Evaluation of Various Factors Affecting Fluorescence Emission Behavior of Ochratoxin A: Effect of pH, Solvent and Salt Composition
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2018, Vol 10, Issue 4
Abstract
In the present work, a design of customized portable fluorescence imaging system was developed (in-house) to quantify the change in fluorescence emission of fungal toxin ochratoxin A (OTA). OTA is naturally fluorescent, and the fluorescence properties of OTA solutions depend on the pH, solvent polarity and the presence of ligand molecule. In this work, the influence of solvent, pH and salt concentration on OTA fluorescence emission was investigated. The fluorescence properties of OTA in aqueous solutions have been investigated by means of steady-state fluorescence at different pH (range 6.8-8.4), Na+ salt ranges from 10 120mM, buffer solutions and in organic solvents. All the fluorescence measurements were performed through the fluorescence imaging system consists of an ultraviolet light at 365nm and a CMOS sensor controlled by an executable interface designed in MATLAB. The obtained image is decomposed into its red, green and blue component (RGB components) and analyzed. For each solution, spiked at a concentration of 20 ^g L-1 OTA with different conditions (pH, solvent and salt composition), the red, green and blue (RGB) coordinates were obtained and plotted to quantify the effect of the fluorescence emitted by the OTA. The higher fluorescence yielding conditions were identified and results were compared with the commonly used fluoroskan microplate reader. The developed design of fluorescence instrument was successfully employed to study of fluorescence behavior of OTA in different environments. As a potential, the proposed design instrument could be employed to quantify the fluorescence behavior of fluorescence exhibiting target molecules. Mycotoxins are the secondary metabolites, which are produced by the several fungal species belonging to the family of Aspergillus, Fusarium, Penicillum [1,2]. Among them, the Aspergillus ochraceus and Penicillium citrinum are the main producers of ochratoxin A (OTA), which is the most widely occurring fungal toxin. Biosynthetically, OTA is the pentaketide derived from the dihydrocoumarins coupled to β-phenylalanine i.e. (S)-2-((R)-5- chloro-8-hydroxy-3-methyl-1-oxoisochroman-7-carboxamido)-3 phenylpropanoic acid (Figure 1) and as contaminant, present in the varieties of foodstuffs and beverages such as cereals, spices, wine grapes [3,4]. The presence of OTA in animal tissue, human blood and milk increases the risk of nephrotoxicity, immunosuppressant, teratogenicity [5,6]. Recently, the International Agency for Research on Cancer (IARC) has been classified the OTA in group 2B (possible carcinogenic agent in human). The maximum residue limit (MRL) for OTA has been set by the European Community in several foodstuffs such as the MRL of OTA in wine is 2μg kg -1 or 5μg kg'1 in unprocessed cereal (European Commission 2006 [7]). Moreover, due to the chronic cases and occurrence of OTA incidences and exposure from contaminated food, there is a need to develop a faster, sensitive, robust and portable method for quantification of OTA. Chromatographic methods, such as high-performance liquid chromatography [8] and thin-layer chromatography [9], are the mainly used for OTA determination. Recently, the advancement in OTA detection methods is based on electropolymerization [10], surface plasmon resonance [11] aptasensors [12,13] utilizing electrochemical and fluorescence- based signal generating principle. Among all, the fluorescence based detection methods gained significant attention due to the ease of reaction, label free detection, diverse measurement methods [14]. The intrinsic fluorescence emission behavior, intensity and sensitivity of the analytical method strongly depends on solution composition, such as concentration and buffer ions, pH of solvent, aqueous-organic phase ratio, temperature etc [14]. Based on the above assumption, in the present work the focus of study was to quantify the effect of pH, solvent composition and temperature variables on the fluorescence emission behavior of OTA by exploration of designing a field portable fluorescence measuring platform. The present results strongly suggested the potential of designed instrument as a portable and affordable cost- effective system for rapid screening and quantification of OTA in real samples. Based on our results, as a generalized fluorescence measuring platform, the proposed platform can be further employed for other target analyte poses fluorescence behavior or in fluorescence-based sensing platforms.
Authors and Affiliations
Atul Sharma, Diana Bueno, Sunil Bhand, Jean Louis Marty, Roberto Muñoz
Keywords
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- EP ID EP588411
- DOI 10.26717/BJSTR.2018.10.001979
- Views 143
- Downloads 0
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