Synthesis of Superelastic, Highly Conductive Graphene Aerogel/Liquid Metal Foam and its Piezoresistive Application.

Graphene aerogel (GA) has important application potential as piezoresistive sensors due to its low density, high conductivity, high porosity, and good mechanical properties. However, the fabrication of GA-based sensors with good mechanical properties and excellent sensing performance is still challenging. Herein, liquid- metal-modified GAs (GA/LM) are proposed for the development of an excellent GA-based sensor. GA/LM with three-dimensional interconnected layered structure exhibits excellent compressive stress of 41 KPa and fast response time (<20 ms). While generally flexible GA composites cannot be compressed beyond 80 % strain without plastic deformation, GA/LM demonstrates a high compressive strength of 60 kPa under a strain of 90 %. A real-time pressure sensor was fabricated based on GA/LM-2 to monitor swallowing, pulse beating, finger, wrist and knee bending, and even plantar pressure during walking. These excellent features enable potential applications in health detection.

Advances in miniature CRISPR-Cas proteins and their applications in gene editing.

The CRISPR-Cas system consists of Cas proteins and single-stranded RNAs that recruit Cas proteins and specifically target the nucleic acid. Some Cas proteins can accurately cleave the target nucleic acid under the guidance of the single-stranded RNAs. Due to its exceptionally high specificity, the CRISPR-Cas system is now widely used in various fields such as gene editing, transcription regulation, and molecular diagnosis. However, the huge size of the most frequently utilized Cas proteins (Cas9, Cas12a, and Cas13, which contain 950-1,400 amino acids) can limit their applicability, especially in eukaryotic gene editing, where larger Cas proteins are difficult to deliver into the target cells. Recently discovered miniature CRISPR-Cas proteins, consisting of only 400 to 800 amino acids, offer the possibility of overcoming this limitation. This article systematically reviews the latest research progress of several miniature CRISPR-Cas proteins (Cas12f, Cas12j, Cas12k, and Cas12m) and their practical applications in the field of gene editing.

A paper-based ratiometric fluorescence sensor based on carbon dots modified with Eu3+ for the selective detection of tetracycline in seafood aquaculture water.

Paper-based ratiometric fluorescence sensors are normally prepared using two or more types of fluorescent materials on a paper chip for simple, low-cost and fast detection. However, the choice of multi-step and one-step modifications on the paper chip affects the analytical performance. Herein, a novel paper-based dual-emission ratiometric fluorescence sensor was designed for the selective detection of tetracycline (TC). Carbon dots (CDs) modified with Eu3+ were combined with a sealed paper-based microfluidic chip by two methods: one-step grafting of CDs-Eu3+ on paper and step-by-step grafting of CDs and Eu3+ on paper. The analytical performance was studied and optimized respectively. The red fluorescence of Eu3+ at 450 nm is enhanced and the blue fluorescence of CDs at 617 nm is quenched by energy transfer in the presence of TC. Under optimal conditions, TC is selectively determined in the linear range from 0.1 µM to 100 µM with a detection limit of 0.03 µM by the step-by-step grafting method. In addition, the sealed paper chip could effectively prevent pollution and volatilization from the reagent. This technique has been used to analyze TC in seafood aquaculture water with satisfactory results.

Application of the Electrospinning Technique in Electrochemical Biosensors: An Overview.

Electrospinning is a cost-effective and flexible technology for producing nanofibers with large specific surface areas, functionalized surfaces, and stable structures. In recent years, electrospun nanofibers have attracted more and more attention in electrochemical biosensors due to their excellent morphological and structural properties. This review outlines the principle of electrospinning technology. The strategies of producing nanofibers with different diameters, morphologies, and structures are discussed to understand the regulation rules of nanofiber morphology and structure. The application of electrospun nanofibers in electrochemical biosensors is reviewed in detail. In addition, we look towards the future prospects of electrospinning technology and the challenge of scale production.

ZnO-CeO2 Hollow Nanospheres for Selective Determination of Dopamine and Uric Acid.

