High-Performance Detection of Exosomes Based on Synergistic Amplification of Amino-Functionalized Fe3O4 Nanoparticles and Two-Dimensional MXene Nanosheets.

Exosomes derived from cancer cells have been recognized as a promising biomarker for minimally invasive liquid biopsy. Herein, a novel sandwich-type biosensor was fabricated for highly sensitive detection of exosomes. Amino-functionalized Fe3O4 nanoparticles were synthesized as a sensing interface with a large surface area and rapid enrichment capacity, while two-dimensional MXene nanosheets were used as signal amplifiers with excellent electrical properties. Specifically, CD63 aptamer attached Fe3O4 nanoprobes capture the target exosomes. MXene nanosheets modified with epithelial cell adhesion molecule (EpCAM) aptamer were tethered on the electrode surface to enhance the quantification of exosomes captured with the detection of remaining protein sites. With such a design, the proposed biosensor showed a wide linear range from 102 particles µL-1 to 107 particles µL-1 for sensing 4T1 exosomes, with a low detection limit of 43 particles µL-1. In addition, this sensing platform can determine four different tumor cell types (4T1, Hela, HepG2, and A549) using surface proteins corresponding to aptamers 1 and 2 (CD63 and EpCAM) and showcases good specificity in serum samples. These preliminary results demonstrate the feasibility of establishing a sensitive, accurate, and inexpensive electrochemical sensor for detecting exosome concentrations and species. Moreover, they provide a significant reference for exosome applications in clinical settings, such as liquid biopsy and early cancer diagnosis.

Simultaneous Recognition of Dopamine and Uric Acid in the Presence of Ascorbic Acid via an Intercalated MXene/PPy Nanocomposite.

Two-dimensional (2D) MXenes have shown a great potential for chemical sensing due to their electric properties. In this work, a Ti3C2Tx/polypyrrole (MXene/PPy) nanocomposite has been synthesized and immobilized into a glassy carbon electrode to enable the simultaneous recognition of dopamine (DA) and uric acid (UA) under the interference of ascorbic acid (AA). The multilayer Ti3C2Tx MXene was prepared via the aqueous acid etching method and delaminated to a single layer nanosheet, benefiting the in-situ growth of PPy nanowires. The controllable preparation strategy and the compounding of PPy material remain great challenges for further practical application. A facile chemical oxidation method was proposed to regulate magnitude and density during the forming process of PPy nanowire, which promotes the conductivity and the electrochemical active site of this as-prepared nanomaterial. The MXene/PPy nanocomposite-modified electrode exhibited the selective determination of DA and UA in the presence of a high concentration of AA, as well as a wide linear range (DA: 12.5-125 µM, UA: 50-500 µM) and a low detection limit (DA: 0.37 µM, UA: 0.15 µM). More importantly, the simultaneous sensing for the co-existence of DA and UA was successfully achieved via the as-prepared sensor.

A Separation-Sensing Membrane Performing Precise Real-Time Serum Analysis During Blood Drawing.

Dynamic and on-site analysis of serum from human blood is crucial, however, state-of-the-art blood-assay methods can only collect single or discrete data of physiological analytes; thus, the online reports of the dynamic fluctuation of key analytes remains a great challenge. Here, we propose a novel separation-sensing membrane by constructing a heterogeneous-nanostructured architecture, wherein a surface nanoporous layer continuously extracts serum, while the biosensing nanochannels underneath dynamically recognise biotargets, thereby achieving a continuous testing of vital clinical indices as blood is drawn. By precisely controlling the pore structure and nanoshape of biosensing crystals, this membrane achieved accurate and online glucose and lactate monitoring in patients with a variety of medical conditions within 1 min, which is one order of magnitude faster than state-of-the-art techniques. Moreover, various kinds of bio-recognisers can be introduced into this membrane to accurately detect glutamate, transaminase, and cancer biomarkers.

