scholarly journals Colorimetric Aptasensor for Detecting Bacillus carboniphilus Using Aptamer Isolated with a Non-SELEX-Based Method

Chemosensors ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 121
Author(s):  
Ho-Kyeong Kim ◽  
Hye-Ri Kim ◽  
Su-Jin Yoon ◽  
Kang-Bong Lee ◽  
Jungbae Kim ◽  
...  
Keyword(s):  
Color Change ◽  
Dissociation Constants ◽  
Limit Of Detection ◽  
Colorimetric Detection ◽  
Microbiologically Influenced Corrosion ◽  
Binding Affinities ◽  
Label Free ◽  
Reliable Performance ◽  
Optimized Conditions ◽  
Induced Aggregation

B. carboniphilus is a naphtha-degradative strain (NDS) that uses hydrocarbons for its growth and causes microbiologically influenced corrosion (MIC) in naphtha pipelines. To date, there have been no studies on receptors or sensors for the detection of B. carboniphilus. We isolate B. carboniphilus-specific aptamers with a non-SELEX-based method, which employs repetitive cycles of centrifugation-based partitioning. The binding affinities of three aptamers are evaluated by obtaining their dissociation constants (Kd), which range from 13.2 to 26.3 nM. The BCA-05 aptamer with the lowest Kd value is employed for a two-stage label-free aptasensing platform to verify the aptamer selectivity using colorimetric detection of B. carboniphilus. This platform starts with the aptamer-bacteria binding step, and the concentration of residual aptamer after binding depends on the amount of the target bacteria. Then, the amount of separated residual aptamer determines the degree of salt-induced aggregation of gold nanoparticles (AuNPs), which results in a color change from red to blue. The AuNP color change is expressed as the ratio of absorbances at 630 and 520 nm (A630/A520). Under optimized conditions, this aptasensor shows reliable performance with a linear correlation in the range 104–107 CFU mL−1 and a limit of detection of 5 × 103 CFU mL−1.

scholarly journals Label-Free Monitoring of Human IgG/Anti-IgG Recognition Using Bloch Surface Waves on 1D Photonic Crystals

Biosensors ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 71 ◽  
Author(s):  
Alberto Sinibaldi ◽  
Agostino Occhicone ◽  
Peter Munzert ◽  
Norbert Danz ◽  
Frank Sonntag ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Surface Waves ◽  
Dissociation Constants ◽  
Limit Of Detection ◽  
Detection System ◽  
Label Free ◽  
Human Igg ◽  
Surface Mass ◽  
On Chip ◽  
Antibody Interactions

Optical biosensors based on one-dimensional photonic crystals sustaining Bloch surface waves are proposed to study antibody interactions and perform affinity studies. The presented approach utilizes two types of different antibodies anchored at the sensitive area of a photonic crystal-based biosensor. Such a strategy allows for creating two or more on-chip regions with different biochemical features as well as studying the binding kinetics of biomolecules in real time. In particular, the proposed detection system shows an estimated limit of detection for the target antibody (anti-human IgG) smaller than 0.19 nM (28 ng/mL), corresponding to a minimum surface mass coverage of 10.3 ng/cm2. Moreover, from the binding curves we successfully derived the equilibrium association and dissociation constants (KA = 7.5 × 107 M−1; KD = 13.26 nM) of the human IgG–anti-human IgG interaction.

scholarly journals Label-Free Colorimetric Detection of Urine Glucose Based on Color Fading Using Smartphone Ambient-Light Sensor

Chemosensors ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 10 ◽  
Author(s):  
Wang ◽  
Guo ◽  
Hu ◽  
Liang ◽  
Li ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Colorimetric Assay ◽  
Point Of Care ◽  
Colorimetric Detection ◽  
Diabetic Patients ◽  
Ambient Light ◽  
Label Free ◽  
Urine Glucose ◽  
Light Sensor

In this work, a label-free colorimetric assay was developed for the determination of urine glucose using smartphone ambient-light sensor (ALS). Using horseradish peroxidase—hydrogen peroxide—3,3′,5,5′-tetramethylbenzidine (HRP-H2O2-TMB) colored system, quantitative H2O2 was added to samples to-be-determined for deepest color. The presence of glucose oxidase in urine led to the formation of H2O2 and the reduction of TMBred. As a result of this, the color of the urine faded and the solution changed from deep blue to light blue. We measured the illuminance of the transmitted light by a smartphone ambient light sensor, and thereby color changes were used to calculate the content of urine glucose. After method validation, this colorimetric assay was practically applied for the determination of urine samples from diabetic patients. Good linearity was obtained in the range of 0.039–10.000 mg/mL (R2 = 0.998), and a limit of detection was 0.005 mg/mL. Our method was had high accuracy, sensitivity, simplicity, rapidity, and visualization, providing a new sensor to be potentially applicable for point-of-care detection of urine glucose.

