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Journal articles on the topic 'Colorimetric approaches'

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Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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1

Majdinasab, Marjan, Sondes Ben Aissa, and Jean Louis Marty. "Advances in Colorimetric Strategies for Mycotoxins Detection: Toward Rapid Industrial Monitoring." Toxins 13, no. 1 (December 24, 2020): 13. http://dx.doi.org/10.3390/toxins13010013.

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Mycotoxins contamination is a global public health concern. Therefore, highly sensitive and selective techniques are needed for their on-site monitoring. Several approaches are conceivable for mycotoxins analysis, among which colorimetric methods are the most attractive for commercialization purposes thanks to their visual read-out, easy operation, cost-effectiveness, and rapid response. This review covers the latest achievements in the last five years for the development of colorimetric methods specific to mycotoxins analysis, with a particular emphasis on their potential for large-scale applications in food industries. Gathering all types of (bio)receptors, main colorimetric methods are critically discussed, including enzyme-linked assays, lateral flow-assays, microfluidic devices, and homogenous in-solution strategies. This special focus on colorimetry as a versatile transduction method for mycotoxins analysis is comprehensively reviewed for the first time.
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Xu, Xiaohan, Yu-Feng Li, Jiating Zhao, Yunyun Li, Jing Lin, Bai Li, Yuxi Gao, and Chunying Chen. "Nanomaterial-based approaches for the detection and speciation of mercury." Analyst 140, no. 23 (2015): 7841–53. http://dx.doi.org/10.1039/c5an01519g.

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Savvin, Sergey B., Vladimir V. Kuznetsov, Yulia V. Ermolenko, Irina Yu Chernikova, and Alla V. Mikhailova. "Green approaches to colorimetric monitoring of calcium in water." Pure and Applied Chemistry 81, no. 11 (October 26, 2009): 2123–29. http://dx.doi.org/10.1351/pac-con-08-10-05.

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Simple, ecologically harmless chemical reactions have always been a point of interest for chemists and analysts as fit to be applied to work in or out of laboratories. A new concept of chemical analysis is exemplified in the article by means of selective determination of calcium ions with the organic reagent arsenazo III (2,2'-[1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo]-bisbenzenearsonic acid disodium salt) with no application of toxic solvents during the seasonal analysis of water in the Yauza River (the city of Moscow).
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Dzantiev, B. B. "APPROACHES FOR IMPROVING SENSITIVITY OF RAPID IMMUNOCHROMATOGRAPHIC TEST SYSTEMS." http://eng.biomos.ru/conference/articles.htm 1, no. 19 (2021): 229–31. http://dx.doi.org/10.37747/2312-640x-2021-19-229-231.

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Various nanodispersed markers and their combinations for immunochromatography with colorimetric and fluorimetric detection are considered and their opportunities for lowering the detection limit are characterized. The influence of the composition of antibody-nanomarker conjugates on analytical parameters of the test systems is described.
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Balusamy, Brabu, Anitha Senthamizhan, and Tamer Uyar. "Functionalized Electrospun Nanofibers as a Versatile Platform for Colorimetric Detection of Heavy Metal Ions in Water: A Review." Materials 13, no. 10 (May 25, 2020): 2421. http://dx.doi.org/10.3390/ma13102421.

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The increasing heavy metal pollution in the aquatic ecosystem mainly driven by industrial activities has raised severe concerns over human and environmental health that apparently necessitate the design and development of ideal strategies for the effective monitoring of heavy metals. In this regard, colorimetric detection provides excellent opportunities for the easy monitoring of heavy metal ions, and especially, corresponding solid-state sensors enable potential opportunities for their applicability in real-world monitoring. As a result of the significant interest originating from their simplicity, exceptional characteristics, and applicability, the electrospun nanofiber-based colorimetric detection of heavy metal ions has undergone radical developments in the recent decade. This review illustrates the range of various approaches and functional molecules employed in the fabrication of electrospun nanofibers intended for the colorimetric detection of various metal ions in water. We highlight relevant investigations on the fabrication of functionalized electrospun nanofibers encompassing different approaches and functional molecules along with their sensing performance. Furthermore, we discuss upcoming prospectus and future opportunities in the exploration of designing electrospun nanofiber-based colorimetric sensors for real-world applications.
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Gummadi, Sowjanya, and Mohana Kommoju. "Colorimetric Approaches To Drug Analysis And Applications – A Review." American Journal of PharmTech Research 9, no. 1 (February 8, 2019): 14–37. http://dx.doi.org/10.46624/ajptr.2019.v9.i1.002.

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Fernandes, Gabriel Martins, Weida R. Silva, Diandra Nunes Barreto, Rafaela S. Lamarca, Paulo Clairmont F. Lima Gomes, João Flávio da S Petruci, and Alex D. Batista. "Novel approaches for colorimetric measurements in analytical chemistry – A review." Analytica Chimica Acta 1135 (October 2020): 187–203. http://dx.doi.org/10.1016/j.aca.2020.07.030.

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8

Brill, Michael H. "Acquisition and reproduction of color images: Colorimetric and multispectral approaches." Color Research & Application 27, no. 4 (June 17, 2002): 304–5. http://dx.doi.org/10.1002/col.10073.

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9

Guo, Yongming, Jing Li, Shuming Chai, and Jingjing Yao. "Nanomaterials for the optical detection of fluoride." Nanoscale 9, no. 45 (2017): 17667–80. http://dx.doi.org/10.1039/c7nr05981g.

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10

Hahn, Jungwoo, Eunghee Kim, Youngsang You, and Young Jin Choi. "Colorimetric switchable linker-based bioassay for ultrasensitive detection of prostate-specific antigen as a cancer biomarker." Analyst 144, no. 14 (2019): 4439–46. http://dx.doi.org/10.1039/c9an00552h.

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11

Zhu, Yaqi, Yang Tian, and Tingting Zheng. "A tri-modal paper device based on flower-like CuSe for the detection of an Alzheimer's disease-associated microRNA marker." Chemical Communications 58, no. 23 (2022): 3771–74. http://dx.doi.org/10.1039/d1cc07050a.

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A tri-modal paper device based on flower-like CuSe was developed for monitoring Alzheimer's disease-related miRNA by integrating colorimetric, photothermal and surface-enhanced Raman scattering approaches.
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12

Clark, A. C., X. Zhang, and N. Kontoudakis. "Simplified measures of copper fractions in wine: colorimetric and filtration‐based approaches." Australian Journal of Grape and Wine Research 26, no. 4 (September 2, 2020): 399–409. http://dx.doi.org/10.1111/ajgw.12450.

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13

Shrivas, Kamlesh, Nidhi Nirmalkar, Santosh Singh Thakur, Ramsingh Kurrey, Deepak Sinha, and Ravi Shankar. "Experimental and theoretical approaches for the selective detection of thymine in real samples using gold nanoparticles as a biochemical sensor." RSC Advances 8, no. 43 (2018): 24328–37. http://dx.doi.org/10.1039/c8ra02627k.

