Broad-Specificity Aptamer of Sulfonamides: Isolation and Its Application in Simultaneous Detection of Multiple Sulfonamides in Fish Sample.

Sulfonamide antibiotics (SAs) are widely used in animal husbandry and aquaculture, and the excess residues of SAs in animal-derived foods will harm the health of consumers. In reality, various SAs were alternately used in animal husbandry and aquaculture, and thus, it is urgent need to develop simple and high-throughput methods for simultaneously detecting multiple SAs or groups of SAs in order to realize rapid screening of total SAs residues in animal-derived foods. We herein isolated a broad-specificity aptamer for SAs by using a multi-SAs systematic evolution of ligands by exponential enrichment (SELEX) strategy. The isolated broad-specificity aptamer has a higher binding affinity to five different SAs including sulfaquinoxaline (SQ), sulfamethoxypyridazine (SMPZ), sulfametoxydiazine (SMD), sulfachloropyridazine (SCP), and sulfapyridine (SPD) and, thus, can be used as a bioreceptor for developing various high-throughput methods for the simultaneous detection or rapid screening of above five SAs. Based on the isolated broad-specificity aptamer and Cy7 (diethylthiatricarbocyanine) displacement strategy, a colorimetric aptasensor was developed for the simultaneous detection of SQ, SMPZ, SMD, SCP, and SPD with a visual detection limit of 2.0-5.0 µM and a spectrometry detection limit of 0.2-0.5 µM. The colorimetric aptasensor was successfully used to detect SQ, SMPZ, SMD, SCP, and SPD in fish muscle with a recovery of 82%-92% and a RSD (n = 5) < 7%. The success of this study provided a promising bioreceptor for developing various high-throughput methods for on-site rapid screening of multiple SAs residues, as well as a simple method for the rapid and cost-effective screening of total SQ, SMPZ, SMD, SCP, and SPD in seafood.

Influence of pH on the adsorption-desorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine in soils with variable surface charge.

In this research, the adsorption/desorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyradazine (SMP) was studied in 6 agricultural soils with predominance of variable charge, both before and after removing organic matter by calcination. DC adsorption was high at acidic pH, and decreased at pH values above 8. Removal of organic matter with calcination caused just a slight decrease in adsorption, and even in some soils adsorption was similar to that in non-calcined samples. The adsorption coefficients (Kd) were higher for the DC- species compared to DC+, DC0 and DC2-. Regarding DC desorption, the values were very low throughout the pH range covered in the study (2-12), both in the calcined samples and in those not subjected to calcination. ENR showed a similar behavior to DC regarding the effect of pH, since ENR adsorption also decreased at basic pH, but the effect of removing organic matter was different, as it caused a clear decrease in ENR adsorption. The species with the highest Kd was in this case ENR0, although ENR+ is also quantitatively important as regards Kd value in calcined samples. For this antibiotic, no differences in desorption were observed between calcined and non-calcined samples. Finally, SMP adsorption also decreased as pH increased, and, in addition, similarly to what happened with ENR, in general, there was a strong decrease in SMP adsorption when organic matter was removed. The species with the highest Kd in this case was SMP+ in non-calcined samples, but SMP0 and SMP- become more relevant in calcined samples. The percentages of SMP desorption were higher than those for the other two antibiotics, and an increase occurs at intermediate pH values, being higher for calcined samples. These results can be considered relevant in terms of increasing the knowledge as regards the possible evolution and fate of the three antibiotics studied. Specifically, for different pH conditions and with different organic matter contents, when they reach soils and other environmental compartments after being discharged as contaminants. This could have important repercussions on public health and the overall environment.

Identification and characterization of Fe3O4/peroxodisulfate advanced oxidation products from sulfameter.

