A sensitive analysis of sulfadimethoxine using an AuNPs/Ag-GO-Nf-based electrochemical immunosensor

Journal of Solid State Electrochemistry - Herein, a strategy was put forward for high-sensitive detection of sulfadimethoxine (SDM) using a label-free electrochemical immunosensor....     

Organic solvents-free technique for determining sulfadimethoxine and its metabolites in chicken meat

A quick and cost-effective technique of sample preparation followed by a reversed-phase high performance liquid chromatography under "organic solvent-free" (=100% aqueous) conditions for the simultaneous quantifying of sulfadimethoxine (SDM) and its metabolites, 6-hydroxy SDM (6-OH) and N(4)-acetyl SDM (N(4)-Ac), in chicken muscle is presented. Analysis by HPLC with photo-diode array detector was performed using a short C1 column with an isocratic 0.04 mol/l citric acid mobile phase. The method was validated by the analyses of spiked chicken muscle samples, resulting recoveries (> or =84%; relative standard deviations < or =6%), analytical total time (<1/2 h/sample, where a batch of 12 samples in 4 h), and limits of quantitation (< or =0.1 microg/g). The decision limits and detection capability were 0.019-0.106 and 0.054-0.112 microg/g, respectively. No organic solvents were used at all.     

SERS detection of ceftriaxone and sulfadimethoxine using copper nanoparticles temporally protected by porous calcium carbonate

The authors describe a new composite based on SERS-active copper nanoparticles (CuNPs; 10?±?2 nm) incorporated into calcium carbonate microspheres (CaCO₃-CuNPs; 3.4?±?0.3 μm). The CaCO₃ coating acts as a temporal protector of CuNPs against oxidation. Incorporated CuNPs have significantly improved stability during storage and a month-long shelf lifetime. The composite was used for SERS detection of rhodamine 6G and two antibacterial drugs (ceftriaxone and sulfadimethoxine). Two analytical formats, one with and one without solid phase extraction, are introduced to demonstrate the flexibility of the method. Both formats imply the dissolution of CaCO₃ matrix before SERS analysis to release CuNP used as SERS substrate. The study of the influence of pH value and acid nature on the SERS signal demonstrated that HCl is the most efficient candidate to release the CuNPs. Sensitivity (expressed as LOD) is shown to be improved by more than one order when solid phase extraction is used. The average SERS enhancement factor is 10^7 which makes the material efficiency comparable to the one of silver nanoparticles. The LOD (<5 μM), precision (RSDs between 20 and 24% at LOD levels), and trueness (apparent recoveries 84–113%) for the two antibiotics (ceftriaxone and sulfadimethoxine) make the method quite useful for quantitative analysis and therapeutic drug monitoring at physiologically relevant concentrations.

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Graphical abstract A composite with temporally stable copper nanoparticles was synthesized, studied, and used for SERS detection of two antibacterial drugs. The analytical efficiency of the composite was found appropriate for quantitative analysis due to Raman enhancement comparable with silver nanostructures.

     

pH-Sensitivity and pH-dependent structural change in polymeric nanoparticles of poly(vinyl sulfadimethoxine)-deoxycholic acid conjugate

pH-Sensitive nanoparticles of poly(vinyl sulfadimethoxine) (PSDM)-deoxycholic acid (DOCA) conjugates were prepared by dialysis at pH 9.0. The average size and the critical aggregation concentration (CAC) of the nanoparticles were 340 nm and 2.5 × 10⁻¹ g/l, respectively. The CAC decreased with decreasing pH as a result of the increase in the hydrophobic nature of the PSDM. Nanoparticle aggregation was observed at pHs ranging from 6.6 to 7.2. The photophysical characteristics of the nanoparticles were examined using a fluorescence probe technique. The microviscosity in the nanoparticle core was measured by 1,6-diphenyl-1,3,5-hexatriene (DPH). The microviscosity changed significantly with decreasing pH from 8.0 to 6.8, indicating a decrease in the rigidity of the inner cores. One interesting feature was that the microviscosity increased sharply at pHs below 6.8. This suggests that in this pH range most of the PSDM became deionized, which caused the reconstitution of new hydrophobic domains inside the nanoparticles.     