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We report a simple, selective and cost effective method for the qualitative and quantitative determination of thymine in a DNA standard and in urine samples using gold nanoparticles (AuNPs) as a label-free colorimetric biochemical sensor.
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14

Cheam, V., and A. S. Y. Chau. "Sulfate in colored waters. II. Evaluation of approaches for correcting historical colorimetric data." Environment International 13, no. 3 (January 1987): 261–70. http://dx.doi.org/10.1016/0160-4120(87)90138-3.

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15

Balusamy, Brabu, Anitha Senthamizhan, and Tamer Uyar. "Functionalized Electrospun Nanofibers as Colorimetric Sensory Probe for Mercury Detection: A Review." Sensors 19, no. 21 (November 2, 2019): 4763. http://dx.doi.org/10.3390/s19214763.

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Mercury is considered the most hazardous pollutant of aquatic resources; it exerts numerous adverse effects on environmental and human health. To date, significant progress has been made in employing a variety of nanomaterials for the colorimetric detection of mercury ions. Electrospun nanofibers exhibit several beneficial features, including a large surface area, porous nature, and easy functionalization; thus, providing several opportunities to encapsulate a variety of functional materials for sensing applications with enhanced sensitivity and selectivity, and a fast response. In this review, several examples of electrospun nanofiber-based sensing platforms devised by utilizing the two foremost approaches, namely, direct incorporation and surface decoration envisioned for detection of mercury ions are provided. We believe these examples provide sufficient evidence for the potential use and progress of electrospun nanofibers toward colorimetric sensing of mercury ions. Furthermore, the summary of the review is focused on providing an insight into the future directions of designing electrospun nanofiber-based, metal ion colorimetric sensors for practical applications.
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Sotoud, Hannieh, Philip Gribbon, Bernhard Ellinger, Jeanette Reinshagen, Peter Boknik, Lars Kattner, Ali El-Armouche, and Thomas Eschenhagen. "Development of a Colorimetric and a Fluorescence Phosphatase-Inhibitor Assay Suitable for Drug Discovery Approaches." Journal of Biomolecular Screening 18, no. 8 (April 19, 2013): 899–909. http://dx.doi.org/10.1177/1087057113486000.

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Protein phosphatases (PP) are interesting drug targets. However, their ubiquitous presence and involvement in different, partially opposing signal pathways suggest that specificity may be achieved rather by targeting their interaction with subunits determining substrate specificity than the enzyme itself. An interesting subunit is phosphatase inhibitor-1 (I-1), which, in its protein kinase A–phosphorylated form (I-1P), inhibits the catalytic subunit of type 1 phosphatase (PP1c). In the current study, we established a colorimetric and a fluorescence-based assay system for the identification of compounds interfering with the inhibitory effect of I-1P on PP1c. The fluorescence assay exhibited 500-fold higher sensitivity toward PP1c. A nine-residue peptide containing the PP1c-binding motif (RVxF) of I-1 stimulated PP1c activity in the presence of I-1P (EC50 27 µM and 2.3 µM in the colorimetric and fluorescence assay, respectively). This suggests that the peptide interfered with the inhibitory effect of I-1P on PP1c and represents a proof-of-principle. The calculated Z′ factor for PP1c (0.84) and the PP1c–I-1P complex (0.73) confirmed the suitability of the fluorescence assay for high-throughput screenings (HTS). By testing several thousand small molecules, we suggest the advantages of kinetic measurements over single-point measurements using the fluorescence-based assay in an HTS format.
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17

Serebrennikova, Kseniya V., Olga D. Hendrickson, Elena A. Zvereva, Demid S. Popravko, Anatoly V. Zherdev, Chuanlai Xu, and Boris B. Dzantiev. "A Comparative Study of Approaches to Improve the Sensitivity of Lateral Flow Immunoassay of the Antibiotic Lincomycin." Biosensors 10, no. 12 (December 3, 2020): 198. http://dx.doi.org/10.3390/bios10120198.

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This study provides a comparative assessment of the various nanodispersed markers and related detection techniques used in the immunochromatographic detection of an antibiotic lincomycin (LIN). Improving the sensitivity of the competitive lateral flow immunoassay is important, given the increasing demands for the monitoring of chemical contaminants in food. Gold nanoparticles (AuNPs) and CdSe/ZnS quantum dots (QDs) were used for the development and comparison of three approaches for the lateral flow immunoassay (LFIA) of LIN, namely, colorimetric, fluorescence, and surface-enhanced Raman spectroscopy (SERS)-based LFIAs. It was demonstrated that, for colorimetric and fluorescence analysis, the detection limits were comparable at 0.4 and 0.2 ng/mL, respectively. A SERS-based method allowed achieving the gain of five orders of magnitude in the assay sensitivity (1.4 fg/mL) compared to conventional LFIAs. Therefore, an integration of a SERS reporter into the LFIA is a promising tool for extremely sensitive quantitative detection of target analytes. However, implementation of this time-consuming technique requires expensive equipment and skilled personnel. In contrast, conventional AuNP- and QD-based LFIAs can provide simple, rapid, and inexpensive point-of-care testing for practical use.
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18

Berro, Fernando, Matteo Lelli, Ilaria Minardi, and Giorgio Virgili. "A procedure for eliminating sulfide interference on silica colorimetric analysis." Mineralogical Magazine 78, no. 6 (November 2014): 1417–22. http://dx.doi.org/10.1180/minmag.2014.078.6.08.

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Two different approaches were tested in this study to suppress sulfide interference in the silicomolybdate method of silica determination, namely: oxidation of sulfide to elemental sulfur; and conversion of the sulfide species to H2S and stripping by air bubbling. Based on the results obtained the latter approach is deemed to represent the better and quicker option to eliminate sulfide interference in silica colorimetric analysis.
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19

Franke, Josef D., Ann L. Braverman, Alison M. Cunningham, Erin E. Eberhard, and Greg A. Perry. "Erythrosin B: a versatile colorimetric and fluorescent vital dye for bacteria." BioTechniques 68, no. 1 (January 2020): 7–13. http://dx.doi.org/10.2144/btn-2019-0066.

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Rapidly assaying cell viability for diverse bacteria species is not always straightforward. In eukaryotes, cell viability is often determined using colorimetric dyes; however, such dyes have not been identified for bacteria. We screened different dyes and found that erythrosin B (EB), a visibly red dye with fluorescent properties, functions as a vital dye for many Gram-positive and -negative bacteria. EB worked at a similar concentration for all bacteria studied and incubations were as short as 5 min. Given EB's spectral properties, diverse experimental approaches are possible to rapidly visualize and/or quantitate dead bacterial cells in a population. As the first broadly applicable colorimetric viability dye for bacteria, EB provides a cost-effective alternative for researchers in academia and industry.
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20

Lim, Christopher, Yangchung Lee, and Lawrence Kulinsky. "Fabrication of a Malaria-Ab ELISA Bioassay Platform with Utilization of Syringe-Based and 3D Printed Assay Automation." Micromachines 9, no. 10 (October 2, 2018): 502. http://dx.doi.org/10.3390/mi9100502.