ZnO-CeO2 hollow nanospheres have been successfully synthesized via the hard templating method, in which CeO2 is used as the support skeleton to avoid ZnO agglomeration. The synthesized ZnO-CeO2 hollow nanospheres possess a large electrochemically active area and high electron transfer owing to the high specific surface area and synergistic effect of ZnO and CeO2. Due to the above advantages, the resulting ZnO-CeO2 hollow spheres display high sensitivities of 1122.86 µA mM-1 cm-2 and 908.53 µA mM-1 cm-2 under a neutral environment for the selective detection of dopamine and uric acid. The constructed electrochemical sensor shows excellent selectivity, stability and recovery for the selective analysis of dopamine and uric acid in actual samples. This study provides a valuable strategy for the synthesis of ZnO-CeO2 hollow nanospheres via the hard templating method as electrocatalysts for the selective detection of dopamine and uric acid.

Dual-Mode Undistorted Visual Fluorescent Sensing Strategy through Manipulating the Coffee-Ring Effect on Microfluidic Paper-Based Chip.

To overcome the insufficient sensitivity due to distortion of the fluorescent images by mobile devices, we first developed a novel dual-mode strategy for undistorted visual fluorescent sensing on µPAD by technically manipulating the coffee-ring effect of the fluid sample. Based on the manipulating coffee-ring effect, we divided the horizontal direction of the resulting fluorescence image into 600 pixels and obtained more accurate quantitative information to avoid image distortion. The bovine serum albumin-stabilized gold nanoclusters-copper ion complex was used as the fluorescent probe, combined with a small imaging box and a smartphone, to achieve a rapid testing of histidine in human urine. The output image was analyzed in dual mode: RGB numerical analysis in pixel units and the direct measurement of the fluorescent strips length (limit of detection (LOD) is 0.021 and 0.5 mM, respectively), and improved antidistortion for visual fluorescent sensing. This strategy can overcome the distortion of a smartphone-visualized fluorescent image and shows great potential for rapid and convenient analysis.

Pb speciation and elemental distribution in leeks by micro X-ray fluorescence and X-ray absorption near-edge structure.

Vegetables are crucial to a human diet as they supply the body with essential vitamins, minerals, etc. Heavy metals that accumulate in plants consequently enter the food chain and endanger people's health. Studying the spatial distribution and chemical forms of elements in plant/vegetable tissues is vital to comprehending the potential interactions between elements and detoxification mechanisms. In this study, leek plants and soil from vegetable gardens near lead-zinc mines were collected and cultivated with 500 mg L-1 PbNO3 solutions for three weeks. Micro X-ray fluorescence was used to map the distribution of Pb and other chemical elements in leek roots, and X-ray absorption near-edge spectroscopy was used to assess the Pb speciation in leek roots and leaves. These findings demonstrated that Pb, Cu, Mn, Cr, Ti and Fe were detected in the outer rings of the root's cross section, and high-intensity points were observed in the epidermis. Zn, K and Ca, on the other hand, were distributed throughout the root's cross section. Leek root and leaf contained significant quantities of lead phosphate and basic lead carbonate at more than 80%, followed by lead sulfide (19%) and lead stearate (11.1%). The capacity of leek roots to convert ambient lead into precipitated lead and fix it on the root epidermis and other inner surfaces is a key mechanism for reducing the toxic effects of Pb.

Recent Advances in Functional Nanomaterials for Electrochemical Sensors and Biosensors.

Considering the unique advantages of the quantum size, volume, surface, and macroscopical quantum tunnel effects, nanomaterials have been paid increasing attention for various applications in environmental, medical, biological, and chemical analyses in recent decades [...].

Simultaneous Determination of Xanthine and Hypoxanthine Using Polyglycine/rGO-Modified Glassy Carbon Electrode.

A novel electrochemical sensor was developed for selective and sensitive determination of xanthine (XT) and hypoxanthine (HX) based on polyglycine (p-Gly) and reduced graphene oxide (rGO) modified glassy carbon electrode (GCE). A mixed dispersion of 7 µL of 5 mM glycine and 1 mg/mL GO was dropped on GCE for the fabrication of p-Gly/rGO/GCE, followed by cyclic voltammetric sweeping in 0.1 M phosphate buffer solution within -0.45~1.85 V at a scanning rate of 100 mV·s-1. The morphological and electrochemical features of p-Gly/rGO/GCE were investigated by scanning electron microscopy and cyclic voltammetry. Under optimal conditions, the linear relationship was acquired for the simultaneous determination of XT and HX in 1-100 µM. The preparation of the electrode was simple and efficient. Additionally, the sensor combined the excellent conductivity of rGO and the polymerization of Gly, demonstrating satisfying simultaneous sensing performance to both XT and HX.

