scholarly journals Microchip systems for immunoassay: an integrated immunoreactor with electrophoretic separation for serum theophylline determination

1998 ◽  
Vol 44 (3) ◽  
pp. 591-598 ◽  
Author(s):  
Nghia H Chiem ◽  
D Jed Harrison
Keyword(s):  
Linear Calibration ◽  
Competitive Immunoassay ◽  
Serum Samples ◽  
Separation Channel ◽  
Serum Theophylline ◽  
Dilution Step ◽  
Microfluidic Immunoassay ◽  
Electroosmotic Pumping ◽  
On Chip ◽  
Electrophoresis Separation

Abstract A glass microchip is described in which reagents and serum samples for competitive immunoassay of serum theophylline can be mixed, reacted, separated, and analyzed. The device functions as an automated microfluidic immunoassay system, creating a lab-on-a-chip. Electroosmotic pumping was used to control first the mixing of 50-fold-diluted serum sample with labeled theophylline tracer in a 1:1 ratio, followed by 1:1 mixing and reaction with anti-theophylline antibody. The 51-nL on-chip mixer gave the same concentration as dilution performed off-chip, within 3%. A 100-pL plug of the reacted solution was then injected into an electrophoresis separation channel integrated within the same chip. Measurements of free and bound tracer by fluorescence detection gave linear calibration curves of signal vs log[theophylline] between 0 and 40 mg/L, with a slope of 0.52 ± 0.03 and an intercept of −0.04 ± 0.04 after a 90-s reaction time. A detection limit of 0.26 mg/L in serum (expressed before the dilution step, actual concentration of 1.3 μg/L at the detector) was obtained. Recovery values were 107% ± 8% for 15 mg/L serum samples.

Development of an Automatic Electrokinetically-Controlled Microfluidic Immunoassay for the Detection of Helicobacter Pylori

2005 ◽  
Author(s):  
Yali Gao ◽  
Guoqing Hu ◽  
Frank Y. H. Lin ◽  
Philip M. Sherman ◽  
Dongqing Li
Keyword(s):  
Helicobacter Pylori ◽  
Detection Limit ◽  
Experimental Studies ◽  
Lab On A Chip ◽  
Protein Antigens ◽  
Immunoassay Technique ◽  
Microfluidic Immunoassay ◽  
Colorimetric Immunoassay ◽  
On Chip ◽  
H Pylori

A novel automatic electrokinetically-controlled immunoassay lab-on-a-chip was developed in this paper. The microchip was made of poly(dimethylsiloxane) (PDMS)/glass using photolithography and replica molding. The immunoassay technique using anti-Helicobacter pylori antibody was applied to detect H. pylori protein antigens. Rhodamine-labeled secondary antibody was employed for signal generation. Experiments were first conducted on a straight microchannel to prove the feasibility of an electrokinetically-driven immunoassay. The detection limit for the coating antigen was found to be 1 ng/μL. Automatic electrokinetically-controlled immunoassay experiments were further carried out on a microchannel network. Numerical simulation and experimental studies were combined for the first time to demonstrate an integrated, electrokinetically-controlled immunoassay lab-on-a-chip. The electrokinetically driven, time-dependent reagent delivery processes were simulated using finite element method (FEM). Fully automatic on-chip experiments were accomplished by sequentially changing the applied electric field. It was found that the lab-on-a-chip can realize much shorter assay time, reduced reagent consumptions and automation while the detection limit is better than the conventional colorimetric immunoassay.

scholarly journals Fabrication of a Selective Sensor Amplification Probe Modified with Multi-Component Zn2SnO4/SnO2 Heterostructured Microparticles as a Robust Electrocatalyst for Electrochemical Detection of Antibacterial Drug Secnidazole