scholarly journals One-Step Hydrothermal Synthesis of N, Fe-Codoped Carbon Dots as Mimic Peroxidase and Application on Hydrogen Peroxide and Glucose Detection

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yan Li ◽  
Yuhui Weng ◽  
Shikong Lu ◽  
Meihua Xue ◽  
Bixia Yao ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Photoelectron Spectroscopy ◽  
Carbon Dots ◽  
Color Change ◽  
Limit Of Detection ◽  
Colorimetric Detection ◽  
Catalytic Efficiency ◽  
Transmission Electron ◽  
One Step ◽  
First Time

In this paper, N, Fe-codoped carbon dots (N, Fe-CDs) were synthesized from β-cyclodextrin, ethylenediamine, and ferric chloride for the first time using a convenient one-step hydrothermal method. The obtained N, Fe-CDs were characterized by various methods including transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The N, Fe-CDs exhibited better catalytic activity than horseradish peroxidase (HRP) and caused an evident color change for 3,3′,5,5′-tetramethylbenzidine in the presence of H2O2. Kinetic experiments show that the apparent Km value for the N, Fe-CDs with TMB (0.40 mM) or H2O2 (0.35 mM) as the substrate was lower than that of HRP (0.43 and 3.70 mM), suggesting that the N, Fe-CDs have a much higher affinity for TMB and H2O2 than HRP. The Km/Vmax value for the N, Fe-CDs (21.74×103·s for H2O2) is significantly lower than that for HRP (42.53×103·s), suggesting that the N, Fe-CDs have a stronger catalytic efficiency for H2O2 than HRP. Furthermore, a highly efficient and sensitive colorimetric detection method for glucose was developed using the N, Fe-CDs as mimic peroxidase to detect the hydrogen peroxide generated by the oxidation of glucose by glucose oxidase. The limit of detection for H2O2 and glucose was found to be 0.52 and 3.0 μM, respectively. The obtained N, Fe-codoped carbon dots, which possess simulated peroxidase activity, can potentially be used in the field of biotechnology.

Colorimetric Detection of Melamine Based on Poly-Thymine Stabilized Gold Nanoparticles

2013 ◽  
Vol 790 ◽  
pp. 619-622
Author(s):  
Chong Jin ◽  
Hui Min Zhao ◽  
Meng Liu ◽  
Jun Ping Tian ◽  
Xie Quan
Keyword(s):  
Gold Nanoparticles ◽  
Color Change ◽  
Limit Of Detection ◽  
Pure Water ◽  
Colorimetric Detection ◽  
Colorimetric Method ◽  
Milk Powder ◽  
Aggregation Process ◽  
Naked Eye ◽  
Fresh Milk

A simple, fast and reliable colorimetric method for melamine detection based on gold nanoparticles (AuNPs) and poly-thymine (poly-T) is reported. Poly-T strands attract AuNPs through static electricity and keep them stable against aggregation in the presence of NaCl. The affinity between melamine and poly-T, hydrogen bond, frees AuNP from the protection provided by poly-T and thus makes AuNPs aggregate in the presence of NaCl. The color change of AuNPs from wine red to blue can be observed immediately by the naked eye during the aggregation process, and can be accurately recorded with the help of a UV/vis spetrophotometer within 5 minutes. The limit of detection (LOD) of melamine in pure water is 0.146 μmol/L with a linear range from 0.2×10-7 mol/L to 10.0×10-7 mol/L. In fresh milk and milk powder, the LOD is respectively as low as 2.37 μmol/L and 5.36 μmol/L.

scholarly journals Microfluidic Paper-Based Analytical Devices for Colorimetric Detection of Lactoferrin

2019 ◽  
Vol 25 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Hiroko Kudo ◽  
Kento Maejima ◽  
Yuki Hiruta ◽  
Daniel Citterio
Keyword(s):  
Color Change ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Colorimetric Detection ◽  
Color Intensity ◽  
Colorimetric Sensing ◽  
Detection Mechanism ◽  
Fiber Network ◽  
Water Dispersible ◽  
Physical Entrapment