Sulfonamides (SAs) are one of the most widely used antibiotics and their residuals in the environment could cause some negative environmental issues. Advanced oxidation such as Fenton-like reaction has been widely applied in the treatment of SAs polluted water. Degradation rates of 95%-99.7% were achieved in this work for the tested 8 SAs, including sulfisomidine, sulfameter (SME), phthalylsulfathiazole, sulfamethoxypyridazine, sulfamonomethoxine, sulfisoxazole, sulfachloropyridazine, and sulfadimethoxine, in the Fe3O4/peroxodisulfate (PDS) oxidation system after the optimization of PDS concentration and pH. Meanwhile, it was found that a lot of unknown oxidation products were formed, which brought up the uncertainty of health risks to the environment, and the identification of these unknown products was critical. Therefore, SME was selected as the model compound, from which the oxidation products were never elucidated, to identify these intermediates/products. With liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS), 10 new products were identified, in which 2-amino-5-methoxypyrimidine (AMP) was confirmed by its standard. The investigation of the oxidation process of SME indicated that most of the products were not stable and the degradation pathways were very complicated as multiple reactions, such as oxidation of the amino group, SO2 extrusion, and potential cross-reaction occurred simultaneously. Though most of the products were not verified due to the lack of standards, our results could be helpful in the evaluation of the treatment performance of SAs containing wastewater.

Detection of fluoroquinolone and sulfonamide residues in poultry eggs in Kunming city, southwest China.

Antibiotic residues contained in poultry eggs pose threat to human health. However, the classes and concentrations of antibiotics in poultry egg in southwestern China is unknown due to insufficient monitoring and research. A total of 513 egg samples were collected from supermarkets and farm markets in Kunming city in 2020 and the levels of 7 antibiotics were analyzed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method. The linear correlation coefficients were above 0.990 for all antibiotics tested. The limits of detection and limits of quantification in poultry eggs were 0.002 to 0.010 µg/g and 0.007 to 0.033 µg/g, respectively. The average recoveries of the 7 analytes from poultry egg samples were 80.00 to 128.01%, with relative standard deviations of less than 13.97%. A total of 93 (18.13%) samples tested positive for antibiotics, with the highest concentration being 2.48 µg/g. The concentration range of ofloxacin, danofloxacin, difloxacin, sulfadimethoxine, sulfamonomethoxine, sulfamethoxypyridazine, and sulfamethoxazole in poultry eggs was 0.01 to 0.37 µg/g, 0.06 to 0.48 µg/g, 0.05 to 0.29 µg/g, 0.03 to 0.16 µg/g, 0.06 to 1.00 µg/g, 0.05 to 0.37, and 0.07 to 2.48 µg/g, respectively. Sulfamonomethoxine was detected from hen eggs with the highest concentration level at 1.00 µg/g. Sulfamethoxazole was detected with the highest concentration level from both duck and quail eggs, at 1.87 and 2.48 µg/g, respectively. The antibiotic with the highest residue level in pheasant eggs was danofloxacin, which was 0.37 µg/g. Sulfamethoxypyridazine was identified in 30 samples with the highest positive rate of 5.85%, sulfadimethoxine was identified in 3 samples with the lowest positive rate of 0.58%. We observed that 7 targeted antibiotic residues in quail eggs and 3 targeted antibiotic residues in pheasant eggs. We also found that there were antibiotic residues in free-range hen eggs and the concentration was not low. The antibiotic with the highest residue level in free-range eggs was sulfamonomethoxine, which was 1.00 µg/g. These findings suggest that continual antibiotic residue monitoring of poultry eggs is essential in China.

Environmental relevance of adsorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine before and after the removal of organic matter from soils.

In this work batch-type experiments were used to study the adsorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyridazine (SMP) in cultivation soils, before and after the removal of soil organic matter. Organic matter removal by calcination resulted not only in C and N removal, but also in increased soil pH, exchangeable basic cations and surface area values. The results indicate a very different behavior depending on the type of antibiotic, showing the adsorption sequence DC > ENR > SMP. Specifically, DC adsorption was very high in untreated soil samples (with organic matter), and was still high (although decreased) after the removal of soil organic matter. Furthermore, the adsorption behavior of DC was clearly dependent on the pH of the medium. Regarding ENR, it also showed high adsorption, although to a lesser extent than DC. However, when soil organic matter was removed, ENR adsorption significantly decreased in all soil samples. As regards SMP, it was adsorbed to a much lesser extent, and the removal of soil organic matter caused an additional drastic decrease in adsorption, reaching negligible values in some samples. Desorption followed the reverse sequence of adsorption, specifically in the order DC < ENR < SMP. In the case of DC, desorption was negligible, both in samples with and without organic matter, while for ENR and SMP, desorption clearly increased for soil samples where organic matter was removed. These results may be of relevance as regards environmental quality and public health, especially to facilitate a correct use of soils and organic amendments in areas that receive the application of substances containing the investigated antibiotics.

