A Suitable Immunosensor for Chloramphenicol Determination: Study of Two Different Competitive Formats

Abstract

Background: deep analytical study was performed on two different formats based on a “competitive” ELISA-type assay to develop a suitable, sensitive and cheap immune device for chloramphenicol determination that could be advantageously applied to the analysis of real matrices (pharmaceutical, food and environmental). Methods: To this purpose peroxidase enzyme as a marker and an amperometric electrode for hydrogen peroxide, as a transducer, were used. Through the first competitive format, chloramphenicol determination was based on the competition between chloramphenicol and conjugated with biotin-avidinperoxidase chloramphenicol, both free in solution, for anti-chloramphenicol immobilized in the membrane, while the second competitive format was based on the competition between free in solution chloramphenicol and immobilized in membrane one, for anti-chloramphenicol biotin-avidin-peroxidase conjugated free in solution. Results: The immunosensor was optimized by comparing the two used different “competitive” working formats on the basis of respective Kaff values, that were found to be about 105 and 104 (mol L-1)-1. The developed immune device displayed good selectivity for Chloramphenicol and LOD (limit of detection) was of the order of 10-9 mol L-1. The immunosensor was also used to test the presence of Chloramphenicol in real matrices such as cow milk, river wastewater and pharmaceutical formulations; recovery tests, using the standard addition method, gave satisfactory results. Conclusion: The results proved the validity of this immune device based on the competition between chloramphenicol and conjugated chloramphenicol obtained using biotin-avidin-peroxidase format, by which it is possible to carry out the analysis of chloramphenicol in milk and in river waste-waters with a % RSD ≤ 5 and with recovery values between 96% and 103%.

A Direct Catalytic Ethanol Fuel Cell (DCEFC) Modified by LDHs, or by Catalase-LDHs, and Improvement in Its Kinetic Performance: Applications for Human Saliva and Disinfectant Products for COVID-19

“…A series of applications, in previous research, was carried out by employing a non-modified fuel cell on real matrices, consisting of alcoholic beverages, such as different types of wines, beers, and spirits, or drugs (hydroalcoholic extracts, etc. ), containing significant percentages of ethanol [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In the present work, the development of modified fuel cells, especially enzymatic, based on catalase immobilization on LDHs through adsorption and crosslinking mechanisms, ensured not only a considerable operational duration greater than at least one month but also a considerable increase in the calibration sensitivity by almost 8-times compared to the simple unmodified fuel cell, as mentioned in the previous paragraph.…”

“…In recent years, a certain number of studies, based on LDHs of the type (Zn II ,Al III (OH) 2 ) + NO 3 − ·H 2 O, were conducted by our research group, obtaining good results, especially from an analytical point of view [ 9 , 10 , 11 , 12 ]. Furthermore, encouraging results have been obtained, both analytical, e.g., on alcoholic drinks, beverages [ 13 , 14 , 15 ], drugs, or pharmaceutical formulations [ 16 , 17 , 18 , 19 , 20 , 21 ], and also for energy purposes with the use of glucose and carbohydrates [ 15 , 22 ] by means of a simple and inexpensive DCEFC. We, therefore, came up with the idea of trying to accelerate the catalytic reaction of our fuel cell by inserting our previously used LDHs, housed inside a small dialysis tube, into the anodic section of the fuel cell (already containing metals, such as Pt and Ru) [ 9 , 10 , 11 ]), as already carried out by our team but using an enzyme instead of LDHs [ 14 ].…”

“…We, therefore, came up with the idea of trying to accelerate the catalytic reaction of our fuel cell by inserting our previously used LDHs, housed inside a small dialysis tube, into the anodic section of the fuel cell (already containing metals, such as Pt and Ru) [ 9 , 10 , 11 ]), as already carried out by our team but using an enzyme instead of LDHs [ 14 ]. In other words, the basic idea is to realize an extremely simple and inexpensive device, starting from the same fuel cell already used in previous works, without essential modifications [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. However, in this case, we operated in open-circuit mode, rather than in a potentiostatic way, since this mode has two undoubted advantages: firstly, it proved to be very reproducible and, secondly, the method does not necessarily require one to determine the Optimized Applied Potential (OAP) [ 13 , 23 , 24 ].…”

Sensitive Portable Electrochemical Sensors for Antibiotic Chloramphenicol by Tin/Reduced Graphene Oxide-Modified Screen-Printed Carbon Electrodes

“…Therefore, an accurate and rapidly sensitive CAP determination method is required for monitoring the trace level of CAP, which leads to the development of various analytical methods for assessing the CAP quantity. High-performance liquid chromatography, 17 liquid chromatography-mass spectrometry, 18 gas chromatography, 19 gas chromatography-mass spectrometry, 20 fluorescence spectrophotometry, 21 surface-enhanced Raman scattering, 22 colorimetry, 23 and immunosensor 24 techniques provide reliable and accurate results for qualitative and quantitative analysis. However, these techniques involve complicated sample preparation and data analysis, high cost of instruments, and long response time.…”