Water-solid contact electrification causes hydrogen peroxide production from hydroxyl radical recombination in sprayed microdroplets.

Contact electrification between water and a solid surface is crucial for physicochemical processes at water-solid interfaces. However, the nature of the involved processes remains poorly understood, especially in the initial stage of the interface formation. Here we report that H2O2 is spontaneously produced from the hydroxyl groups on the solid surface when contact occurred. The density of hydroxyl groups affects the H2O2 yield. The participation of hydroxyl groups in H2O2 generation is confirmed by mass spectrometric detection of 18O in the product of the reaction between 4-carboxyphenylboronic acid and 18O-labeled H2O2 resulting from 18O2 plasma treatment of the surface. We propose a model for H2O2 generation based on recombination of the hydroxyl radicals produced from the surface hydroxyl groups in the water-solid contact process. Our observations show that the spontaneous generation of H2O2 is universal on the surfaces of soil and atmospheric fine particles in a humid environment.

Ultrahighly Sensitive and Selective Glutathione Sensor Based on Carbon Dot-Functionalized Solution-Gate Graphene Transistor.

A new type of carbon dot (CD)-functionalized solution-gated graphene transistor (SGGT) sensor was designed and fabricated for the highly sensitive and highly selective detection of glutathione (GSH). The CDs were synthesized via a one-step hydrothermal method using DL-thioctic acid and triethylenetetramine (TETA) as sources of S, N, and C. The CDs have abundant amino and carboxyl groups and were used to modify the surface of the gate electrode of SGGT as probes for detecting GSH. Remarkably, the CDs-SGGT sensor exhibited excellent selectivity and ultrahigh sensitivity to GSH, with an ultralow limit of detection (LOD) of up to 10-19 M. To the best of our knowledge, the sensor outperforms previously reported systems. Moreover, the CDs-SGGT sensor shows rapid detection and good stability. More importantly, the detection of GSH in artificial serum samples was successfully demonstrated.

Organic Electrochemical Transistor Based on Hydrophobic Polymer Tuned by Ionic Gels.

Hydrophobic conjugated polymers have poor ionic transport property, so hydrophilic side chains are often grafted for their application as organic electrochemical transistors (OECTs). However, this modification lowers their charge transport ability. Here, an ionic gel interfacial layer is applied to improve the ionic transport while retaining the charge transport ability of the polymers. By using the ionic gels comprising gel matrix and ionic liquids as the interfacial layers, the hydrophobic polymer achieves the OECT feature with high transconductance, low threshold voltage, high current on/off ratio, short switching time, and high operational stability. The working mechanism is also revealed. Moreover, the OECT performance can be tuned by varying the types and ratios of ionic gels. With the proposed ionic gel strategy, OECTs can be effectively realized with hydrophobic conjugated polymers.

Dual-recognition-based determination of ctDNA via the clamping function of peptide nucleic acid and terminal protection of small-molecule-linked DNA.

A new dual-recognition fluorescent biosensor for circulating tumor DNA (ctDNA) detection has been developed, which combines the clamping function of peptide nucleic acid (PNA) and terminal protection of small-molecule-linked DNA (TPSMLD). Taking the tumor-specific E542K mutation and methylation of the PIK3CA gene as the target ctDNA, a low detection limit of 0.3161 pM ctDNA is achieved with good selectivity. This study not only offers a sensitive, selective and accurate ctDNA detection method, but can also be used to detect the target in complex biological samples.

A micro-/nano-chip and quantum dots-based 3D cytosensor for quantitative analysis of circulating tumor cells.