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6700
Author(s):  
Ramaraj Sukanya ◽  
Karuppaiah Balamurugan ◽  
Shen-Ming Chen ◽  
Ramachandran Rajakumaran ◽  
K. Muthupandi ◽  
...  
Keyword(s):  
Blood Serum ◽  
Electrochemical Detection ◽  
Differential Pulse ◽  
Electrochemical Analysis ◽  
Antibacterial Drug ◽  
Linear Calibration ◽  
Serum Samples ◽  
Pulse Voltammetry ◽  
Related Compounds ◽  
Selective Sensor

In this study, we synthesized heterostructured zinc stannate/tin oxide microparticles (ZTO/TO MPs) by a simple coprecipitation method and used them as an effective electrode material for the electrochemical detection of the antibacterial drug secnidazole (SCZ). The as-prepared ZTO/TO MPs were characterized by XRD, Raman, FE-SEM, HR-TEM, EDX, and XPS analyses. The physiochemical studies clearly proved that the fabricated ZTO/TO MPs were formed in a heterostructure phase without other impurities. A glassy carbon electrode modified with the synthesized ZTO/TO MPs showed an excellent and improved electrocatalytic activity in the electrochemical reduction of SCZ. Using differential pulse voltammetry (DPV), an impressive linear calibration range, extending from 0.01 to 193 μM, was observed, coupled with a detection limit of 0.0054 μM and a sensitivity of 0.055 μA/μM. In addition, the ZTO/TO MPs/GCE showed very good selectivity for the detection of SCZ in the presence of a number of biological, inorganic, and structurally related compounds. Finally, the ZTO/TO MPs/GCE was investigated for the analysis of SCZ in human blood serum samples. A very good recovery was obtained when spiking the blood serum with SCZ, highlighting the good applicability of the ZTO/TO MPs/GCE for the electrochemical analysis of SCZ in complex biological samples.

scholarly journals Metallization of Organically Modified Ceramics for Microfluidic Electrochemical Assays

Micromachines ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 605 ◽  
Author(s):  
Bonabi ◽  
Tähkä ◽  
Ollikainen ◽  
Jokinen ◽  
Sikanen
Keyword(s):  
Three Dimensional ◽  
Amperometric Detection ◽  
Optical Transparency ◽  
Near Ultraviolet ◽  
Electrochemically Active ◽  
Organically Modified ◽  
On Chip ◽  
Electrophoresis Separation ◽  
Substantial Interest ◽  
Uv Range

Organically modified ceramic polymers (ORMOCERs) have attracted substantial interest in biomicrofluidic applications owing to their inherent biocompatibility and high optical transparency even in the near-ultraviolet (UV) range. However, the processes for metallization of ORMOCERs as well as for sealing of metallized surfaces have not been fully developed. In this study, we developed metallization processes for a commercial ORMOCER formulation, Ormocomp, covering several commonly used metals, including aluminum, silver, gold, and platinum. The obtained metallizations were systematically characterized with respect to adhesion (with and without adhesion layers), resistivity, and stability during use (in electrochemical assays). In addition to metal adhesion, the possibility for Ormocomp bonding over each metal as well as sufficient step coverage to guarantee conductivity over topographical features (e.g., over microchannel edges) was addressed with a view to the implementation of not only planar, but also three-dimensional on-chip sensing elements. The feasibility of the developed metallization for implementation of microfluidic electrochemical assays was demonstrated by fabricating an electrophoresis separation chip, compatible with a commercial bipotentiostat, and incorporating integrated working, reference, and auxiliary electrodes for amperometric detection of an electrochemically active pharmaceutical, acetaminophen.

