Capillary and Electrodynamic Forces-Driven Separation Detection of Metal Ions Using a Disposable Microfluidic Sensor with a Composite Electrode.

A disposable microfluidic channel sensor printed on a plastic platform was developed to analyze heavy metal ions (HMIs) as a model target species. Precise separation and detection of multiple targets were established by symmetrically applying a small AC potential on the carbon channel walls to induce an electrodynamic force. The separation device was constructed by covering it with a plastic lid to achieve capillary action in the channel. The sample flow rate was regulated by the hydrophilicity of the lid plastic and electrodynamic convection by the AC field, which was characterized by the contact angle measurement and the additional electrodynamic force. The flow variables and their relevance to the capillary phenomena were demonstrated, and the analytical parameters were optimized. The working electrode was modified with poly(diamino terthiophene) anchored with nanosized graphene oxide (pDATT/GO) to enhance the detection performance. The experimental variables for separating and detecting the target species were optimized according to the AC frequency and amplitude, sample flow rate, electrolytes, pH, temperature, and applied potential for detection. The linear dynamic ranges were between 0.1 and 200.0 ppb, with detection limits of 0.04 ± 0.023, 0.29 ± 0.05, 0.07 ± 0.011, and 0.14 ± 0.06 ppb for Cu2+ Cd2+, Hg2+, and Pb2+, respectively. Finally, the reliability of the proposed method was evaluated through analysis of HMIs in real water samples. The results were matched to those obtained through parallel analysis using ICP-MS at a 95% confidence level.

Pair of chiral 2D silver(I) enantiomers: chiral recognition of L- and D-histidine via differential pulse voltammetry.

Self-assembly of AgPF6 with a pair of chiral tridentate ligands (1S,1'S,1''S,2R,2'R,2''R) and (1R,1'R,1''R,2S,2'S,2''S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)triisonicotinate (s,r-L) and (r,s-L) in a mixture of methanol and dioxane yields 2D sheets consisting of [Ag(s,r-L)](PF6)·3C4H8O2·0.5H2O and [Ag(r,s-L)](PF6)·3C4H8O2·0.5H2O, respectively. The differential pulse voltammetric (DPV) technique using the pair of chiral 2D-sheet enantiomers was employed for chiral discrimination of amino acid enantiomers, and was found to be an effective tool for enantio-recognition of L- and D-histidines. Both the size and the binding site of amino acids were strongly dependent on electrochemical enantio-recognition via the chiral 2D sheets.

Exosomal microRNAs array sensor with a bioconjugate composed of p53 protein and hydrazine for the specific lung cancer detection.

For the early diagnosis of lung cancer, a novel strategy to detect microRNAs encapsulated in exosomes with immunomagnetic isolation was demonstrated for the selective extraction of exo-miRNAs from patient serum. Here, miRNA was captured from lysed exosomes in specially designed capture probe modified magnetic beads, followed by T4 DNA polymerase-mediated in situ formation of chimeric 5'-miRNA-DNA-3' (Target). The poly-(2,2':5',2''-terthiophene-3'-(p-benzoic acid)) (pTBA)-modified electrode harbors Probe-1 DNA that hybridizes to the 5' end of the chimera, followed by hybridization of Probe-2 DNA to the 3' end of the chimera, resulting in the formation of a 20-nucleotide-long dsDNA consensus sequence for p53 protein binding. A bioconjugate composed of p53 and hydrazine assembled on AuNPs (p53-AuNPs-Hyd) recruits the p53 protein to recognize a specific sequence, forming the final sensor probe (pTBA-Probe-1:Target/Probe-2:bioconjugate), where hydrazine functions as an electrocatalyst to generate amperometric signal from the reduction of H2O2. This sensor has double specificity via selective capture of the target in Probe-1 and p53 recognition, which shows excellent analytical performance, revealing a dynamic range between 100 aM and 10 pM with a detection limit of 92 (±0.1) aM. For practical applications, we prepared a multiplexed array sensor to simultaneously detect four exo-miRNAs (miRNA-21, miRNA-155, miRNA-205, and miRNA-let-7b) up to femtomolar levels from 1.0 mL to 125 µL of cell culture (A549, MCF-7 and BEAS-2B) media and lung cancer patient serum samples, respectively.

Disposable amperometric immunosensor with a dual monomers-based bioconjugate for granzyme B detection in blood and cancer progress monitoring of patients.

A disposable amperometric biosensor with a dual monomers-based bioconjugate was developed for granzyme B (GzmB) detection and for monitoring of the cancer progression of patients before and after immunotherapy. The biosensor was fabricated by immobilizing a GzmB monoclonal antibody (Ab1) on a poly3'-(2-aminopyrimidyl)-2,2':5',2''-terthiophene/gold nanoparticle (pPATT/AuNP) layer. The bioconjugate nanoparticles were synthesized through self-assembly of a monomer mixture of 2,2:5,2-terthiophene-3-(p-benzoic acid) (TBA) and PATT onto AuNPs, followed by chemical binding of brilliant cresyl blue (BCB) on TBA and GzmB polyclonal antibody (Ab2) on the PATT layer. Each sensing layer was investigated by surface analysis and electrochemical experiments. The sensor performance was assessed with selectivity, stability, reproducibility, detection limit, and real sample analysis. Under the optimized conditions, the dynamic range of GzmB was in two slopes from 3.0 to 50.0 pg/ml and from 50.0 to 1000.0 pg/ml with a detection limit of 1.75 ± 0.14 pg/ml (RSD ≤5.2%). GzmB monitoring was performed for the patient's serum samples, where a low level of GzmB was observed for lung cancer patients before immunotherapy (10.51 ± 0.99 pg/ml, RSD ≤6.2%), and the level was increased after therapy (17.19 ± 2.22 pg/ml, RSD ≤2.6%). Moreover, a significantly higher level was present in healthy persons (34.40 ± 3.92 pg/ml, RSD ≤1.4%). The cancer progression of patients before and after therapy was evaluated by monitoring GzmB levels in human serum using the proposed sensor.

