scholarly journals Printed, Flexible Lactate Sensors: Design Considerations Before Performing On-Body Measurements

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Margaret E. Payne ◽  
Alla Zamarayeva ◽  
Veronika I. Pister ◽  
Natasha A. D. Yamamoto ◽  
Ana Claudia Arias
Keyword(s):  
Enzyme Activity ◽  
Salt Concentration ◽  
Reference Electrode ◽  
Body Measurements ◽  
Lactate Oxidase ◽  
Buffer Solution ◽  
Counter Electrodes ◽  
Sensor Performance ◽  
Activity Measurements ◽  
Nacl Concentration

Abstract This work reports the process of sensor development, optimization, and characterization before the transition to on-body measurements can be made. Sensors using lactate oxidase as a sensing mechanism and tetrathiafulvalene as a mediator were optimized for sporting applications. Optimized sensors show linear range up to 24 mM lactate and sensitivity of 4.8 μA/mM which normalizes to 68 μA*cm−2/mM when accounting for surface area of the sensor. The optimized sensors were characterized 3 different ways: using commercially available reference and counter electrodes, using printed reference and counter electrodes, and using a printed reference electrode with no counter electrode. Sensors intended for measuring sweat must be selective in the presence of sweat constituents. Thus, in addition to traditional characterization in pH 7.0 buffer, we characterized sensor performance in solutions intended to approximate sweat. Sensor performance in pH 7.0 buffer solution was not reflective of sensor performance in artificial sweat, indicating that further characterization is necessary between sensor measurement in pH 7.0 buffer and on-body measurements. Furthermore, we performed enzyme activity measurements and sensor measurements concurrently in five different salts individually, finding that while NH4Cl and MgCl2 do not affect enzyme activity or sensor performance in physiologically relevant ranges of salt concentration, NaCl concentration or KCl concentration decreases enzyme activity and sensor current. On the other hand, CaCl2 induced a nonlinear change in sensor performance and enzyme activity with increasing salt concentration.

Poly Silk Peptide Film PH Sensor Based on Zero Current Potentiometry

2012 ◽  
Vol 450-451 ◽  
pp. 554-556
Author(s):  
Ming Ming Ma ◽  
Zhi Tong ◽  
Yong Wen
Keyword(s):  
Graphite Electrode ◽  
Ph Sensor ◽  
Reference Electrode ◽  
Pencil Graphite Electrode ◽  
Solution Ph ◽  
Counter Electrodes ◽  
System A ◽  
Zero Current ◽  
In Series ◽  
Silk Peptide

A poly silk peptide film pH sensor has been developed using zero current potentiometry system. A poly silk peptide film coated pencil graphite electrode is connected in series between the working and counter electrodes of a potentiostat, and immersed in solution together with a reference electrode. When the solution pH varies, the resulting zero current potentiometry is linear with the values of the solution pH in the range of 1.81 to 11.58. This pH sensor shows high stability, accuracy, selectivity and reproduction.

scholarly journals A Novel Microfluidic Point-of-Care Biosensor System on Printed Circuit Board for Cytokine Detection

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 4011 ◽  
Author(s):  
Daniel Evans ◽  
Konstantinos Papadimitriou ◽  
Nikolaos Vasilakis ◽  
Panagiotis Pantelidis ◽  
Peter Kelleher ◽  
...  
Keyword(s):  
Printed Circuit Board ◽  
Point Of Care ◽  
Reference Electrode ◽  
Circuit Board ◽  
Enzyme Linked Immunosorbent Assay ◽  
Interferon Gamma Release Assay ◽  
Counter Electrodes ◽  
Printed Circuit ◽  
Cytokine Detection ◽  
Biosensor System

Point of Care (PoC) diagnostics have been the subject of considerable research over the last few decades driven by the pressure to detect diseases quickly and effectively and reduce healthcare costs. Herein, we demonstrate a novel, fully integrated, microfluidic amperometric enzyme-linked immunosorbent assay (ELISA) prototype using a commercial interferon gamma release assay (IGRA) as a model antibody binding system. Microfluidic assay chemistry was engineered to take place on Au-plated electrodes within an assay cell on a printed circuit board (PCB)-based biosensor system. The assay cell is linked to an electrochemical reporter cell comprising microfluidic architecture, Au working and counter electrodes and a Ag/AgCl reference electrode, all manufactured exclusively via standard commercial PCB fabrication processes. Assay chemistry has been optimised for microfluidic diffusion kinetics to function under continual flow. We characterised the electrode integrity of the developed platforms with reference to biological sampling and buffer composition and subsequently we demonstrated concentration-dependent measurements of H2O2 depletion as resolved by existing FDA-validated ELISA kits. Finally, we validated the assay technology in both buffer and serum and demonstrate limits of detection comparable to high-end commercial systems with the addition of full microfluidic assay architecture capable of returning diagnostic analyses in approximately eight minutes.

