Simultaneous Detection of Biomarkers in Urine Using a Multicalibration Potentiometric Sensing Array Combined with a Portable Analyzer.

Domestic monitoring devices make real-time and long-term health monitoring possible, allowing people to track their health status regularly. Uric acid (UA), creatinine, and urea in urine are three important biomarkers for various diseases, especially kidney diseases. This work proposed a 10-channel potentiometric sensing array containing a UA electrode group, a creatinine electrode group, a urea electrode group, a pH electrode group, and one pair of reference channels, which could be connected with a portable potentiometric analyzer, realizing the simultaneous detection of UA, creatinine, urea, and pH in urine. The prepared Pt/carbon nanotubes (CNTs)-uricase, creatinine deiminase, Au@urease, and polyaniline were employed as the sensing materials, showing responses to four targets with high sensitivity and selectivity. To improve the accuracy of domestic monitoring, a calibration channel was integrated into each electrode group to calibrate the basic potential of the sensing channels, and the influences of pH and temperature on the responses were investigated through the pH electrode group and an external temperature probe to calibrate the slope and intercept. With the preset of the deduced calibration parameters and computational formula for the four targets in the analyzer in Lab Mode, the concentrations of UA, creatinine, and urea and the pH of the human urine samples were directly displayed on the screen of the analyzer in Practical Mode. The agreement of these results with those obtained from commercial kits and pH meters reveals the high potential of these methods for developing domestic devices to facilitate health monitoring.

Identification of antibiotic residues in aquatic products with surface-enhanced Raman scattering powered by 1-D convolutional neural networks.

Universal and fast antibiotic residues detection technology is imperative for the control of food safety in aquatic products. However, accurate surface-enhanced Raman scattering (SERS) quantitative detection of complicated samples is still a challenge. A recognition method powered by deep learning and took advantage of the unique fingerprint information merits of SERS was proposed. Herein, the spectra were collected by Ag nanofilm SERS substrate prepared by self-assembly of Ag nanoparticles on water/oil interface. A SERS-based database of commonly used antibiotics in aquatic products was set up, which is suitable for employed as input data for learning and training. The results show that the five types of antibiotics are successfully distinguished through principal component analysis (PCA) and each antibiotic in every type was successfully distinguished. Furthermore, one-dimensional convolutional neural networks (1-D CNN) was used to distinguish the antibiotics, and the results show that all the test samples were correctly predicted by 1-D CNN model. The results of this research suggest the great potential of the combination of SERS spectra with deep learning as a method for rapid and highly accurate identification of antibiotic residues in aquatic products.

A bioinspired porous-designed hydrogel@polyurethane sponge piezoresistive sensor for human-machine interfacing.

Conductive coating sponge piezoresistive pressure sensors are attracting much attention because of their simple production and convenient signal acquisition. However, manufacturing sponge-structure pressure-sensing materials with high compressibility and wide pressure detection ranges is difficult because of the instability of rigid and brittle conductive coatings at large strains. Herein, a tough conductive hydrogel@polyurethane (PU) sponge with a porous design is prepared via immersion of a polyurethane sponge in a low-cost and biocompatible polyvinyl alcohol (PVA)/glycerin (Gl)/sodium chloride (NaCl) solution. The sensor based on the hydrogel/elastomer sponge composite material exhibits a compressible range of 0-93%, a pressure detection range of 100 Pa-470.2 kPa, and 10 000-cycle stability (80% strain) because of the compressibility, flexibility, and toughness of the porous hydrogel coating. Benefiting from the resistance change mechanism of microporous compression, the sensor also exhibits a wide range of linear resistance changes, and the corresponding sensitivity and gauge factor (GF) are -0.083 kPa-- (100 Pa-10.0 kPa) and -1.33 (1-60% strain), respectively. Based on its flexibility, compressibility, and wide-ranging linear resistance changes, the proposed sensor has huge potential application in human activity monitoring, electronic skin, and wearable electronic devices.

Poly(vinyl alcohol)/phosphoric acid gel electrolyte@polydimethylsiloxane sponge for piezoresistive pressure sensors.

