverse surface plasmons of MXenes allow for efficient light absorption and light-to-heat conversion, making MXenes promising agents for photothermal therapy (PTT). To date, near-infrared (NIR) light lasers have been used in PTT studies explicitly in a continuous mode. We hypothesized that pulsed NIR lasers have certain advantages for the development of tailored PTT treatment targeting tumor cells. The pulsed lasers offer a wide range of controllable parameters, such as power density, duration of pulses, pulse frequency, and so on. Consequently, they can lower the total energy applied and enable the ablation of tumor cells while sparing adjacent healthy tissues. We show for the first time that a pulsed 1064 nm laser could be employed for selective ablation of cells loaded with Ti₃C₂T_x MXene. We demonstrate both low toxicity and good biocompatibility of this MXene in vitro, as well as a favorable safety profile based on the experiments in vivo. Furthermore, we analyze the interaction of MXene with cells in several cell lines and discuss possible artifacts of commonly used cellular metabolic assays in experiments with MXenes. Overall, these studies provide a basis for the development of efficient and safe protocols for minimally invasive therapies for certain tumors.

Engineered 2D materials for optical bioimaging and path toward therapy and tissue engineering

Two-dimensional (2D) layered materials as a new class of nanomaterial are characterized by a list of exotic properties. These layered materials are investigated widely in several biomedical applications. A comprehensive understanding of the state-of-the-art developments of 2D materials designed for multiple nanoplatforms will aid researchers in various fields to broaden the scope of biomedical applications. Here, we review the advances in 2D material-based biomedical applications. First, we introduce the classification and properties of 2D materials. Next, we summarize surface and structural engineering methods of 2D materials where we discuss surface functionalization, defect, and strain engineering, and creating heterostructures based on layered materials for biomedical applications. After that, we discuss different biomedical applications. Then, we briefly introduced the emerging role of machine learning (ML) as a technological advancement to boost biomedical platforms. Finally, the current challenges, opportunities, and prospects on 2D materials in biomedical applications are discussed.

Graphical abstract

Biomedical engineering of two-dimensional MXenes

The emergence of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides, referred to MXenes, with a general chemical formula of M_n+1X_nT_x have aroused considerable interest and shown remarkable potential applications in diverse fields. The unique ultrathin lamellar structure accompanied with charming electronic, optical, magnetic, mechanical and biological properties make MXenes as a kind of promising alternative biomaterials for versatile biomedical applications, as well as uncovering many new fundamental scientific discoveries. Herein, the current state-of-the-art advances of MXenes-related biomaterials are systematically summarized in this comprehensive review, especially focusing on the synthetic methodologies, design and surface engineering strategies, unique properties, biological effects, and particularly the property-activity-effect relationship of MXenes at the nano-bio interface. Furthermore, the elaborated MXenes for varied biomedical applications, such as biosensors and biodevices, antibacteria, bioimaging, therapeutics, theranostics, tissue engineering and regenerative medicine, are illustrated in detail. Finally, we discuss the current challenges and opportunities for future advancement of MXene-based biomaterials in-depth on the basis of the present situation, aiming to facilitate their early realization of practical biomedical applications.

High Performance Polycarbonate Nanocomposites Mechanically Boosted with Titanium Carbide in Material Extrusion Additive Manufacturing

Herein, a polycarbonate (PC) polymer is melt extruded together with titanium carbide (TiC) nano powder for the development of advanced nanocomposite materials in material extrusion (MEX) 3D printing. Raw material for the 3D printing process was prepared in filament form with a thermomechanical extrusion process and specimens were built to be tested according to international standards. A thorough mechanical characterization testing course (tensile, flexural, impact, microhardness, and dynamic mechanical analysis-DMA) was conducted on the 3D printed specimens. The effect of the ceramic filler loading was also investigated. The nanocomposites' thermal and stoichiometric properties were investigated with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), energy-dispersive X-ray spectroscopy (EDS), and Raman respectively. The specimens' 3D printing morphology, quality, and fracture mechanism were investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM) respectively. The results depicted that the addition of the filler decidedly enhances the mechanical response of the virgin polymer, without compromising properties such as its processability or its thermal stability. The highest improvement of 41.9% was reported for the 2 wt.% filler loading, making the nanocomposite suitable for applications requiring a high mechanical response in 3D printing, in which the matrix material cannot meet the design requirements.

