scholarly journals Magnetically-actuated, bead-enhanced silicon photonic immunosensor

2015 ◽  
Vol 7 (20) ◽  
pp. 8539-8544 ◽  
Author(s):  
Enrique Valera ◽  
Melinda S. McClellan ◽  
Ryan C. Bailey
Keyword(s):  
Limit Of Detection ◽  
Magnetic Actuation ◽  
Protein Biomarker ◽  
Magnetically Actuated ◽  
Low Concentrations ◽  
Silicon Photonic ◽  
Optical Immunosensor ◽  
Representative Protein

Magnetic actuation has been introduced to an optical immunosensor technology resulting in improvements in both rapidity and limit of detection for an assay quantitating low concentrations of a representative protein biomarker.

Silicon Micro-Photonic Structure for Ultra-Sensitive Biosensing

2003 ◽  
Vol 797 ◽  
Author(s):  
Bradley Schmidt ◽  
Vilson Almeida ◽  
Christina Manolatou ◽  
Stefan Preble ◽  
Michal Lipson
Keyword(s):  
Nano Particles ◽  
Particle Detection ◽  
Strong Light ◽  
Extinction Cross Section ◽  
Low Concentrations ◽  
Silicon Photonic ◽  
Micron Size ◽  
Planar Silicon ◽  
Single Particle Detection ◽  
Metal Nano Particles

ABSTRACTWe demonstrate a micron-size planar silicon photonic device that is able to detect low concentrations of metal nano-particles approaching single particle detection. This sensitivity is achieved by using strong light confining structures that enhance the extinction cross-section of metal nano-particles by orders of magnitude. Structures were fabricated and measurements of the transmission spectra of the devices demonstrate the detection of 10 nm diameter gold particles resting on the device with a density of fewer than 2 particles per 104 nm2 (the area of the sensing region surface). Using such a device, in a fluidic platform, one could detect the presence of a single metal nano-particle specifically bound to various analytes, enabling ultrasensitive detection of analytes including DNA, RNA, proteins, and antigens.

scholarly journals Stability-Indicating Photochemical Method for the Assay of Thiamine by Spectrophotometry

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Iqbal Ahmad ◽  
Syed Haider Abbas ◽  
Zubair Anwar ◽  
Muhammad Ali Sheraz ◽  
Sofia Ahmed ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
The United States ◽  
Limit Of Quantification ◽  
Chromatography Method ◽  
Stability Indicating ◽  
Low Concentrations ◽  
Photochemical Method ◽  
Significant Difference ◽  
Liquid Chromatography Method ◽  
States Pharmacopeia

A stability-indicating photochemical method has been developed for the assay of thiamine (TH) salts in aqueous solution and in fresh and aged vitamin preparations. It is based on the photooxidation of TH by UV irradiation to form thiochrome (TC) in alkaline solution. The TC : TH ratio under controlled conditions of light intensity, temperature, pH, exposure time, and irradiation distance is constant and can be used to determine the concentration of UV irradiated TH solutions. TC, on extraction with isobutanol from the photodegraded solution of TH, has been determined by the UV spectrophotometric method at 370 nm. It exhibits a high intensity of absorption in the UV region that can be used for the assay of even low concentrations of TH. Under optimum conditions, Beer’s law is obeyed in the concentration range of 0.20–2.00 mg/100 ml (R2 = 09998). The limit of detection (LOD) and limit of quantification (LOQ) are 0.0076 and 0.0231 mg/100 ml, respectively. The method has been validated and applied to aqueous solutions and vitamin preparations. The results have statistically been compared with the United States Pharmacopeia liquid chromatography method. It has been found that there is no significant difference between the two methods at 95% confidence level.

Analytical validation of eight methods of thyroglobulin measurement in fine-needle aspiration washouts

2020 ◽  
pp. 000456322096836
Author(s):  
Florence Boux de Casson ◽  
Rémi Beloeil ◽  
Anne-Sophie Gauchez ◽  
Charlotte Oris ◽  
Monique Leban ◽  
...  
Keyword(s):  
Matrix Effect ◽  
Limit Of Detection ◽  
Needle Aspiration ◽  
Decision Threshold ◽  
Serum Samples ◽  
Cervical Lymph Nodes ◽  
Analytical Error ◽  
Low Concentrations ◽  
The Matrix ◽  
Assay Methods