Rapid high-performance liquid chromatographic determining technique of sulfamonomethoxine, sulfadimethoxine, and sulfaquinoxaline in eggs without use of organic solvents

A determining technique of sulfonamides (SAs) (sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and sulfaquinoxaline (SQ)) in eggs, without use of organic solvents, is developed utilizing a high-performance liquid chromatography (HPLC) interfaced with a photo-diode array detector. The sample preparation was performed by homogenizing with perchloric acid solution using a handy ultrasonic-homogenizer followed by a centrifugal ultra-filtration unit. An analytical column and an isocratic mobile phase for HPLC are a reversed-phase C₄ column ( mm i.d.) and 0.18 mol l⁻¹ citric acid solution, respectively. The proposed technique was shown to be linear (r>0.998) over the concentration range 0.1-2.0 μg g⁻¹. Average recoveries of three SAs (spiked 0.05, 0.1, 0.15, and 0.2 μg g⁻¹) ranged from 80.3 to 88.4%, with relative standard deviations (R.S.D.s) between 3.4 and 5.8%. The practical detection limits and total time required for the analysis of one sample were < 0.05 μg g⁻¹ and <30 min, respectively. In all the processes, no organic solvents were used at all.     

Demethylation reactions of 4-amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzenesulfonamide (sulfadimethoxine) in strongly basic aqueous solution

Hydrolysis of 1 in strongly basic aqueous solution afforded mono- and didemethylated products 2,3 and 4 , that are postulated as the metabolites of 1 in some animals. This hydrolytic demethylation was shown to proceed stepwise via mono-demethylation to give 2 and 3 , followed by their further demethylation to 4 . The hydrolytic reactivity of 1–3 was rationalized based on MO calculation results and ¹³C nmr data.     

Application of shielded column liquid chromatography for determination of sulfamonomethoxine, sulfadimethoxine, and their N4-acetyl metabolites in milk

A hazardous-chemical free method for simultaneous determination of sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and their N4-acetyl metabolites in raw milk using shielded column liquid chromatography is developed. The target analytes are extracted by mixing with ethanol-acetic acid (97:3, v/v) followed by centrifugation. The procedure uses a Hisep shielded hydrophobic phase (SHP) column, isocratic elution with 0.1% acetic acid solution (pH 3.1, in water)-ethanol (75:25, v/v), and a photo-diode array detector. Average recoveries from samples spiked at 25-500 ng/ml for each drug were >81% with relative standard deviations within 5%. The limits of quantitation were <25 ng/ml.     

Effect of pH and small inorganic ions on binding of sulfadimethoxine and sulfaphenazole to human serum albumin measured by circular dichroism

The binding of sulfadimethoxine and sulfaphenazole to human serum albumin (HSA) has been shown by circular dichroism measurements to be dependent on the N-B transition. The secondary drug binding sites were found to be optically active in the B conformation form in HSA but optically inactive in the N form. Moreover, the drug-HSA interaction in Tris-HCl buffer seems to be more sensitive to the conformational change in HSA, compared with that in the phosphate buffer.     

Aptamer based photometric assay for the antibiotic sulfadimethoxine based on the inhibition and reactivation of the peroxidase-like activity of gold nanoparticles

It is known that gold nanoparticles (AuNPs) possess peroxidase-like activity. They can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine by H₂O₂ which leads to a color change from red to blue. It is shown here that the peroxidase-like activity of AuNPs can be inhibited by passivating its surface passivation with a ssDNA aptamer against sulfadimethoxine. If, however, the target molecule (sulfadimethoxine) is present, the aptamer is desorbed from the AuNPs surface, and this results in the reactivation of the catalytic property of the AuNPs. The color change of the solution (from purple to blue) is related to the analyte concentration, and this can be judged visually or by UV-visible absorptiometry at 650 nm. The assay, under optimized conditions, has a detection limit of 10 ng·mL^?1 of sulfadimethoxine, and the calibration plot is linear over a rather wide concentration range (0.01–1000 μg·mL^?1). The assay can be performed within <15 min, is sensitive, and therefore is well suited for fast screening in food analysis. Conceivably, it can be extended to many other small analytes for which aptamers are available.

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Graphical abstract Aptamer based photometric assay for sulfadimethoxine(SDM) based on the inhibition and reactivation of the peroxidase-like activity of gold nanoparticles (AuNPs) was performed with a rather wide linear range (0.01–1000 μg?mL^?1) and low detection limit of 10 ng?mL^?1.