Ionic liquid exfoliated Ti3C2Tx MXene nanosheets for photoacoustic imaging and synergistic photothermal/chemotherapy of cancer

Ti₃C₂T_x MXene is a new type of two-dimensional material with good biocompatibility and a good photothermal effect, and shows great potential in cancer treatment. In this study, few-layer ionic liquid (IL)-Ti₃C₂T_x MXene nanosheets were synthesized using IL stripping technology, which have high chemical stability, and allow photoacoustic imaging and synergistic photothermal/chemotherapy of cancer. Under 808 nm laser irradiation, the nanosheets have strong absorption in the near-infrared region, and high photothermal conversion efficiency (∼63.91%). Using DOX as a model drug, the IL-Ti₃C₂T_x MXene@DOX nanosheets exhibited high drug loading capacity and pH-/photosensitivity, which will further promote the drug release of the nanosheets in an acidic tumor microenvironment and under 808 nm laser irradiation. In vitro and in vivo experiments showed that IL-Ti₃C₂T_x MXene@DOX has good biological safety, allows remarkable photoacoustic imaging, and can effectively kill cancer cells with synergistic photothermal/chemotherapy. Therefore, IL-Ti₃C₂T_x MXene nanosheets are expected to provide powerful and useful two-dimensional nanoplatforms for various biomedical applications.

Synergic Antitumor Effect of Photodynamic Therapy and Chemotherapy Mediated by Nano Drug Delivery Systems

This review provides a summary of recent progress in the development of different nano-platforms for the efficient synergistic effect between photodynamic therapy and chemotherapy. In particular, this review focuses on various methods in which photosensitizers and chemotherapeutic agents are co-delivered to the targeted tumor site. In many cases, the photosensitizers act as drug carriers, but this review, also covers different types of appropriate nanocarriers that aid in the delivery of photosensitizers to the tumor site. These nanocarriers include transition metal, silica and graphene-based materials, liposomes, dendrimers, polymers, metal–organic frameworks, nano emulsions, and biologically derived nanocarriers. Many studies have demonstrated various benefits from using these nanocarriers including enhanced water solubility, stability, longer circulation times, and higher accumulation of therapeutic agents/photosensitizers at tumor sites. This review also describes novel approaches from different research groups that utilize various targeting strategies to increase treatment efficacy through simultaneous photodynamic therapy and chemotherapy.

Redox Chemistry-Enabled Stepwise Surface Dual Nanoparticle Engineering of 2D MXenes for Tumor-Sensitive T1&T2 MRI-Guided Photonic Breast-Cancer Hyperthermia in NIR-II Biowindow

With the fast advent of two-dimensional (2D) MXenes, several therapeutic paradigms based on 2D MXene flourish, but it still lacks a generic strategy for MXenes’ functionalization to achieve theranostic functionalities...

MXenes in photomedicine: Advances and prospects

MXenes and their related nanocomposites with superior physicochemical properties such as high surface area, ease of synthesis and functionalization, high drug loading capacity, collective therapy potentials, pH-triggered drug release behavior,...

Blood compatibility evaluations of two-dimensional Ti3C2Txnanosheets

Two-dimensional (2D) nanomaterial Ti3C2Tx is a novel biomaterial used for medical apparatus. For its application, biosafety serves as a prerequisite for their use in vivo. So far, no research has systematically reported how Ti3C2Tx interacts with various components in the blood. In this work, we evaluated the hemocompatibility of Ti3C2Tx nanosheets which we prepared by HF etching. Effects of the concentration and size of Ti3C2Tx on the morphology and hemolysis rate of human red blood cells (RBCs), the structure and conformation of plasma proteins, the complement activation, as well as in vitro blood coagulation were studied. In general, Ti3C2Tx takes on good blood compatibility, but in the case of high concentration (>30 μg/mL) and "Small size" (about 100 nm), it led to the rupture of RBCs membrane and a higher rate of hemolysis. Meanwhile, platelets and complement were inclined to be activated with the increased concentration, accompanying the changed configuration of plasma proteins dependent on concentration. Surprisingly, the presence of Ti3C2Tx did not significantly disrupt the coagulation. In vitro cell culture, the results prove that when the Ti3C2Tx concentration is as high as 60μg/mL and still has good biological safety. By establishing a fuzzy mathematical model, it was proved that the hemocompatibility of Ti3C2Tx is more concentration-dependent than size-dependent, and the hemolysis rate is the most sensitive to the size and concentration of the Ti3C2Tx. These findings provide insight into the potential use of Ti3C2Tx as biofriendly nanocontainers for biomaterials in vivo.

