Latest ArticlesWe propose a concept for ligase detection by conversion of aggregation-based homogeneous analysis into surface-tethered electrochemical assay through streptavidin (SA)-biotin interaction. Sortase A (SrtA) served as the model analyte and two biotinylated peptides (bio-LPETGG and GGGK-bio) were used as the substrates. SrtA-catalyzed ligation of the peptide substrates led to the generation of bio-LPETGGGK-bio. The ligation product (bio-LPETGGGK-bio) induced the aggregation and color change of SA-modified gold nanoparticles (AuNPs) through the SA-biotin interactions, which could be assayed by the colorimetric method. Furthermore, we found that the bio-LPETGGGK-bio could trigger the assembly of tetrameric SA proteins with the formation of the (SA-bio-LPETGGGK-bio)n assemblies through the same interactions. The above results were further confirmed by atomic force microscopy and fluorescent imaging. The insulated assemblies were in-situ fabricated at the SA-modified gold electrode, thus hindering the electron transfer of [Fe(CN)6]3−/4− and leading to an increase in the electron-transfer resistance. The capability of the method for the detection of SrtA both in vitro and Staphylococcus aureus (S. aureus) has been demonstrated. SrtA with a concentration down to 1 pmol/L has been determined by the electrochemical analysis, which is lower than that achieved by the colorimetric assay (50 pmol/L). By integrating the advantages of homogeneous reaction and heterogeneous detection, the strategy serves as an ideal means for the fabrication of various sensing platforms by adopting biotin-labeled and sequence-specific peptide or nucleic acid substrates.
Rapid screening of foodborne pathogens is of great significance to ensure food safety. A microfluidic biosensor based on immunomagnetic separation, enzyme catalysis and electrochemical impedance analysis was developed for rapid and sensitive detection of S. typhimurium. First, the bacterial sample, the magnetic nanoparticles (MNPs) modified with capture antibodies, and the enzymatic probes modified with detection antibodies and glucose oxidase (GOx) were simultaneously injected into the microfluidic chip, followed by mixing and incubation to form MNP-bacteria-probe sandwich complexes. Then, glucose with high impedance was injected into the chip and catalyzed by the GOx on the complexes into hydrogen peroxide with high impedance and gluconic acid with low impedance, which was finally measured using the low-cost interdigitated microelectrode and the electrochemical impedance analyzer to determine the target bacteria. Under the optimal conditions, this biosensor could quantitatively detect S. typhimurium at the concentrations from 1.6 × 102 CFU/mL to 1.6 × 106 CFU/mL in 1 h with the low detection limit of 73 CFU/mL. Besides, this biosensor was demonstrated with good feasibility for practical applications by detecting the S. typhimurium spiked chicken meat samples.
Bismuth-rich Bi5O7Br is a promising photocatalyst for pollutant removal owing to its stability and appropriate band structure in comparison with bismuth oxybromide. However, bulk-phase Bi5O7Br suffers from poor light absorption and high charge recombination rates resulting in poor activity. Elemental doping is a powerful strategy to enhance photocatalytic activity. In this study, we prepared a series of Br auto-doped ultrathin Bi5O7Br nanotubes and explored the effect of Br doping on photocatalytic NO removal. The optimal doping content was determined via a photocatalytic NO removal experiment, which revealed the optimal ratio of Bi and Br was approximately 3:1. In situ diffuse reflectance infrared Fourier transform spectroscopy (In situ DRIFT) and density functional theory (DFT) studies revealed that NO removal mechanism catalyzed by Br doped Bi5O7Br. Our work presents a new strategy for the enhancement of photocatalytic pollutant degradation by bismuth oxyhalide photocatalysts.