Combating infections from drug-resistant bacteria: Unleashing synergistic broad-spectrum antibacterial power with high-entropy MXene/CDs.

The growing resistance of bacteria to antibiotics has posed challenges in treating associated bacterial infections, while the development of multi-model antibacterial strategies could efficient sterilization to prevent drug resistance. High-entropy MXene has emerged as a promising candidate for antibacterial synergy with inherent photothermal and photodynamic properties. Herein, a high-entropy nanomaterial of MXene/CDs was synthesized to amplify oxidative stress under near-infrared laser irradiation. Well-exfoliated MXene nanosheets have proven to show an excellent photothermal effect for sterilization. The incorporation of CDs could provide photo-generated electrons for MXene nanosheets to generate ROS, meanwhile reducing the recombination of electron-hole pairs to further accelerate the generation of photo-generated electrons. The MXene/CDs material demonstrates outstanding synergistic photothermal and photodynamic effects, possesses excellent biocompatibility and successfully eliminates drug-resistant bacteria as well as inhibits biofilm formation. While attaining a remarkable killing efficiency of up to 99.99% against drug-resistant Escherichia coli and Staphylococcus aureus, it also demonstrates outstanding antibacterial effects against four additional bacterial strains. This work not only establishes a synthesis precedent for preparing high-entropy MXene materials with CDs but also provides a potential approach for addressing the issue of drug-resistant bacterial infections.

Bifunctional electrochemical biosensor based on PB-MXene films for the real-time analysis and detection of living cancer cells.

Circulating tumor cells (CTCs) are important prognostic markers for cancer diagnosis and metastasis, and their detection is an important means to detect cancer metastasis. Herein, we construct a novel bifunctional electrochemical biosensor based on the PB-MXene composite films. A simple electrostatic self-assembly approach was employed to prepare a film composed of PB nanocubes on the MXene substrates. Given that the PB is an artificial peroxidase for H2O2 sensing, the PB-MXene films can realize the real-time monitoring of H2O2 secretion from living CTCs. Besides, the anti-CEA attached biosensors can be utilized to quantify the corresponding CTCs. The synergic effects of the MXene with a large specific area and PB with enzyme-free catalysis for H2O2 resulted in PB-MXene films exhibiting high electrocatalytic and low cytotoxicity for both H2O2 sensing and living CTCs capturing. As a result, the biosensor shows a low detection limit of 0.57 µM towards H2O2 with a wide linear range (1 µM to 500 µM), as well as an excellent sensing performance for CTCs (an extremely low detection limit of 9 cells/mL in a wide linear range of 1.3 ×101 to 1.3 ×106 cells/mL). Moreover, the prepared biosensor showed satisfactory stability and anti-interference ability for potential applications in clinical cancer diagnosis and tumor metastasis.

Hierarchical Au nanoarrays functionalized 2D Ti2CTx MXene membranes for the detection of exosomes isolated from human lung carcinoma cells.

Exosome is considered an important biomarker of liquid biopsy in early cancer screening, which can reflect the physiological and pathological status of cancer cells. Herein, we construct a novel electrochemical biosensor based on hierarchical Au nanoarray-modified 2D Ti2CTx MXene membranes for sensitive detection of exosomes. Ti2CTx MXene nanosheets were fabricated as the building blocks for preparing 2D membranes as the sensing platform via vacuum filtration. To enhance the conductivity of the MXene membrane, for the first time, hierarchical Au nanoarrays were further deposited in situ on the MXene membrane surface. The combination of MXene membrane with a large specific area and hierarchical Au nanoarrays with excellent conductivity make higher electrocatalytic and more active sites in aptamer immobilization. In this strategy, the composite membrane modified by EpCAM recognized aptamer can specifically capture target exosomes, meanwhile, these target exosomes anchor aptamer for CD63 to further enhance the sensing sensitivity and accuracy of the biosensor. As a result, the biosensor achieved high sensitivity and reliable performance for exosome sensing, with a low detection limit (58 particles/µL) in the linear range of 1 × 102 to 1 × 107 particles/µL. In addition, this biosensor showed satisfactory electrochemical stability and anti-interference ability for the detection of exosomes in real serum samples.