MXenes-A New Class of Two-Dimensional Materials: Structure, Properties and Potential Applications

A new class of two-dimensional nanomaterials, MXenes, which are carbides/nitrides/carbonitrides of transition and refractory metals, has been critically analyzed. Since the synthesis of the first family member in 2011 by Yury Gogotsi and colleagues, MXenes have quickly become attractive for a variety of research fields due to their exceptional properties. Despite the fact that this new family of 2D materials was discovered only about ten years ago, the number of scientific publications related to MXene almost doubles every year. Thus, in 2021 alone, more than 2000 papers are expected to be published, which indicates the relevance and prospects of MXenes. The current paper critically analyzes the structural features, properties, and methods of synthesis of MXenes based on recent available research data. We demonstrate the recent trends of MXene applications in various fields, such as environmental pollution removal and water desalination, energy storage and harvesting, quantum dots, sensors, electrodes, and optical devices. We focus on the most important medical applications: photo-thermal cancer therapy, diagnostics, and antibacterial treatment. The first results on obtaining and studying the structure of high-entropy MXenes are also presented.

In Situ Controllable Fabrication of Two-Dimensional Magnetic Fe3O4/TiO2@Ti3C2Tx Composites for Highly Efficient Phosphopeptides Enrichment

Highly efficient enrichment of phosphopeptides is of great significance for phosphoproteomics-related biological and pathological processes research, but it remains challenging due to the lack of affinity materials which hold high enrichment efficiency and capacity. Ti₃C₂T_x MXene, a novel two-dimensional material with outstanding physicochemical properties, has attracted wide research interests for application in various fields. However, there are few reports on the use of MXene-derived materials for phosphopeptides separation in the biomedical field. In this work, we proposed a facile one-pot method that in situ oxidation and modification of Ti₃C₂T_x MXene, to prepare two-dimensional (2D) magnetic Fe₃O₄/TiO₂@Ti₃C₂T_x composites for potential application in phosphopeptides enrichment. Benefiting from the outstanding magnetic responsiveness and multiaffinity sites (Ti-O, Fe-O, and NH₂ groups), the Fe₃O₄/TiO₂@Ti₃C₂T_x composites possessed excellent enrichment performance with high sensitivity (0.1 fmol μL^-1), excellent selectivity (β-casein: bovine serum albumin = 1:5000, molar ratio), good repeatability (5 times), and high enrichment capacity (200 mg g^-1). Moreover, the results of selective enrichment of phosphopeptides from nonfat milk, human saliva, human serum, and rat brain lysates indicated the great potential of Fe₃O₄/TiO₂@Ti₃C₂T_x composites in low-abundance phosphopeptides enrichment from complex biological samples. This work has put forward a versatile method to prepare magnetic MXene composites and promoted the use of MXene composites in phosphoproteome in biomedicine.

2D materials for bone therapy

Due to their prominent physicochemical properties, 2D materials are broadly applied in biomedicine. Currently, 2D materials have achieved great success in treating many diseases such as cancer and tissue engineering as well as bone therapy. Based on their different characteristics, 2D materials could function in various ways in different bone diseases. Herein, the application of 2D materials in bone tissue engineering, joint lubrication, infection of orthopedic implants, bone tumors, and osteoarthritis are firstly reviewed comprehensively together. Meanwhile, different mechanisms by which 2D materials function in each disease reviewed below are also reviewed in detail, which in turn reveals the versatile functions and application of 2D materials. At last, the outlook on how to further broaden applications of 2D materials in bone therapies based on their excellent properties is also discussed.

