Search Results (16)

Acidovorax citrulli (Ac) is an important pathogenic bacterium causing bacterial fruit blotch (BFB) in Cucurbitaceae plants and is an important quarantine pest in China. This study was conducted to establish a rapid, convenient, and accurate visual method for detecting A. citrulli. A. citrulli-specific primers and a prober were designed based on the conserved region of the YD-repeat protein gene. Loop-mediated isothermal amplification combined with lateral flow dipstick (LAMP-LFD) was used to establish an assay for the rapid visual detection of A. citrulli by optimizing the reaction temperature and time. The specificity, sensitivity, and performance of the optimized LAMP-LFD assay were evaluated using the genomic DNA of the tested isolates, A. citrulli pure culture, infested seeds, commercial seeds, and leaf samples. The optimal assay temperature and time were 64 °C and 60 min, respectively. The assay specifically detected A. citrulli, and no cross-reactions were observed with the genomic DNA of other closely related species. The detection sensitivity of the LAMP-LFD for detecting pure genomic DNA, the bacterial suspension, bacterial amount on seeds (colony-forming units (CFU)·g⁻¹), and infection rate of seeds (%) were 1 fg·μL⁻¹, 8 CFU·mL⁻¹, 5 CFU·g⁻¹, and 0.05% infestation per reaction, respectively. The positive detection rate of the LAMP-LFD assay was 20–100% in seed samples (n = 1000 seeds) with 0.05–0.1% infestation. The LAMP-LFD assay rapidly and accurately detected A. citrulli in seeds and leaf tissues carrying pathogens. This assay thus offers the advantages of easy operation, rapidity, high specificity and sensitivity, low cost (no need for complex and expensive precision instruments), visualization of detection results, good stability, and strong applicability, which can be used for epidemiological studies and disease management. Full article

This study investigates the properties of solution-processed hybrid polyimide (PI) nanocomposites containing a variety of nanofillers, including polyaniline copolymer-modified clay (PNEA), nanographene sheets (NGSs), and carbon nanotube sheets (CNT-PVDFs). Through a series of experiments, the flow behavior of poly(amic acid) (PAA) solution and PAA suspension containing polyaniline copolymer-modified clay (PNEA) is determined as a function of the shear rate, processing temperature, and polymerization time. It is shown that the neat PAA solution exhibits a complex rheological behavior ranging from shear thickening to Newtonian behavior with increasing shear rate and testing temperature. The presence of modified clay in PAA solution significantly reduced the viscosity of PAA. Differential scanning calorimetry (DSC) analysis showed that polyimide–nanographene sheet (PI NGS) nanocomposites processed at a high spindle speed (100 rpm) have lower total heat of decomposition, which is indicative of improved fire retardancy. The effect of processing temperature on the specific capacitance of a polyimide–CNT-PVDF composite containing electrodeposited polypyrrole is determined using cyclic voltammetry (CV). It is shown that the hybrid composite working electrode material processed at 90 °C produces a remarkably higher overall stored charge when compared to the composite electrode material processed at 250 °C. Consequently, the specific capacitance obtained at a scan rate of 5 mV/s for the hybrid nanocomposite processed at 90 °C is around 858 F/g after one cycle, which is about 6.3 times higher than the specific capacitance of 136 F/g produced by the hybrid nanocomposite processed at 250 °C. These findings show that the properties of the hybrid nanocomposites are remarkably influenced by the processing conditions and highlight the need for process optimization. Full article

A paper-based surface enhancement of a Raman scattering substrate consisting of silver-nanowires stacked on glass-fiber filter paper was prepared. At the same time, the DNA-embedding molecule Eva Green was introduced as a signaling molecule for surface-enhanced Raman scattering (SERS) detection. Polymerase chain reaction (PCR) was used to amplify target genes and the method was developed into a rapid molecular diagnostic system. The total detection time of the developed detection method was 40 min, including 30 min of PCR amplification and 10 min of SERS measurement. After 30 PCR cycles, bacterial DNA with an initial concentration of 20 fg/μL and a bacterial suspension with an initial concentration of 7.2 × 10¹ CFUs/mL could be detected. When the enrichment culture time was 4 h, target bacteria with an initial contamination inoculation volume of 1.5 CFUs/mL could be detected in artificially contaminated samples. The method is fast and highly sensitive, and has not been applied to the detection of V. parahaemolyticus. Full article

