3D printing of Ti3C2-MXene-incorporated composite scaffolds for accelerated bone regeneration

L-Cysteine functionalized magnetite nanoparticle adorned Ti3C2-MXene nanohybrid based screen printed immunosensor for oral cancer biomarker detection

Nanohybrid based non-invasive biosensing platforms are emerging as promising alternatives to detect biomarkers in complex and diverse bio-fluids toward ultrasensitive point-of-care diagnostics. Herein, we report the development of a highly sensitive, facile, non-invasive, label free, affordable, and innovative electrochemical screen printed immunosensor for identifying CYFRA 21-1, an established and crucial biomarker for oral cancer. Until now, no work has been reported utilizing a titanium carbide Ti3C2 MXene nanosheet and L-cysteine (L-Cyst) functionalized magnetite nanoparticle (MNPs) nanohybrid based immunosensor for electrochemical detection of CYFRA 21-1. The L-Cyst@MNPs/Ti3C2-MXene nanohybrid was synthesized via the co-precipitation method and later deposited on a gold screen printed electrode (GSPE) offering enhanced surface area and electrochemical properties. The nanohybrid modified GSPE was then surface immobilized with monoclonal antibodies (anti-CYFRA-21-1) to fabricate an anti-CYFRA-21-1/L-Cyst@MNPs/Ti3C2-MXene/GSPE immunoelectrode and the non-specific locations of the immunoelectrode were covered with bovine serum albumin (BSA). The spectroscopic, morphological, and structural analyses of the synthesized nanohybrid and the fabricated electrodes were performed using different analytical techniques. The electrochemical studies of modified electrodes were evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The fabricated BSA/anti-CYFRA-21-1/L-Cyst@MNPs/Ti3C2-MXene/GSPE immunosensor has shown an excellent limit of detection of 0.023 ng mL-1, a linear detection range of (0.5-30) ng mL-1, a sensitivity of 277.28 μA (ng mL-1)-1 cm-2 and a lower limit of quantification of 0.618 ng mL-1 for electrochemical CYFRA 21-1 determination. Hence, this L-Cyst@MNPs/Ti3C2-MXene nanohybrid could also be explored as a potential candidate for determining other cancer biomarkers.

Biodegradable polyvinyl alcohol/nano-hydroxyapatite composite membrane enhanced by MXene nanosheets for guided bone regeneration

MXene, as a new category of two-dimensional nanomaterials, exhibits a promising prospect in biomedical applications due to its ultrathin structure and morphology, as well as a range of remarkable properties such as biological, chemical, electronic, and optical properties. In this work, different concentrations of MXene (M) were added to polyvinyl alcohol (PVA, P)/nano-hydroxyapatite (n-HA, H) mixed solution, and series of PVA/n-HA/MXene (PHM) composite membranes were obtained by combining sol-gel and freeze-drying processes. Morphology, chemical composition, surface, and mechanical properties of the prepared PHM membranes were characterized by various techniques. Subsequently, the swelling and degradation performances of the composite membranes were tested by swelling and degradation tests. In addition, in vitro studies like cell adhesion, cytotoxicity, proliferation, osteogenic differentiation, and antibacterial properties of MC3T3-E1 were also evaluated. The results showed that the addition of MXene could apparently improve the composite membranes' physicochemical properties, bioactivity, and osteogenic differentiation. Specially, PHM membrane had the best comprehensive properties when the concentration of MXene was set as 2.0% w/v. In a word, the addition of MXene has a positive effect on improving the mechanical properties, osteogenic induction, and antibacterial properties of PH composite membranes, and the prepared PHM composite membranes possess potential applications for guided bone regeneration.

Research Progress on Ti3C2Tx-Based Composite Materials in Antibacterial Field

The integration of two-dimensional Ti3C2Tx nanosheets and other materials offers broader application options in the antibacterial field. Ti3C2Tx-based composites demonstrate synergistic physical, chemical, and photodynamic antibacterial activity. In this review, we aim to explore the potential of Ti3C2Tx-based composites in the fabrication of an antibiotic-free antibacterial agent with a focus on their systematic classification, manufacturing technology, and application potential. We investigate various components of Ti3C2Tx-based composites, such as metals, metal oxides, metal sulfides, organic frameworks, photosensitizers, etc. We also summarize the fabrication techniques used for preparing Ti3C2Tx-based composites, including solution mixing, chemical synthesis, layer-by-layer self-assembly, electrostatic assembly, and three-dimensional (3D) printing. The most recent developments in antibacterial application are also thoroughly discussed, with special attention to the medical, water treatment, food preservation, flexible textile, and industrial sectors. Ultimately, the future directions and opportunities are delineated, underscoring the focus of further research, such as elucidating microscopic mechanisms, achieving a balance between biocompatibility and antibacterial efficiency, and investigating effective, eco-friendly synthesis techniques combined with intelligent technology. A survey of the literature provides a comprehensive overview of the state-of-the-art developments in Ti3C2Tx-based composites and their potential applications in various fields. This comprehensive review covers the variety, preparation methods, and applications of Ti3C2Tx-based composites, drawing upon a total of 171 English-language references. Notably, 155 of these references are from the past five years, indicating significant recent progress and interest in this research area.

