Ion imprinted polymers integrated into a multi-functional microfluidic paper-based analytical device for trace cadmium detection in water.

A novel multi-functional microfluidic paper-based analytical device (µPAD) integrated with ion imprinted polymers (IIPs) was proposed for specific, portable and low-cost detection of cadmium (Cd(II)) in water. The IIP was grafted on paper and integrated into the µPAD for separation of Cd(II) through multi-layer design. The paper-based screen printed carbon electrode (pSPCE) modified with reduced graphene oxide was fabricated and combined with the µPAD for electrochemical sensing of the separated Cd(II). Reduced graphene oxide (rGO) was prepared via electroreduction on the working electrode surface of the pSPCE (rGO/pSPCE), which provided a sensitization effect with an improved signal for Cd(II) detection. The µPAD developed with the integrated IIP and combined with rGO/pSPCE is able to detect Cd(II) with a linear range from 1 ng ml-1 to 100 ng ml-1 and a detection limit of 0.05 ng ml-1. The accuracy of this µPAD was evaluated with spiked real water samples and compared with that of the inductively coupled plasma mass spectrometry (ICP-MS) method, from which the recovery values ranged from 96.5% to 114.2% with RSDs <10% between the two methods. This µPAD demonstrated its advantages of low-cost, portability, and suitability for highly sensitive detection of Cd(II), making it a valuable tool for on-site analysis.

An Electrochemical Sensor Based on Three-Dimensional Porous Reduced Graphene and Ion Imprinted Polymer for Trace Cadmium Determination in Water.

Three-dimensional (3D) porous graphene-based materials have displayed attractive electrochemical catalysis and sensing performances, benefiting from their high porosity, large surface area, and excellent electrical conductivity. In this work, a novel electrochemical sensor based on 3D porous reduced graphene (3DPrGO) and ion-imprinted polymer (IIP) was developed for trace cadmium ion (Cd(II)) detection in water. The 3DPrGO was synthesized in situ at a glassy carbon electrode (GCE) surface using a polystyrene (PS) colloidal crystal template and the electrodeposition method. Then, IIP film was further modified on the 3DPrGO by electropolymerization to make it suitable for detecting Cd(II). Attributable to the abundant nanopores and good electron transport of the 3DPrGO, as well as the specific recognition for Cd(II) of IIP, a sensitive determination of trace Cd(II) at PoPD-IIP/3DPrGO/GCE was achieved. The proposed sensor exhibited comprehensive linear Cd(II) responses ranging from 1 to 100 µg/L (R2 = 99.7%). The limit of detection (LOD) was 0.11 µg/L, about 30 times lower than the drinking water standard set by the World Health Organization (WHO). Moreover, PoPD-IIP/3DPrGO/GCE was applied for the detection of Cd(II) in actual water samples. The satisfying recoveries (97-99.6%) and relative standard deviations (RSD, 3.5-5.7%) make the proposed sensor a promising candidate for rapid and on-site water monitoring.

A Novel Electrochemical Sensor Based on Electropolymerized Ion Imprinted PoPD/ERGO Composite for Trace Cd(II) Determination in Water.

A novel electrochemical sensor based on electropolymerized ion imprinted poly (o-phenylenediamine) PoPD/electrochemical reduced graphene (ERGO) composite on glass carbon electrode (GCE) was fabricated for selective and sensitive determination of trace Cd(II) in water. ERGO was first deposited on the surface of GCE by electrochemical cyclic voltammetry (CV) scanning to enhance the electron transport activity at electrode surface. The ion imprinted polymer (IIP) of imprinted PoPD was then in situ electropolymerized on ERGO via CV scanning with oPD as functional monomer and Cd(II) ions as template, following removal of the template using electrochemical peroxidation method. The obtained imprinted PoPD/RERGO composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray energy spectroscopy (EDS) for the observation of their morphologies and components. The electrochemical behavior of the imprinted PoPD/ERGO/GCE was performed by CV and SWASV. The fabricated sensor of the imprinted PoPD/ERGO/GCE showed a good selectivity toward target Cd(II) ions in the presence of other heavy metal ions. Under the optimized experimental conditions, the sensor exhibited a good linear relationship between SWASV stripping peak values and Cd(II) concentration in the range of 1 to 50 ng/mL, with the limit of detection as 0.13 ng/mL (S/N = 3). The proposed electrochemical sensor of imprinted PoPD/ERGO/GCE was successfully applied for trace Cd(II) determination in real water samples.