scholarly journals Immunoassay of muscle-specific creatine kinase with a monoclonal antibody and application to myogenesis and muscular dystrophy

1983 ◽  
Vol 213 (2) ◽  
pp. 417-425 ◽  
Author(s):  
G E Morris ◽  
L P Head
Keyword(s):  
Monoclonal Antibody ◽  
Creatine Kinase ◽  
Enzyme Activity ◽  
Total Protein ◽  
Plasma Concentrations ◽  
Thigh Muscle ◽  
Cell Protein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Activity Measurements

A competition e.l.i.s.a. (enzyme-linked immunosorbent assay) is described that enables direct measurement of the muscle-specific polypeptide of chick creatine kinase (M-CK) in extracts of differentiating muscle-cell cultures and in blood plasma samples, even in the presence of embryonic, or brain-type, creatine kinase. The characteristics of the assay can be considerably improved by the use of a monoclonal antibody, CK-ART, instead of rabbit antisera, and we offer an explanation for this in terms of heterogeneity of antibody affinities in polyclonal antisera. In addition to native enzyme, the assay will measure creatine kinase unfolded and inactivated by 8 M-urea treatment. During chick muscle differentiation in vitro, M-CK increased from 7.5% of the total creatine kinase at 24h to 76.0% at 143h, in good agreement with isoenzyme separation data. As a percentage of the total cell protein, M-CK increased by 156-340-fold over the same period and constituted 0.38-0.56% of the total protein in late cultures. E.l.i.s.a. measurements on 17-20-day embryonic thigh-muscle extracts, which contain almost exclusively M-CK, agree well with enzyme activity and radioimmunoassay. M-CK constituted 0.7-1.6% of the total protein in 17-19-day embryonic thigh muscle. Plasma M-CK concentrations in normal 2-8-week-old chickens were found to be in the range 0.5-0.9 micrograms/ml. Plasma concentrations of 32-56 micrograms/ml were found in 8-week-old dystrophic chickens by both e.l.i.s.a. and enzyme-activity measurements. The results suggest that inactive or unfolded forms of M-CK do not normally exist, in any significant amounts, in cell and tissue extracts or in freshly prepared samples of plasma.

Abstract WP153: Post-Stroke Physical Exercise Improves Cognition in Middle-Aged Female Rats

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Sharnikha Saravanan ◽  
Weizhao Zhao ◽  
Kunjan R Dave ◽  
Miguel A Perez-Pinzon ◽  
Ami P Raval
Keyword(s):  
Enzyme Activity ◽  
Physical Exercise ◽  
Cognitive Decline ◽  
Fear Conditioning ◽  
Enzyme Activities ◽  
Female Rats ◽  
Male Rats ◽  
Mitochondrial Enzyme ◽  
Post Stroke ◽  
Activity Measurements

Background: A woman’s risk of a stroke increases exponentially following the onset of menopause, andpost-stroke cognitive decline is a significant consequence of stroke survivors. Our earlier study demonstrated that physical exercise (PE) reduced post-stroke brain injury and improved cognitive functions in male rats. The focus of our study is on the improvement of post-stroke cognitive function in female rats. Methods: Reproductively senescent Sprague-Dawley female rats were exposed to transient middle cerebral artery occlusion (tMCAO; 90 min) and randomly assigned to either PE or sham-PE groups. After 3-5 days, rats underwent sham-PE (0m/min speed) or PE (15m/min speed) for 30 mins either every day (continuous) or alternate day for five times on treadmill. The rats that underwent the alternate day paradigm were treated with ER-β agonist (DPN; 1mg/kg) or vehicle-DMSO immediately following PE/sham-PE sessions to determine the synergistic effect. Twenty-one days after the last PE/sham-PE, rats were tested for hippocampal-dependent contextual fear conditioning and freeze time was measured. Rat brains were processed for histology and infarct area was measured with MCID software. From a separate cohort of rat subjected to PE or sham-PE, brain tissue was harvested for various biochemical assays and mitochondrial enzyme activity measurements. Results: Post-tMCAO continuous PE did not reduce ischemic damage. However, alternate PE regimen with or without ER-β agonist reduced infract volume by 20% (p < 0.05) and 23% (p < 0.05), respectively as compared to no-PE. Similarly, alternate PE showed increased freezing on the second day of fear conditioning by 15% (p < 0.05), indicating improved spatial memory. Individual mitochondrial complex I, II, III and IV enzyme activity measurements demonstrated significant improvement in complex III-IV enzyme activities in the alternate PE treated group as compared to sham-PE. Conclusion: An alternate day PE paradigm and ER-β activation improves post-stroke mitochondrial enzyme activities and cognition in reproductively senescent female rats. Future studies delineating underlying mechanism could help identify therapies to prevent/reduce cognitive decline in menopausal female stroke patients.