Hydrogen Evolution and Oxygen Reduction Reactions in Acidic Media Catalyzed by Pd4 S Decorated N/S Doped Carbon Derived from Pd Coordination Polymer.

The template-free synthesis and the characterization of an active electrocatalyst are performed for both the hydrogen evolution and oxygen reduction reactions in acidic media. In this work, the unique chelation mode of benzene-1,4-dithiocarboxamide (BDCA) is first used to synthesize a novel palladium-BDCA coordination polymer (PdBDCA) as a precursor of palladium sulfide nanoparticles-decorated nitrogen and sulfur doped carbon (Pd4 S-SNC). The newly synthesized PdBDCA and Pd4 S-SNC nanoparticles are characterized using chemical, electrochemical, and surface analysis methods. Notably, the nanoparticles obtained at 700 °C exhibit the remarkable catalytic property for the hydrogen evolution reaction in 0.5 m H2 SO4 , showing the overpotential of 32 mV (vs reversible hydrogen electrode (RHE)) and Tafel slope of 52 mV dec-1 , which are comparable to that of Pt/C. The catalyst also shows a high oxygen reduction activity, offering the half-wave and onset potentials of 0.92 and 0.77 V (vs RHE) in 0.5 m H2 SO4 , with improved methanol tolerance and long-term stability compared with Pt/C. The present study gives a way for the design of excellent electrocatalyst for the energy conversion devices in the corrosive acidic environment.

Chiral Pd6L8 Nanocube Pairs: Recognition of Chiral Amino Acids via Electrochemistry.

The self-assembly of PdX2 (X- = ClO4- and PF6-) with C3-symmetric l- and d-L [L = (2S,2'S,2″S)- and (2R,2'R,2″R)-[benzenetricarbonyltris(azanediyl)]tris(3-phenylpropane-2,1-diyl)triisonicotinate] produces the chiral nanocube pair [Pd6(l-L)8](X)12 and [Pd6(d-L)8](X)12 (X- = ClO4- and PF6-, respectively) with an inner cavity of 12.3 × 12.3 × 12.3 Å3. These chiral nanocubes are effective for the enantiorecognition of various chiral amino acids via the square-wave-voltammetry technique. In the present study, the site of enantiorecognition was confirmed by density functional theory calculated interactions between each nanocube and the chiral amino acids, and the calculated interactions were coincident with the shifts of the electrochemical oxidation potentials.

Nano-biosensor for the in vitro lactate detection using bi-functionalized conducting polymer/N, S-doped carbon; the effect of αCHC inhibitor on lactate level in cancer cell lines.

A robust amperometric sensor was developed for the lactate detection in the extracellular matrix of cancer cells. The sensor was fabricated by separately immobilizing nicotinamide adenine dinucleotide (NAD+) onto a carboxylic acid group and lactate dehydrogenase (LDH) onto an amine group of bi-functionalized conducting polymer (poly 3-(((2,2':5',2″-terthiophen)-3'-yl)-5-aminobenzoic acid (pTTABA)) composited with N, S-doped porous carbon. Morphological features of the composite layer and sensor performance were investigated using FE-SEM, XPS, and electrochemical methods. The experimental parameters were optimized to get the best results. The calibration plot showed a linear dynamic range between 0.5 µM and 4.0 mM with the detection limit of 112 ± 0.02 nM. The proposed sensor was applied to detect lactate in a non-cancerous (Vero) and two cancer (MCF-7 and HeLa) cell lines. Among these cell lines, MCF-7 was mostly affected by the administration of lactate transport inhibitor, α-cyano-4-hydroxycinnamate (αCHC), followed by HeLa and Vero, respectively. Furthermore, the effect of αCHC concentration and treatment time on the lactate level in the cell lines were demonstrated. Finally, cytotoxicity studies were also performed to evaluate the effect of αCHC on cell viability.

Electrodynamic Force Derived in-Channel Separation and Detection of Au Nanoparticles Using an Electrochemical AC Microfluidic Channel.

In this study, we have established the separation of Au nanoparticles (AuNPs) using a symmetrical AC electric field applied-electrochemical microfluidic device composed of carbon channel and detection electrodes. The lateral movement of AuNPs in the channel under the AC field was analyzed by simulation using the mathematically derived equations, which were formulated from Newtonian fluid mechanics. It shows that the nanoparticles are precisely separated according to their respective mass or size difference in a short time. The experimental parameters affecting the separation and detection of AuNPs were optimized in terms of applied frequency, amplitude, flow rate, buffer concentration, pH dependency, and temperature. The final separation was performed at 1.0 V amplitude with 8.0 MHz frequency at 0.4 µL/min flow rate for the separation, and the potential of 1.0 V was applied for the amperometric detection of AuNPs in a 0.1 M PBS. Before and after the separation, AuNPs (diameter range: 3-60 nm) were confirmed by UV-visible spectroscopy and transmission electron microscopy. In this case, the separation resolution was 3 nm with an enhanced separation efficiency of up to 597,503 plates/m for the AuNPs. In addition, the amperometric current response of the detection electrode under the AC field application was also enhanced by the sensitivity 5-fold compared with the absence of the AC field.