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Lab-on-a-Chip-Based Devices for Rapid and Accurate Measurement of Nanomaterial Toxicity
Published in Suresh C. Pillai, Yvonne Lang, Toxicity of Nanomaterials, 2019
Mehenur Sarwar, Amirali Nilchian, Chen-zhong Li
Two optical detection methods which are commonly used include colorimetry and fluorescence. In colorimetry, a biochemical interaction results in a reaction product which absorbs light in a specific wavelength. This leads to it appearing to the naked eye as a unique colour. On the other hand, in a fluorescence event the reaction compound absorbs light in the non-visible range and then emits light at a higher wavelength due to radiative relaxation.
Spectroscopy and Fluorimetry
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
It has been stated that direct measurement of the UV-visible absorption spectrum is of little help as a qualitative test for drugs in biological fluids because these spectra are very similar for compounds having the same chromophores. However, there is a considerable body of literature (especially in forensic toxicology) on spot tests for the identification of drugs in body fluids327 (Table 4.3). Some of these tests involve a chemical reaction producing very specific colors, and can be adapted for qualitative analysis of the drugs by measuring the change in absorption in the visible region. This process is generally termed colorimetry, although the qualitative step is exactly the same as for the ultraviolet spectroscopic methods already described. Some typical colorimetric assays are described below and a comprehensive list is shown in Table 4.4. Because many colorimetric spot tests are very dependent on such factors as pH, temperature, and time, these parameters are very critical in the development and application of quantitative colorimetric assays.
In vitro and molecular docking studies on a novel Brevibacillus borstelensis NOB3 bioactive compounds as anticancer, anti-inflammatory, and antimicrobial activity
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Hend A. Hamedo, Aya A. Elkashef, Mohamed A. I. Mansour, Naglaa Elshafey
The effect of bioactive compounds extracted from B. borstelensis NOB3 on cancer cell viability was determined by an MTT assay against cervical HeLa cells. The mitochondrial succinate dehydrogenase enzyme converts MTT into insoluble formazan crystals (purple), which are then solubilized by DMSO and evaluated spectrophotometrically. This assay is based on colorimetry. This assay is frequently utilized to determine cell viability and to evaluate the cytotoxic effects of medicines on cell lines in vitro since a decrease shown by the MTT can only occur in metabolically active cells. The outcomes demonstrated that B. borstelensis NOB3 ethyl acetate extracts had promising antitumor efficacy against cervical HeLa cells. HeLa cells were cultivated in a 96-well plate at different extract dosages, and viability rates were measured following exposure to the extract to ascertain the degree of inhibition of HeLa cell proliferation. The ethyl acetate extract of B. borstelensis contained 62.5 g/ml of cell-free NOB3, which decreased the viability of HeLa cells by 37.5%, as shown in Figure 9 In addition, as the extract concentration increased, the cell viability dropped sharply, as demonstrated in Figure 10 Based on these findings, the IC50 value for inhibiting the availability of the HeLa cell line was 68.46 g/ml.
Recent advances in electrochemical and optical sensing of the organophosphate chlorpyrifos: a review
Published in Critical Reviews in Toxicology, 2022
Athira Sradha S, Louis George, Keerthana P, Anitha Varghese
Colorimetric sensors are governed by the principle of change in color due to a physical or chemical change in the environment. Popular approaches used in colorimetric sensing of CP often include the use of AuNPs as colorimetric probe as they are capable of exhibiting different colors depending on their several conditions. The primary principle involved relies on the change in color of AuNPs under dispersed and aggregated conditions. A colorimetric aptasensor developed using AuNPs, CP specific aptamer and polyethyl-eneimine (PEI), functions on this principle. In the absence of CP, the CP specific aptamer binds to PEI via electrostatic interactions and this causes the AuNPs to remain dispersed and their color remains red. However, in presence of CP since the aptamer binds to CP, there is sufficient quantity of PEI to induce aggregation of AuNPs causing the color to change from red to blue. The aggregation of the citrated-AuNPs were caused due to the electrostatic interactions between the amine functional groups of PEI and citrate ions of the AuNPs (Soongsong et al. 2021).
Smartphone technology facilitates point-of-care nucleic acid diagnosis: a beginner’s guide
Published in Critical Reviews in Clinical Laboratory Sciences, 2021
Vinoth Kumar Rajendran, Padmavathy Bakthavathsalam, Peter L. Bergquist, Anwar Sunna
A large number of pyrophosphate ions that can chelate metal ions are produced during LAMP-based DNA amplification, leaving the calcein free to emit fluorescence as a proxy for hydrogen ions [117]. Hydrogen ions released during amplification change the pH of the solution, and pH-sensitive dyes like phenol red, neutral red and m-Cresol purple can be used as colorimetric reporters for the detection of PCR [118]. In another approach, oligonucleotides labeled with gold nanoparticles can be added at the end of amplification to produce a visual color change [119]. Colorimetric methods that rely on visual inspection of color change provide a qualitative yes/no result. Smartphone capabilities can be utilized to capture the images in RGB (red, green, blue) format and obtain the pixel intensity of each RGB channel [120]. The intensity analysis allows better quantitative characterization of the colorimetric signal. The intensity of color change is correlated to the concentration of pathogen using the smartphone image analysis tool. Gold nanoparticle-based colorimetric detection of DNA was achieved using a digital lock-in amplifier within a smartphone [121]. In this approach, the audio jack was used as a detector and drove the laser diode to achieve improved and sensitive detection. Digital lock-in, amplifier-based colorimetric detection had a detection limit of 0.77 nmol of DNA which was 5.7 times better than a laboratory grade ultraviolet-visible spectrophotometer.