EFFECT OF SOLUBLE SALTS ON PLANT RESPONSE TO AND ABSORPTION OF PHOSPHORUS

1963 ◽  
Vol 43 (2) ◽  
pp. 210-218 ◽  
Author(s):  
W. S. Ferguson ◽  
R. A. Hedlin
Keyword(s):  
Salt Concentration ◽  
Saline Soil ◽  
Soil Phosphorus ◽  
Soil Extract ◽  
Plant Response ◽  
Phosphorus Fertilizer ◽  
Soluble Salts ◽  
Higher Plant ◽  
Phosphorus Absorption ◽  
Nacl Concentration

Fertilizer experiments indicated that much higher plant response to phosphorus occurred on moderately saline than on non-saline soil. Soil analyses showed that this difference could not be explained by the amount of sodium bicarbonate extractable phosphorus contained in these two soils.Greenhouse experiments with artificially salinized soil indicated that the uptake of phosphorus by barley plants was related to the salt concentration in the soil. Phosphorus absorption increased with increasing salt concentration, reached a maximum when the saturation soil extract measured approximately 6 millimhos, and then declined with further increases in salt concentration. This relationship was similar for fertilized and unfertilized plants. However, the increase in phosphorus absorption was much greater when phosphorus fertilizer was applied.The same relationship between salt concentration and phosphorus absorption was obtained with increasing NaCl concentration in liquid cultures. Maximum phosphorus absorption by barley occurred when the solution contained between 0.05 and 0.10 molar NaCl This relationship is attributed to the effect of salts on the physiology of the plant rather than the effect of salts on phosphorus solubility.

scholarly journals Two-Channel Graphene pH Sensor Using Semi-Ionic Fluorinated Graphene Reference Electrode

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4184
Author(s):  
Dae Hoon Kim ◽  
Woo Hwan Park ◽  
Hong Gi Oh ◽  
Dong Cheol Jeon ◽  
Joon Mook Lim ◽  
...  
Keyword(s):  
Electrolyte Solution ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Ph Value ◽  
Characteristic Curve ◽  
Reference Electrode ◽  
Reference Channel ◽  
Buffer Solution ◽  
Positive Direction ◽  
Effect Transistor

A reference electrode is necessary for the working of ion-sensitive field-effect transistor (ISFET)-type sensors in electrolyte solutions. The Ag/AgCl electrode is normally used as a reference electrode. However, the Ag/AgCl reference electrode limits the advantages of the ISFET sensor. In this work, we fabricated a two-channel graphene solution gate field-effect transistor (G-SGFET) to detect pH without an Ag/AgCl reference electrode in the electrolyte solution. One channel is the sensing channel for detecting the pH and the other channel is the reference channel that serves as the reference electrode. The sensing channel was oxygenated, and the reference channel was fluorinated partially. Both the channels were directly exposed to the electrolyte solution without sensing membranes or passivation layers. The transfer characteristics of the two-channel G-SGFET showed ambipolar field-effect transistor (FET) behavior (p-channel and n-channel), which is a typical characteristic curve for the graphene ISFET, and the value of VDirac was shifted by 18.2 mV/pH in the positive direction over the range of pH values from 4 to 10. The leakage current of the reference channel was 16.48 nA. We detected the real-time pH value for the two-channel G-SGFET, which operated stably for 60 min in the buffer solution.

Fluorometric Assay of Serum Acid or Alkaline Phosphatase, Either in Solution or on a Semisolid Surface

1975 ◽  
Vol 21 (12) ◽  
pp. 1791-1794 ◽  
Author(s):  
Bernd Rietz ◽  
George G Guilbault
Keyword(s):  
Alkaline Phosphatase ◽  
Enzyme Activity ◽  
Acid Phosphatase ◽  
Clinical Laboratory ◽  
Serum Alkaline Phosphatase ◽  
Buffer Solution ◽  
Citrate Buffer ◽  
Enzymatic Action ◽  
Stable Substrate ◽  
Serum Acid Phosphatase

Abstract We describe enzymatic fluorometric methods for determining activities of serum alkaline phosphatase and of serum acid phosphatase in solution and on silicone rubber pads. 4-Methylumbelliferone phosphate is used as substrate, in either tris(hydroxymethyl)aminomethane or citrate buffer. In solution, the reaction is measured at 37 °C in a 3-ml Pyrex cuvette. Measurements on the pads are also made at 37 °C, after establishing a stable substrate film by lyophilizing all reagents on the surface of the pads. Only 20 to 30 µl of substrate solution, 50 µl of buffer solution, and 1 to 10 µl of blood are necessary, making a total volume of 51 to 60 µl for each assay. The rate of appearance of the fluorescent 4-methylumbelliferone liberated from 4-methylumbelliferone phosphate by the enzymatic action is measured and equated to enzyme activity. Calibration plots of the change in fluorescence per minute vs. enzyme activity for measurements in solution and on pads show a good proportionality in the range of 30.8 to 633 U/liter for alkaline phosphatase and in the range of 0.265 to 5.3 King— Armstrong units for acid phosphatase, indicating the usefulness of these methods in the clinical laboratory.

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