A Mediated BOD Biosensor Based on Immobilized B. Subtilis on Three-Dimensional Porous Graphene-Polypyrrole Composite.

We have developed a novel mediated biochemical oxygen demand (BOD) biosensor based on immobilized Bacillus subtilis (B. subtilis) on three-dimensional (3D) porous graphene-polypyrrole (rGO-PPy) composite. The 3D porous rGO-PPy composite was prepared using hydrothermal method following with electropolymerization. Then the 3D porous rGO-PPy composite was used as a support for immobilizing negatively charged B. subtilis denoted as rGO-PPy-B through coordination and electrostatic interaction. Further, the prepared rGO-PPy-B was used as a microbial biofilm for establishing a mediated BOD biosensor with ferricyanide as an electronic acceptor. The indirect determination of BOD was performed by electrochemical measuring ferrocyanide generated from a reduced ferricyanide mediator using interdigited ultramicroelectrode array (IUDA) as the working electrode. The experimental results suggested a good linear relationship between the amperometric responses and BOD standard concentrations from 4 to 60 mg/L, with a limit detection of 1.8 mg/L (S/N ≥ 3). The electrochemical measurement of real water samples showed a good agreement with the conventional BOD5 method, and the good anti-interference as well as the long-term stability were well demonstrated, indicating that the proposed mediated BOD biosensor in this study holds a potential practical application of real water monitoring.

Essential Roles of TIM-1 and TIM-4 Homologs in Adaptive Humoral Immunity in a Zebrafish Model.

TIM-1 and TIM-4 proteins have become increasingly attractive for their critical functions in immune modulation, particularly in CD4(+) Th2 cell activation. Thus, these proteins were hypothesized to regulate adaptive humoral immunity. However, further evidence is needed to validate this hypothesis. This study describes the molecular and functional characteristics of TIM-1 and TIM-4 homologs from a zebrafish (Danio rerio) model (D. rerio TIM [DrTIM]-1 and DrTIM-4). DrTIM-1 and DrTIM-4 were predominantly expressed in CD4(+) T cells and MHC class II(+) APCs under the induction of Ag stimulation. Blockade or knockdown of both DrTIM-1 and DrTIM-4 significantly decreased Ag-specific CD4(+) T cell activation, B cell proliferation, Ab production, and vaccinated immunoprotection against bacterial infection. This result suggests that DrTIM-1 and DrTIM-4 serve as costimulatory molecules required for the full activation of adaptive humoral immunity. DrTIM-1 was detected to be a trafficking protein located in the cytoplasm of CD4(+) T cells. It can translocate onto the cell surface under stimulation by TIM-4-expressing APCs, which might be a precise regulatory strategy for CD4(+) T cells to avoid self-activation before APCs stimulation. Furthermore, a unique alternatively spliced soluble DrTIM-4 variant was identified to exert a negative regulatory effect on the proliferation of CD4(+) T cells. The above findings highlight a novel costimulatory mechanism underlying adaptive immunity. This study enriches the current knowledge on TIM-mediated immunity and provides a cross-species understanding of the evolutionary history of costimulatory systems throughout vertebrate evolution.

Design and validation of a low cost surface plasmon resonance bioanalyzer using microprocessors and a touch-screen monitor.

An economical and high-performance bioanalyzer, with no use of laptop computer, based on the use of TSPR1k23 biosensors was systematically designed, and validated experimentally for its high performance. The analyzer is composed of a micro-flow cell, a thermoelectric cooler (TEC), a clamp, a touch-screen monitor, and an electronic control unit (ECU) incorporated with photoelectric conversion device. The micro-flow cell is made of stainless steel with high thermal conductivity, and the micro-flow system is based on PID temperature-controlled algorithm to keep the constant temperature (25 degrees C) of the liquid sample via thermal exchange with the clamp. With a peristaltic pump implemented by an injection loop flow system, the bioanalyzer allows the core sensor to be completely exposed to samples. The touch-screen monitor displays the normalized response signal values updated every 0.25s, with a typical noise level less than 5RU (response unit) within 2h. The bioanalyzer was validated using hepatitis B surface antigen (HBsAg) as an example. Anti-HBsAg monoclonal antibody is adhered to the surface of the sensor chip by a bifunctional cross-linker with the technology of self-assembly. The duration of the HBsAg measurement only lasts 5min with a dilution factor ranging from 200 to 1200, optimized with a R-squared value 0.998. The results suggested that the bioanalyzer has higher selectivity, lower cost, expanded detection limit, and shorter measuring time as compared with the HBsAg ELISA kit, especially for low concentrations of analyte.