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We report on the fabrication of a syringe-based platform for automation of a colorimetric malaria-Ab assay. We assembled this platform from inexpensive disposable plastic syringes, plastic tubing, easily-obtainable servomotors, and an Arduino microcontroller chip, which allowed for system automation. The automated system can also be fabricated using stereolithography (SLA) to print elastomeric reservoirs (used instead of syringes), while platform framework, including rack and gears, can be printed with fused deposition modeling (FDM). We report on the optimization of FDM and SLA print parameters, as well as post-production processes. A malaria-Ab colorimetric test was successfully run on the automated platform, with most of the assay reagents dispensed from syringes. Wash solution was dispensed from an SLA-printed elastomeric reservoir to demonstrate the feasibility of both syringe and elastomeric reservoir-based approaches. We tested the platform using a commercially available malaria-Ab colorimetric assay originally designed for spectroscopic plate readers. Unaided visual inspection of the assay solution color change was sufficient for qualitative detection of positive and negative samples. A smart phone application can also be used for quantitative measurement of the assay color change.
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Wang, Tse-Yao, Yi-Tzu Lee, Hsien-Yi Chen, Cheng-Hao Ko, Chi-Tsung Hong, Jyun-Wei Wen, Tzung-Hai Yen, and Chao-Min Cheng. "A Paper-Based Analytical Device for Analysis of Paraquat in Urine and Its Validation with Optical-Based Approaches." Diagnostics 11, no. 1 (December 22, 2020): 6. http://dx.doi.org/10.3390/diagnostics11010006.

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Paraquat is a highly toxic herbicide. Paraquat poisoning is often fatal and is an important public health threat in many places. The quick identification and timely initiation of treatment based on timely analysis of the paraquat concentration in urine/serum could improve the prognosis for patients. However, current paraquat concentration measurements are time-consuming and difficult to implement due to the expensive and bulky equipment required. To address these practical challenges, paper-based devices have emerged as alternative diagnostic tools for improving point-of-care testing. In this study, we demonstrate the successful use of a paper-based analytical device for the accurate detection of urine paraquat concentration. The developed paper-based analytical device employs colorimetric paraquat concentration measurements. The R2 value for the urine paraquat standard curve was 0.9989, with a dynamic range of 0–100 ppm. The limit of detection was 3.01 ppm. Two other optical-based approaches, Spectrochip and NanoDrop, were used for comparison. The results suggest that the developed paper-based analytical device is comparable to other colorimetric measurements, as determined by Bland–Altman analysis. The device was clinically validated using urine from six paraquat-poisoned patients. The results prove that the developed paper-based analytical device is accurate, easy-to-use, and efficient for urine paraquat concentration measurement, and may enable physicians to improve clinical management.
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Šídlo, Michal, Přemysl Lubal, and Pavel Anzenbacher. "Colorimetric Chemosensor Array for Determination of Halides." Chemosensors 9, no. 2 (February 18, 2021): 39. http://dx.doi.org/10.3390/chemosensors9020039.

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The halide anions are essential for supporting life. Therefore, halide anion analyses are of paramount importance. For this reason, we have performed both qualitative and quantitative ana- lyses of halides (chloride, bromide, iodide) using the Tl(III) complex of azodye, 4-(2-pyridylazo)re- sorcinol (PAR), a potential new chemical reagent/sensor that utilizes the substitution reaction whereas the Tl(III)PAR complex reacts with a halide to yield a more stable thallium(III)-halide while releasing the PAR ligand in a process accompanied by color change of the solution. The experimental conditions (e.g., pH, ratio metal ion-to-ligand ratio, etc.) for the substitution reaction between the metal complex and a halide were optimized to achieve increased sensitivity and a lower limit of detection (chloride 7 mM, bromide 0.15 mM, iodide 0.05 mM). It is demonstrated that this single chemosensor can, due to release of colored PAR ligand and the associated analyte-specific changes in the UV/VIS spectra, be employed for a multicomponent analysis of mixtures of anions (chloride + bromide, chloride + iodide, bromide + iodide). The spectrophotometric data evaluated by artificial neural networks (ANNs) enable distinguishing among the halides and to determine halide species concentrations in a mixture. The Tl(III)-PAR complex was also used to construct sensor arrays utilizing a standard 96-well plate format where the output was recorded at several wavelengths (up to 7) using a conventional plate reader. It is shown that the data obtained using a digital scanner employing only three different input channels may also be successfully used for a subsequent ANN analysis. The results of all approaches utilized for data evaluation were similar. To increase the practical utility of the chemosensor, we have developed a test paper strip indicator useful for routine naked-eye visual determination of halides. This test can also be used for halide anion determination in solutions using densitometer. The methodology described in this paper can be used for a simple, inexpensive, and fast routine analysis both in a laboratory as well as in a field setting.
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Vargas, Alejandro P., Francisco Gámez, Javier Roales, Tânia Lopes-Costa, and José M. Pedrosa. "A Paper-Based Ultrasensitive Optical Sensor for the Selective Detection of H2S Vapors." Chemosensors 9, no. 2 (February 19, 2021): 40. http://dx.doi.org/10.3390/chemosensors9020040.

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A selective and inexpensive chemical paper-based sensor for the detection of gaseous H2S is presented. The triggering of the sensing mechanism is based on an arene-derivative dye which undergoes specific reactions in the presence of H2S, allowing for colorimetric analysis. The dye is embedded into a porous cellulose matrix. We passively exposed the paper strips to H2S generated in situ, while the absorbance was monitored via an optic fiber connected to a spectrophotometer. The kinetics of the emerging absorbance at 534 nm constitute the sensor response and maintain a very stable calibration signal in both concentration and time dimensions for quantitative applications. The time and concentration dependence of the calibration function allows the extraction of unusual analytical information that expands the potential comparability with other sensors in the literature, as the limit of detection admissible within a given exposure time. The use of this specific reaction ensures a very high selectivity against saturated vapors of primary interferents and typical volatile compounds, including alkanethiols. The specific performance of the proposed sensor was explicitly compared with other colorimetric alternatives, including standard lead acetate strips. Additionally, the use of a smartphone camera to follow the color change in the sensing reaction was also tested. With this straightforward method, also affordable for miniature photodiode devices, a limit of detection below the ppm scale was reached in both colorimetric approaches.
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Faura, Georgina, Gerard Boix-Lemonche, Anne Kristin Holmeide, Rasa Verkauskiene, Vallo Volke, Jelizaveta Sokolovska, and Goran Petrovski. "Colorimetric and Electrochemical Screening for Early Detection of Diabetes Mellitus and Diabetic Retinopathy—Application of Sensor Arrays and Machine Learning." Sensors 22, no. 3 (January 18, 2022): 718. http://dx.doi.org/10.3390/s22030718.

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In this review, a selection of works on the sensing of biomarkers related to diabetes mellitus (DM) and diabetic retinopathy (DR) are presented, with the scope of helping and encouraging researchers to design sensor-array machine-learning (ML)-supported devices for robust, fast, and cost-effective early detection of these devastating diseases. First, we highlight the social relevance of developing systematic screening programs for such diseases and how sensor-arrays and ML approaches could ease their early diagnosis. Then, we present diverse works related to the colorimetric and electrochemical sensing of biomarkers related to DM and DR with non-invasive sampling (e.g., urine, saliva, breath, tears, and sweat samples), with a special mention to some already-existing sensor arrays and ML approaches. We finally highlight the great potential of the latter approaches for the fast and reliable early diagnosis of DM and DR.
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Otrisal, Pavel, Camelia Diaconu, Ovidiu Bratu, Florentina Ionita Radu, Zdenek Melicharik, and Simona Bungaru. "New approaches regarding the protection forces’ health against the effects of some toxic substances." Romanian Journal of Military Medicine 122, no. 3 (December 1, 2019): 106–9. http://dx.doi.org/10.55453/rjmm.2019.122.3.15.