Liver is the foremost organ of human being for drug metabolism, and it played a significant role in toxicity evaluation of drugs. Establishing a liver model in vitro can accelerate the process of the drug screening and new drug research and development. We provide a 3D printing based hepatic sinusoid-on-a-chip microdevice that reconstitutes organ-level liver functions to create a drug screening model of toxicity evaluation on chip. The microfluidic device, which recapitulates the hepatic sinusoid microenvironment, consists of PET polyporous membranes which mimic the perisinusoidal space, and experience fluid flow to mimic the hepatic arterial capillaries. The PET membrane was used to separate the hepatocyte and endotheliocyte. The endotheliocyte was cultured on the downside of the membrane and the hepatocyte were 3D seeded on the membrane via the 3D printer. This device was used to reproduce the in vitro liver model for drug toxicity assays. The expression of several biomarkers of liver was compared with the monoculture and 2D cultured conditions, and the results reveal that this organ-on-a-chip microdevice mimics the drug hepatoxicity that has not been possible by 2D cell-based and animal models, providing a useful platform for screening the drugs and developing an effective therapy in hepatopathy.
Peracetic acid (PAA)-based system is becoming an emerging advanced oxidation process (AOP) for effective removal of organic contaminants from water. Various approaches have been tested to activate PAA, while no previous researches reported the application of metal-organic frameworks (MOFs) materials for PAA activation. In this study, zeolitic imidazole framework (ZIF)-67, a representative MOFs, was facile synthesized via direct-mixing method at room temperature, and tested for PAA activation and sulfachloropyridazine (SCP) degradation. The as-synthesized ZIF-67 exhibited excellent performance for PAA activation and SCP degradation with 100% of SCP degraded within 3 min, owing to the specific MOFs structure and abundant Co2+ sites. The pseudo-first-order kinetic model was applied to fit the kinetic data, with rate constant k1 of ZIF-67 activated PAA system 34.2 and 156.5 times higher than those of conventional Co3O4 activated PAA and direct oxidation by PAA. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that CH3C(O)OO· played a major role in this PAA activation system. Then, the Fukui index based on density functional theory (DFT) calculation was used to predict the possible reaction sites of SCP for electrophilic attack by CH3C(O)OO·. In addition, the degradation pathway of SCP was proposed based on Fukui index values and intermediates detection, which mainly included the S-N bond cleavage and SO2 extrusion and followed by further oxidation, dechlorination, and hydroxylation. Therefore, ZIF-67 activated PAA is a novel strategy and holds strong potential for the removal of emerging organic contaminants (EOCs) from water.
Osteonecrosis of the femoral head (ONFH) is a devastating musculoskeletal disease characterized by the impaired circulation of bone. The purpose of this study was to explore the underlying mechanisms of the protective effect of icariin on the glucocorticoid-induced injury of bone microvascular endothelial cells (BMECs). Normal BMECs were extracted from the femoral heads by enzymatic isolation and magnetic-activated cell sorting methods. Dexamethasone and icariin were used to intervene BMECs in microfluidic organ chips, and phalloidin staining was conducted to observe the cell morphology and viability. Then next-generation transcriptome sequencing and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were performed to identify the differentially expressed genes (DEGs) in different groups. Through the microfluidic organ chip, it can be observed that after dexamethasone intervention, the filamentous structure in cell fibers disappeared and the cell morphology changed from spindle to round until death. Icariin could relieve these changes and showed a protective effect on glucocorticoid-damaged BMECs. In addition, 201 DEGs were detected between the icariin protection group and the dexamethasone group, which were significantly enriched in 17 signaling pathways. 8 of the top ten selected hub genes (IL6, PTGS2, VEGFA, etc.) were confirmed by qRT-PCR. Transcription factors (TFs)-gene network showed 63 connections between 18 TFs and 12 DEGs. For instance, GATA2 could regulate 5 DEGs. The associations between 92 miRNA and 12 DEGs were visualized in a miRNA-gene network. The hub miRNA, has-mir-335–5p was predicted to interact with 8 DEGs (PTGS2, VEGFA, etc.). Microfluidic organ chips could provide excellent morphological results for cell experiments, by which it could be observed that icariin showed a protective effect on the glucocorticoid-induced injury of BMECs. Beside, these DEGs, possible regulatory TF (GATA2, FOXC1, etc.) and miRNA (has-mir-335–5p) might be dysregulated in the initiation of ONFH and have prospective importance in ONFH diagnosis and therapy.