Adsorption/desorption of sulfamethoxypyridazine and enrofloxacin in agricultural soils.

Adsorption and desorption processes were studied for the antibiotics sulfamethoxypyridazine (SMP) and enrofloxacin (ENR) in 20 agricultural soils devoted to wheat-potato and vine cultivation. Batch experiments were used to conduct kinetic studies, as well as to evaluate adsorption and desorption for different concentrations of antibiotics. The results indicated that adsorption curves were linear for SMP, while presented a certain curvature in the case of ENR. The adsorption of both antibiotics was fitted to a linear equation and to the Freundlich model. In the case of the linear equation, the values of the distribution coefficient Kd were lower for SMP (0.9-26.0 L kg-1) than for ENR (121-2345 L kg-1). In the Freundlich model, the values of the adsorption constant KF ranged between 1.7 and 34.0 Ln µmol1-n kg-1 for SMP, and between 829 and 3019 Ln µmol1-n kg-1 for ENR. A multiple regression analysis showed that, in the case of SMP, 78% of the variance of the adsorption parameter Kd was explained by soil organic carbon (SOC) and exchangeable magnesium (Mge) contents, while for ENR no significant relation was found. In addition, for SMP, 66% of the variance of KF was explained by SOC, and for ENR 45% of the variability of KF was explained by nitrogen content. Desorption rates were higher for SMP (reaching up to 24%) than for ENR (which reached up to 7%). Desorption percentages showed a potential relation with the adsorption parameter Kd for both SMP and ENR. These results could be useful to elucidate the evolution and dynamics of these emerging pollutants in soils and other environmental compartments, which could be of aid in controlling public health risks associated to them.

New Heteroleptic Ruthenium(II) Complexes with Sulfamethoxypyridazine and Diimines as Potential Antitumor Agents.

Two new complexes of Ru(II) with mixed ligands were prepared: [Ru(bpy)2smp](PF6) (1) and [Ru(phen)2smp](PF6) (2), in which smp = sulfamethoxypyridazine; bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline. The complexes have been characterized by elemental and conductivity analyses; infrared, NMR, and electrospray ionization mass spectroscopies; and X-ray diffraction of single crystal. Structural analyses reveal a distorted octahedral geometry around Ru(II) that is bound to two bpy (in 1) or two phen (in 2) via their two heterocyclic nitrogens and to two nitrogen atoms from sulfamethoxypyridazine-one of the methoxypyridazine ring and the sulfonamidic nitrogen, which is deprotonated. Both complexes inhibit the growth of chronic myelogenous leukemia cells. The interaction of the complexes with bovine serum albumin and DNA is described. DNA footprinting using an oligonucleotide as substrate showed the complexes' preference for thymine base rich sites. It is worth notifying that the complexes interact with the Src homology SH3 domain of the Abl tyrosine kinase protein. Abl protein is involved in signal transduction and implicated in the development of chronic myelogenous leukemia. Nuclear magnetic resonance (NMR) studies of the interaction of complex 2 with the Abl-SH3 domain showed that the most affected residues were T79, G97, W99, and Y115.

Aqueous chlorination of sulfamethazine and sulfamethoxypyridazine: Kinetics and transformation products identification.