Polypyrrole (PPy)-capped silver nanowire (Ag NW) nanomaterials (core–shell rod-shaped Ag NW@PPy) were synthesized using a one-port suspension polymerization technique. The thickness of the PPy layer on the 50 nm thickness/15 μm length Ag NW was effectively controlled to 10, 40, 50, and 60 nm. Thin films cast from one-dimensional conductive Ag NW@PPy formed a three-dimensional (3D) conductive porous network structure and provided excellent electrochemical performance. The 3D Ag NW@PPy network can significantly reduce the internal resistance of the electrode and maintain structural stability. As a result, a high specific capacitance of 625 F/g at a scan rate of 1 mV/s was obtained from the 3D porous Ag NW@PPy composite film. The cycling performance over a long period exceeding 10,000 cycles was also evaluated. We expect that our core–shell-structured Ag NW@PPy composites and their 3D porous structure network films can be applied as electrochemical materials for the design and manufacturing of supercapacitors and other energy storage devices. Full article

Electrochemical behavior of novel electrode materials based on polydiphenylamine-2-carboxylic acid (PDPAC) binary and ternary nanocomposite coatings was studied for the first time. Nanocomposite materials were obtained in acidic or alkaline media using oxidative polymerization of diphenylamine-2-carboxylic acid (DPAC) in the presence of activated IR-pyrolyzed polyacrylonitrile (IR-PAN-a) only or IR-PAN-a and single-walled carbon nanotubes (SWCNT). Hybrid electrodes are electroactive layers of stable suspensions of IR-PAN-a/PDPAC and IR-PAN-a/SWCNT/PDPAC nanocomposites in formic acid (FA) formed on the flexible strips of anodized graphite foil (AGF). Specific capacitances of electrodes depend on the method for the production of electroactive coatings. Electrodes specific surface capacitances C_s reach 0.129 and 0.161 F∙cm⁻² for AGF/IR-PAN-a/PDPAC_ac and AGF/IR-PAN-a/SWCNT/PDPAC_ac, while for AGF/IR-PAN-a/PDPAC_alk and AGF/IR-PAN-a/SWCNT/PDPAC_alk C_s amount to 0.135 and 0.151 F∙cm⁻². Specific weight capacitances C_w of electrodes with ternary coatings reach 394, 283, 180 F∙g⁻¹ (AGF/IR-PAN-a/SWCNT/PDPAC_ac) and 361, 239, 142 F∙g⁻¹ (AGF/IR-PAN-a/SWCNT/PDPAC_alk) at 0.5, 1.5, 3.0 mA·cm⁻² in an aprotic electrolyte. Such hybrid electrodes with electroactive nanocomposite coatings are promising as a cathode material for SCs. Full article

The electrochemical behavior of new electrode materials based on poly-N-phenylanthranilic acid (P-N-PAA) composites with reduced graphene oxide (RGO) was studied for the first time. Two methods of obtaining RGO/P-N-PAA composites were suggested. Hybrid materials were synthesized via in situ oxidative polymerization of N-phenylanthranilic acid (N-PAA) in the presence of graphene oxide (GO) (RGO/P-N-PAA-1), as well as from a P-N-PAA solution in DMF containing GO (RGO/P-N-PAA-2). GO post-reduction in the RGO/P-N-PAA composites was carried out under IR heating. Hybrid electrodes are electroactive layers of RGO/P-N-PAA composites stable suspensions in formic acid (FA) deposited on the glassy carbon (GC) and anodized graphite foil (AGF) surfaces. The roughened surface of the AGF flexible strips provides good adhesion of the electroactive coatings. Specific electrochemical capacitances of AGF-based electrodes depend on the method for the production of electroactive coatings and reach 268, 184, 111 F∙g⁻¹ (RGO/P-N-PAA-1) and 407, 321, 255 F∙g⁻¹ (RGO/P-N-PAA-2.1) at 0.5, 1.5, 3.0 mA·cm⁻² in an aprotic electrolyte. Specific weight capacitance values of IR-heated composite coatings decrease as compared to capacitance values of primer coatings and amount to 216, 145, 78 F∙g⁻¹ (RGO/P-N-PAA-1_IR) and 377, 291, 200 F∙g⁻¹ (RGO/P-N-PAA-2.1_IR). With a decrease in the weight of the applied coating, the specific electrochemical capacitance of the electrodes increases to 752, 524, 329 F∙g⁻¹ (AGF/RGO/P-N-PAA-2.1) and 691, 455, 255 F∙g⁻¹ (AGF/RGO/P-N-PAA-1_IR). Full article