Simultaneous and quantitative detection of multiple exosomal microRNAs (miRNAs) was successfully performed by a surface-enhanced Raman scattering (SERS) assay consisting of Raman probes and capture probes. In this design, the asymmetric core-shell structured Au@Au@Ag nanoparticles were first synthesized by layer-by-layer self-assembly method and modified with different Raman molecules and recognition sequences (polyA-DNA) to prepare the surface-enhanced Raman probes. Then, the streptavidin-modified magnetic beads were used to immobilize the biotinylated DNA capture sequences (biotin-DNA) to obtain capture probes. In the presence of target exosomal miRNAs, the Raman probes and capture probes could bind to the target exosomal miRNAs in the partial hybridization manner. Thus, the developed SERS sensor could indicate the target miRNAs levels in the buffer solution. Using breast cancer-related miRNAs as model targets, the limits of detection of this sensor were determined to be 1.076 fmol/L for synthetic miR-21, 0.068 fmol/L for synthetic miR-126, and 4.57 fmol/L for synthetic miR-1246, respectively. Such SERS sensors were further employed to detect the miR-21 in 20% human serum and the extraction solution of exosomes, respectively. Therefore, simultaneous and multiplex detection of cancer-related exosomal miRNAs by this assay could provide new opportunities for further biomedical applications.
Exosomes are now raising focus as a prospective biomarker for cancer diagnostics and prognosis owing to its unique bio-origin and composition. Exosomes take part in cellular communication and receptor mediation and transfer their cargos (e.g., proteins, mRNA and DNA). Quantitative analysis of tumor-related nucleic acid mutations can be a potential method to cancer diagnosis and prognosis in early stages. Here we present an integrated microfluidic system for exosome on-chip isolation and lung cancer RNA analysis through droplet digital PCR (ddPCR). Gradient dilution experiments show great linearity over a large concentration range with R2 = 0.9998. Utilizing the system, four cell lines and two mutation targets were parallelly detected for mutation analysis. The experiments demonstrated mutation heterogeneity and the results were agree with cell researches. These results proved our integrated microfluidic system as a promising means for early cancer diagnosis and prognosis in the era of liquid biopsy.
The temperature monitoring of treated cancer cells is critical in photothermal therapy. Current methods of detecting intracellular temperatures have low accuracy and poor spatial resolution, which limits their application to photothermal therapy. Herein, a strategy for targeted recognition and selective capture of MCF-7 breast cancer cells based on fluorescent polymer poly(N-isopropylacrylamide-benzoxadiazole-2-vinyl-4,4-dimethyl azlactone, PNMV) and modified gold nanobipyramids (AuNBPs-PNMV) was developed for temperature sensing during photothermal therapy. A mucin-1 protein aptamer (Apt) was applied to selectively target mucin-1 protein overexpressed on the surfaces of the MCF-7 cells, which can reduce interference by affinity interaction between the Apt and proteins. During photothermal therapy, the significant AuNBPs photothermal effect increases the fluorescence intensity of PNMV with temperature. Irradiation of MCF-7 cells cultured with AuNBPs-PNMV@Apt by an 808 nm laser increases the temperature of the system, while the cells can be inactivated because of the remarkable AuNBPs-PNMV@Apt photothermal effect. The results indicate that variation in the fluorescence of AuNBPs-PNMV@Apt can be applied as thermometers to monitor the intracellular effect of photothermal therapy.
Transition metal selenides attract significant attention as advanced anode materials for sodium-ion batteries (SIBs) in recent years due to their appropriate working potential and high theoretic capacity. However, the poor structural stability and rate capability limit their further practical applications. Herein, zeolite imidazole framework-8/zeolite imidazole framework-67 is used as a template to prepare Co0.85Se and ZnSe nanoparticles embed in N-doped carbon matrix successfully, and then coated a carbon layer (ZCS@NC@C) by in-situ polymerization. One side, the N-doped carbon matrix with rich pore structure not only shorten the diffusion path of Na+ and improve the conductivity of the electrode, but also prevent structural collapse and agglomeration of active particles during the sodium insertion/extraction process. On the other side, the carbon shell preparation by coating can form a protective layer to buffer the volumetric stress generated in the electrochemical process and further improve the electrical conductivity. As a result, the as-prepared ZCS@NC@C anode material exhibits an excellent electrochemical performance for SIBs. This investigation provides a promising approach to optimize the electrochemical performance of SIBs by incorporating active metal compounds into conductive carbons to form multidimensional structure.
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