Chimeric Peptides Self-Assembling on Titanium Carbide MXenes as Biosensing Interfaces for Activity Assay of Post-translational Modification Enzymes

Titanium Carbide-Based Spatiotemporally Selectable-Activated Entropy-Driven DNA Nanoplatform for Amplified MicroRNA Imaging and Photothermal Therapy In Vivo

Engineering an elaborate nanotheranostic platform that can achieve spatiotemporally selective microRNA (miRNA) imaging and imaging-guided therapy in time is critical for precise cancer diagnosis and efficient treatment, yet remains a challenge. Herein, we present an on-site-activatable nanotheranostic platform (Ti3C2-NEDR) that engineers a photothermal-activated entropy-driven strand displacement reaction (NEDR) module on a photothermal conversion module (Ti3C2) for achieving spatiotemporally controlled miRNA-21 imaging in vivo and imaging-guided photothermal therapy only by varying the power of the near-infrared (NIR) laser. The upstream NIR photothermal conversion module, Ti3C2, can act not only as a DNA circuit carrier to deliver the NEDR module but also as a photothermal agent to activate the downstream NEDR module in low-power NIR laser irradiation. Once the NEDR module is activated by the NIR laser, the entropy-driven strand displacement reaction can be innated by intracellular miRNA-21 to generate an amplified fluorescence signal for the spatiotemporally selective imaging of miRNA-21 in vivo. Thereafter, the imaging-guided in vivo photothermal therapy can be achieved in time only by switching to the high-power NIR laser. It is envisioned that this strategy of NIR light-activated spatiotemporally selective miRNA imaging and imaging-guided on-demand therapy may expand the nanotheranostic platform for precise cancer diagnosis and personalized therapy in time, providing a remarkable prospect in biomedical diagnosis and therapy.

Life at the interface: Engineering bio-nanomaterials through interfacial molecular self-assembly

Interfacial self-assembly describes the directed organization of molecules and colloids at phase boundaries. Believed to be fundamental to the inception of primordial life, interfacial assembly is exploited by a myriad of eukaryotic and prokaryotic organisms to execute physiologic activities and maintain homeostasis. Inspired by these natural systems, chemists, engineers, and materials scientists have sought to harness the thermodynamic equilibria at phase boundaries to create multi-dimensional, highly ordered, and functional nanomaterials. Recent advances in our understanding of the biophysical principles guiding molecular assembly at gas-solid, gas-liquid, solid-liquid, and liquid-liquid interphases have enhanced the rational design of functional bio-nanomaterials, particularly in the fields of biosensing, bioimaging and biotherapy. Continued development of non-canonical building blocks, paired with deeper mechanistic insights into interphase self-assembly, holds promise to yield next generation interfacial bio-nanomaterials with unique, and perhaps yet unrealized, properties. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

DNA-Peptide Interaction-Modulated Charge Reversal in Biomimetic Nanochannels for Simple and Efficient Detection of Histone Deacetylases

Protein acetylation, a fundamental post-translational modification, plays a critical role in the regulation of gene expression and cellular processes. Monitoring histone deacetylases (HDACs) is important for understanding epigenetic dynamics and advancing the early diagnosis of malignancies. Here, we leverage the dynamic characteristics of DNA-peptide interactions in biomimetic nanochannels to develop a HDAC detection method. In specific, the catalysis of peptide deacetylation by HDACs triggers alterations in the charge states of the nanochannel surface to accommodate DNA molecules. Then, the interaction between DNA and peptides shifts the nanochannel surface charge from positive to negative, leading to a reversal of the ion current rectification (ICR). By calculation of the ICR ratio, quantitative detection of HDACs can be efficiently achieved using the nanochannel-based method in an enzyme-free and label-free manner. Our experimental results demonstrate that HDACs can be detected by using this method within a concentration range of 0.5-500 nM. The innate simplicity and efficiency of this strategy may render it a valuable tool for advancing both fundamental research and clinical applications in the realm of epigenetics and personalized medicine.