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In the past, finding out the chemical resistance of the barrier materials designated for the production of individual protective equipment ofthe protection forces (policemen, firefighters, soldiers) was based on the need to respond to protection against weapons of mass destruction. Simple chemical methods based on indicating the colorimetric reactions were used. It was necessary to switch to more universal methods due to a change in the security of the environment and the need to focus on toxic industrial materials. The universality is due to using sensitive QCM sensors equipped with a special detection layer and some special carbon electrodes. The paper deals with new methods that are used to determine the chemical resistance of the barrier materials against the permeation of toxic substances, primarily in field conditions. However, they can also be used in stationary chemical laboratory conditions. Keywords: Permeation, barrier material, PIEZOTEST, KONDUKTOTEST, SORPTEST.
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Zhang, Hao, and Xi Jiang. "A Colorimetric and “Turn-On” Fluorescent Chemosensor for Metal Ion Based on Rhodamine Derivative." Advanced Materials Research 955-959 (June 2014): 267–70. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.267.

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The recognition and sensing of biologically and environmentally important species has emerged as a significant goal in the field of chemical sensors in recent years1. Fluorogenic methods in conjunction with suitable probes are preferable approaches for the measurement of these analytes because fluorimetry is rapidly performed, is nondestructive, is highly sensitive, is suitable for high-throughput screening applications2,3. We synthesized rhodamine derivatives compounds by a Schiff base reaction.
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Contreras-Trigo, Braulio, Víctor Díaz-García, and Patricio Oyarzún. "A Novel Preanalytical Strategy Enabling Application of a Colorimetric Nanoaptasensor for On-Site Detection of AFB1 in Cattle Feed." Sensors 22, no. 23 (November 29, 2022): 9280. http://dx.doi.org/10.3390/s22239280.

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Aflatoxin contamination of cattle feed is responsible for serious adverse effects on animal and human health. A number of approaches have been reported to determine aflatoxin B1 (AFB1) in a variety of feed samples using aptasensors. However, rapid analysis of AFB1 in these matrices remains to be addressed in light of the complexity of the preanalytical process. Herein we describe an optimization on the preanalytical stage to minimize the sample processing steps required to perform semi-quantitative colorimetric detection of AFB1 in cattle feed using a gold nanoparticle-based aptasensor (nano-aptasensor). The optical behavior of the nano-aptasensor was characterized in different organics solvents, with acetonitrile showing the least interference on the activity of the nan-aptasensor. This solvent was selected as the extractant agent for AFB1-containing feed, allowing for the first time, direct colorimetric detection from the crude extract (detection limit of 5 µg/kg). Overall, these results lend support to the application of this technology for the on-site detection of AFB1 in the dairy sector.
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Mamaeva, Anastasiya A., Vladimir I. Martynov, Sergey M. Deyev, and Alexey A. Pakhomov. "Comparison of Colorimetric and Fluorometric Chemosensors for Protein Concentration Determination and Approaches for Estimation of Their Limits of Detection." Chemosensors 10, no. 12 (December 17, 2022): 542. http://dx.doi.org/10.3390/chemosensors10120542.

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Here, we present a direct comparison of different dyes and assays for the determination of protein concentrations. We compared the classical Bradford assay with two modern assays based on the fluorogenic dyes QuDye and ProteOrange and showed that the Bradford reagent achieved excellent results in the determination of protein concentrations as compared with more modern rivals. We also showed that standard approaches for determining the limit of detection (LoD) and limit of quantification (LoQ) may not work correctly with the tested dyes. We proposed a new approach that extends the standard algorithm for LoD and LoQ determination. This approach works well with both classical colorimetric and fluorogenic dyes, as well as with nontrivial fluorescent probes.
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Vilela, Diana, María Cristina González, and Alberto Escarpa. "Sensing colorimetric approaches based on gold and silver nanoparticles aggregation: Chemical creativity behind the assay. A review." Analytica Chimica Acta 751 (November 2012): 24–43. http://dx.doi.org/10.1016/j.aca.2012.08.043.

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Liu, Yan, Haijia Jin, Wenting Zou, and Rong Guo. "Protein-mediated sponge-like copper sulfide as an ingenious and efficient peroxidase mimic for colorimetric glucose sensing." RSC Advances 10, no. 48 (2020): 28819–26. http://dx.doi.org/10.1039/d0ra05496h.

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Strenuous efforts have been made to develop nanozymes for achieving the performance of natural enzymes, but the fabrication of high-performance and biocompatible nanozymes via facile and versatile approaches has always been a great challenge.
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Piovarci, Ivan, Sopio Melikishvili, Marek Tatarko, Tibor Hianik, and Michael Thompson. "Detection of Sub-Nanomolar Concentration of Trypsin by Thickness-Shear Mode Acoustic Biosensor and Spectrophotometry." Biosensors 11, no. 4 (April 11, 2021): 117. http://dx.doi.org/10.3390/bios11040117.

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The determination of protease activity is very important for disease diagnosis, drug development, and quality and safety assurance for dairy products. Therefore, the development of low-cost and sensitive methods for assessing protease activity is crucial. We report two approaches for monitoring protease activity: in a volume and at surface, via colorimetric and acoustic wave-based biosensors operated in the thickness-shear mode (TSM), respectively. The TSM sensor was based on a β-casein substrate immobilized on a piezoelectric quartz crystal transducer. After an enzymatic reaction with trypsin, it cleaved the surface-bound β-casein, which increased the resonant frequency of the crystal. The limit of detection (LOD) was 0.48 ± 0.08 nM. A label-free colorimetric assay for trypsin detection has also been performed using β-casein and 6-mercaptohexanol (MCH) functionalized gold nanoparticles (AuNPs/MCH-β-casein). Due to the trypsin cleavage of β-casein, the gold nanoparticles lost shelter, and MCH increased the attractive force between the modified AuNPs. Consequently, AuNPs aggregated, and the red shift of the absorption spectra was observed. Spectrophotometric assay enabled an LOD of 0.42 ± 0.03 nM. The Michaelis–Menten constant, KM, for reverse enzyme reaction has also been estimated by both methods. This value for the colorimetric assay (0.56 ± 0.10 nM) is lower in comparison with those for the TSM sensor (0.92 ± 0.44 nM). This is likely due to the better access of the trypsin to the β-casein substrate at the surface of AuNPs in comparison with those at the TSM transducer.
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Wikantyasning, Erindyah Retno, Ummi Kalsum, Suharti Nurfiani, Muhammad Da'i, and Zakky Cholisoh. "Allylamine-Conjugated Polyacrylic Acid and Gold Nanoparticles for Colorimetric Detection of Bacteria." Materials Science Forum 1029 (May 2021): 137–44. http://dx.doi.org/10.4028/www.scientific.net/msf.1029.137.