Background Thyroglobulin (Tg) assay in washout fluids of fine needles, after cervical lymph nodes aspiration, is used for detecting metastases from differentiated thyroid carcinomas. Assay methods are the same as for Tg in serum. However, with non-serum samples, methods require extensive validation to notably check for the absence of matrix effect. This study fits this context. Our objectives were to assess analytic performances, in washout fluid, of eight different Tg assay methods and to compare them to validated data in serum. Methods Eleven medical laboratories participated in this study. The matrix tested was phosphate-buffer saline containing 1% bovine serum albumin (PBS-1% BSA). Samples used were dilutions, in this buffer, of Certified Reference Material (CRM 457). We verified, for all methods, the limit of detection, precision, linearity, trueness and accuracy. Results In PBS-1% BSA, the functional sensitivities (FS) were comparable to those expected for serum. All the methods were linear. The relative biases of trueness were between –24.5 and 10.2% around 1  µg/L. Total analytical error was ≤40% near the functional sensitivity values. Conclusion No quantitatively important matrix effect was observed. All the methods showed their ability to measure Tg in PBS-1% BSA, over the concentration range of interest, with acceptable total analytical error. We validated the functional sensitivity value as a decision threshold in thyroidectomized patients after treatment and with low concentrations of serum Tg.

scholarly journals Porous Silicon Photonic Crystals Coated with Ag Nanoparticles as Efficient Substrates for Detecting Trace Explosives Using SERS

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 872 ◽  
Author(s):  
Furu Zhong ◽  
Zhaofeng Wu ◽  
Jixi Guo ◽  
Dianzeng Jia
Keyword(s):  
Porous Silicon ◽  
Photonic Crystals ◽  
Limit Of Detection ◽  
Picric Acid ◽  
Single Layer ◽  
Trace Detection ◽  
Assay Condition ◽  
Silicon Photonic ◽  
Relative Standard ◽  
Explosive Properties

Picric acid (PA) is an organic substance widely used in industry and military, which poses a great threat to the environment and security due to its unstable, toxic, and explosive properties. Trace detection of PA is also a challenging task because of its highly acidic and anionic character. In this work, silver nanoparticles (AgNPs)-decorated porous silicon photonic crystals (PS PCs) were controllably prepared as surface-enhanced Raman scattering (SERS) substrates using the immersion plating solution. PA and Rhodamine 6G dye (R6G) were used as the analyte to explore the detection performance. As compared with single layer porous silicon, the enhancement factor of PS PCs substrates is increased to 3.58 times at the concentration of 10−6 mol/L (R6G). This additional enhancement was greatly beneficial to the trace-amount-detection of target molecules. Under the optimized assay condition, the platform shows a distinguished sensitivity with the limit of detection of PA as low as 10−8 mol/L, the linear range from 10−4 to 10−7 mol/L, and a decent reproducibility with a relative standard deviation (RSD) of ca. 8%. These results show that the AgNPs-modified PS PCs substrates could also find further applications in biomedical and environmental sensing.

Trace Analysis of Phenols in Water by Gas Chromatography

1975 ◽  
Vol 32 (2) ◽  
pp. 292-294 ◽  
Author(s):  
Derek A. J. Murray
Keyword(s):  
Gas Chromatography ◽  
Lower Limit ◽  
Water Samples ◽  
Trace Analysis ◽  
Organic Material ◽  
Limit Of Detection ◽  
Internal Standard ◽  
Low Concentrations ◽  
Trimethylsilyl Derivatives ◽  
Derivatives Of

A method for analysis of low concentrations of phenols, cresols, and xylenols in water samples was developed. O-xylene was added to the sample as an internal standard and the sample was extracted once with chloroform to remove a portion of the total organic material present. The trimethylsilyl derivatives of the phenols were formed and analysis completed by gas chromatography. The method was rapid and required a minimum of sample manipulation. The lower limit of detection was 0.100 mg/liter for phenol, 0.025 mg/liter for cresols, and 0.050 mg/liter for xylenols.

High affinity Ca2+–Mg2+ ATPase in the distal tubule of the mouse kidney

1987 ◽  
Vol 65 (10) ◽  
pp. 2093-2098 ◽  
Author(s):  
Michèle G. Brunette ◽  
Sylvie Blouin ◽  
Meathan Chan
Keyword(s):  
Proximal Tubule ◽  
Kinetic Parameters ◽  
Atp Hydrolysis ◽  
Limit Of Detection ◽  
Distal Tubule ◽  
Mouse Kidney ◽  
Distal Nephron ◽  
Low Concentrations ◽  
Distal Tubules ◽  
Shed Light