2D MXene Nanomaterials for Versatile Biomedical Applications: Current Trends and Future Prospects

Research on 2D nanomaterials is still in its early stages. Most studies have focused on elucidating the unique properties of the materials, whereas only few reports have described the biomedical applications of 2D nanomaterials. Recently, important questions about the interaction of 2D MXene nanomaterials with biological components have been raised. 2D MXenes are monolayer atomic nanosheets derived from MAX phase ceramics. As a new type of inorganic nanosystems, they are being widely used in biology and biomedicine. This review introduces the latest developments in 2D MXenes for the most advanced biomedical applications, including preparation and surface modification strategies, treatment modes, drug delivery, antibacterial activity, bioimaging, sensing, and biocompatibility. Besides, this review also discusses the current development trends and prospects of 2D inorganic nanosheets for further clinical applications. These emerging 2D inorganic MXenes will play an important role in next-generation cancer treatments.

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.

MXene and black phosphorus based 2D nanomaterials in bioimaging and biosensing: progress and perspectives

Bioimaging and biosensing have garnered interest in early cancer diagnosis due to the ability of gaining in-depth insights into cellular functions and providing a wide range of diagnostic parameters. Emerging 2D materials of multielement MXenes and monoelement black phosphorous nanosheets (BPNSs) with unique intrinsic physicochemical properties such as a tunable bandgap and layer-dependent fluorescence, high carrier mobility and transport anisotropy, efficient fluorescence quenching capability, desirable light absorption and thermoelastic properties, and excellent biocompatibility and biosafety properties provide promising nano-platforms for bioimaging and biosensing applications. In view of the growing attention on the rising stars of the post-graphene age in the progress of bioimaging and biosensing, and their common feature characteristics as well as complementarity for constructing complexes, the main objective of this review is to reveal the recent advances in the design of MXene or BPNS based nanoplatforms in the field of bioimaging and biosensing. The preparation and surface functionalization methods, biosafety, and other important aspects of bioimaging and biosensing applications of MXenes and BPNSs have been assessed systematically, along with highlighting the main challenges in further biomedical application. The review not only focuses on the advancements in 2D materials for use in bioimaging and biosensing but also assesses the possibility of their future potential in bioapplications.

MXenes for Cancer Therapy and Diagnosis: Recent Advances and Current Challenges

MXenes endowed with several attractive physicochemical attributes, namely, specific large surface area, significant electrical conductivity, magnetism, low toxicity, luminescence, and high biocompatibility, have been considered as promising candidates for cancer therapy and theranostics. These two-dimensional (2D) nanostructures endowed with photothermal, chemotherapeutic synergistic, and photodynamic effects have shown promising potential for decidedly effectual and noninvasive anticancer treatments. They have been explored for photothermal/chemo-photothermal therapy (PTT) and for targeted anticancer drug delivery. Remarkably, MXenes with their unique optical properties have been employed for bioimaging and biosensing, and their excellent light-to-heat transition competence renders them an ideal biocompatible and decidedly proficient nanoscaled agent for PTT appliances. However, several important challenging issues still linger regarding their stability in physiological environments, sustained/controlled release of drugs, and biodegradability that need to be addressed. This Perspective emphasizes the latest advancements of MXenes and MXene-based materials in the domain of targeted cancer therapy/diagnosis, with a focus on the current trends, important challenges, and future perspectives.