Single cell elemental (SC) analysis of isogenic cell cultures can be done using inductively coupled plasma (ICP-MS) detection. However, 2D cell cultures are just models to simplify the complexity of real tissue samples. Here, we show for the first time the capabilities of the technique (SC-ICP-MS) to analyze single cell suspensions of isolated cells from tissues. An optimized cocktail of proteolytic and collagenolytic enzymes was applied in a single preparation step with cellular yields up to 28% using 0.5 g of fresh rat spleen and liver, respectively. The retrieved cells revealed adequate morphology and stability to be examined by SC-ICP-MS. Quantitative elemental analysis of P, S, Cu, and Fe from disaggregated cells from rat spleen and liver tissues revealed levels of Fe of 7–16 fg/cell in the spleen and 8–12 fg/cell in the liver, while Cu was about 3–5 fg/cell in the spleen and 1.5–2.5 fg/cell in the liver. Evaluation of the transmembrane protein transferrin receptor 1 (TfR1) expression levels in disaggregated cells was also conducted by using a Nd-labelled antibody against this cell surface biomarker. Quantitative results showed significantly lower expression in the disaggregated cells than in the cell model HepG2, in agreement with the overexpression of this biomarker in tumor cells. In this proof of concept study, the tissue disaggregation protocol has shown to maintain the elemental intracellular content of cells as well as the presence of relevant antigens. This opens a completely new area of research for SC-ICP-MS in tissue samples as a complementary strategy with validation capabilities. Full article

A fractal, flower petal-like CuS-CuO/G-C3N4 nanocomposite is prepared and applied in a symmetric two-electrode supercapacitor. The preparation of CuS-CuO/G-C3N4 is carried out through the hydrothermal method, in which salts of copper are dissolved and mixed with a suspension of G-C3N4 nanoparticles. A symmetric two-electrode supercapacitor, formed from CuS-CuO/G-C3N4 paste on Au-plates is investigated. The measurements are carried out in diluted 0.5 M HCl, and Whatman filter paper is used as a separator. The supercapacitor electric properties are determined by measuring the charge/discharge, cyclic voltammetry, impedance, and lifetime parameters. An enhancement in the charge/discharge time from 65 to 420 s was recorded while decreasing the current density (J) from 1.0 to 0.3 A/g. The cyclic voltammetry behavior is studied from 50 to 300 mV·s⁻¹, causing a direct increase in the produced J values. The specific capacitance (C_S) and energy density (E) values are 370 F/g and 37 W·h·kg⁻¹, respectively. The magnificent properties of the prepared supercapacitor qualify it for industrial applications as an alternative to batteries. Full article

The interaction between fish skin gelatin (FG) and pea protein isolate (PPI) was investigated at the air-water interface (A-W) before and after a high intensity (275 W, 5 min) ultrasound treatment (US). We analyzed the properties of the single protein suspensions as well as an equal ratio of FG:PPI (MIX), in terms of ζ-potential, particle size, molecular weight, bulk viscosity and interfacial tension. The foaming properties were then evaluated by visual analysis and by Turbiscan Tower. Confocal laser scanning microscopy (CLSM) was employed to explore the role of the proteins on the microstructure of foams. The results showed that the ultrasound treatment slightly influenced physicochemical properties of the proteins, while in general, did not significantly affect their behavior both in bulk and at the air-water interface. In particular, PPI aggregate size was reduced (−48 nm) while their negative charges were increased (−1 mV) after the treatment. However, when the proteins were combined, higher molecular weight of aggregates, higher foam stability values (+14%) and lower interfacial tension (IFT) values (47.2 ± 0.2 mN/m) were obtained, leading us to assume that a weak interaction was developed between them. Full article