Piezoresistive pressure sensors based on flexible, ultrasensitive, and squeezable conductive sponges have recently attracted significant attention. However, the preparation of cost-effective conductive sponges with good stability and wide strain range for pressure sensing remains a challenge. Herein, a conductive poly(vinyl alcohol)/phosphoric acid gel electrolyte@polydimethylsiloxane (PVA/H3PO4@PDMS) composite was fabricated by impregnating a PDMS sponge into a PVA/H3PO4 gel electrolyte. The conductivity of the as-prepared sponges was determined using a gel electrolyte polymer film. The sponge exhibited good sensitivity of 0.1145 kPa-1 in the low-pressure range (0-6.5 kPa), short response time (70 ms), and durability for over 2700 s (6000 cycles). The gauge factor of the PVA/H3PO4@PDMS sponge was 5.51, 1.49, and 0.33 at the strain range of 0-10%, 10-30%, and 30-80%, respectively. Based on these outstanding sensing performances, the sponges were applied for the detection of various human motions, such as vocal cord vibration, joint bending, respiratory rate, and pulse signal detection. Further, the sponge demonstrated their great potential in the fabrication of electronic skin and high-performance flexible wearable electronics. Therefore, the obtained PVA/H3PO4 gel electrolyte used as a sponge conductive coating material is a readily available and inexpensive material that can reduce the cost of composite materials for pressure sensing.

Sensitive immunoassay of cardiac troponin I using an optimized microelectrode array in a novel integrated microfluidic electrochemical device.

A sensitive and portable microfluidic electrochemical array device (µFED) was developed for the immunoassay of trace amounts of human cardiac troponin I (cTnI), which is an attractive biomarker for acute myocardial infarction (AMI). The classical "sandwich" method was adopted for the immunoassay. The capture antibody was immobilized using a self-assembled monolayer (SAM) technique, and the process was reorganized to be compatible with the bonding process. The detection antibody was labeled with alkaline phosphatase (AP) for signal amplification. The performance of the µFED was improved by eliminating the shielding effect of the microelectrode array (MEA) integrated in the µFED. The effects of the interstice and the width of the MEA on the response peak current were analyzed and simulated. The concentration gradient, about 3% of the gradient at the surface, was considered as the criterion for estimation of the optimal interstice between electrodes, and its effectiveness was proved. A stable and miniaturized reference electrode was integrated in the µFED, and its potential deviation was less than 5 mV in 15 min. These efforts resulted in the enhanced immunoassay performance of the µFED. A low limit of detection of about 5 pg/mL was obtained in serum samples, and the response current was proportional to the logarithm of concentration from 50 pg/mL to 1 µg/mL. The immunoassay process was accomplished in 15 min. The µFED was thus qualified and is a promising candidate for point-of-care immunoassay of cTnI. Graphical abstract.

Effect of film thickness and evaporation rate on co-evaporated SnSe thin films for photovoltaic applications.

SnSe thin films were deposited by a co-evaporation method with different film thicknesses and evaporation rates. A device with a structure of soda-lime glass/Mo/SnSe/CdS/i-ZnO/ITO/Ni/Al was fabricated. Device efficiency was improved from 0.18% to 1.02% by a film thickness of 1.3 µm and evaporation rate of 2.5 Å S-1 via augmentation of short-circuit current density and open-circuit voltage. Properties (electrical, optical, structural) and scanning electron microscopy measurements were compared for samples. A SnSe thin-film solar cell prepared with a film thickness of 1.3 µm and evaporation rate of 2.5 Å S-1 had the highest electron mobility, better crystalline properties, and larger grain size compared with the other solar cells prepared. These data can be used to guide growth of high-quality SnSe thin films, and contribute to development of efficient SnSe thin-film solar cells using an evaporation-based method.

Reduction of acrylamide level through blanching with treatment by an extremely thermostable L-asparaginase during French fries processing.