A light-driven dual-nanotransformer with deep tumor penetration for efficient chemo-immunotherapy.

Designing a transformable nanosystem with improved tumor accumulation and penetration by tuning multiple physicochemical properties remains a challenge. Here, a near-infrared (NIR) light-driven nanosystem with size and charge dual-transformation for deep tumor penetration is developed. Methods: The core-shell nanotransformer is realized by integrating diselenide-bridged mesoporous organosilica nanoparticles as a reactive oxygen species (ROS)-responsive core with an indocyanine green (ICG)-hybrid N-isopropyl acrylamide layer as a thermosensitive shell. After loading doxorubicin (DOX), negatively charged nanomedicine prevents DOX leakage, rendering prolonged blood circulation time and high tumor accumulation. Results: Upon NIR light irradiation, mild photothermal effects facilitate the dissociation of the thermosensitive shell to achieve negative-to-positive charge reversal. Meanwhile, ICG-generated ROS cleave the diselenide bond of the organosilica core, resulting in rapid matrix degradation that produces DOX-containing smaller fragments. Such a light-driven dual-transformable nanomedicine simultaneously promotes deep tumor penetration and implements sufficient chemotherapy, along with evoking robust immunogenic cell death effects in vitro and in vivo. With the combination of a programmed cell death protein-1 (PD-1) checkpoint blockade, the nanotransformer remarkably blocks primary tumor growth and pulmonary metastasis of breast cancer with low systemic toxicity. Conclusions: This study develops a promising strategy to realize high tumor accumulation and deep penetration of light-transformable nanomedicine for efficient and safe chemo-immunotherapy.

Specific recognition and photothermal release of circulating tumor cells using near-infrared light-responsive 2D MXene nanosheets@hydrogel membranes.

2D materials with attractive optical properties are promising for individualized cancer immunotherapy. Isolation, capture, and release of circulating tumor cells (CTCs) are of great significance for promoting the process of early diagnosis of cancers. MXene nanosheets incorporated gelatin hydrogel offers the possibility of achieving near-infrared (NIR) light response to initiate the photothermal effect. Herein, the design and preparation of Ti3C2Tx MXene nanosheets-embedded thermoresponsive gelatin hydrogel membrane with NIR light-responsive for the specific capture and release of CTCs were reported. The membrane was fabricated by casting Ti3C2Tx-embedded gelatin onto a substrate and then modified with epithelial-cell adhesion-molecule antibody (anti-EpCAM) for the specific recognition and separation of CTCs from whole blood. The captured cells can be released without damage with dual-mode containing temperature-responsive release (gelatin deconstructed at 37 °C) and photothermal site-release (Ti3C2Tx induced by NIR light). Furthermore, we were able to achieve an average efficient release rate of 89 % of captured cells with stable cell viability of 87 % via the NIR light irradiation. This work may provide the promising potential for retrieval of single cells in clinical diagnosis.

Multifunctional Gold Nano-Cytosensor With Quick Capture, Electrochemical Detection, and Non-Invasive Release of Circulating Tumor Cells for Early Cancer Treatment.