BACKGROUND: Due to the high transfer ability of cancer cell, cancer has been regarded as a world-wide high mortality disease. Quantitative analysis of circulating tumor cells (CTCs) can provide some valuable clinical information that is particularly critical for cancer diagnosis and treatment. Along with the rapid development of micro-/nano-fabrication technique, the three-dimensional (3D) bionic interface-based analysis method has become a hot research topic in the area of nanotechnology and life science. Micro-/nano-structure-based devices have been identified as being one of the easiest and most effective techniques for CTCs capture applications. METHODS: We demonstrated an electrospun nanofibers-deposited nickel (Ni) micropillars-based cytosensor for electrochemical detection of CTCs. Breast cancer cell line with rich EpCAM expression (MCF7) were selected as model CTCs. The ultra-long poly (lactic-co-glycolic acid) (PLGA) nanofibers were firstly-crosswise stacked onto the surface of Ni micropillars by electrospinning to construct a 3D bionic interface for capturing EpCAM-expressing CTCs, following immuno-recognition with quantum dots functionalized anti-EpCAM antibody (QDs-Ab) and forming immunocomplexes on the micro-/nano-chip. RESULTS: The Ni micropillars in the longitudinal direction not only play a certain electrical conductivity in the electrochemical detection, but also its special structure improves the efficiency of cell capture. The cross-aligned nanofibers could simulate the extracellular matrix to provide a good microenvironment which is better for cell adhesion and physiological functions. Bioprobe containing quantum dots will release Cd2+ in the process of acid dissolution, resulting in a change in current. Beneath favourable conditions, the suggested 3D cytosensor demonstrated high sensitivity with a broad range of 101-105 cells mL-1 and a detection limit of 8 cells mL-1. CONCLUSIONS: We constructed a novel 3D electrochemical cytosensor based on Ni micropillars, PLGA electrospun nanofibers and quantum dots bioprobe, which could be used to highly sensitive and selective analysis of CTCs. More significantly, the 3D cytosensor can efficiently identify CTCs from whole blood, which suggested the potential applications of our technique for the clinical diagnosis and therapeutic monitoring of cancers.

Enzymatic fluorescent supramolecular hydrogel with aggregation-induced emission characteristics for sensing alkaline phosphatase.

Alkaline phosphatase is an important biomarker for medical diagnosis. An enzymatic fluorescence supramolecular hydrogel with AIE properties was developed and used for sensing alkaline phosphatase in vitro and in living cells. In the presence of ALP, K(TPE)EFYp was partially converted to the hydrogelator K(TPE)EFY and self-assembled into nanofibers to form Hydrogel. With the sol-gel transition and the AIE effect, the fluorescence emission was turned on. The linear concentration range of ALP activity in vitro quantified by this method was determined as 0-3 U/L with aLODat 0.02 U/L. In addition, cell imaging and serum experiment showed that K(TPE)EFYp could also be used to detect ALP activity in living cells and biological samples.

Carboxyl graphene modified PEDOT:PSS organic electrochemical transistor for in situ detection of cancer cell morphology.

Circulating tumor cells in human peripheral blood play an important role in cancer metastasis. In addition to the size-based and antibody-based capture and separation of cancer cells, their electrical characterization is important for rare cell detection, which can prove fatal in point-of-care testing. Herein, an organic electrochemical transistor (OECT) biosensor made of solution-gated carboxyl graphene mixed with PEDOT:PSS for the detection of cancer cells in situ is reported. Carboxyl graphene was used in this work to modulate cancer cell morphology, which differs significantly from normal blood cells, to achieve rare cancer cell detection. When the concentration of carboxyl graphene mixed in PEDOT:PSS was increased from 0 to 5 mg mL-1, the cancer cell surface area increased from 218 µm2 to 530 µm2, respectively. A change in cell morphology was also detected by the OECT. Negative charges in the cancer cells induced a positive shift in gate voltage, which was approximately 40 mV for spherical-shaped cells. When the cell surface area increased, transfer curves of transistor revealed a negative shift in gate voltage. Therefore, the sensor can be used for in situ detection of cancer cell morphology during the cell capture process, which can be used to identify whether the captured cells are deformable.

Magneto-controllable capture and release of cancer cells by using a micropillar device decorated with graphite oxide-coated magnetic nanoparticles.