Designer Micro-/Nanocrumpled MXene Multilayer Coatings Accelerate Osteogenesis and Regulate Macrophage Polarization

Effective tissue regeneration and immune responses are essential for the success of biomaterial implantation. Although the interaction between synthetic materials and biological systems is well-recognized, the role of surface topographical cues in regulating the local osteoimmune microenvironment─specifically, their impact on host tissue and immune cells, and their dynamic interactions─remains underexplored. This study addresses this gap by investigating the impact of surface topography on osteogenesis and immunomodulation. We fabricated MXene/hydroxyapatite (HAP)-coated surfaces with controlled 2.5D nano-, submicro-, and microscale topographical patterns using our custom bottom-up patterning method. These engineered surfaces were employed to assess the behavior of osteoblast precursor cells and macrophage polarization. Our results demonstrate that MXene/HAP-coated surfaces with microscale crumpled topography significantly influence osteogenic activity and macrophage polarization: these surfaces notably enhanced osteoblast precursor cell spreading, proliferation, and differentiation and facilitated a shift in macrophages toward an anti-inflammatory, prohealing M2 phenotype. The observed cell responses indicate that the physical cues from the crumpled topographies, combined with the chemical cues from the MXene/HAP coatings, synergistically create a favorable osteoimmune microenvironment. This study presents the first evidence of employing MXene/HAP-multilayer coated surfaces with finely crumpled topography to concurrently facilitate osteogenesis and immunomodulation for improved implant-to-tissue integration. The tunable topographic patterns of these coatings coupled with a facile and scalable fabrication process make them widely applicable for various biomedical purposes. Our results highlight the potential of these multilayer coatings with controlled topography to improve the in vivo performance and fate of implants by modulating the host response at the material interface.

Multifunctional MXene-Based Platforms for Soft and Bone Tissue Regeneration and Engineering

MXenes and their composites hold great promise in the field of soft and bone tissue regeneration and engineering (TRE). However, there are challenges that need to be overcome, such as ensuring biocompatibility and controlling the morphologies of MXene-based scaffolds. The future prospects of MXenes in TRE include enhancing biocompatibility through surface modifications, developing multifunctional constructs, and conducting in vivo studies for clinical translation. The purpose of this perspective about MXenes and their composites in soft and bone TRE is to critically evaluate their potential applications and contributions in this field. This perspective aims to provide a comprehensive analysis of the challenges, advantages, limitations, and future prospects associated with the use of MXenes and their composites for soft and bone TRE. By examining the existing literature and research, the review seeks to consolidate the current knowledge and highlight the key findings and advancements in MXene-based TRE. It aims to contribute to the understanding of MXenes' role in promoting soft and bone TRE, addressing the challenges faced in terms of biocompatibility, morphology control, and tissue interactions.

Potential Biosafety of Mxenes: Stability, Biodegradability, Toxicity and Biocompatibility

MXenes are two-dimensional nanomaterials with unique properties that are widely used in various fields of research, mostly in the field of energy. Fewer publications are devoted to MXene application in biomedicine and the question is: are MXenes safe for use in biological systems? The sharp edges of MXenes provide the structure of "nanoknives" which cause damage in direct physical contact with cells. This is effectively used for antibacterial research. However, on the other hand, most studies in cultured cells and rodents report that they do not cause obvious signs of cytotoxicity and are fully biocompatible. The aim of our review was to consider whether MXenes can really be considered non-toxic and biocompatible. Often the last two concepts are confused. We first reviewed aspects such as the stability and biodegradation of MXenes, and then analyzed the mechanisms of toxicity and their consequences for bacteria, cultured cells, and rodents, with subsequent conclusions regarding their biocompatibility.