The purpose of this study was to investigate whether Ca2+–Mg2+ ATPase in the distal tubule (where calcium transport is active, against a gradient, and hormone dependent) presents some characteristics different from those observed in the proximal tubule, and whether these characteristics are likely to shed light on the respective roles of this enzyme at the two sites of the nephron. The Ca2+- and Mg2+-dependent ATP hydrolysis was measured in microdissected segments of the distal nephron, the kinetic parameters were determined, and the influence of magnesium upon the sensitivity to calcium was examined. Results were compared with those obtained in the proximal tubule, and in purified membranes as reported by others. In the distal tubule, low concentrations of Mg2+ (< 10−7 M) did not influence ATP hydrolysis. At concentrations above 10−7 M, Mg2+ increased ATP hydrolysis according to Michaelis kinetics (apparent Km = 11.3 ± 2.4 μM, Vmax = 219 ± 26 pmol∙mm−1∙20 min−1). The addition of 1 μM Ca2+ decreased the apparent Km for Mg2+ and the Vmax for Mg2+. Similar results were obtained in the proximal tubule. At low Mg2+ concentrations, Ca2+ also stimulated ATP hydrolysis according to Michaelis kinetics with an apparent Km value for Ca2+ of 0.18 ± 0.06 and 0.10 ± 0.03 μM Ca2+ (ns) and a Vmax of 101 ± 12 and 89 ± 9 pmol∙mm−1∙20 min−1 (ns) in the distal and proximal tubules, respectively. In the two segments, the addition of Mg2+ strongly decreased the sensitivity to 1 μM Ca2+ so that at 1 mM Mg2+, the Ca2+-dependent ATPase activity was at the limit of detection. In conclusion, the kinetic parameters of the Ca2+- and Mg2+-dependent ATP hydrolysis were similar at the two sites of the nephron, and were also similar to those reported for the enzyme present in purified basolateral membranes. The nonadditive effect of the two cations Ca2+ and Mg2+ suggests that the two ATPase activities belong to the same enzyme, and this enzyme is the same in the proximal and distal tubules. Differences in Ca2+ transport characteristics should be attributed to factors other than variations in the nature of the Ca2+–Mg2+ ATPase.

scholarly journals A New Clark-Type Layered Double Hydroxides-Enzyme Biosensor for H2O2 Determination in Highly Diluted Real Matrices: Milk and Cosmetics

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1878
Author(s):  
Mauro Tomassetti ◽  
Riccardo Pezzilli ◽  
Giuseppe Prestopino ◽  
Francesco Di Biagio ◽  
Corrado Di Natale ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Limit Of Detection ◽  
Gas Diffusion ◽  
Milk Samples ◽  
Low Concentrations ◽  
Enzyme Biosensor ◽  
H2o2 Determination ◽  
Double Hydroxides ◽  
Real Matrices

A new catalase amperometric biosensor for hydroperoxides detection has been built as part of research aimed at the development of biosensors based on layered double hydroxides (LDH) used as support for enzyme immobilization. The fabricated device differs from those developed so far, usually based on an LDH enzyme nanocomposite adsorbed on a glassy carbon (GC) electrode and cross-linked by glutaraldehyde, since it is based on an amperometric gas diffusion electrode (Clark type) instead of a GC electrode. The new biosensor, which still uses LDH synthesized by us and catalase enzyme, is robust and compact, shows a lower LOD (limit of detection) value and a linearity range shifted at lower concentrations than direct amperometric GC biosensor, but above all, it is not affected by turbidity or emulsions, or by the presence of possible soluble species, which are reduced to the cathode at the same redox potential. This made it possible to carry out accurate and efficient determination of H2O2 even in complex or cloudy real matrices, also containing very low concentrations of hydrogen peroxide, such as milk and cosmetic products, i.e., matrices that would have been impossible to analyze otherwise, using conventional biosensors based on a GC–LDH enzyme. An inaccuracy ≤7.7% for cosmetic samples and ≤8.0% for milk samples and a precision between 0.7 and 1.5 (as RSD%), according to cosmetic or milk samples analyzed, were achieved.

scholarly journals CRISPR/Cas13a signal amplification linked immunosorbent assay (CLISA)

2019 ◽  
Author(s):  
Qian Chen ◽  
Tian Tian ◽  
Erhu Xiong ◽  
Po Wang ◽  
Xiaoming Zhou
Keyword(s):  
Immunosorbent Assay ◽  
Signal Amplification ◽  
Limit Of Detection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Inflammatory Factor ◽  
Early Diagnosis Of Cancer ◽  
Low Concentrations ◽  
Conventional Elisa ◽  
Amplification Strategy ◽  
Endothelial Growth Factor