Aiming to highly efficient capture and analysis of circulating tumor cells, a micropillar device decorated with graphite oxide-coated magnetic nanoparticles is developed for magneto-controllable capture and release of cancer cells. Graphite oxide-coated, Fe3 O4 magnetic nanoparticles (MNPs) are synthesized by solution mixing and functionalized with a specific antibody, following by the immobilization of such modified MNPs on our designed micropillar device. For the proof-of-concept study, a HCT116 colorectal cancer cell line is employed to exam the capture efficiency. Under magnetic field manipulation, the high density packing of antibody-modified MNPs on the micropillars increases the local concentration of antibody, as well as the topographic interactions between cancer cells and micropillar surfaces. The flow rate and the micropillar geometry are optimized by studying their effects on capture efficiency. Then, a different number of HCT116 cells spiked in two kinds of cell suspension are investigated, yielding capture efficiency >70% in culture medium and >40% in blood sample, respectively. Moreover, the captured HCT116 cells are able to be released from the micropillars with a saturated efficiency of 92.9% upon the removal of applied magnetic field and it is found that 78% of the released cancer cells are viable, making them suitable for subsequent biological analysis.

Biocompatible TiO2 nanoparticle-based cell immunoassay for circulating tumor cells capture and identification from cancer patients.

We demonstrate the isolation of circulating tumor cells (CTCs) with a biocompatible nano-film composed of TiO2 nanoparticles. Due to the enhanced topographic interaction between nano-film and cancer cell surface, cancer cells (HCT116) spiked into PBS and healthy blood can be recovered from the suspension, whose efficiencies were respectively 80 % and 50 %. Benifit from the biocompatibility of this nano-film, in-situ culture of the captured cancer cells is also available, which provides an alternative selection when the capture cell number was inadequate or the sample cannot be analyzed immediately. For the proof-of-concept study, we use this nano-film to separate the circulating tumor cells from the colorectal and gastric cancer patient peripheral blood samples and the captured CTCs are identified by a three-colored immunocytochemistry method. We investigated the cancer cells capture strength at the nano-bio interface through exposing the cells to fluid shear stress in microfluidic device, which can be utilized to increase the purity of CTCs. The result indicated that 50 % of the captured cells can be detached from the substrate when the fluid shear stress was 180 dyn cm(-2). By integration of this CTCs capture nano-film with other single cell analysis device, we expected to further explore their applications in genome sequencing based on the captured CTCs.

Ps-Pt nanozyme-based synergistic signal amplification biosensor for highly sensitive colorimetric detection of protein.

Immunosorbent assay is one of the most popular immunological screening techniques which has been widely used for the clinical diagnosis of alpha-fetoprotein (AFP). While traditional immunosorbent assay (ELISA) suffers from low detection sensitivity due to its low intensity of colorimetric signal. To improve the sensitivity of AFP detection, we developed a new and sensitive immunocolorimetric biosensor by combining Ps-Pt nanozyme with terminal deoxynucleotidyl transferase (TdT)-mediated polymerization reaction. The determination of AFP was achieved by measuring the visual color intensity produced by the catalytic oxidation reaction of the 3,3',5,5'-tetramethylbenzidine (TMB) solution with Ps-Pt and horseradish peroxidase (HRP). Owing to the synergistic catalysis of Ps-Pt and horseradish peroxidase HRP enriched in polymerized amplification products, this biosensor exhibited a significant color change within 25 s in the presence of 10-500 pg/mL AFP. This proposed method allowed for the specific detection of AFP with a detection limit of 4.30 pg/mL and even 10 pg/mL target protein could be distinguished clearly by visual observation. Furthermore, this biosensor could be applied to analysis of AFP in the complex sample and could be easily extended to the detection of other proteins.

Three-Dimensional PLGA Nanofiber-Based Microchip for High-Efficiency Cancer Cell Capture.

A 3D network capture substrate based on poly(lactic-co-glycolic acid) (PLGA) nanofibers was studied and successfully used for high-efficiency cancer cell capture. The arc-shaped glass micropillars were prepared by chemical wet etching and soft lithography. PLGA nanofibers were coupled with micropillars by electrospinning. Given the size effect of the microcolumn and PLGA nanofibers, a three-dimensional of micro-nanometer spatial network was prepared to form a network cell trapping substrate. After the modification of a specific anti-EpCAM antibody, MCF-7 cancer cells were captured successfully with a capture efficiency of 91%. Compared with the substrate composed of 2D nanofibers or nanoparticles, the developed 3D structure based on microcolumns and nanofibers had a greater contact probability between cells and the capture substrate, leading to a high capture efficiency. Cell capture based on this method can provide technical support for rare cells in peripheral blood detection, such as circulating tumor cells and circulating fetal nucleated red cells.