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The increasing resistance of pathogenic bacteria to the pharmaceutical compound could be a very important issue for public health. A sensitive, fast and accurate approaches for bacteria detection are going to be needed to enhance the effectiveness of treatment. This study aimed to develop a colorimetric sensor based on allylamine-conjugated polyacrylic acid and gold nanoparticles (AuNPs- AAm-PAA) for bacteria detection. Allylamine was conjugated to the polyacrylic acid and mixed with the gold colloid to form a self-assembled AuNPs-AAm-PAA. The polymer-modified gold nanoparticles were characterized for the particle size, zeta potential, reversibility using TEM, particle size analyzer, and UV-Vis spectrophotometer, respectively. The system was observed to detect bacteria and observed by the naked eye, UV-Vis spectrophotometer, and TEM. The results showed that AuNPs-PAA-AAm solution showed an absorbance peak at 530 nm, AuNPs particle size of 25.67 nm ± 2.68, and zeta potential -31.4 ± 4.5 mV. Introduction of bacteria into the Au-AAm-PAA solution resulted in a color change from red to purple at concentrations of 6x108 CFU/mL of Staphylococcus aureus and Escherichia coli. TEM analysis revealed the binding of aggregated gold nanoparticles around the outer membrane of bacteria. The sensor system based on conjugated polymer and gold nanoparticles demonstrated a promising way for bacteria detection.
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33

Meletiadis, Joseph, Johan W. Mouton, Jacques F. G. M. Meis, and Paul E. Verweij. "In Vitro Drug Interaction Modeling of Combinations of Azoles with Terbinafine against Clinical Scedosporium prolificans Isolates." Antimicrobial Agents and Chemotherapy 47, no. 1 (January 2003): 106–17. http://dx.doi.org/10.1128/aac.47.1.106-117.2003.

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ABSTRACT The in vitro interaction between terbinafine and the azoles voriconazole, miconazole, and itraconazole against five clinical Scedosporium prolificans isolates after 48 and 72 h of incubation was tested by a microdilution checkerboard (eight-by-twelve) technique. The antifungal effects of the drugs alone and in combination on the fungal biomass as well as on the metabolic activity of fungi were measured using a spectrophotometric method and two colorimetric methods, based on the lowest drug concentrations showed 75 and 50% growth inhibition (MIC-1 and MIC-2, respectively). The nature and the intensity of the interactions were assessed using a nonparametric approach (fractional inhibitory concentration [FIC] index model) and a fully parametric response surface approach (Greco model) of the Loewe additivity (LA) no-interaction theory as well as a nonparametric (Prichard model) and a semiparametric response surface approaches of the Bliss independence (BI) no-interaction theory. Statistically significant synergy was found between each of the three azoles and terbinafine in all cases, although with different intensities. A 27- to 64-fold and 16- to 90-fold reduction of the geometric mean of the azole and terbinafine MICs, respectively, was observed when they were combined, resulting in FIC indices of <1 to 0.02. Using the MIC-1 higher levels of synergy were obtained, , which were more consistent between the two incubation periods than using the MIC-2. The strongest synergy among the azoles was found with miconazole using the BI-based models and with voriconazole using the LA-based models. The synergistic effects both on fungal growth and metabolic activity were more potent after 72 h of incubation. Fully parametric approaches in combination with the modified colorimetric method might prove useful for testing the in vitro interaction of antifungal drugs against filamentous fungi.
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Chen, Xiaohu, Ryan Wreyford, and Noushin Nasiri. "Recent Advances in Ethylene Gas Detection." Materials 15, no. 17 (August 23, 2022): 5813. http://dx.doi.org/10.3390/ma15175813.

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The real-time detecting and monitoring of ethylene gas molecules could benefit the agricultural, horticultural and healthcare industries. In this regard, we comprehensively review the current state-of-the-art ethylene gas sensors and detecting technologies, covering from preconcentrator-equipped gas chromatographic systems, Fourier transform infrared technology, photonic crystal fiber-enhanced Raman spectroscopy, surface acoustic wave and photoacoustic sensors, printable optically colorimetric sensor arrays to a wide range of nanostructured chemiresistive gas sensors (including the potentiometric and amperometric-type FET-, CNT- and metal oxide-based sensors). The nanofabrication approaches, working conditions and sensing performance of these sensors/technologies are carefully discussed, and a possible roadmap for the development of ethylene detection in the near future is proposed.
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Cadoni, Enrico, Alex Manicardi, and Annemieke Madder. "PNA-Based MicroRNA Detection Methodologies." Molecules 25, no. 6 (March 12, 2020): 1296. http://dx.doi.org/10.3390/molecules25061296.

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MicroRNAs (miRNAs or miRs) are small noncoding RNAs involved in the fine regulation of post-transcriptional processes in the cell. The physiological levels of these short (20–22-mer) oligonucleotides are important for the homeostasis of the organism, and therefore dysregulation can lead to the onset of cancer and other pathologies. Their importance as biomarkers is constantly growing and, in this context, detection methods based on the hybridization to peptide nucleic acids (PNAs) are gaining their place in the spotlight. After a brief overview of their biogenesis, this review will discuss the significance of targeting miR, providing a wide range of PNA-based approaches to detect them at biologically significant concentrations, based on electrochemical, fluorescence and colorimetric assays.
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36

Rotscholl, Ingo, Klaus Trampert, and Franz Schmidt. "Spectral ray data for optical simulations." Advanced Optical Technologies 8, no. 1 (February 25, 2019): 55–65. http://dx.doi.org/10.1515/aot-2018-0049.

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Abstract This paper summarizes selected approaches, to generate spectral ray data for different types of spectrally varying light sources including only angular variable as well as spatial and angular variable sources. This includes a description of their general ideas and applications, the required measurements, and their mathematical concepts. Finally, achieved results for an Red/Green/Blue/White-light emitting diode (RGBW-LED) system are shown. Ray tracing simulations of a spatially and angularly spectral varying LED system combined with a spectrally sensitive optical system are qualitatively and quantitatively compared to a colorimetric far-field measurement of the same system. The results demonstrate the potential and benefits of spectral ray files in general.
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37

Zhu, Yuteng, and Graham D. Finlayson. "A Mathematical Investigation into the Design of Prefilters That Make Cameras More Colorimetric." Sensors 20, no. 23 (December 2, 2020): 6882. http://dx.doi.org/10.3390/s20236882.