     

Characterization of binding sites for sulfadimethoxine and its major metabolite, N4-acetylsulfadimethoxine, on human and rabbit serum albumin

In order to gain an understanding of protein binding of sulfadimethoxine (SDM) and its major metabolite, N4-acetylsulfadimethoxine (N4-AcSDM), the binding of SDM and N4-AcSDM to human and rabbit serum albumin (HSA and RSA) was investigated using circular dichroism (CD), fluorescence and dialysis techniques. The CD spectral characteristics of the compounds bound to the albumins suggested that the drug-binding sites on the HSA and RSA had somewhat different asymmetries. The binding constants for SDM-HSA and -RSA interaction were smaller than those for N4-AcSDM. Two specific drug-binding sites were found on RSA, similarly to HSA, from the results of competitive displacement using fluorescence probes. Moreover, SDM and N4-AcSDM were found to share the same first binding site on the albumins. It can be presumed from the displacement data with a series of p-aminobenzoates that the characteristics of the binding sites (such as depth and width of the hydrophobic cleft) for SDM and N4-AcSDM on RSA may be almost the same, but the characteristics of these drug-binding sites on HSA may be somewhat different.     

Confirmation of sulfamethazine, sulfathiazole, and sulfadimethoxine residues in condensed milk and soft-cheese products by liquid chromatography/tandem mass spectrometry

A liquid chromatography/tandem mass spectrometry method (LC/MS/MS) is described for the simultaneous detection of 3 sulfonamide drug residues at 1.25 ppb in condensed milk and soft-cheese products. The 3 sulfonamide drugs of interest are sulfathiazole (STZ), sulfamethazine (SMZ), and sulfadimethoxine (SDM). The method includes extraction of the product with phosphate buffer, centrifugation of the diluted product, and application of a portion of the extract onto a polymeric solid-phase extraction cartridge. The cartridge is washed with water, and the sulfonamides are eluted with methanol. After evaporation, the residue is dissolved in 0.1% formic acid solution, and the solution is filtered before analysis by LC/MS/MS. The LC/MS/MS program involved a series of time-scheduled selected-reaction monitoring transitions. The transitions of MH+ to the common product ions at m/z 156, 108, and 92 were monitored for each residue. In addition, SMZ and SDM had a fourth significant and unique product ion transition that could be measured. Validation was performed with control and fortified-control condensed bovine milk with 2.5, 5, and 10 ppb sulfonamides. This method was applied to imported flavored and unflavored condensed milk and cream cheese bars. The presence of STZ and SMZ residues was confirmed in 3 out of 6 products.     

Determination of sulfadimethoxine in milk with aptamer‐functionalized Fe3O4/graphene oxide as magnetic solid‐phase extraction adsorbent prior to HPLC

An aptamer (Apt) functionalized magnetic material was prepared by covalently link Apt to Fe₃O₄/graphene oxide (Fe₃O₄/GO) composite by 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride and N‐hydroxysuccinimide, and then characterized by FTIR spectroscopy, X‐ray diffraction, and vibration sample magnetometry. The obtained composite of Fe₃O₄/GO/Apt was employed as magnetic solid‐phase extraction adsorbent for the selective preconcentration of sulfadimethoxine prior to analysis by high‐performance liquid chromatography. Under the optimal conditions (sample pH of 4.0, sorbent dosage of 20 mg, extraction time of 3 h, and methanol‐5% acetic acid solution as eluent), a good linear relationship was obtained between the peak area and concentration of sulfadimethoxine in the range of 5.0 to 1500.0 µg/L with correlation coefficient of 0.9997. The limit of detection (S/N = 3) was 3.3 µg/L. The developed method was successfully applied to the analysis of sulfadimethoxine in milk with recoveries in the range of 75.9‐92.3% and relative standard deviations less than 8.1%. The adsorption mechanism of Fe₃O₄/GO/Apt toward sulfadimethoxine was studied through the adsorption kinetics and adsorption isotherms, and the results show that the adsorption process fits well with the pseudo‐second‐order kinetic model and the adsorbate on Fe₃O₄/GO/Apt is multilayer and heterogeneous.