MXene in the lens of biomedical engineering: synthesis, applications and future outlook

MXene is a recently emerged multifaceted two-dimensional (2D) material that is made up of surface-modified carbide, providing its flexibility and variable composition. They consist of layers of early transition metals (M), interleaved with n layers of carbon or nitrogen (denoted as X) and terminated with surface functional groups (denoted as Tx/Tz) with a general formula of Mn+1XnTx, where n = 1-3. In general, MXenes possess an exclusive combination of properties, which include, high electrical conductivity, good mechanical stability, and excellent optical properties. MXenes also exhibit good biological properties, with high surface area for drug loading/delivery, good hydrophilicity for biocompatibility, and other electronic-related properties for computed tomography (CT) scans and magnetic resonance imaging (MRI). Due to the attractive physicochemical and biocompatibility properties, the novel 2D materials have enticed an uprising research interest for application in biomedicine and biotechnology. Although some potential applications of MXenes in biomedicine have been explored recently, the types of MXene applied in the perspective of biomedical engineering and biomedicine are limited to a few, titanium carbide and tantalum carbide families of MXenes. This review paper aims to provide an overview of the structural organization of MXenes, different top-down and bottom-up approaches for synthesis of MXenes, whether they are fluorine-based or fluorine-free etching methods to produce biocompatible MXenes. MXenes can be further modified to enhance the biodegradability and reduce the cytotoxicity of the material for biosensing, cancer theranostics, drug delivery and bio-imaging applications. The antimicrobial activity of MXene and the mechanism of MXenes in damaging the cell membrane were also discussed. Some challenges for in vivo applications, pitfalls, and future outlooks for the deployment of MXene in biomedical devices were demystified. Overall, this review puts into perspective the current advancements and prospects of MXenes in realizing this 2D nanomaterial as a versatile biological tool.

Molecular insights into MXene destructing the cell membrane as a “nano thermal blade”

The decreased transparency denotes the approach of MXene, which indicated that the penetration process is unspontaneous. After excitation with a light beam, heat is transported through an efficient thermal conduction pathway.

Theoretical and Experimental Studies of Ti3C2 MXene for Surface-Enhanced Raman Spectroscopy-Based Sensing

Recent advances in MXenes with high carrier mobility show great application prospects in the surface-enhanced Raman scattering (SERS) field. However, challenges remain regarding the improvement of the SERS sensitivity. Herein, an effective strategy considering charge-transfer resonance for semiconductor-based substrates is presented to optimize the SERS sensitivity with the guidance of the density functional theory calculation. The theoretical calculation predicted that the excellent SERS enhancement for methylene blue (MeB) on Ti₃C₂ MXene can be excited by both 633 and 785 nm lasers, and the Raman enhanced effect is mainly originated from the charge-transfer resonance enhancement. In this work, the Ti₃C₂ MXenes exhibit an excellent SERS sensitivity with an enhancement factor of 2.9 × 10⁶ and a low detection limit of 10^-7 M for MeB molecules. Furthermore, the SERS enhancement of Ti₃C₂ and Au-Ti₃C₂ substrates exhibit higher selectivity on different molecules, which contributes to the detection of target molecules in complex solution environments. This work can provide some theoretical and experimental basis for the research on SERS activity of other MXene materials.

Engineering Mono-Chalcogen Nanomaterials for Omnipotent Anticancer Applications: Progress and Challenges

Belonging to the chalcogen group, the elements selenium (Se) and tellurium (Te) are located in Group VI-A of the periodic table. Zero-valent nanodimensioned Se (nano-Se) and Te (nano-Te) have displayed important biomedical applications in recent years. The past two decades have witnessed an explosion in novel cancer treatment strategies using nano-Se and nano-Te as aggressive weapons against tumors. Indeed, they are both inorganic nanomedicines that suppress tumor cell proliferation, diffusion, and metastasis. Abundant synthesis strategies for rational and precise surface decoration of nano-Se and nano-Te make them significant players in resisting cancers by means of powerful multi-modal treatment methods. This review focuses on the design and engineering of nano-Se- and nano-Te-based nanodelivery systems and their precise uses in cancer treatment. The corresponding anticancer molecular mechanisms of nano-Se and nano-Te are discussed in detail. Given their different photo-induced behaviors, the presence or absence of near infrared illumination is used as a defining characteristic when describing the anticancer applications of nano-Se and nano-Te. Finally, the challenges and future prospects of nano-Se and nano-Te are summarized and highlighted.