Lactoferrin is an abundant glycoprotein in human body fluids and is known as a biomarker for various diseases. Therefore, point-of-care testing (POCT) for lactoferrin is of interest. Microfluidic paper-based analytical devices (µPADs) have gained a lot of attention as next-generation POCT device candidates, due to their inexpensiveness, operational simplicity, and being safely disposable. This work presents a colorimetric sensing approach for quantitative lactoferrin analysis. The detection mechanism takes advantage of the high affinity of lactoferrin to ferric ions (Fe3+). Lactoferrin is able to displace an indicator from a colorimetric 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-Fe3+ complex, resulting in a color change. A 5-Br-PADAP-Fe3+ complex was encapsulated into water-dispersible poly(styrene- block-vinylpyrrolidone) particles, whose physical entrapment in the cellulosic fiber network results in the immobilization of the complex to the paper matrix. The complex-encapsulating particles showed a color change response in accordance with lactoferrin concentration. Both color intensity-based paper well plates and distance readout-based µPADs are demonstrated. Color intensity-based devices allowed quantitative analysis of lactoferrin concentrations with a limit of detection of 110 µg/mL, using a smartphone and a color readout app. On the other hand, distance readout-based µPADs showed changes of the length of colored sections in accordance with lactoferrin concentration. In summary, we successfully developed both colorimetric intensity-based paper wells and distance-based µPADs for lactoferrin detection. This work demonstrates a user-friendly colorimetric analysis platform for lactoferrin without requiring lab equipment and expensive antibodies.

scholarly journals Highly Sensitive and Selective Colorimetric Detection of Creatinine Based on Synergistic Effect of PEG/Hg2+–AuNPs

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1424 ◽  
Author(s):  
Xia ◽  
Zhu ◽  
Bian ◽  
Li ◽  
Liu ◽  
...  
Keyword(s):  
Color Change ◽  
Limit Of Detection ◽  
Colorimetric Detection ◽  
High Sensitivity ◽  
Peak Shift ◽  
Creatinine Concentration ◽  
Highly Sensitive ◽  
Coordination Effect ◽  
Bovine Serum Sample

A colorimetric sensor, based on the synergistic coordination effect on a gold nanoparticle (AuNP) platform has been developed for the determination of creatinine. The sensor selects citrate stabilized AuNPs as a platform, polyethylene glycol (PEG) as a decorator, and Hg2+ as a linkage to form a colorimetric probe system (PEG/Hg2−–AuNPs). By forming hydrogen bond between the oxygen-containing functional groups of PEG and citrate ions on the surface of AuNPs, this probe shows good stability. PEG coordinated with Hg2+ synergistically and specifically on the surface of dispersed AuNPs, and the existence of creatinine could induce the aggregation of AuNPs with a corresponding color change and an obvious absorption peak shift within 5 min. This PEG/Hg2+–AuNPs probe towards creatinine shows high sensitivity, and a good linear relationship (R2 = 0.9948) was obtained between A620–522 nm and creatinine concentration, which can achieve the quantitative calculations of creatinine. The limit of detection (LOD) of this PEG/Hg2+–AuNPs probe was estimated to be 9.68 nM, lower than that of many other reported methods (Supplementary Materials Table S3). Importantly, the sensitive probe can be successfully applied in a urine simulating fluid sample and a bovine serum sample. The unique synergistic coordination sensing mechanism applied in the designation of this probe further improves its high selectivity and specificity for the detection of creatinine. Thus, the proposed probe may give new inspirations for colorimetric detection of creatinine and other biomolecules.

scholarly journals A Convenient and Label-Free Colorimetric Detection for L-Histidine Based on Inhibition of Oxidation of 3,3′,5,5′-Tetramethylbenzidine-H2O2 System Triggered by Copper Ions

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhikun Zhang ◽  
Wenmeng Zhao ◽  
Cuixia Hu ◽  
Yapeng Cao ◽  
Yumin Liu ◽  
...  
Keyword(s):  
Copper Ions ◽  
Colorimetric Detection ◽  
Colorimetric Method ◽  
Imidazole Ring ◽  
Tissue Growth ◽  
The Body ◽  
Label Free ◽  
Optimized Conditions ◽  
Colorimetric Reaction ◽  
H2o2 System

L-Histidine (L-His) is an essential amino acid, which is used to synthesize proteins and enzymes. The concentration of L-His in the body is controlled to regulate tissue growth and repair of tissues. In this study, a rapid and sensitive method was developed for colorimetric L-his detection using Cu2+ ions to inhibit the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system. H2O2 can oxidize TMB to oxTMB in the presence of copper, and the change in color from colorless (TMB) to blue (oxTMB) is similar to that observed in the presence of peroxidase. However, because the imidazole ring and carboxyl group of L-His can coordinate with Cu2+ ions to form stable L-His–Cu2+ complexes, the color of the TMB–H2O2 solution remains unchanged after the addition of L-His. Therefore, because L-His effectively hinders the colorimetric reaction of TMB with H2O2, this assay can be used to quantitatively determine the concentration of L-His in samples. Under optimized conditions, our colorimetric sensor exhibited two linear ranges of 60 nM to 1 μM and 1 μM to 1 mM for L-His detection and a detection limit of 50 nM (S/N = 3); furthermore, the assay can be performed within 20 min. Moreover, the proposed assay was used to determine the concentration of L-His in urine samples, suggesting that this convenient and label-free colorimetric method presents promising applications in bioanalytical chemistry and clinical diagnosis.