Green Synthesis and Biosafety Assessment of MXene

The rise of MXene-based materials with fascinating physical and chemical properties has attracted wide attention in the field of biomedicine, because it can be exploited to regulate a variety of biological processes. The biomedical applications of MXene are still in its infancy, nevertheless, the comprehensive evaluation of MXene's biosafety is desperately needed. In this review, the composition and the synthetic methods of MXene materials are first introduced from the view of biosafety. The evaluation of the interaction between MXene and cells, as well as the safety of different forms of MXene applied in vivo are then discussed. This review provides a basic understanding of MXene biosafety and may bring new inspirations to the future applications of MXene-based materials in biomedicine.

A Ti3C2 MXene-integrated near-infrared-responsive multifunctional porous scaffold for infected bone defect repair

Infected bone defect repair has long been a major challenge in orthopedic surgery. Apart from bacterial contamination, excessive generation of reactive oxygen species (ROS), and lack of osteogenesis ability also threaten the defect repair process. However, few strategies have been proposed to address these issues simultaneously. Herein, we designed and fabricated a near-infrared (NIR)-responsive, hierarchically porous scaffold to address these limitations in a synergetic manner. In this design, polymethyl methacrylate (PMMA) and polyethyleneimine (PEI) were used to fabricate the porous PMMA/PEI scaffolds via the anti-solvent vapor-induced phase separation (VIPS) process. Then, Ti3C2 MXenes were anchored on the scaffolds through the dopamine-assisted co-deposition process to obtain the PMMA/PEI/polydopamine (PDA)/MXene scaffolds. Under NIR laser irradiation, the scaffolds were able to kill bacteria through the direct contact-killing and synergetic photothermal effect of Ti3C2 MXenes and PDA. Moreover, MXenes and PDA also endowed the scaffolds with excellent ROS-scavenging capacity and satisfying osteogenesis ability. Our experimental results also confirmed that the PMMA/PEI/PDA/MXene scaffolds significantly promoted new bone formation in an infected mandibular defect model. We believe that our study provides new insights into the treatment of infected bone defects.

Biodegradable and biocompatible alginate/gelatin/MXene composite membrane with efficient osteogenic activity and its application in guided bone regeneration

Guided bone regeneration (GBR) utilizes a barrier membrane to maintain the osteogenic space and promote osseointegration of the implants. Developing a novel biomaterial to meet the mechanical and biological performance requirements of GBR membrane (GBRM) remains a huge challenge. Here, the sodium alginate (SA, S)/gelatin (G)/MXene (M) composite membrane (SGM) was prepared by combining sol-gel and freeze-drying processes. The incorporation of MXene improved the mechanical properties and hydrophilicity of the SA/G (SG) membrane, and also enhanced its cell proliferation and osteogenic differentiation. More importantly, when the concentration of MXene is 0.25%W/V, the SGM composite membrane exhibited the best tensile strength (40 MPa), high swelling rate (1012%), and appropriate degradation rate (40%). Meanwhile, the biological improvements were more significant. Therefore, the appropriate amount addition of MXene has a positive and obvious effect on the improvements of the mechanical properties, biocompatibility, and osteogenic induction of the SG composite membranes. This work provides a more extendable development idea for the application of SGM composite membrane as GBRM.

Applications of X-Ray-Based Characterization in MXene Research

X-rays are a penetrating form of high-energy electromagnetic radiation with wavelengths ranging from 10 pm to 10 nm. Similar to visible light, X-rays provide a powerful tool to study the atoms and elemental information of objects. Different characterization methods based on X-rays are established, such as X-ray diffraction, small- and wide-angle X-ray scattering, and X-ray-based spectroscopies, to explore the structural and elemental information of varied materials including low-dimensional nanomaterials. This review summarizes the recent progress of using X-ray related characterization methods in MXenes, a new family of 2D nanomaterials. These methods provide key information on the nanomaterials, covering synthesis, elemental composition, and the assembly of MXene sheets and their composites. Additionally, new characterization methods are proposed as future research directions in the outlook section to enhance understanding of MXene surface and chemical properties. This review is expected to provide a guideline for characterization method selection and aid in precise interpretation of the experimental data in MXene research.