ABSTRACTThe enzyme-linked immunosorbent assay (ELISA) is a basic technique used in analytical and clinical investigations. However, conventional ELISA is still not sensitive enough to detect ultra-low concentrations of biomarkers for the early diagnosis of cancer, cardiovascular risk, neurological disorders, and infectious diseases. Herein we show a mechanism utilizing the CRISPR/Cas13a-based signal export amplification strategy, which double-amplifies the output signal by T7 RNA polymerase transcription and CRISPR/Cas13a collateral cleavage activity. This process is termed the CRISPR/Cas13a signal amplification linked immunosorbent assay (CLISA). The proposed method was validated by detecting an inflammatory factor, human interleukin-6 (human IL-6), and a tumor marker, human vascular endothelial growth factor (human VEGF), which achieved limit of detection (LOD) values of 45.81 fg/mL (2.29 fM) and 32.27 fg/m (0.81 fM), respectively, demonstrating that CLISA is at least 102-fold more sensitive than conventional ELISA.

scholarly journals Analysis of Bioavailable Toluene by Using Recombinant Luminescent Bacterial Biosensors with Different Promoters

2020 ◽  
Author(s):  
Guey-Horng Wang ◽  
Teh-Hua Tsai ◽  
Chun-Chi Kui ◽  
Chiu-Yu Cheng ◽  
Tzu-Ling Huang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Organic Compounds ◽  
Luminescence Intensity ◽  
Limit Of Detection ◽  
Measurement Range ◽  
T7 Promoter ◽  
E Coli ◽  
Low Concentrations ◽  
Relative Standard ◽  
Acceptable Deviation

Abstract In this study, we constructed recombinant luminescent Escherichia coli with T7, T3, and SP6 promoters inserted between tol and lux genes as toluene biosensors and evaluated their sensitivity, selectivity, and specificity for measuring bioavailable toluene in in groundwater and river water. The luminescence intensity of each biosensor depended on temperature, incubation time, ionic strength, and concentrations of toluene and coexisting organic compounds. Toluene induced the highest luminescence intensity in recombinant lux-expressing E. coli with the T7 promoter [T7-lux-E. coli, limit of detection (LOD) = 0.05 μM], followed by that in E. coli with the T3 promoter (T3-lux-E. coli, LOD = 0.2 μM) and SP6 promoter (SP6-lux-E. coli, LOD = 0.5 μM). Luminescence activities may have been synergistically or antagonistically affected by coexisting organic compounds other than toluene; nevertheless, low concentrations of benzoate and toluene analogs had no such effect. In reproducibility experiments, the biosensors had low relative standard deviation (4.3%–5.8%). SP6-lux-E. coli demonstrated high adaptability to environmental interference. T7-lux-E. coli biosensor—with low LOD, wide measurement range (0.05–500 μM), and acceptable deviation (−14.3% to 9.1%)—is an efficient toluene biosensor. This is the first study evaluating recombinant lux E. coli with different promoters for their potential application in toluene measurement in actual water bodies.

Effect of Pentosan Polysulphate Administration in Man on the Formation of Covalent Complexes Between Heparin Cofactor II and Thrombin Generated in Plasma by Contact Activation

1986 ◽  
Vol 56 (03) ◽  
pp. 295-298 ◽  
Author(s):  
F Dol ◽  
P Sié ◽  
D Dupouy ◽  
B Boneu
Keyword(s):  
Limit Of Detection ◽  
Polyacrylamide Gel Electrophoresis ◽  
Contact Activation ◽  
Heparin Cofactor Ii ◽  
Competitive Binding Assay ◽  
Thrombin Inhibition ◽  
Low Concentrations ◽  
Sds Page ◽  
Pentosan Polysulphate ◽  
Pharmacologically Active

SummaryAn assay for the quantification of pentosan polysulphate (PPS) in plasma is described. As PPS has been shown to potentiate thrombin inhibition by the second heparin cofactor (HC II), the principle of this assay was to measure the formation of covalent complexes between HC II and the thrombin generated in plasma after contact activation and recalcification. The complexes were quantified by using purified 125I-HC II added to the plasma as a tracer and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The assay was sensitive to low PPS concentrations (limit of detection: 0.1 μg/ml) and therefore suitable for the measurement of PPS in plasma after its administration to man.The clearance of PPS was studied in 3 subjects receiving respectively 10, 50 and 100 mg intravenously (IV) and in 3 subjects receiving 35 mg subcutaneously (SC). PPS was still detectable 8 h after 50 and 100 mg IV and 6 h after 35 mg SC. The activated partial thromboplastin time (APTT) was, in comparison, relatively insensitive but for concentrations above 1 μg/ ml the values derived from the APTT and from the SDS-PAGE method fitted. The results were also in general agreement with those reported by McGregor et al. (5) who used a sensitive competitive binding assay. This indicates that low concentrations of PPS previously measured chemically are also pharmacologically active in plasma.

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