scholarly journals Simple monitoring of pH and urea in whole blood using wearable smart woman pad

Bioimpacts ◽  
2020 ◽  
Author(s):  
Bambang Kuswandi ◽  
Nur Andriani ◽  
Ari S Nugraha
Keyword(s):  
Blood Cell ◽  
Microfluidic Device ◽  
Red Blood Cell ◽  
Whole Blood ◽  
Color Change ◽  
Clinical Laboratory ◽  
Limit Of Detection ◽  
Colorimetric Detection ◽  
Real Samples ◽  
Paper Microfluidic

Introduction: In this work, we used a thread-paper microfluidic device (μTPAD) system, where a threaded part for the handling of the whole blood samples and a paper part for the reaction of plasma with immobilized bioreagents integrated into woman pad as a wearable sensing device namely as smart women pad. The μTPAD as a wearable smart woman pad is developed for the detection of pH and urea in mensuration blood as real samples. Methods: This combined device was constructed to cover the elements required, that is, separation of red blood cell, conditioning, analyte reaction, and colorimetric detection. The color change in sensing areas was measured in the RGB values via a smartphone using the Color Grab after a smart woman pad was used. The thread allowed red blood cell sampling and separation, while the paper microfluidic device was used for conditioning, biorecognition, and colorimetric transduction of pH and urea as analytes. Results: The time needed for analysis was measured as 110 s using the equilibrium method for both analytes, with a limit of detection (LOD) of 72.55 μg/mL for urea, with precision around 1.68%, while for pH around 0.80%. The smart woman pad allowed rapid detection of pH and urea in menstruation blood as real samples for monitoring of the kidney functions, and the results showed an agreement with the conventional methods that have been generally used in the clinical laboratory. Conclusion: The smart woman pad has the potential to be used as a wearable device to monitor the health status of the user via its blood mensuration analysis.

scholarly journals Resorcinol Functionalized Gold Nanoparticles for Formaldehyde Colorimetric Detection

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 302 ◽  
Author(s):  
Carlos Martínez-Aquino ◽  
Ana Costero ◽  
Salvador Gil ◽  
Pablo Gaviña
Keyword(s):  
Gold Nanoparticles ◽  
Color Change ◽  
Limit Of Detection ◽  
Colorimetric Detection ◽  
Detection Mechanism ◽  
Gas Phases ◽  
Functionalized Gold Nanoparticles ◽  
Composite Wood

Gold nanoparticles functionalized with resorcinol moieties have been prepared and used for detecting formaldehyde both in solution and gas phases. The detection mechanism is based on the color change of the probe upon the aggregation of the nanoparticles induced by the polymerization of the resorcinol moieties in the presence of formaldehyde. A limit of detection of 0.5 ppm in solution has been determined. The probe can be deployed for the detection of formaldehyde emissions from composite wood boards.

scholarly journals 2-LED-µSpectrophotometer for Rapid On-Site Detection of Pathogens Using Noble-Metal Nanoparticle-Based Colorimetric Assays

2020 ◽  
Vol 10 (8) ◽  
pp. 2658 ◽  
Author(s):  
Cornelia Reuter ◽  
Matthias Urban ◽  
Manuel Arnold ◽  
Ondrej Stranik ◽  
Andrea Csáki ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Pathogen Detection ◽  
Color Change ◽  
Colorimetric Assay ◽  
Point Of Care ◽  
Colorimetric Detection ◽  
Dna Amplification ◽  
Metal Nanoparticle ◽  
Colorimetric Assays ◽  
Induced Aggregation

Novel point-of-care compatible methods such as colorimetric assays have become increasingly important in the field of early pathogen detection. A simple and hand-held prototype device for carrying out DNA-amplification assay based on plasmonic nanoparticles in the colorimetric detection is presented. The low-cost device with two channels (sample and reference) consists of two spectrally different light emitting diodes (LEDs) for detection of the plasmon shift. The color change of the gold-nanoparticle-DNA conjugates caused by a salt-induced aggregation test is examined in particular. A specific and sensitive detection of the waterborne human pathogen Legionella pneumophila is demonstrated. This colorimetric assay, with a simple assay design and simple readout device requirements, can be monitored in real-time on-site.

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