Surface-modified Ti3C2 MXene nanosheets for mesenchymal stem cell osteogenic differentiation via photothermal conversion

In the field of bone tissue engineering, the practical application of growth factors is limited by various factors such as systemic toxicity, instability, and the potential to induce inflammation. To circumvent these limitations, the use of physical signals, such as thermal stimulation, to regulate stem cells has been proposed as a promising alternative. The present study aims to investigate the potential of the two-dimensional nanomaterial Ti₃C₂ MXene, which exhibits unique photothermal properties, to induce osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) via photothermal conversion. Surface modification of Ti₃C₂ MXene nanosheets with PVP (Ti₃C₂-PVP) was employed to enhance their colloidal stability in physiological solutions. Characterization and cellular experiments showed that Ti₃C₂-PVP nanosheets have favorable photothermal properties and biocompatibility. Our study demonstrated that the induction of photothermal stimulation by co-culturing Ti₃C₂-PVP nanosheets with BMSCs and subsequent irradiation with 808 nm NIR significantly promoted cell proliferation, adhesion and osteogenic differentiation of BMSCs. In conclusion, the results of this study suggest that Ti₃C₂-PVP is a promising material for bone tissue engineering applications as it can modulate the cellular functions of BMSCs through photothermal conversion.

3D bioprinting of human mesenchymal stem cells-laden hydrogels incorporating MXene for spontaneous osteodifferentiation

Contemporary advances in three-dimensional (3D) bioprinting technologies have enabled the fabrication of tailored live 3D tissue mimetics. Furthermore, the development of advanced bioink materials has been highlighted to accurately reproduce the composition of a native extracellular matrix and mimic the intrinsic properties of laden cells. Recent research has shown that MXene is one of promising nanobiomaterials with osteogenic activity for bone grafts and scaffolds due to its unique atomic structure of three titanium layers between two carbon layers. In this study, the MXene-incorporated gelatin methacryloyl (GelMA) and hyaluronic acid methacryloyl (HAMA) (i.e., GelMA/HAMA-MXene) bioinks were prepared to explore if they have the potential to enable the spontaneous osteodifferentiation of human mesenchymal stem cells (hMSCs) when the hMSCs-laden GelMA/HAMA-MXene bioinks were 3D printed. The physicochemical and rheological characteristics of the GelMA/HAMA-MXene hydrogels were proven to be unprecedentedly favorable supportive matrices suited for the growth and survival of hMSCs. Furthermore, hMSCs were shown to spontaneously differentiate into osteoblasts within GelMA-HAMA/MXene composites to provide favorable microenvironments for osteogenesis. Therefore, our results suggest that the remarkable biofunctional advantages of the MXene-incorporated GelMA/HAMA bioink can be utilized in a wide range of strategies for the development of effective scaffolds in bone tissue regeneration.

Additively Manufactured MAX- and MXene-Composite Scaffolds for Bone Regeneration- Recent Advances and Future Perspectives

Human bones can suffer from various injuries, such as fractures, bone cancer, among others, which has initiated research activities towards bone replacement using advanced bio-materials. However, it is still challenging to design bio-scaffolds with bone-inducing agents to regenerate bone defects. In this regard, MAX-phases and MXenes (early transition metal carbides and/or nitrides) have gained notable attention due to their unique hydrophilicity, bio-compatibility, chemical stability, and photothermal properties. They can be used in bone tissue engineering as a suitable replacement or reinforcement for common bio-materials (polymers, bio-glasses, metals, or hydroxyapatite). To fabricate bio-scaffolds, additive manufacturing is prospective due to the possibility of controlling porosity and creating complex shapes with high resolution. Until now, no comprehensive article summarizing the existing state-of-the-art related to bone scaffolds reinforced by MAX-phases and MXenes fabricated by additive manufacturing has been published. Therefore, our article addresses the reasons for using bone scaffolds and the importance of choosing the most suitable material. We critically discuss the recent developments in bone tissue engineering and regenerative medicine using MAX-phases and MXenes with a particular emphasis on manufacturing, mechanical properties, and bio-compatibility. Finally, we discuss the existing challenges and bottlenecks of bio-scaffolds reinforced by MAX-phases and MXenes before deriving their future potential.

MXene-Functionalized Ferroelectric Nanocomposite Membranes with Modulating Surface Potential Enhance Bone Regeneration