Fabrication of PEDOT:PSS-based solution gated organic electrochemical transistor array for cancer cells detection.

Organic electrochemical transistor (OECT) was applied in chemical and biological sensing. In this work, we developed a simple and repeatable method to fabricate OECT array, which had been successfully used to detect cancer cells. PEDPT:PSS conductive film between source and drain electrodes were patterned through photolithography, which can achieve uniform devices with same electrical characterization. When MCF-7 cancer cells are captured on the PEDOT:PSS surface via specifical antibody, the transfer characteristic of OECT shifts to higher gate electrode voltage due to the electrostatic interaction between cancer cells and device. The effective gate voltage shift can reach about 63 mV when the concentration of cancer cells increased to 5000. The shift of effective gate voltage is related to the cancer cell morphology, which is increased in the first 1 h and decreased when the capture time was larger than 1 h. The device of OECT array can increase the sample flux and make the detection result more accurate. It is expected that OECT array will have promising practical applications in single cancer cell detection in the future.

Electric field-assisted MnO2 nanomaterials for rapid capture and in situ delivery of circulating tumour cells.

The heterogeneity of cancer has become a major obstacle to treatment, and the development of an efficient, fast, and accurate drug delivery system is even more urgent. In this work, we designed a device that integrated multiple functions of cell capture, in situ manipulation, and non-destructive release on a single device. With an applied electric field, an intelligent device based on MnO2 nanomaterials was used to realize efficient and rapid capture of cancer cells in both patients' blood and artificial blood samples. This device could capture cancer cells with high efficiency (up to about 93%) and strong specificity in blood samples, the capture time was nearly 50 min faster than that of natural sedimentation, and reduce the effects on cells caused by long-time in vitro culture. In addition, Mn3+ on the surface of the MnO2 substrate was reduced to Mn2+ by an electrochemical method, partial dissolution occurred, and then the captured cells were non-destructively released with rapid speed (about 8 s) and high efficiency (about 94 ± 2%). For in situ regulation, upon applying a pulse electric field, the captured cells were perforated nondestructively, and extracellular molecules could be delivered to the captured cells with well-performed dose and temporal controls. As a proof-of-concept application, we proved that the device could capture circulating tumor cells in peripheral blood faster and achieve in situ drug delivery. Finally, it can also quickly release circulating tumour cells for subsequent analysis, highlighting its accuracy, due to which it is widely used in medical treatment, basic tumor research and drug development.

Effects of fenugreek seed extracts on growth performance and intestinal health of broilers.

The purpose of this experiment was to study the effects of fenugreek seed extract (FSE) on the growth performance, intestinal morphology, intestinal immunity and cecal micro-organisms in yellow-feathered broilers. A total of 240 one-day-old male yellow-feathered broilers were selected and randomly assigned to four treatments with 6 replicates per group and ten broilers per replicate. Started from the third day, birds were fed with basal diet (CON group) or basal diet supplemented with 30 mg/kg Zinc bacitracin (ZB group), or basal diet supplemented with 50 (D-FSE group) or 100 (H-FSE group) mg/kg FSE, respectively. The experiment lasted for 56 d. The results showed that dietary FSE supplementation improved average daily weight gain (ADG) and ratio of feed to weight gain (F: G) (P < 0.01), increased intestinal villus height (VH), villus height to crypt depth ratio (V/C) (P < 0.05), serum concentrations of IL-10, and the contents of secretory immunoglobulin A (sIgA) (P < 0.05), as well as decreased the activity of iNOS (P < 0.05). The high-throughput sequencing results showed that dietary FSE supplementation increased the alpha diversity of cecal microbes, and Firmicutes, Bacteroidetes, Verrucomicrobia and Proteobacteria taken up 95% of all phyla detected, FSE significantly reduced Campylobacter, Synergistes, and Lachnoclostridium abundance (P ≤ 0.05). There were significant difference in more than 30 KEGG pathways between FSE added group and control group or ZB group. FSE supplementation, in other words, maintained gut microbiota homeostasis while improving broiler growth performance. As a result, FSE has the potential to replace prophylactic antibiotic use in poultry production system.