Bacterial L-asparaginase catalyzes the hydrolysis of L-asparagine to L-aspartic acid. It is normally used as an antineoplastic drug applied in lymphoblastic leukemia chemotherapy and as a food processing aid in baked or fried food industry to inhibit the formation of acrylamide. The present study demonstrates cloning, expression, and characterization of a thermostable L-asparaginase from Thermococcus zilligii AN1 TziAN1_1 and also evaluates the potential for enzymatic acrylamide mitigation in French fries using this enzyme. The recombinant L-asparaginase was purified to homogeneity by nickel-affinity chromatography. The purified enzyme displayed the maximum activity at pH 8.5 and 90 °C, and the optimum temperature was the highest ever reported. The K m, k cat, and k cat/K m values toward L-asparagine were measured to be 6.08 mM, 3267 s(-1), and 537.3 mM(-1) s(-1), respectively. The enzyme retained 70 % of its original activity after 2 h of incubation at 85 °C. When potato samples were treated with 10 U/mL of L-asparaginase at 80 °C for only 4 min, the acrylamide content in final French fries was reduced by 80.5 % compared with the untreated control. Results of this study revealed that the enzyme was highly active at elevated temperatures, reflecting the potential of the T. zilligii L-asparaginase in the food processing industry.

Recent research progress on microbial L-asparaginases.

L-Asparaginases (EC 3.5.1.1) are enzymes that catalyze the hydrolysis of L-asparagine to L-aspartic acid and found in a variety of organisms from microorganisms to mammals. However, they are mainly expressed and produced by microorganisms. Microbial L-asparaginases have received sustained attention due to their irreplaceable role in the therapy of acute lymphoblastic leukemia and for their inhibition of acrylamide formation during food processing. In this article, we review the application of microbial L-asparaginases in medical treatments and acrylamide mitigation. In addition, we describe in detail recent advances in the existing sources, purification, production, properties, molecular modification, and immobilization of L-asparaginase.

Direct electron transfer of glucose oxidase immobilized on a mesoporous silica KIT-6 matrix to screen-printed electrodes.

The direct electron transfer of glucose oxidase (GOx) immobilized on a large-pore mesoporous silica KIT-6 matrix fixed to a screen-printed electrode (SPE) and its application as a disposable biosensor were studied. KIT-6 plays a vital role in this method through immobilizing GOx and facilitating the electron communication between the active centers of GOx and the surface of the SPE. GOx immobilized on KIT-6 maintains its bioactivity and structure and displays stable and well-defined redox peaks with a formal potential of -428 mV (vs. Saturated Calomel Electrode), with a heterogeneous electron transfer rate constant of 4.15 s(-1) in phosphate buffer (0.05 M, pH 6.0). Upon the addition of glucose into air-saturated phosphate buffer solution, the reduction peak current decreases, which can be used analytically for glucose detection. The biosensor exhibits a linear response to glucose concentration ranging from 0 to 2.83 mM and a sensitivity of 7.29 microA (mM)(-1) cm(-2) at an applied potential of -0.5 V. The present work provides a promising strategy for fabricating a novel and disposable mediator-free glucose biosensor, which could be potentially mass-produced through further development.

Electrochemical detection of DNA hybridization by using a zirconia modified renewable carbon paste electrode.

A simple, polishable and renewable DNA biosensor was fabricated based on a zirconia modified carbon paste electrode. Zirconia was mixed with graphite powder and paraffin wax to produce the paste for the electrode, and response-optimized at 56% graphite powder, 19% ZrO(2) and 25% paraffin wax. An oligonucleotide probe with a terminal 5'-phosphate group was attached to the surface of the electrode via the strong affinity of zirconia for phosphate groups. DNA immobilization and hybridization were characterized by cyclic voltammetry and differential pulse voltammetry, using methylene blue as indicator. Examination of changes in response with complementary or non-complementary DNA sequences showed that the developed biosensor had a high selectivity and sensitivity towards hybridization detection (< or =2x10(-10) M complementary DNA detectable). The surface of the biosensor can be renewed quickly and reproducibly (signal RSD+/-4.6% for five successive renewals) by a simple polishing step.