Rapid and effective bone defect repair remains a challenging issue for clinical treatment. Applying biomaterials with endogenous surface potential has been widely studied to enhance bone regeneration, but how to regulate the electric potential and surface morphology of the implanted materials precisely to achieve an optimal bioelectric microenvironment is still a major challenge. The aim of this study is to develop electroactive biomaterials that better mimic the extracellular microenvironment for bone regeneration. Hence, MXene/polyvinylidene fluoride (MXene/PVDF) ferroelectric nanocomposite membranes were prepared by electrospinning. Physicochemical characterization demonstrated that Ti₃C₂T_x MXene nanosheets were wrapped in PVDF shell layer and the surface morphology and potential were modulated by altering the content of MXene, where uniform distribution of fibers and enhanced electric potential can be obtained and precisely assembled into a natural extracellular matrix (ECM) in bone tissue. Consequently, the MXene/PVDF membranes facilitated cell adhesion, stretching, and growth, showing good biocompatibility; meanwhile, their intrinsic electric potential promoted the recruitment of osteogenic cells and accelerated the differentiation of osteoblast. Furthermore, 1 wt % MXene/PVDF membrane with a suitable surface potential and better topographical structure for bone regeneration qualitatively and quantitatively promoted bone tissue formation in a rat calvarial bone defect after 4 and 8 weeks of healing. The fabricated MXene/PVDF ferroelectric nanocomposite membranes show a biomimetic microenvironment with a sustainable electric potential and optimal 3D topographical structure, providing an innovative and well-suited strategy for application in bone regeneration.

Three-Dimensional Impression of Biomaterials for Alveolar Graft: Scoping Review

Craniofacial bone defects are one of the biggest clinical challenges in regenerative medicine, with secondary autologous bone grafting being the gold-standard technique. The development of new three-dimensional matrices intends to overcome the disadvantages of the gold-standard method. The aim of this paper is to put forth an in-depth review regarding the clinical efficiency of available 3D printed biomaterials for the correction of alveolar bone defects. A survey was carried out using the following databases: PubMed via Medline, Cochrane Library, Scopus, Web of Science, EMBASE, and gray literature. The inclusion criteria applied were the following: in vitro, in vivo, ex vivo, and clinical studies; and studies that assessed bone regeneration resorting to 3D printed biomaterials. The risk of bias of the in vitro and in vivo studies was performed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr and the SYRCLE risk of bias tool, respectively. In total, 92 publications were included in the final sample. The most reported three-dimensional biomaterials were the PCL matrix, β-TCP matrix, and hydroxyapatite matrix. These biomaterials can be combined with different polymers and bioactive molecules such as rBMP-2. Most of the included studies had a high risk of bias. Despite the advances in the research on new three-dimensionally printed biomaterials in bone regeneration, the existing results are not sufficient to justify the application of these biomaterials in routine clinical practice.

Recent advances in 2D metal carbides and nitrides (MXenes): synthesis and biological application

As a new two-dimensional (2D) material, transition metal carbides and nitrides (MXenes) have attracted much attention because of their excellent physical and chemical properties. In recent years, MXenes have been widely applied in the biological field due to their high biocompatibility, abundant surface groups, good conductivity, and photothermal properties. Here, the main synthesis methods of MXenes and the analysis of the advantages and disadvantages of each method are presented in detail. Then, the latest developments of MXenes in the biological field, including biosensing, antibacterial activity, reactive oxygen species (ROS) and free radical scavenging, tissue repair and antitumor therapy are comprehensively reviewed. Finally, the current challenges and future development trends of MXenes in biological applications are discussed.

MXene-Graphene Composites: A Perspective on Biomedical Potentials

MXenes, transition metal carbides and nitrides with graphene-like structures, have received considerable attention since their first discovery. On the other hand, Graphene has been extensively used in biomedical and medicinal applications. MXene and graphene, both as promising candidates of two-dimensional materials, have shown to possess high potential in future biomedical applications due to their unique physicochemical properties such as superior electrical conductivity, high biocompatibility, large surface area, optical and magnetic features, and extraordinary thermal and mechanical properties. These special structural, functional, and biological characteristics suggest that the hybrid/composite structure of MXene and graphene would be able to meet many unmet needs in different fields; particularly in medicine and biomedical engineering, where high-performance mechanical, electrical, thermal, magnetic, and optical requirements are necessary. However, the hybridization and surface functionalization should be further explored to obtain biocompatible composites/platforms with unique physicochemical properties, high stability, and multifunctionality. In addition, toxicological and long-term biosafety assessments and clinical translation evaluations should be given high priority in research. Although very limited studies have revealed the excellent potentials of MXene/graphene in biomedicine, the next steps should be toward the extensive research and detailed analysis in optimizing the properties and improving their functionality with a clinical and industrial outlook. Herein, different synthesis/fabrication methods and performances of MXene/graphene composites are discussed for potential biomedical applications. The potential toxicological effects of these composites on human cells and tissues are also covered, and future perspectives toward more successful translational applications are presented. The current state-of-the-art biotechnological advances in the use of MXene-Graphene composites, as well as their developmental challenges and future prospects are also deliberated. Due to the superior properties and multifunctionality of MXene-graphene composites, these hybrid structures can open up considerable new horizons in future of healthcare and medicine.