An enzymatic assay of chloramphenicol coupled with fluorescence reaction

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

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 rapid fluorescence detecting platform: applicable to sense carnitine and chloramphenicol in food samples

A new long-wavelength latent florescent probe, termed “BCC” for sensitive determination of coenzyme A, carnitine and chloramphenicol.

Extraction and determination of chloramphenicol in feed water, milk, and honey samples using an ionic liquid/sodium citrate aqueous two-phase system coupled with high-performance liquid chromatography

A green, simple, non-toxic, and sensitive sample pretreatment procedure coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of chloramphenicol (CAP) that exploits an aqueous two-phase system based on imidazolium ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim]BF(4)) and organic salt (Na(3)C(6)H(5)O(7)) using a liquid-liquid extraction technique. The influence factors on partition behaviors of CAP were studied, including the type and amount of salts, the pH value, the volume of [Bmim]BF(4), and the extraction temperature. Extraction efficiency of the CAP was found to increase with increasing temperature and the volume of [Bmim]BF(4). Thermodynamic studies indicated that hydrophobic interactions were the main driving force, although electrostatic interactions and salting-out effects were also important for the transfer of the CAP. Under the optimal conditions, 90.1% of the CAP could be extracted into the ionic liquid-rich phase in a single-step extraction. This method was practical when applied to the analysis of CAP in feed water, milk, and honey samples with a linear range of 2~1,000 ng mL(-1). The method yielded a limit of detection of 0.3 ng mL(-1) and a limit of quantification of 1.0 ng mL(-1). The recovery of CAP was 90.4-102.7% from aqueous samples of real feed water, milk, and honey samples by the proposed method. This novel process is much simpler and more environmentally friendly and is suggested to have important applications for the separation of antibiotics.

Molecularly imprinted polymer microspheres for solid-phase extraction of chloramphenicol residues in foods

Preparation of molecularly imprinted polymer microspheres (MIPMs) for chloramphenicol (CAP) by aqueous suspension polymerization is reported for the first time in this study. The resulting MIPMs had the ability to specifically adsorb CAP, and the molecularly imprinted solid phase extraction (MISPE) based on the MIPMs was shown to be applicable for clean-up and preconcentration of trace CAP in milk and shrimp samples with high recoveries of 92.7% and 84.9%, respectively. Combined with MISPE, the conventional HPLC-UV analysis sensitivity for CAP in foods could be significantly increased.

Fluorogenic and fluorescent labeling reagents with a benzofurazan skeleton

Fluorogenic and fluorescent labeling reagents having a benzofurazan (2,1,3-benzoxadiazole) skeleton such as 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), 4-N,N-dimethylaminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (DBD-F), 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (ABD-F), ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), 4-hydrazino-7-nitro-2,1,3-benzoxadiazole (NBD-H), 4-N,N-dimethylaminosulfonyl-7-hydrazino-2,1,3-benzoxadiazole (DBD-H), 4-nitro-7-N-piperazino-2,1,3-benzoxadiazole (NBD-PZ), 4-N,N-dimethylaminosulfonyl-7-N-piperazino-2,1,3-benzoxadiazole (DBD-PZ), 4-(N-chloroformylmethyl-N-methyl)amino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole (DBD-COCl) and 7-N,N-dimethylaminosulfonyl-4-(2,1,3-benzoxadiazolyl) isothiocyanate (DBD-NCS) are reviewed in terms of synthetic method, reactivity, fluorescence characteristics, sensitivity and application to analytes.

On-column derivatization for the analysis of homocysteine and other thiols by capillary electrophoresis with laser-induced fluorescence detection

On-column derivatization and capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection has been developed for the fully automated assay of homocysteine and other thiols. The unique feature of this CE technique comes from the direct injection of a sample including homocysteine, enabling the derivatization with 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadizole (ABD-F) to be accomplished in the capillary. After the derivatization for 10 min at 50 degrees C, the homocysteine was analyzed within 7 min under an applied electric field of 333 V cm(-1). The detection limit obtained for homocysteine with on-column LIF detection was 5.0 nM, as compared to 2.5 nM with pre-column LIF detection. The method is a very simple, fast, and practical approach for the fully automated assay of homocysteine and other thiols contained in low-volume and low-concentration samples.