A Capillary Electrophoresis Platform With “On-Chip” Electrochemical Detection: Experimental and Computational Flow Studies

2001 ◽  
Author(s):  
Thomas J. Roussel ◽  
Robert S. Keynton ◽  
Kevin M. Walsh ◽  
Mark M. Crain ◽  
John F. Naber ◽  
...  
Keyword(s):  
Capillary Electrophoresis ◽  
Electrochemical Detection ◽  
Power Supply ◽  
Electroosmotic Flow ◽  
Plug Flow ◽  
Finite Element Models ◽  
Separation Channel ◽  
Flow Models ◽  
On Chip ◽  
Electrochemical Potentials

Abstract The purpose of this study was to compare experimental electrokinetic plug flow velocities to computational flow models of microfabricated capillaries. Electroosmotic flow studies of dichlorofluorescein and electrophoretic separation of dopamine and catechol in a microfabricated capillary electrophoresis (CE) system were performed both experimentally and computationally. A “balanced cross design” consisting of a bent 2 cm long injection channel and a straight 2 cm long separation channel was used. The geometry of the capillary was 65 μm wide and 20 μm deep. For the fluorescein study, separation voltages ranging between 0.25 kV and 1 kV were applied, while voltages ranging from 100 V to 550 V were used in the separation studies. Laser Induced Fluorescent (LIF) images were obtained for flow visualization and qualitative analysis in the electroosmotic flow studies, while electrochemical potentials were acquired using “on-chip” electrodes interfaced to a custom-designed power supply and electrochemical detection (ECD) circuit. Finite element models of the experimental device were generated and flows were simulated using commercially available software. For the electroosmotic flow studies, the computational results were found to be within ± 11% of the experimentally obtained values. Similarly, the results of the computational separations of catechol and dopamine predicted plug velocities that were within ± 7.6% of the experimentally determined values.

scholarly journals Integrated On-Chip Microfluidic Immunoassay for Rapid Biomarker Detection

2016 ◽  
Vol 159 ◽  
pp. 53-57 ◽  
Author(s):  
N. Garg ◽  
D. Vallejo ◽  
D. Boyle ◽  
I. Nanayakkara ◽  
A. Teng ◽  
...  
Keyword(s):  
Biomarker Detection ◽  
Microfluidic Immunoassay ◽  
On Chip

scholarly journals On-Chip Glucose Detection Based on Glucose Oxidase Immobilized on a Platinum-Modified, Gold Microband Electrode

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 249
Author(s):  
Julia Madden ◽  
Colm Barrett ◽  
Fathima R. Laffir ◽  
Michael Thompson ◽  
Paul Galvin ◽  
...  
Keyword(s):  
Glucose Oxidase ◽  
Electrochemical Impedance ◽  
Linear Sweep Voltammetry ◽  
Deposition Process ◽  
Glucose Detection ◽  
Serum Samples ◽  
Counter Electrodes ◽  
Electrodeposition Process ◽  
Force Microscopy ◽  
On Chip

We report the microfabrication and characterization of gold microband electrodes on silicon using standard microfabrication methods, i.e., lithography and etching techniques. A two-step electrodeposition process was carried out using the on-chip platinum reference and gold counter electrodes, thus incorporating glucose oxidase onto a platinum-modified, gold microband electrode with an o-phenylenediamine and ß-cyclodextrin mixture. The as-fabricated electrodes were studied using optical microscopy, scanning electron microscopy, and atomic force microscopy. The two-step electrodeposition process was conducted in low sample volumes (50 µL) of both solutions required for biosensor construction. Cyclic voltammetry and electrochemical impedance spectroscopy were utilised for electrochemical characterization at each stage of the deposition process. The enzymatic-based microband biosensor demonstrated a linear response to glucose from 2.5–15 mM, using both linear sweep voltammetry and chronoamperometric measurements in buffer-based solutions. The biosensor performance was examined in 30 µL volumes of fetal bovine serum. Whilst a reduction in the sensor sensitivity was evident within 100% serum samples (compared to buffer media), the sensor demonstrated linear glucose detection with increasing glucose concentrations (5–17 mM).