Laser photothermal-conversion membranes have great potential applications in many different fields, including laser ignition. However, the demand for real-time, high heat output calls for an extra heat-releasing pattern other than the traditional luminous energy–thermal, energy-conversion mechanism. Herein, it was found that fluorinated graphene (FG) was a promising candidate for laser photothermal conversion due to the extra chemical energy–thermal, energy-conversion process, which originated from a self-redox reaction under laser irradiation. Moreover, an easy sonochemical, exfoliation–filtration protocol was provided for the preparation of the fluorinated, graphene-based, free-standing membranes. In brief, FG flakes were arranged into flower-like patterns and formed freestanding, carpet-like membranes with layered structures with the filtration of FG suspension, which was obtained from exfoliating fluorographite in N-methylpyrrolidone. Furthermore, this contribution also revealed that modifying the FG membranes with polytetrafluoroethylene (PTFE) was helpful for improving the photothermal-conversion properties. With the construction of the FG/PTFE composited structure, higher heat output could be achieved when a laser pulse is applied to the composite membranes. This work revealed the great potential of fluorinated graphene in laser photothermal conversion, and provided an alternative route of introducing a chemical energy–thermal, energy-conversion process for achieving high heat output under laser irradiation. Full article

As one of the most outstanding high-efficiency and environmentally friendly energy storage devices, the supercapacitor has received extensive attention across the world. As a member of transition metal oxides widely used in electrode materials, manganese dioxide (MnO₂) has a huge development potential due to its excellent theoretical capacitance value and large electrochemical window. In this paper, MnO₂ was prepared at different temperatures by a liquid phase precipitation method, and polyaniline/manganese dioxide (PANI/MnO₂) composite materials were further prepared in a MnO₂ suspension. MnO₂ and PANI/MnO₂ synthesized at a temperature of 40 °C exhibit the best electrochemical performance. The specific capacitance of the sample MnO₂-40 is 254.9 F/g at a scanning speed of 5 mV/s and the specific capacitance is 241.6 F/g at a current density of 1 A/g. The specific capacitance value of the sample PANI/MnO₂-40 is 323.7 F/g at a scanning speed of 5 mV/s, and the specific capacitance is 291.7 F/g at a current density of 1 A/g, and both of them are higher than the specific capacitance value of MnO₂. This is because the δ-MnO₂ synthesized at 40 °C has a layered structure, which has a large specific surface area and can accommodate enough electrolyte ions to participate the electrochemical reaction, thus providing sufficient specific capacitance. Full article

Colonization of crops by toxigenic fungi causes important economic losses, which are expected to increase with global change. The presence of mycotoxins in crops affects food security by reducing the edible yield and nutritional values and making cereal consumption unsafe. An efficient method to reduce mycotoxin content is to avoid the appearance of fungi or toxigenesis. This has been traditionally achieved with antifungal chemicals that negatively affect soil and ecosystem health. Current research aims for methods that less harmful for the environment, such as natural proteins or biocontrol. We tested crop-associated fungi against two possible growth-inhibiting proteins: Fusarium graminearum Antifungal Protein (Fg-AFP) and Latrodectin-II (Ltd-II). The first is produced by Fusarium graminearum to compete with other fungi, and the latter is found in Latrodectus hesperus venom and has just recently been correctly purified. In a first assay, we exposed four Aspergillus strains cultured on PDA (potato dextrose agar) against on-surface cellulose discs with 10 µL of different Fg-AFP and Ltd-II concentrations (7 µg/µL, 3.5 µg/µL, 1.4 µg/µL, and 0.7 µg/µL). All tests were carried out in triplicate. Results show that Fg-AFP inhibited development of three of the strains, while Ltd-II did not but may have affected secondary metabolism due to a variation in spore production and pigmentation (no further analysis regarding this event was fulfilled). We subsequently selected Aspergillus niger and A. flavus strains based on their importance in maize crops and sensitivity to the proteins, for a second assay, in which we evenly extended 30 µL of the proteins (1.5 µg/µL) separately on plaques containing PDA. The growth surface was represented over time, the specific growth rate corresponded with the curve slope, and latent period was calculated by obtaining the equation of the line from the slope and the intersection point. An initial diameter of 4 mm was assumed for 2 µL of spore suspension (10⁵ spores/mL) inoculated on the center of the plaque. All tests were carried out in triplicate. Results show that Fg-AFP reduced A. niger and A. flavus growth by 46.3% and 24.3%, respectively, extending fungal latent period by 68.4% and 52.6%, respectively. Ltd-II had no effect on A. flavus, but increased A. niger growth by 18.4%, prolonging the latent period by 67.5%. Toxin production was assessed by thin-layer chromatography under UV light after following a toxin extraction protocol with chloroform and toluene:acetonitrile for quantifying ochratoxin A, and chloroform and methanol for aflatoxin B1 production. Regarding toxigenesis results, ochratoxin A production by A. niger did not vary when it was exposed to the proteins, but aflatoxin B1 synthesis by A. flavus increased with both treatments. Though these proteins have growth-limiting potential, they must be evaluated under wider concentration ranges to assess their effect on toxigenesis and usage as an alternative to harmful chemicals. Full article