Boronic Acid-Decorated Carbon Dot-Based Semiselective Multichannel Sensor Array for Cytokine Discrimination and Oral Cancer Diagnosis

Cytokines are essential components of the immune system and are recognized as significant biomarkers. However, detection of a single cytokine is not precise and reliable enough to satisfy the requirements for diagnosis. Herein, we developed a pattern recognition-based method for the multiplexed sensing of cytokines, which involves three-color-emitting boronic acid-decorated carbon dots (BCDs) and arginine-modified titanium carbide (Ti3C2 MXenes) as the sensor array. Initially, the fluorescence signals of the three BCDs were quenched by Ti3C2 MXenes. In the presence of cytokines, the fluorescence intensity of the BCDs was restored or further quenched by different cytokines. The fluorescence response occurs in two steps: first, boronic acid interacts with cis-diol functional groups of cytokines, and second, arginine headgroup selectively interacts with glycans. By exploiting the different competing binding of the BCDs and the cytokines toward Ti3C2 MXenes, seven cytokines and their mixtures can be effectively discriminated at a concentration of 20 ng mL-1. Furthermore, our sensor array demonstrated an excellent performance in classifying human oral cancer saliva samples from healthy individuals with clinically relevant specificity. The noninvasive method offers a rapid approach to cytokine analysis, benefiting early and timely clinical diagnosis and treatment.

Enzyme activity termination by titanium carbide nanosheet and its application for the detection of deoxyribonuclease I

Deoxyribonuclease I (DNase I) is a typical nuclease that plays key roles in many physiological processes and the development of a novel biosensing strategy for DNase I detection is of fundamental significance. In this study, a fluorescence biosensing nanoplatform based on a two-dimensional (2D) titanium carbide (Ti₃C₂) nanosheet for sensitive and specific detection of DNase I was reported. Fluorophore-labeled single-stranded DNA (ssDNA) can be spontaneously and selectively adsorbed on Ti₃C₂ nanosheet through the hydrogen bond and metal chelate interaction between phosphate groups of ssDNA and titanium of Ti₃C₂ nanosheet, resulting in effective quenching of the fluorescence emitted by fluorophore. Notably, it was found the enzyme activity of DNase I will be terminated by the Ti₃C₂ nanosheet. Therefore, the fluorophore-labeled ssDNA was firstly digested by DNase I and the "post-mixing" strategy of Ti₃C₂ nanosheet was chosen to evaluate the enzyme activity of DNase I, which provided the possibility of improving the accuracy of the biosensing method. Experimental results demonstrated that this method can be utilized for quantitative analysis of DNase I activity and exhibited a low detection limit of 0.16 U/ml. Additionally, the evaluation of DNase I activity in human serum samples and the screening of inhibitors with this developed biosensing strategy were successfully realized, implying that it has high potential as a promising nanoplatform for nuclease analysis in bioanalytical and biomedical fields.

A switchable Cas12a enabling CRISPR-based direct histone deacetylase activity detection

The efficient and robust signal reporting ability of CRISPR-Cas system exhibits huge value in biosensing, but its applicability for non-nucleic acid analyte detection relies on the coupling of additional recognition modules. To address this limitation, we described a switchable Cas12a and exploited it for CRISPR-based direct analysis of histone deacetylase (HDAC) activity. Starting from the acetylation-mediated inactivation of Cas12a by anti-CRISPR protein AcrVA5, we demonstrated that the acetyl-inactivated Cas12a could be reversibly activated by HDAC-mediated deacetylation based on computational simulations (e.g., deep learning and protein-protein docking analysis) and experimental verifications. By leveraging this switchable Cas12a for both target sensing and signal amplification, we established a sensitive one-pot assay capable of detecting deacetylase sirtuin-1 with sub-nanomolar sensitivity, which is 50 times lower than the standard two-step peptide-based assay. The versability of this assay was validated by the sensitive assessment of cellular HDAC activities in different cell lines with good accuracy, making it a valuable tool for biochemical studies and clinical diagnostics.

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.

Tailoring Peptide Self-Assembly and Formation of 2D Nanoribbons on Mica and HOPG Surface

Studying the interactions between biomolecules and material interfaces play a crucial role in the designing and synthesizing of functional bionanomaterials with tailored structure and function. Previously, a lot of studies were performed on the self-assembly of peptides in solution through internal and external stimulations, which mediated the creation of peptide nanostructures from zero-dimension to three-dimension. In this study, we demonstrate the self-assembly behavior of the GNNQQNY peptide on the surface of mica and highly oriented pyrolytic graphite through tailoring the self-assembly conditions. Various factors, such as the type of dissolvent, peptide concentration, pH value, and evaporation period on the formation of peptide nanofibers and nanoribbons with single- and bi-directional arrays are investigated. It is found that the creation of peptide nanoribbons on both mica and HOPG can be achieved effectively through adjusting and optimizing the experimental parameters. Based on the obtained results, the self-assembly and formation mechanisms of peptide nanoribbons on both material interfaces are discussed. It is expected that the findings obtained in this study will inspire the design of motif-specific peptides with high binding affinity towards materials and mediate the green synthesis of peptide-based bionanomaterials with unique function and application potential.