Pseudohyponatremia Revisited: A Modern-Day Pitfall

2011 ◽  
Vol 135 (4) ◽  
pp. 516-519
Author(s):  
Philip Fortgens ◽  
Tahir S Pillay
Keyword(s):  
Water Concentration ◽  
Short Review ◽  
Ion Selective Electrodes ◽  
Selective Electrode ◽  
Serum Samples ◽  
Water Fraction ◽  
Low Sodium ◽  
Dilution Step ◽  
Patients At Risk ◽  
Subsequent Calculation

Abstract Factitiously low sodium estimations are a hazard in most modern clinical laboratories. Most modern high-throughput analyzers use indirect ion-selective electrodes to estimate electrolyte concentrations in serum samples. This analysis is preceded by a dilution step of the sample. If the water concentration is altered by the presence of increased lipid or protein, the dilution step and the subsequent calculation of concentration by the analyzer results in a falsely low sodium value. This places patients at risk, particularly if the factitious result is acted upon by the physician. In this short review, we highlight this problem and review the methodology and situations where this artifact can occur and discuss strategies to circumvent this problem. When factitious results are suspected, whole blood sodium can be assessed using a direct ion-selective electrode, by measurement of osmolality, or by calculation of the serum water fraction and applying a correction to the reported value.

scholarly journals Voltammetric Determination of Captopril Using Chlorpromazine as a Homogeneous Mediator

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Hossein Bahramipur ◽  
Fahimeh Jalali
Keyword(s):  
Electron Transfer ◽  
Limit Of Detection ◽  
Linear Sweep Voltammetry ◽  
Pharmaceutical Formulations ◽  
Electron Transfer Reaction ◽  
Linear Calibration ◽  
Serum Samples ◽  
Catalytic Rate Constant ◽  
Relative Standard

Chlorpromazine was used as a homogeneous electrocatalyst in the oxidation of captopril. The anodic peak current of chlorpromazine was increased substantially in the presence of low concentrations of captopril (pH 4). Cyclic voltammetry and chronoamperometry were used to study the kinetics of the catalytic electron transfer reaction. The values of electron transfer coefficient () and catalytic rate constant () were estimated to be 0.34 and , respectively. Linear sweep voltammetry was used for the determination of captopril in the presence of chlorpromazine. A linear calibration curve was obtained in the concentration range of captopril of 10.0–300.0 μM, with a limit of detection of 3.65 μM. The relative standard deviation (RSD%) for 5 replicate measurements of captopril (100 μM) was 1.96%. The method was applied to the determination of captopril in pharmaceutical formulations and blood serum samples with satisfactory results.

scholarly journals Programmable µChopper Device with On-Chip Droplet Mergers for Continuous Assay Calibration

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 620 ◽  
Author(s):  
Nan Shi ◽  
Christopher J. Easley
Keyword(s):  
Real Time ◽  
Salt Water ◽  
Real Time Control ◽  
Large Signal ◽  
Linear Calibration ◽  
Excitation Light ◽  
Abrupt Decrease ◽  
The Real ◽  
Time Calibration ◽  
On Chip

While droplet-based microfluidics is a powerful technique with transformative applications, most devices are passively operated and thus have limited real-time control over droplet contents. In this report, an automated droplet-based microfluidic device with pneumatic pumps and salt water electrodes was developed to generate and coalesce up to six aqueous-in-oil droplets (2.77 nL each). Custom control software combined six droplets drawn from any of four inlet reservoirs. Using our μChopper method for lock-in fluorescence detection, we first accomplished continuous linear calibration and quantified an unknown sample. Analyte-independent signal drifts and even an abrupt decrease in excitation light intensity were corrected in real-time. The system was then validated with homogeneous insulin immunoassays that showed a nonlinear response. On-chip droplet merging with antibody-oligonucleotide (Ab-oligo) probes, insulin standards, and buffer permitted the real-time calibration and correction of large signal drifts. Full calibrations (LODconc = 2 ng mL−1 = 300 pM; LODamt = 5 amol) required <1 min with merely 13.85 nL of Ab-oligo reagents, giving cost-savings 160-fold over the standard well-plate format while also automating the workflow. This proof-of-concept device—effectively a microfluidic digital-to-analog converter—is readily scalable to more droplets, and it is well-suited for the real-time automation of bioassays that call for expensive reagents.

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