Circulating tumor cells (CTCs) are metastatic tumor cells that shed into the blood from solid primary tumors, and their existence significantly increases the risk of metastasis and recurrence. The timely discovery and detection of CTCs are of considerable importance for the early diagnosis and treatment of metastasis. However, the low number of CTCs hinders their detection. In the present study, an ultrasensitive electrochemical cytosensor for specific capture, quantitative detection, and noninvasive release of EpCAM-positive tumor cells was developed. The biosensor was manufactured using gold nanoparticles (AuNPs) to modify the electrode. Three types of AuNPs with controllable sizes and conjugated with a targeting molecule of monoclonal anti-EpCAM antibody were used in this study. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) of the cytosensors were performed to evaluate the cell capture efficiency and performance. The captured 4T1 cells by the AuNPs hindered electron transport efficiency, resulting in increased EIS responses. The cell capture response recorded using EIS or DPV indicated that the optimal AuNPs size should be 17 nm. The cell capture response changed linearly with the concentration range from 8.0 × 10 to 1 × 107 cells/mL, and the limit of detection was 50 cells/mL. After these measurements, glycine-HCl (Gly-HCl) was used as an antibody eluent to destroy the binding between antigen and antibody to release the captured tumor cells without compromising their viability for further clinical research. This protocol realizes rapid detection of CTCs with good stability, acceptable assay precision, significant fabrication reproducibility with a relative standard deviation of 2.09%, and good recovery of cells. Our results indicate that the proposed biosensor is promising for the early monitoring of CTCs and may help customize personalized treatment options.

Biomimetic immunomagnetic gold hybrid nanoparticles coupled with inductively coupled plasma mass spectrometry for the detection of circulating tumor cells.

Immunomagnetic beads are important tools for the isolation and detection of circulating tumor cells (CTCs). However, the current immunomagnetic bead technique provides poor CTC separation purity due to nonspecific binding of background cells. Furthermore, immunomagnetic beads have not been appropriately functionalized for enabling CTC analysis and quantification. In this work, bimetallic magnetic gold nanoparticles were prepared and coated with leukocyte membranes to form leukocyte membrane-camouflaged nanoparticles. After conjugation with the antibody of epithelial cell adhesion molecule (EpCAM), the biomimetic immunomagnetic gold nanoparticles (CM-Fe3O4@Au-Ab) showed a high specific recognition ability on mock (EpCAM-positive) CTCs and a reduced interaction with leukocytes. We subsequently optimized the conditions for CTC separation, including the concentration of nanoparticles and the incubation time. Under the optimized conditions, CM-Fe3O4@Au-Ab exhibited high CTC capture efficiency with negligible background cell binding in mock clinical blood samples. More importantly, gold probes were tagged on the surface of these separated CTCs. When coupled with ICP-MS analysis, the number of CTCs and gold signals exhibited a good linear relationship, and a low limit of detection was obtained, enabling us to estimate the number of CTCs in blood samples. Hence, we expected that CM-Fe3O4@Au-Ab could provide an opportunity to surmount the limitations of current CTC detection.

Simultaneous biosensing of catechol and hydroquinone via a truncated cube-shaped Au/PBA nanocomposite.

A simultaneous testing of the trace catechol (CC) and hydroquinone (HQ) was achieved via an ultrasensitive phenolic biosensor constructed by the truncated cube-shaped gold/Prussian blue analogue (Au/PBA) nanocomposites. A facile charge-assembly strategy was developed to drive the successive mutual attractions for the crystallization among [Fe(CN)6]3-, Co2+, and [AuCl4]- reactants, benefiting the in-situ growth of Au nanoparticles on all faces of the PBA truncated nanocubes. On account of this special architecture, numerous 10 nm Au particles can rapidly gather the electrons from the enzyme reaction to a PBA crystal due to their high conductivity, and then the current signals will be significantly magnified through the reversible redox of the PBA. Using this nanomaterial, the as-prepared biosensor has shown an extreme wide linear range (CC: 0.2-550 µM, HQ: 1-550 µM) and an ultralow detection limit (CC: 0.06 ±â€¯0.001 µM, HQ: 0.3 ±â€¯0.007 µM) for the independent detections of CC and HQ. More importantly, when the two targets coexist, this biosensor can simultaneously exhibit the obvious and accurate responses of CC and HQ at the different potentials (0.17 V for CC and 0.07 V for HQ) with the high sensitivities and rare mutually interferences.