The Applications of Electrochemical Immunosensors in the Detection of Disease Biomarkers: A Review.

Disease-related biomarkers may serve as indicators of human disease. The clinical diagnosis of diseases may largely benefit from timely and accurate detection of biomarkers, which has been the subject of extensive investigations. Due to the specificity of antibody and antigen recognition, electrochemical immunosensors can accurately detect multiple disease biomarkers, including proteins, antigens, and enzymes. This review deals with the fundamentals and types of electrochemical immunosensors. The electrochemical immunosensors are developed using three different catalysts: redox couples, typical biological enzymes, and nanomimetic enzymes. This review also focuses on the applications of those immunosensors in the detection of cancer, Alzheimer's disease, novel coronavirus pneumonia and other diseases. Finally, the future trends in electrochemical immunosensors are addressed in terms of achieving lower detection limits, improving electrode modification capabilities and developing composite functional materials.

Engineered nanomedicines block the PD-1/PD-L1 axis for potentiated cancer immunotherapy.

Immunotherapy, in particular immune checkpoint blockade (ICB) therapy targeting the programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis, has remarkably revolutionized cancer treatment in the clinic. Anti-PD-1/PD-L1 therapy is designed to restore the antitumor response of cytotoxic T cells (CTLs) by blocking the interaction between PD-L1 on tumour cells and PD-1 on CTLs. Nevertheless, current anti-PD-1/PD-L1 therapy suffers from poor therapeutic outcomes in a large variety of solid tumours due to insufficient tumour specificity, severe cytotoxic effects, and the occurrence of immune resistance. In recent years, nanosized drug delivery systems (NDDSs), endowed with highly efficient tumour targeting and versatility for combination therapy, have paved a new avenue for cancer immunotherapy. In this review article, we summarized the recent advances in NDDSs for anti-PD-1/PD-L1 therapy. We then discussed the challenges and further provided perspectives to promote the clinical application of NDDS-based anti-PD-1/PD-L1 therapy.

Modular Introduction of endo-Binding Sites in a Macrocyclic Cavity towards Selective Recognition of Neutral Azacycles.

Macrocycles with a functionalized interior, which is a general cavity feature of bioreceptors, are relatively hard to synthesize. Here we report a modular strategy to customize diverse endo-binding sites in the macrocycle cavity. Only two steps are needed. First, one V-shaped functional module bearing an embedded binding site and two 2,5-dimethoxyphenyls as reaction modules are connected. Then the condensation of the resulting monomer and paraformaldehyde directly produces the designed macrocycle. V-shaped monomers are deliberately used to guarantee the binding sites equatorially directing inward into the cavity and 2,5-dimethoxyphenyls standing axially as macrocycle sidewalls. More than a dozen endo-functionalized macrocyclic receptors have been constructed. Host-guest complexation studies show that macrocycle BP1-decorated interior OH moieties can strongly encapsulate neutral azacycles by forming inner hydrogen bonds, giving a high association constant of 4.59×104  M-1 in non-polar media.

Anchoring zinc-doped carbon dots on a paper-based chip for highly sensitive fluorescence detection of copper ions.

In this work, zinc-doped carbon dots (Zn-CDs) were anchored on a three-dimensional wheel type paper-based microfluidic chip, and were decorated with 6-mercaptonicotinic acid (MNA) and L-cysteine (L-Cys) for highly sensitive and rapid fluorescence detection of Cu2+. Zn-CDs were first anchored on paper through the amide bonds between the carboxyl groups of the Zn-CDs and the amino groups of the paper. Afterwards, Zn-CDs were decorated with MNA and L-Cys, effectively preventing the Zn-CDs from aggregation. The nitrogen atom on the pyridine ring and the carboxylic acid groups in MNA and L-Cys coordinated with Cu2+ to form a nonfluorescent ground-state complex, causing the fluorescence quenching of the Zn-CDs. The three-dimensional rotary design could simplify the operation process and achieve simultaneous analysis of multiple samples with different concentrations. Under optimal conditions, the fluorescent sensor exhibits linear response for the determination of Cu2+ in the range from 0.1 to 60 µg L-1 with the detection limit (LOD) of 0.018 µg L-1. The proposed strategy provides a novel way for the highly sensitive detection of Cu2+ in a complex water environment.