Engineering of 2D transition metal carbides and nitrides MXenes for cancer therapeutics and diagnostics

The 2D layered structured material with unique surface terminations and properties have showed great potential in variety of biomedical research fields including drug delivery and cancer therapeutics which forms the major focus of this review. MXenes as a multifunctional two-dimensional (2D) nanomaterial, has also received momentous research interest in oncology resulting from its intriguing structure and fascinating properties of magnetism and photodynamic properties such as luminescent, conductivity, magnetism, non-toxicity and its bio compatibility. This reported review intends to cover exclusively the synthesis and utilization of MXenes in oncological applications, and subsequently its future outlook in cancer therapeutic, diagnostic and theranostics. The versatile and unique physio-chemistry of MXenes permits fine tuning of its properties towards oncological applications ranging from the cancer therapeutic (e.g., photothermal therapy, photodynamic therapy, radiation therapy, chemotherapy) to cancer imaging (e.g., CT/MRI/PA imaging) as well as cancer theranostic applications. We have started the discussion by portraying the broad picture of physio-chemical aspects of MXenes followed by its drug delivery functionalities. Subsequently, ROS mediated therapeutic strategies of photodynamic therapy and radiotherapy as well as light triggered functionalities of MXenes were detailed comprehensively. In the middle of the gallery, various imaging and sensing aspects of MXenes were elucidated. Finally, we have concluded by explaining the combined therapy and diagnostic functions (theranostics) of MXenes. To put it in perspective, the current challenges and new opportunities in MXenes also discussed will give great realistic insights to motivate further research in realizing MXene as an intelligent oncological tool.

Nb-Doped MXene With Enhanced Energy Storage Capacity and Stability

MXenes present unique features as materials for energy storage; however, limited interlayer distance, and structural stability with ongoing cycling limit their applications. Here, we have developed a unique method involving incorporating Nb atoms into MXene (Ti₃C₂) to enhance its ability to achieve higher ionic storage and longer stability. Computational analysis using density functional theory was performed that explained the material structure, electronic structure, band structure, and density of states in atomistic detail. Nb-doped MXene showed a good charge storage capacity of 442.7 F/g, which makes it applicable in a supercapacitor. X-ray diffraction (XRD) indicated c-lattice parameter enhancement after Nb-doping in MXene (from 19.2A° to 23.4A°), which showed the effect of the introduction of an element with a larger ionic radius (Nb). Also, the bandgap changes from 0.9 eV for pristine MXene to 0.1 eV for Nb-doped MXene, which indicates that the latter has the signature of increased conductivity due to more metallic nature, in support of the experimental results. This work presents not only the effect of doping in MXene but also helps to explain the phenomena involved in changes in physical parameters, advancing the field of energy storage based on 2D materials.

2D Nanomaterials for Cancer Theranostic Applications

2D nanomaterials with unique nanosheet structures, large surface areas, and extraordinary physicochemical properties have attracted tremendous interest. In the area of nanomedicine, research on graphene and its derivatives for diverse biomedical applications began as early as 2008. Since then, many other types of 2D nanomaterials, including transition metal dichalcogenides, transition metal carbides, nitrides and carbonitrides, black phosphorus nanosheets, layered double hydroxides, and metal-organic framework nanosheets, have been explored in the area of nanomedicine over the past decade. In particular, a large surface area makes 2D nanomaterials highly efficient drug delivery nanoplatforms. The unique optical and/or X-ray attenuation properties of 2D nanomaterials can be harnessed for phototherapy or radiotherapy of cancer. Furthermore, by integrating 2D nanomaterials with other functional nanoparticles or utilizing their inherent physical properties, 2D nanomaterials may also be engineered as nanoprobes for multimodal imaging of tumors. 2D nanomaterials have shown substantial potential for cancer theranostics. Herein, the latest progress in the development of 2D nanomaterials for cancer theranostic applications is summarized. Current challenges and future perspectives of 2D nanomaterials applied in nanomedicine are also discussed.