Highly sensitive microRNA detection by a duplex-specific nuclease amplification triggered three-dimensional DNA machine.

MicroRNAs play important roles in disease diagnosis and therapy. However, current methods for microRNA detection suffer from low sensitivity and cannot directly detect short microRNAs. Herein, we have developed a highly sensitive and selective fluorescent method for direct microRNA detection by combining the duplex-specific nuclease-assisted recycling amplification and the nicking enzyme-powered three-dimensional DNA walker. Target microRNA initiates duplex-specific nuclease-assisted recycling amplification, releasing numerous bipedal walking strands. The released bipedal walking strands hybridize with carboxyfluorescein-labeled track DNA and form nicking recognition site. Driven by the hydrolysis of the nicking enzyme, the bipedal walking strand autonomously moves along the track strand, releasing a large number of carboxyfluorescein-labeled DNA fragments and generating obvious fluorescence signals. This dual-signal amplification method can directly detect microRNA 21 as low as 130 fM and has good selectivity. The proposed method is not only simple for nucleic acid design, but also can be used as a universal method for the highly sensitive detection of all RNAs.

A sensitive platform for DNA detection based on organic electrochemical transistor and nucleic acid self-assembly signal amplification.

Highly sensitive detection of DNA is of great importance for the detection of genetic damage and errors for the diagnosis of many diseases. Traditional highly sensitive organic electrochemical transistor (OECT)-based methods mainly rely on good conductivity materials, which may be limited by complex synthesis and modification steps. In this work, DNA biosensor based on OECT and hybridization chain reaction (HCR) signal amplification was demonstrated for the first time. Au nanoparticles were electrochemically deposited on the Au gate electrode to increase the surface area. Then, the HCR products, long negatively charged double-stranded DNA, were connected to the target by hybridization, which can increase the effective gate voltage offset of OECT. This sensor exhibited high sensitivity and even 0.1 pM target DNA could be directly detected with a significant voltage shift. In addition, it could discriminate target DNA from the mismatched DNA with good selectivity. This proposed method based on HCR in DNA detection exhibited an efficient amplification performance on OECT, which provided new opportunities for highly sensitive and selective detection of DNA.

Tailoring the Energy Band Structure and Interfacial Morphology of the ETL via Controllable Nanocluster Size Achieves High-Performance Planar Perovskite Solar Cells.

Planar-type perovskite solar cells (p-PSCs) based on SnO2 have garnered further attention due to their simple and low-temperature fabrication. Improving the critical properties of the electron transport layer (ETL) is an effective way to enhance the performance of p-PSC devices. Here, a brand-new method is developed to relieve the contact recombination caused by the rough fluorine-doped tin oxide (FTO) surface and further boosts the electrical concentration of the ETL. A SnO2-ethylene diamine tetraacetic acid (EDTA) acylamide compound (SEAC) with hydrogen bond-induced adjustable cluster size is reported for the first time. The rational choice of the SEAC cluster size is the key for obtaining the smooth interfacial morphology of the ETL on the rugged FTO substrate. In addition, the energy band gap decreases with the increasing cluster size, and consequently, results in improved electrical conductivity of the SEAC. The upshifted Fermi energy level leads to higher electron concentration, which is an important physical quantity of the ETL. The PSC devices based on the optimized SEAC achieve an improved power conversion efficiency of 21.29% with negligible J-V hysteresis due to significantly enhanced electron transport and reduced contact charge recombination at the ETL/perovskite interface. In general, this paper comes up with a unique strategy to improve the quality of the SnO2-based ETL.

Enhanced adsorption-based atmospheric water harvesting using a photothermal cotton rod for freshwater production in cold climates.