Sequential colorimetric sensing of cupric and mercuric ions by regulating the etching process of triangular gold nanoplates.

A triangular gold nanoplate (AuNPL)-based colorimetric assay is presented for ultrasensitive determination of cupric ions (Cu2+) and mercuric ions (Hg2+) in sequence. AuNPLs were found to be etched efficiently when producing triiodide ions (I3-) by a redox reaction between Cu2+ and iodide ions (I-), leading to a change of the shape of AuNPLs from triangular to sphere along with a color change from blue to pink. In the presence of Hg2+ the etching of AuNPLs was suppressed due to the consumption of I- by the formation of HgI2. With an increase of the concentration of the Hg2+ a transformation from sphere to triangular in the shape of AuNPLs occurred with a color change from pink to blue. The evolution of AuNPLs from etching to anti-etching state by sequential addition of Cu2+ and Hg2+ was accompanied with color variations and band shifts of localized surface plasmon resonance (LSPR), allowing for visual and spectroscopic determination of Cu2+ and Hg2+ successively within 15 min. In the range 0.01-1.5 µM for Cu2+ and 0.02-3.0 µM for Hg2+, the linear relationship between the band shift values and the target ions concentration was found good (R2 > 0.996). The limit of detections (3S/k) was 19 nM for Cu2+ and 9 nM for Hg2+, respectively. The lowest visual estimation concentration was 80 nM for both Cu2+ and Hg2+ through the distinguishable color changes. This system exhibited desirable selectivity for Cu2+ and Hg2+ over other common ions tested. The method has been successfully applied to sequential determination of Cu2+ and Hg2+ in real water and food samples. Graphical abstract Scheme 1 Schematic illustration for sequential detection of Cu2+ and Hg2+ based on etching of AuNPLs.

Applications of magnetic materials separation in biological nanomedicine.

As a result of their advantages for superparamagnetic properties, good biocompatibility, and high binding capacity, functionalized magnetic materials became widely popular over the past couple of decades, being applied on large scale in various processes of sample preparation for biomedicine. In this work, we perform an in-depth review on the current progress in the field of magnetic bead separation, discussing in detail the physical basis of this process, various synthesis methods and surface modification strategies. We place special focus of attention as well on the latest applications of magnetic polymer microspheres in cell separation, protein purification, immobilized enzyme, nucleic acid separation, and extraction of bioactive compounds with low molecular weight. Existing problems are highlighted and possible trends of magnetic separation techniques for biomedicine in the future are proposed.

A novel hydrogen peroxide sensor based on electrodeposited copper/cuprous oxide nanocomposites.

In this work, copper/cuprous oxide (Cu/Cu2O) nanocomposites were electrodeposited on a fluorine doped tin oxide (FTO) glass substrate for sensitive determination of hydrogen peroxide (H2O2). The Cu/Cu2O nanocomposites were synthesized on FTO at a constant current density of -0.4 mA cm-2 in 0.3 M CuSO4 (pH 9.5) under magnetic agitation. The composition and morphology of Cu/Cu2O nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. Taking advantage of the synergistic effects of Cu and Cu2O, the fabricated Cu/Cu2O/FTO electrode showed excellent electrocatalytic activity towards the oxidation of H2O2. The electrocatalytic performance of Cu/Cu2O/FTO was evaluated by linear sweep voltammetry and amperometry. Under optimized conditions, the developed sensor exhibited a wide linear range of 0.2-2000 µM for the determination of H2O2 with a detection limit of 0.04 µM (S/N = 3). In addition, the proposed H2O2 sensor was successfully applied for the determination of H2O2 in milk samples, indicating that the electrodeposited Cu/Cu2O nanocomposites are promising nanomaterials for electrochemical sensors.

Rotational Paper-Based Microfluidic-Chip Device for Multiplexed and Simultaneous Fluorescence Detection of Phenolic Pollutants Based on a Molecular-Imprinting Technique.