The resistivity of different films and structures containing fluorinated graphene (FG) flakes and chemical vapor deposition (CVD)-grown graphene of various fluorination degrees under tensile and compressive strains due to bending deformations was studied. Graphene and multilayer graphene films grown by means of the chemical vapor deposition (CVD) method were transferred onto the flexible substrate by laminating and were subjected to fluorination. They demonstrated a weak fluorination degree (F/C lower 20%). Compressive strains led to a strong (one-two orders of magnitude) decrease in the resistivity in both cases, which was most likely connected with the formation of additional conductive paths through fluorinated graphene. Tensile strain up to 3% caused by the bending of both types of CVD-grown FG led to a constant value of the resistivity or to an irreversible increase in the resistivity under repeated strain cycles. FG films created from the suspension of the fluorinated graphene with a fluorination degree of 20–25%, after the exclusion of design details of the used structures, demonstrated a stable resistivity at least up to 2–3% of tensile and compressive strain. The scale of resistance changes ΔR/R0 was found to be in the range of 14–28% with a different sign at the 10% tensile strain (bending radius 1 mm). In the case of the structures with the FG thin film printed on polyvinyl alcohol, a stable bipolar resistive switching was observed up to 6.5% of the tensile strain (bending radius was 2 mm). A further increase in strain (6.5–8%) leads to a decrease in ON/OFF current ratio from 5 down to 2 orders of magnitude. The current ratio decrease is connected with an increase under the tensile strain in distances between conductive agents (graphene islands and traps at the interface with polyvinyl alcohol) and thickness of fluorinated barriers within the active layer. The excellent performance of the crossbar memristor structures under tensile strain shows that the FG films and structures created from suspension are especially promising for flexible electronics. Full article

Due to the reduced ability of most harmed tissues to self-regenerate, new strategies are being developed in order to promote self-repair assisted or not by biomaterials, among these tissue engineering (TE). Human adipose-derived mesenchymal stem cells (hASCs) currently represent a promising tool for tissue reconstruction, due to their low immunogenicity, high differentiation potential to multiple cell types and easy harvesting. Gelatin is a natural biocompatible polymer used for regenerative applications, while nanodiamond particles (NDs) are used as reinforcing nanomaterial that might modulate cell behavior, namely cell adhesion, viability, and proliferation. The development of electrospun microfibers loaded with NDs is expected to allow nanomechanical sensing due to local modifications of both nanostructure and stiffness. Two aqueous suspensions with 0.5 and 1% w/v NDs in gelatin from cold water fish skin (FG) were used to generate electrospun meshes. Advanced morpho- and micro-structural characterization revealed homogeneous microfibers. Nanoindentation tests confirmed the reinforcing effect of NDs. Biocompatibility assays showed an increased viability and proliferation profile of hASCs in contact with FG_NDs, correlated with very low cytotoxic effects of the materials. Moreover, hASCs developed an elongated cytoskeleton, suggesting that NDs addition to FG materials encouraged cell adhesion. This study showed the FG_NDs fibrous scaffolds potential for advanced TE applications. Full article

Nickel magnetic nanowires (NWs) have attracted significant attention due to their unique properties, which are useful for basic studies and technological applications, for example in biomedicine. Their structure and magnetic properties were systematically studied in the recent years. In this work, Ni NWs with high aspect ratios (length/diameter ~250) were fabricated by electrodeposition into commercial anodic aluminum oxide templates. The templates were then etched and the NWs were suspended in water, where their hydrodynamic size was evaluated by dynamic light scattering. The magnetic response of these NWs as a function of an external magnetic field indicates a dominant shape anisotropy with propagation of the vortex domain wall as the main magnetization reversal process. The suspension of Ni NWs was used in the synthesis of two types of polyacrylamide ferrogels (FGs) by free radical polymerization, with weight fractions of Ni NWs in FGs of 0.036% and 0.169%. The FGs were reasonably homogeneous. The magnetic response of these FGs (hysteresis loops) indicated that the NWs are randomly oriented inside the FG, and their magnetic response remains stable after embedding. Full article