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By placing a color filter in front of a camera we make new spectral sensitivities. The Luther-condition optimization solves for a color filter so that the camera’s filtered sensitivities are as close to being linearly related to the XYZ color matching functions (CMFs) as possible, that is, a filter is found that makes the camera more colorimetric. Arguably, the more general Vora-Value approach solves for the filter that best matches all possible target spectral sensitivity sets (e.g., any linear combination of the XYZ CMFs). A concern that we investigate here is that the filters found by the Luther and Vora-Value optimizations are different from one another. In this paper, we unify the Luther and Vora-Value approaches to prefilter design. We prove that if the target of the Luther-condition optimization is an orthonormal basis—a special linear combination of the XYZ CMFs which are orthogonal and are in unit length—the discovered Luther-filter is also the filter that maximizes the Vora-Value. A key advantage of using the Luther-condition formulation to maximize the Vora-Value is that it is both simpler to implement and converges to its optimal answer more quickly. Experiments validate our method.
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38

Bi, Jingran, Chuan Tian, Gong-Liang Zhang, Hongshun Hao, and Hong-Man Hou. "Detection of Histamine Based on Gold Nanoparticles with Dual Sensor System of Colorimetric and Fluorescence." Foods 9, no. 3 (March 9, 2020): 316. http://dx.doi.org/10.3390/foods9030316.

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Gold nanoparticles (Au-NPs), with the dual sensor system of colorimetric and fluorescence responses, were developed for the determination of histamine as a spoilage monitor for distinguishing lifetime and freshness of aquatic products. Upon addition of histamine, the absorption coefficient orders of magnitude via the interaction of free electrons and photons were affected, and the characteristic absorption peak of Au-NPs was red-shifted from 520 nm to 664 nm. Meanwhile, the large amino groups in the networks of histamine-Au-NPs with high molecular orbital exhibited excellent fluorescence behavior at 415 nm. Au-NPs offered a range of 0.001–10.0 μM and 0.01–1.0 μM with a limit of detection of 0.87 nM and 2.04 nM by UV-vis and fluorescence spectrum assay, respectively. Moreover, Au-NPs could be used to semiquantitatively analyze histamine with the naked eye, since the significant colorimetric and fluorescence reaction of Au-NPs solution that coincided with different concentrations of histamine can be observed as the histamine concentration was 0.1–1.0 μM. Both of the dual-sensor systems of Au-NPs were successfully applied to the quantitative analysis of histamine in fresh salmon muscle, suggesting the simplicity and rapidity in the dual detection approaches of Au-NPs might be suitable for spoilage assay of aquatic food to ensure food safety.
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39

Sha, Mizaj Shabil, Muni Raj Maurya, Mithra Geetha, Bijandra Kumar, Aboubakr M. Abdullah, and Kishor Kumar Sadasivuni. "A Smart Colorimetric Platform for Detection of Methanol, Ethanol and Formic Acid." Sensors 22, no. 2 (January 13, 2022): 618. http://dx.doi.org/10.3390/s22020618.

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Carbon dioxide (CO2) is a greenhouse gas in the atmosphere and scientists are working on converting it to useful products, thereby reducing its quantity in the atmosphere. For converting CO2, different approaches are used, and among them, electrochemistry is found to be the most common and more efficient technique. Current methods for detecting the products of electrochemical CO2 conversion are time-consuming and complex. To combat this, a simple, cost-effective colorimetric method has been developed to detect methanol, ethanol, and formic acid, which are formed electrochemically from CO2. In the present work, the highly efficient sensitive dyes were successfully established to detect these three compounds under optimized conditions. These dyes demonstrated excellent selectivity and showed no cross-reaction with other products generated in the CO2 conversion system. In the analysis using these three compounds, this strategy shows good specificity and limit of detection (LOD, ~0.03–0.06 ppm). A cost-effective and sensitive Internet of Things (IoT) colorimetric sensor prototype was developed to implement these dyes systems for practical and real-time application. Employing the dyes as sensing elements, the prototype exhibits unique red, green, and blue (RGB) values upon exposure to test solutions with a short response time of 2 s. Detection of these compounds via this new approach has been proven effective by comparing them with nuclear magnetic resonance (NMR). This novel approach can replace heavy-duty instruments such as high-pressure liquid chromatography (HPLC), gas chromatography (G.C.), and NMR due to its extraordinary selectivity and rapidity.
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40

Török, Zoltan-Mihály, Arthur Frederic Blaser, Kiana Kavianynejad, Carlos Gonzalo Moya Gual de Torrella, Lawrence Nsubuga, Yogendra Kumar Mishra, Horst-Günter Rubahn, and Roana de Oliveira Hansen. "Breath Biomarkers as Disease Indicators: Sensing Techniques Approach for Detecting Breath Gas and COVID-19." Chemosensors 10, no. 5 (April 29, 2022): 167. http://dx.doi.org/10.3390/chemosensors10050167.

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Extensive research shows that there is a close correlation between a disease diagnostic and the patient’s exhale breath gas composition. It has been demonstrated, for example, that patients with a diabetes diagnosis have a certain level of acetone fume in their exhale breath. Actually, symptoms from many other diseases could be easily diagnosed if appropriate and reliable gas sensing technologies are available. The COVID-19 pandemic has created demand for a cheap and quick screening tool for the disease, where breath biomarker screening could be a very promising approach. It has been shown that COVID-19 patients potentially present a simultaneous increase in ethanal (acetaldehyde) and acetone in their exhale breath. In this paper, we explore two different sensing approaches to detect ethanal/acetone, namely by colorimetric markers, which could for example be integrated into facemasks, and by a breathalyzer containing a functionalized quartz crystal microbalance. Both approaches can successfully detect the presence of a biomarker gas on a person’s breath and this could potentially revolutionize the future of healthcare in terms of non-invasive and early-stage detection of various diseases.
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41

Aldewachi, Hasan, Nicola Woodroofe, and Philip Gardiner. "Study of the Stability of Functionalized Gold Nanoparticles for the Colorimetric Detection of Dipeptidyl Peptidase IV." Applied Sciences 8, no. 12 (December 12, 2018): 2589. http://dx.doi.org/10.3390/app8122589.

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In this report, we investigated three stabilization strategies of gold nanoparticles and their practical application for the visual detection of dipeptidyl peptidase IV (DPP-IV). Citrate-capped gold nanoparticles (Au NPs) are generally unstable in high-ionic-strength samples. Au NPs are easily tagged with various proteins and biomolecules rich in amino acids, leading to important biomedical applications including targeted drug delivery, cellular imaging, and biosensing. The investigated assays were based on different modes of stabilization, such as the incorporation of polyethylene glycol (PEG) groups, stabilizer peptide, and bifunctionalization. Although all approaches provided highly stable Au NP platforms demonstrated by zeta potential measurements and resistance to aggregation in a high-ionic-strength saline solution, we found that the Au NPs modified with a separate stabilizer ligand provided the highest stability and was the only platform that demonstrated sensitivity to the addition of DPP-IV, whilst PEGylated and peptide-stabilized Au NPs showed no significant response.
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42

Vуsotska, Olena, Konstantin Nosov, Igor Hnoevyi, Andrii Porvan, Lyubov Rysovana, Alexandr Dovnar, Mikhail Babakov, and Marharyta Kalenichenko. "Image processing procedure for remote recording of the Gambusia sp. introduced into a water for anti-malaria." Technology audit and production reserves 1, no. 2(63) (January 17, 2022): 14–18. http://dx.doi.org/10.15587/2706-5448.2022.252297.