In this study, we first present rotational paper-based microfluidic chips (RPADs) combined with a molecular-imprinting (MIP) technique to detect phenolic pollutants. The proposed rotational paper-based microfluidic chips could implement qualitative and quantitative analysis of two different phenolic contaminants, 4-nitrophenol (4-NP) and 2,4,6-trinitrophenol (TNP), simultaneously. Qualitative and quantitative analysis could be implemented simultaneously through fluorescence-intensity changes depending on the structures of quantum dots combined with a molecular-imprinting technique. Moreover, the rotational paper-based microfluidic chips provide a low cost, flexible, and easy way to operate the entire process conveniently. Under the optimal conditions, the proposed sensors showed high sensitivity and selectivity. Our final experimental results illustrated that the detection limits of 4-NP and TNP in the paper-based quantum-dot MIP (PQ-MIP) RPADs ranged from 0.5 to 20.0 mg/L, with detection limits of 0.097 and 0.071 mg/L, respectively. This novel rotational paper-based microfluidic device shows great potential and versatility for multiplexed, portable, and rapid testing of environmental and biological samples in the future.

Pueribacillus theae gen. nov., sp. nov., isolated from Pu'er tea.

A novel bacterial strain, designated T8T, isolated from ripened Pu'er tea, was investigated by using a polyphasic taxonomic approach. Cells stained Gram-positive and were aerobic, sporogenous and rod-shaped with flagella. Phylogenetic analysis of 16S rRNA gene sequences revealed the strain belonged to the family Bacillaceae in the class Bacilli and represented an independent taxon separated from other genera. Strain T8T shared low levels of 16S rRNA gene sequence similarity (<94 %) to members of other genera in the family Bacillaceae and was most closely related to Bacillus composti SgZ-9T (93.3 % sequence similarity). The DNA G+C content of strain T8T was 40 mol%. The major fatty acids (>10 %) of strain T8T were iso-C15 : 0 and iso-C16 : 0. The strain had a cell-wall type A1γ peptidoglycan with meso-diaminopimelic acid as the diagnostic diamino acid. MK-7 (62 %), MK-6 (31 %) and MK-8 (7 %) were detected as the isoprenoid quinones. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine and six unidentified phospholipids. On the basis of the polyphasic evidence presented, strain T8T is considered to represent a novel genus and species in the family Bacillaceae, for which we propose the name Pueribacillus theae gen. nov., sp. nov. The type strain is T8T (=CGMCC 1.15924T=KCTC 333888T).

Functional Hyperbranched Polylysine as Potential Contrast Agent Probes for Magnetic Resonance Imaging.

Researchers have never stopped questing contrast agents with high resolution and safety to overcome the drawbacks of small-molecule contrast agents in clinic. Herein, we reported the synthesis of gadolinium-based hyperbranched polylysine (HBPLL-DTPA-Gd), which was prepared by thermal polymerization of l-lysine via one-step polycondensation. After conjugating with folic acid, its potential application as MRI contrast agent was then evaluated. This contrast agent had no obvious cytotoxicity as verified by WST assay and H&E analysis. Compared to Gd(III)-diethylenetriaminepentaacetic acid (Gd-DTPA) (r1 = 4.3 mM(-1) s(-1)), the FA-HBPLL-DTPA-Gd exhibited much higher longitudinal relaxivity value (r1 = 13.44 mM(-1) s(-1)), up to 3 times higher than Gd-DTPA. The FA-HBPLL-DTPA-Gd showed significant signal intensity enhancement in the tumor region at various time points and provided a long time window for MR examination. The results illustrate that FA-HBPLL-DTPA-Gd will be a potential candidate for tumor-targeted MRI.

Nanoscale zero-valent iron incorporated with nanomagnetic diatomite for catalytic degradation of methylene blue in heterogeneous Fenton system.

Nanoscale zero-valent iron (nZVI) incorporated with nanomagnetic diatomite (DE) composite material was prepared for catalytic degradation of methylene blue (MB) in heterogeneous Fenton system. The material was constructed by two facile steps: Fe3O4 magnetic nanoparticles were supported on DE by chemical co-precipitation method, after which nZVI was incorporated into magnetic DE by liquid-phase chemical reduction strategy. The as-prepared catalyst was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, magnetic properties measurement and nitrogen adsorption-desorption isotherm measurement. The novel nZVI@Fe3O4-diatomite nanocomposites showed a distinct catalytic activity and a desirable effect for degradation of MB. MB could be completely decolorized within 8 min and the removal efficiency of total organic carbon could reach to 90% after reaction for 1 h.