Solar energy-powered adsorption-based atmospheric water harvesting (ABAWH) is an emerging technology for freshwater production, especially in water-scarce regions that are remote and landlocked. Numerous water adsorbents have been used in ABAWH devices to convert molecule to liquid water. However, it is still challenging to harvest water from the air in cold winter, owing to the water adsorption of sorbents decreasing significantly at low temperature. Herein, we designed and fabricated an ABAWH device by integrating composited ionic liquids (CILs) with carbon nanotubes (CNTs) photothermal materials on the surface of cotton rod fibers. CILs extract water from the air. CNTs enable light-to-heat conversion and drive the solar evaporation process. Importantly, the cotton rods offer a backbone porous structure to maintain its internal temperature at 20 °C under solar irradiation, and thus promote the water adsorption performance of CILs at low environmental temperature. Freshwater is successfully harvested under environment temperature of 6 °C, 30% RH and solar irradiation intensity of 0.6 kW m-2. The water yield can achieve 1.49 kg per m2 per day in an outdoor environment. We believe that the ABAWH device offers a promising approach to effectively harvest water from the air at low temperature and humidity conditions.

Acoustic Droplet-Assisted Superhydrophilic-Superhydrophobic Microarray Platform for High-Throughput Screening of Patient-Derived Tumor Spheroids.

Cell-based high-throughput screening is a key step in the current disease-based research, drug development, and precision medicine. However, it is challenging to establish a rapid culture and screening platform for rare cells (patient-derived) due to the obvious differences between the traditional 2D cell model and the tumor microenvironment, as well as the lack of a low-consumption screening platform for low numbers of cells. Here, we developed an acoustic drop-assisted superhydrophilic-superhydrophobic microarray platform for the rapid culture and screening of a few cells. By employing hydrophilic and hydrophobic microarrays, we can automatically distribute the cell suspension into uniform droplets, and these cells can spontaneously form compact 3D cell spheroids within 36 h (similar to the microenvironment of tumors in vivo). By using the acoustic droplet ejection device, we can accurately inject a drug solution with a volume of ∼pL to ∼nL into the droplet, and the whole process can be completed within 20 ms (one print). By using three different cell lines (Caco-2, MCF-7, and HeLa) to optimize the platform, the culture and screening of five patients' colon cancer were subsequently realized. Using three conventional chemotherapeutics (5-fluorouracil, cetuximab, and panitumumab) of various concentrations, the best treatment was screened out and compared with the actual treatment effect of the patients, and the results were extremely similar. As a proof-of-concept application, we have proved that our platform can quickly cultivate patient samples and effectively screen the best treatment methods, highlighting its wide application in precision medicine, basic tumor research, and drug development.

An Integrated Optofluidic Platform Enabling Total Phosphorus On-Chip Digestion and Online Real-Time Detection.

This paper presents a total phosphorus online real-time monitoring system integrated with on-chip digestion based on the merits of optofluidic technology. The integrated optofluidic device contains a hollow optical fiber employed for pretreatment and digestion of phosphorus solution samples, a polydimethylsiloxane (PDMS)-based micromixer with convergent-divergent walls designed to enable sufficient mixing and chromogenic reaction, and a couple of optical fiber collimators attached with a Z-shaped flow cell for optical detection. Details of system design and fabrication are introduced in this paper. In the experiment, on-chip digestion of four typical phosphates in aqueous solution including organophosphorus and inorganic phosphorus is investigated under different reaction conditions, such as digestion temperature, concentration of oxidant and pH value, and the optimal reaction parameters are explored under different conditions. Meanwhile, we demonstrate the online real-time monitoring function of the optofluidic device, and the digestion mechanisms of four different phosphates are analyzed and discussed. Compared with the national standard method, we find that the measurement accuracy and sensitivity are acceptable when the concentration of total phosphorus is between 0.005-0.9 mg/L (by weight of P) in aqueous solution, which covers the range defined in the national standard. The traditional digestion time of several hours is greatly reduced to less than 10 s, and the content of total phosphorus can be obtained in a few minutes. The integrated optofluidic device can significantly shorten the test time and reduce the sample amount, and also provides a versatile platform for the real-time detection and analysis of many biochemical samples.