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The object of research is the procedure for processing digital images for remote registration of Gambusia sp., introduced into water bodies to combat malaria, which threatens not only the African region, but also other latitudes of the world. One of the most problematic areas of research is the elimination of the masking effect of a biological object under conditions of interference (for example, water turbidity) that make it difficult to recognize Gambusia sp. on digital images taken from aboard light drones. In the course of the study, approaches were used that allow dividing a digital image into segments and sub-segments, followed by determining the ratio of the colorimetric parameters of the RGB model of the bottom section. Dispersion and correlation analysis of mean values and mean square deviation values of the RGB model parameters were used. The standard deviation was considered as the degree of diversity of colorimetric parameters in the color of a biological object. The proposed procedure made it possible to reveal a moderate negative correlation between the predominance of green and yellow-orange-red phytopigments in the dynamics of the Margalef model of phytocenosis succession in the places of introduction and habitation of Gambusia sp. This is due to the fact that the shielding of phytocenosis areas by Gambusia sp. is reflected in the nature of the relationship of the colorimetric parameters of the RGB model of the bottom area, namely, they affect the correlation between the average values of the parameters G/(R+G+B) and R/G or between the mean value and the standard deviation of the parameter G/(R+G+B). This makes it possible to use Gambusia sp. in regions affected by malaria, a wide range of light drones with remote photofixation of relatively low quality. The implementation of these possibilities will require much less material costs and a small number of personnel than underwater video filming and other known methods for studying the ichthyofauna of small water bodies in conditions of interference. It is about the registration of the results of the introduction of Gambusia sp. in such water bodies to fight malaria.
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43

Politaeva, N. A., I. V. Illin, A. M. Oparina, and A. S. Donetskova. "New energy approaches to the use of waste biosorbents of microalgae Chlorella kessleri (Chlorellaceae, Chlorellales)." Povolzhskiy Journal of Ecology, no. 3 (November 13, 2022): 322–35. http://dx.doi.org/10.35885/1684-7318-2022-3-322-335.

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The use of microalgae Chlorella kessleri VKPM A1-11 ARM (RF, NPO Algobiotechnology) for environmental and energy purposes is considered. The results of our study of the use of C. kessleri microalgae biomass as a biosorbent to purify model wastewater from Cu2+ ions under static conditions are presented. Biosorption is a promising technology for the treatment of industrial effluents containing various heavy metal compounds, but the issues of economic benefits of using biosorbents, their environmental safety and the cost of disposal of used sorbents are subject to much discussion. The paper proposes to dispose the used biosorbent formed after wastewater treatment from copper as an additional fuel. The copper concentration in the filtrate was determined by colorimetric analysis with sodium diethyldithiocarbamate. The cleaning efficiency and sorption capacity of the dry mass of C. kessleri were obtained by calculation. The maximum sorption capacity for Cu2+ ions was 4.2 mg/g. The purification efficiency reached 87% at the initial concentration of Cu2+ ions being 97 mg/l. Tests to estimate the specific heat of combustion of C. kessleri biomass and used biosorbents based thereon were carried out by the calorimetric method using a bomb calorimeter. The specific heats of combustion were 22,125 kJ/kg and 21,674 kJ/kg, respectively. A comparison of these values with traditional energy carriers is given. A technological scheme has been developed for a waste-free cycle of using C. kessleri to treat wastewater from industrial enterprises with the production of several valuable resources as end products, such as purified water, energy resources, fertilizers, and recycled metals. The obtained results of our study can be applied in technologies for post-treatment of wastewater from various industrial enterprises using biological non-waste resources.
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44

Burin, Raquel, and Devendra H. Shah. "Phenelzine and Amoxapine Inhibit Tyramine and d-Glucuronic Acid Catabolism in Clinically Significant Salmonella in A Serotype-Independent Manner." Pathogens 10, no. 4 (April 13, 2021): 469. http://dx.doi.org/10.3390/pathogens10040469.

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Non-typhoidal Salmonella ingeniously scavenges energy for growth from tyramine (TYR) and d-glucuronic acid (DGA), both of which occur in the host as the metabolic byproducts of the gut microbial metabolism. A critical first step in energy scavenging from TYR and DGA in Salmonella involves TYR-oxidation via TYR-oxidoreductase and production of free-DGA via β-glucuronidase (GUS)-mediated hydrolysis of d-glucuronides (conjugated form of DGA), respectively. Here, we report that Salmonella utilizes TYR and DGA as sole sources of energy in a serotype-independent manner. Using colorimetric and radiometric approaches, we report that genes SEN2971, SEN3065, and SEN2426 encode TYR-oxidoreductases. Some Salmonella serotypes produce GUS, thus can also scavenge energy from d-glucuronides. We repurposed phenelzine (monoaminoxidase-inhibitor) and amoxapine (GUS-inhibitor) to inhibit the TYR-oxidoreductases and GUS encoded by Salmonella, respectively. We show that phenelzine significantly inhibits the growth of Salmonella by inhibiting TYR-oxidoreductases SEN2971, SEN3065, and SEN2426. Similarly, amoxapine significantly inhibits the growth of Salmonella by inhibiting GUS-mediated hydrolysis of d-glucuronides. Because TYR and DGA serve as potential energy sources for Salmonella growth in vivo, the data and the novel approaches used here provides a better understanding of the role of TYR and DGA in Salmonella pathogenesis and nutritional virulence.
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45

Rahbar, Mohammad, Siyi Zou, Mahroo Baharfar, and Guozhen Liu. "A Customized Microfluidic Paper-Based Platform for Colorimetric Immunosensing: Demonstrated via hCG Assay for Pregnancy Test." Biosensors 11, no. 12 (November 25, 2021): 474. http://dx.doi.org/10.3390/bios11120474.

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Over the past decades, paper-based lateral flow immunoassays (LFIAs) have been extensively developed for rapid, facile, and low-cost detection of a wide array of target analytes in a point-of-care manner. Conventional home pregnancy tests are the most significant example of LFAs, which detect elevated concentrations of human chorionic gonadotrophin (hCG) in body fluids to identify early pregnancy. In this work, we have upgraded these platforms to a higher version by developing a customized microfluidic paper-based analytical device (μPAD), as the new generation of paper-based point-of-care platforms, for colorimetric immunosensing. This will offer a cost-efficient and environmentally friendly alternative platform for paper-based immunosensing, eliminating the need for nitrocellulose (NC) membrane as the substrate material. The performance of the developed platform is demonstrated by detection of hCG (as a model case) in urine samples and subsequently indicating positive or negative pregnancy. A dual-functional silane-based composite was used to treat filter paper in order to enhance the colorimetric signal intensity in the detection zones of μPADs. In addition, microfluidic pathways were designed in a manner to provide the desired regulated fluid flow, generating sufficient incubation time (delays) at the designated detection zones, and consequently enhancing the obtained signal intensity. The presented approaches allow to overcome the existing limitations of μPADs in immunosensing and will broaden their applicability to a wider range of assays. Although, the application of the developed hCG μPAD assay is mainly in qualitative (i.e., positive or negative) detection of pregnancy, the semi-quantitative measurement of hCG was also investigated, indicating the viability of this assay for sensitive detection of the target hCG analyte within the related physiological range (i.e., 10–500 ng/mL) with a LOD value down to 10 ng/mL.
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46

Baik, Sangyul, Jihyun Lee, Eun Je Jeon, Bo-yong Park, Da Wan Kim, Jin Ho Song, Heon Joon Lee, Seung Yeop Han, Seung-Woo Cho, and Changhyun Pang. "Diving beetle–like miniaturized plungers with reversible, rapid biofluid capturing for machine learning–based care of skin disease." Science Advances 7, no. 25 (June 2021): eabf5695. http://dx.doi.org/10.1126/sciadv.abf5695.