Fluorometric microassays for the determination of cathepsin L and cathepsin S activities in tissue extracts

We established a continuous semi-microassay, and for large-scale studies both a stopped and a continuous microtiter plate assay for the fluorometric determination of cathepsin L and cathepsin S activities in body fluids, tissues or cell extracts in the presence of cathepsin B. For the detection of enzymatic activities we used the synthetic substrate Z-Phe-Arg-AMC, and for discrimination between cathepsin L, S and cathepsin B the specific inhibitor CA-074 for blocking interfering cathepsin B activities was applied. Furthermore, we took advantage of the stability of cathepsin S at pH 7.5 for further differentiation between cathepsin L and cathepsin S activities. The kinetic assays were characterized in terms of imprecision, analytical sensitivity, accuracy and substrate concentration. The within-run coefficients of variation were found to be 4.9%-7.2% for the continuous semi-microassay, 10.3%-11.7% for the stopped, and 4.5%-11.8% for the continuous microtiter plate assay. The between-days coefficients of variation for the continuous semi-microassay were 8.1%-8.9%, while for the stopped and continuous microtiter plate assays the coefficients were 11.2%-13.5% and 5.8%-12.2%, respectively. Compared to the continuous semi-microassay, the stopped and the continuous microtiter plate assays showed 3-fold and 11-fold higher sensitivity, respectively. Comparison between the continuous enzyme activity assays at substrate concentrations of 40 microM and 200 microM demonstrated a significant correlation of r = 0.97 and r = 0.99, respectively. The newly developed microtiter plate assay will allow efficient, sensitive and high precision determination of cathepsin L and cathepsin S activities in large-scale studies of cysteine-cathepsin dependent diseases.

Antihyperglycemic activities of cryptolepine analogues: an ethnobotanical lead structure isolated from Cryptolepis sanguinolenta

Cryptolepine (1) is a rare example of a natural product whose synthesis was reported prior to its isolation from nature. In the previous paper we reported the discovery of cryptolepine's antihyperglycemic properties. As part of a medicinal chemistry program designed to optimize natural product lead structures originating from our ethnobotanical and ethnomedical field research, a series of substituted and heterosubstituted cryptolepine analogues was synthesized. Antihyperglycemic activity was measured in vitro and in an NIDDM mouse model to generate the first structure-bioactivity study about the cryptolepine nucleus.

Determination of homocysteine and other thiols in human plasma by capillary electrophoresis

A new capillary electrophoresis (CE) assay for thiols in human plasma, including homocysteine, which is an indicator of several clinical states has been developed. The thiols were derivatized quantitatively at 50 degrees C, pH 8.0 with a fluorogenic reagent, ADB-F (4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole), which is about 30 times faster compared to the other fluorogenic reagent, SBD-F (ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate). The separation of ABD-thiols was performed in a 50 mM sodium phosphate buffer (pH 2.1) using a bare fused silica capillary (27 cm x 50 microns i.d.) at 25 degrees C. With the electric field of 560 V cm-1, the time needed for the separation of homocysteine, glutathione and cysteine was less than 8 min. A filter-type ultraviolet detector and a 512-channel diode-array detector (DAD) were employed for ABD-thiol analysis. DAD was used to confirm the ABD-thiol peaks. The limits of detection (S/N = 3) for homocysteine, glutathione, and cysteine were 0.5, 1 and 2 microM at 220 nm, respectively.

Derivatization of thiol-containing compounds

The determination of thiol-containing compounds in biological fluids is important in biochemistry and clinical chemistry. In this paper, derivatization reagents for thiols are reviewed with respect to their reactivity, selectivity, spectroscopic characteristics and their applicability especially to high-performance liquid chromatography. Derivatization used in ultraviolet and electrochemical detection. The derivatization reagents contain a functional group, e.g. an N-substituted maleimide, active halogen or aziridine, which react with the thiol group. Derivatization for use in flow injection analysis, thin-layer chromatography or gas chromatography-mass spectrometry is also described.