Fascinating MXene nanomaterials: emerging opportunities in the biomedical field

In recent years, there has been rapid progress in MXene research due to its distinctive two-dimensional structure and outstanding properties. Especially in biomedical applications, MXenes have attracted widespread favor with numerous studies on biosafety, bioimaging, therapy, and biosensing, although their development is still in the experimental stage. A comprehensive understanding of the current status of MXenes in biomedicine will promote their use in clinical applications. Here, we review advances in MXene research. First, we introduce the methods of synthesis, surface modification and functionalization of MXenes. Then, we summarize the biosafety and biocompatibility, paving the way for specific biomedical applications. On this basis, MXene nanostructures are described with respect to their use in antibacterial, bioimaging, cancer therapy, tissue regeneration and biosensor applications. Finally, we discuss MXene as a promising candidate material for further applications in biomedicine.

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.

Polydopamine-assisted immobilization of silk fibroin and its derived peptide on chemically oxidized titanium to enhance biological activity in vitro

Biochemical modification can endow the surface of implants with superior biological activity. Herein, silk fibroin (SF) protein and its anionic derivative peptides (Cs) were covalently immobilized onto a titanium implant surface via a polydopamine layer. The successful conjugation of SF and Cs was revealed by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and contact angle measurements. The addition of Cs prevented the conformational transition of silk fibroin to silk II. The deposition of apatite on its surface was significantly accelerated, and the bioactive composite coating was observed to enhance protein adsorption and cell proliferation. More importantly, it also promoted the osteogenic differentiation of bone marrow stem cells (BMSCs) for the quantitative and qualitative detection of alkaline phosphatase (ALP) and alizarin red (ARS). Overall, the stable performance and enhanced osteogenic property of the composite coating promote an extensive application for clinical titanium-based implants.

Ex vivo and in vivo fluorescence detection and imaging of adenosine triphosphate

Background

Ex vivo and in vivo detection and imaging of adenosine triphosphate (ATP) is critically important for the diagnosis and treatment of diseases, which still remains challenges up to present.

Results

We herein demonstrate that ATP could be fluorescently detected and imaged ex vivo and in vivo. In particular, we fabricate a kind of fluorescent ATP probes, which are made of titanium carbide (TC) nanosheets modified with the ROX-tagged ATP-aptamer (TC/Apt). In the constructed TC/Apt, TC shows superior quenching efficiency against ROX (e.g., ~ 97%). While in the presence of ATP, ROX-tagged aptamer is released from TC surface, leading to the recovery of fluorescence of ROX under the 545-nm excitation. Consequently, a wide dynamic range from 1 μM to 1.5 mM ATP and a high sensitivity with a limit of detection (LOD) down to 0.2 μM ATP can be readily achieved by the prepared TC/Apt. We further demonstrate that the as-prepared TC/Apt probe is feasible for accurate discrimination of ATP in different samples including living cells, body fluids (e.g., mouse serum, mouse urine and human serum) and mouse tumor models.

Conclusions

Fluorescence detection and imaging of ATP could be readily achieved in living cells, body fluids (e.g., urine and serum), as well as mouse tumor model through a new kind of fluorescent ATP nanoprobes, offering new powerful tools for the treatment of diseases related to abnormal fluctuation of ATP concentration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00930-4.

Recent Advance in the Fabrication of 2D and 3D Metal Carbides-Based Nanomaterials for Energy and Environmental Applications

Two-dimensional (2D) nanomaterials have attracted increased interest and exhibited extended applications from nanotechnology to materials science, biomedicine, tissue engineering, as well as energy storage and environmental science. With the development of the synthesis and fabrication of 2D materials, a new family of 2D materials, metal carbides (MCs), revealed promising applications in recent years, and have been utilized for the fabrication of various functional 2D and three-dimensional (3D) nanomaterials for energy and environmental applications, ascribing to the unique physical and chemical properties of MCs. In this review, we present recent advance in the synthesis, fabrication, and applications of 2D and 3D MC-based nanomaterials. For this aim, we first summarize typical synthesis methods of MCs, and then demonstrate the progress on the fabrication of 2D and 3D MC-based nanomaterials. To the end, the applications of MC-based 2D and 3D materials for chemical batteries, supercapacitors, water splitting, photodegradation, removal of heavy metals, and electromagnetic shielding are introduced and discussed. This work provides useful information on the preparation, hybridization, structural tailoring, and applications of MC-based materials, and is expected to inspire the design and fabrication of novel and functional MXene materials with improved performance.