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Recent advances in bioinspired nano/microstructures have received attention as promising approaches with which to implement smart skin-interfacial devices for personalized health care. In situ skin diagnosis requires adaptable skin adherence and rapid capture of clinical biofluids. Here, we report a simple, all-in-one device consisting of microplungers and hydrogels that can rapidly capture biofluids and conformally attach to skin for stable, real-time monitoring of health. Inspired by the male diving beetle, the microplungers achieve repeatable, enhanced, and multidirectional adhesion to human skin in dry/wet environments, revealing the role of the cavities in these architectures. The hydrogels within the microplungers instantaneously absorb liquids from the epidermis for enhanced adhesiveness and reversibly change color for visual indication of skin pH levels. To realize advanced biomedical technologies for the diagnosis and treatment of skin, our suction-mediated device is integrated with a machine learning framework for accurate and automated colorimetric analysis of pH levels.
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47

Gong, Zhaoyuan, Hiu Ting Chan, Qilei Chen, and Hubiao Chen. "Application of Nanotechnology in Analysis and Removal of Heavy Metals in Food and Water Resources." Nanomaterials 11, no. 7 (July 9, 2021): 1792. http://dx.doi.org/10.3390/nano11071792.

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Toxic heavy metal contamination in food and water from environmental pollution is a significant public health issue. Heavy metals do not biodegrade easily yet can be enriched hundreds of times by biological magnification, where toxic substances move up the food chain and eventually enter the human body. Nanotechnology as an emerging field has provided significant improvement in heavy metal analysis and removal from complex matrices. Various techniques have been adapted based on nanomaterials for heavy metal analysis, such as electrochemical, colorimetric, fluorescent, and biosensing technology. Multiple categories of nanomaterials have been utilized for heavy metal removal, such as metal oxide nanoparticles, magnetic nanoparticles, graphene and derivatives, and carbon nanotubes. Nanotechnology-based heavy metal analysis and removal from food and water resources has the advantages of wide linear range, low detection and quantification limits, high sensitivity, and good selectivity. There is a need for easy and safe field application of nanomaterial-based approaches.
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48

Svoboda, Petr, David Kostal, Ivan Křupka, and Martin Hartl. "Study of Scale Effect in a Starved Elastohydrodynamically Lubricated Contact." Applied Mechanics and Materials 821 (January 2016): 138–43. http://dx.doi.org/10.4028/www.scientific.net/amm.821.138.

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The article describes an experimental investigation of scale effect in a starved elastohydrodynamically lubricated contact on lubricant film thickness. Lubricant film thickness and its distribution is one of the most important parameters determining the performance and life of machine parts. Current experimental and numerical studies are mostly connected with oil lubrication. However, greases are used in more than 80 % of all rolling bearings where the starvation phenomenon occurs most frequently. The aim of this work is to compare two approaches to measuring film thickness of different greases. The use of multiple contacts optical test rig based on thin film colorimetric interferometry for film thickness measurement has enables to obtain film thickness of starved contact and the film distribution. The experimental observation of full-scale model of bearing will help to understand better the behavior of real bearing. The evaluation of the experiment was made by chromatic interferometry. This method is used to measure thin lubrication films.
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49

Ebner, Katharina, Lukas J. Pfeifenberger, Claudia Rinnofner, Veronika Schusterbauer, Anton Glieder, and Margit Winkler. "Discovery and Heterologous Expression of Unspecific Peroxygenases." Catalysts 13, no. 1 (January 16, 2023): 206. http://dx.doi.org/10.3390/catal13010206.

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Since 2004, unspecific peroxygenases, in short UPOs (EC. 1.11.2.1), have been explored. UPOs are closing a gap between P450 monooxygenases and chloroperoxidases. These enzymes are highly active biocatalysts for the selective oxyfunctionalisation of C–H, C=C and C-C bonds. UPOs are secreted fungal proteins and Komagataella phaffii (Pichia pastoris) is an ideal host for high throughput screening approaches and UPO production. Heterologous overexpression of 26 new UPOs by K. phaffii was performed in deep well plate cultivation and shake flask cultivation up to 50 mL volume. Enzymes were screened using colorimetric assays with 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (DMP), naphthalene and 5-nitro-1,3-benzodioxole (NBD) as reporter substrates. The PaDa-I (AaeUPO mutant) and HspUPO were used as benchmarks to find interesting new enzymes with complementary activity profiles as well as good producing strains. Herein we show that six UPOs from Psathyrella aberdarensis, Coprinopsis marcescibilis, Aspergillus novoparasiticus, Dendrothele bispora and Aspergillus brasiliensis are particularly active.
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50

Arias-Alpízar, Kevin, Ana Sánchez-Cano, Judit Prat-Trunas, Elena Sulleiro, Pau Bosch-Nicolau, Fernando Salvador, Inés Oliveira, Israel Molina, Adrián Sánchez-Montalvá, and Eva Baldrich. "Magnetic Bead Handling Using a Paper-Based Device for Quantitative Point-of-Care Testing." Biosensors 12, no. 9 (August 25, 2022): 680. http://dx.doi.org/10.3390/bios12090680.

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Microfluidic paper-based analytical devices (μPADs) have been extensively proposed as ideal tools for point-of-care (POC) testing with minimal user training and technical requirements. However, most μPADs use dried bioreagents, which complicate production, reduce device reproducibility and stability, and require transport and storage under temperature and humidity-controlled conditions. In this work, we propose a μPAD produced using an affordable craft-cutter and stored at room temperature, which is used to partially automate a single-step colorimetric magneto-immunoassay. As a proof-of-concept, the μPAD has been applied to the quantitative detection of Plasmodium falciparum lactate dehydrogenase (Pf-LDH), a biomarker of malaria infection. In this system, detection is based on a single-step magneto-immunoassay that consists of a single 5-min incubation of the lysed blood sample with immuno-modified magnetic beads (MB), detection antibody, and an enzymatic signal amplifier (Poly-HRP). This mixture is then transferred to a single-piece paper device where, after on-chip MB magnetic concentration and washing, signal generation is achieved by adding a chromogenic enzyme substrate. The colorimetric readout is achieved by the naked eye or using a smartphone camera and free software for image analysis. This μPAD afforded quantitative Pf-LDH detection in <15 min, with a detection limit of 6.25 ng mL−1 when the result was interpreted by the naked eye and 1.4 ng mL−1 when analysed using the smartphone imaging system. Moreover, the study of a battery of clinical samples revealed concentrations of Pf-LDH that correlated with those provided by the reference ELISA and with better sensitivity than a commercial rapid diagnostic test (RDT). These results demonstrate that magneto-immunoassays can be partly automated by employing a μPAD, achieving a level of handling that approaches the requirements of POC testing.
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