Recent progress and advances in the environmental applications of MXene related materials

MXenes are a new type of two-dimensional (2D) transition metal carbide or carbonitride material with a 2D structure similar to graphene. The general formula of MXenes is M_n+1X_nT_x, in which M is an early transition metal element, X represents carbon, nitrogen and boron, and T is a surface oxygen-containing or fluorine-containing group. These novel 2D materials possess a unique 2D layered structure, large specific surface area, good conductivity, stability, and mechanical properties. Benefitting from these properties, MXenes have received increasing attention and emerged as new substrate materials for exploration of various applications including, energy storage and conversion, photothermal treatment, drug delivery, environmental adsorption and catalytic degradation. The progress on various applications of MXene-based materials has been reviewed; while only a few of them covered environmental remediation, surface modification of MXenes has never been highlighted. In this review, we highlight recent advances and achievements in surface modification and environmental applications (such as environmental adsorption and catalytic degradation) of MXene-based materials. The current studies on the biocompatibility and toxicity of MXenes and related materials are summarized in the following sections. The challenges and future directions of the environmental applications of MXene-based materials are also discussed and highlighted.

Ti3C2Tx MXene-derived TiO2/C-QDs as oxidase mimics for the efficient diagnosis of glutathione in human serum

A Ti₃C₂T_x MXene-derived TiO₂/C-QD oxidase mimic was developed and used for the efficient diagnosis of glutathione in human serum.

Novel Two-Dimensional Magnetic Titanium Carbide for Methylene Blue Removal over a Wide pH Range: Insight into Removal Performance and Mechanism

Two-dimensional (2D) layer-structured titanium carbide MXenes (e.g., 2D Ti₃C₂ MXene) have received tremendous attention owing to their excellent properties and unique 2D planar topology. Nevertheless, there are still several challenges to be addressed for well dispersibility and easy separation from a heterogeneous system, hindering the practical applications. Herein, 2D Ti₃C₂ MXene, as the most typical member of 2D MXenes, is functionalized with magnetic Fe₃O₄ nanoparticles via an in situ growth approach (designated as MXene@Fe₃O₄), which exhibits the intriguing phenomenon on methylene blue (MB) adsorption in the environmental remediation realm. The maximum adsorption capacity of the MXene@Fe₃O₄ composites for MB is calculated to be 11.68 mg·g^-1 by a Langmuir isotherm model. A thermodynamic study of the adsorption demonstrates that the reaction process is exothermic and entropy-driven. Attractively, the removal process is a pH-independent process, and the optimal MB adsorption capacity is achieved at pH = 3 or 11, which is ascribed to electrostatic interactions and the hydrogen bond effect. X-ray diffraction, Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation results reveal that the adsorption process is based on a combination of Ti-OH···N bonding, electrostatic attraction, and reductivity. Furthermore, multiple cycle runs demonstrate an excellent stability and reusability of MXene@Fe₃O₄ composites. This study provides a promising approach for the alternative removal of MB and broadens the potential application of 2D MXene for the treatment of practical acidic or alkaline wastewater.

Biocompatible Two-Dimensional Titanium Nanosheets for Multimodal Imaging-Guided Cancer Theranostics

Photothermal therapy (PTT) based on two-dimensional (2D) nanomaterials has shown significant potential in cancer treatment. However, developing 2D nanomaterial-based theranostic agents with good biocompatibility and high therapeutic efficiency remains a key challenge. Bulk titanium (Ti) has been widely used as biomedical materials for their reputable biocompatibility, whereas nanosized Ti with a biological function remains unexplored. In this work, the 2D Ti nanosheets (NSs) are successfully exfoliated from nonlayer bulk Ti and utilized as an efficient theranostic nanoplatform for dual-modal computed tomography/photoacoustic (CT/PA) imaging-navigated PTT. Besides the excellent biocompatibility obtained by TiNSs as expected, they are found to show strong absorption ability with an extinction coefficient of 20.8 L g^-1 cm^-1 and high photothermal conversion ability with an efficiency of 61.5% owing to localized surface plasmon resonances, which exceeds most of other well-known photothermal agents, making it quite promising for PTT against cancer. Furthermore, the metallic property and light-heat-acoustic transformation endow 2D Ti with the strong CT/PA imaging signal and efficient cancer therapy, simultaneously. This work highlights the enormous potential of nanosized Ti in both the diagnosis and treatment of cancer. As a paradigm, this study also paves a new avenue for the elemental transition-metal-based cancer theranostics.