Sulfonamides (SNs) are synthetic antimicrobial agents. These substances are continually introduced into the environment, and they may spread and maintain bacterial resistance in the different compartments. The chlorination of 2 SNs, namely, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP), was investigated to study their reactivity with chlorine at typical concentrations for water treatment conditions. Experiments conducted in purified water show an acceleration of SMT and SMP degradation of a factor 1.5 by comparison to drinking water matrix. This difference is due to pH variation and competitive reactions between SNs and mineral and organic compounds, with chlorine in drinking water. In the presence of an excess of chlorine (6.7 µmol·L-1 ) in ultrapure water at pH 7.2, second-order degradation rate constants were equal to 4.5 × 102 M-1 ·s-1 and 5.2 × 102 M-1 ·s-1 for SMT and SMP, respectively. The structures of transformation products were investigated by liquid chromatography tandem mass spectrometry analyses with equimolar concentrations between chlorine and SNs. SO2 elimination, cyclization, and electrophilic substitutions were the main pathways of by-products formation. Moreover, the toxicity of the proposed structures was predicted by using toxicity estimation software tool program. The results indicated that most by-products may present developmental toxicity.

Polymorphism, Intermolecular Interactions, and Spectroscopic Properties in Crystal Structures of Sulfonamides.

The antibiotics family of sulfonamides has been used worldwide intensively in human therapeutics and farm livestock during decades. Intermolecular interactions of these sulfamides are important to understand their bioactivity and biodegradation. These interactions are also responsible for their supramolecular structures. The intermolecular interactions in the crystal polymorphs of the sulfonamides, sulfamethoxypyridazine, and sulfamethoxydiazine, as models of sulfonamides, have been studied by using quantum mechanical calculations. Different conformations in the sulphonamide molecules have been detected in the crystal polymorphs. Several intermolecular patterns have been studied to understand the molecular packing behavior in these antibiotics. Strong intermolecular hydrogen bonds and π-π interactions are the main driving forces for crystal packing in these sulfonamides. Different stability between polymorphs can explain the experimental behavior of these crystal forms. The calculated infrared spectroscopy frequencies explain the main intermolecular interactions in these crystals.

Routine antibiotic prophylaxis after normal vaginal birth for reducing maternal infectious morbidity.

BACKGROUND: Infectious morbidities contribute to considerable maternal and perinatal morbidity and mortality, including women at no apparent increased risk of infection. To reduce the incidence of infections, antibiotics are often administered to women after uncomplicated childbirth, particularly in settings where women are at higher risk of puerperal infectious morbidities. OBJECTIVES: To assess whether routine administration of prophylactic antibiotics to women after normal (uncomplicated) vaginal birth, compared with placebo or no antibiotic prophylaxis, reduces postpartum maternal infectious morbidities and improves outcomes. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2017), LILACS, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (22 August 2017) and reference lists of retrieved studies. SELECTION CRITERIA: We planned to include randomised or quasi-randomised trials evaluating the use of prophylactic antibiotics versus placebo or no antibiotic prophylaxis. Trials using a cluster-randomised design would have been eligible for inclusion, but we found none.In future updates of this review, we will include studies published in abstract form only, provided sufficient information is available to assess risks of bias. We will consider excluded abstracts for inclusion once the full publication is available, or the authors provide more information.Trials using a cross-over design are not eligible for inclusion in this review. DATA COLLECTION AND ANALYSIS: Two review authors conducted independent assessment of trials for inclusion and risks of bias. They independently extracted data and checked them for accuracy, resolving differences in assessments by discussion. They evaluated methodological quality using standard Cochrane criteria and the GRADE approach.We present the summaries as risk ratios (RRs) and mean difference (MDs) using fixed- or random-effect models. For one primary outcome we found considerable heterogeneity and interaction. We explored further using subgroup analysis to investigate the effects of the randomisation unit. All review authors discussed and interpreted the results. MAIN RESULTS: One randomised controlled trial (RCT) and two quasi-RCTs contributed data on 1779 women who had uncomplicated vaginal births, comparing different antibiotic regimens with placebo or no treatment. The included trials took place in the 1960s (one trial) and 1990s (two trials). The trials were conducted in France, the USA and Brazil. Antibiotics administered included: oral sulphamethoxypyridazine or chloramphenicol for three to five days, and intravenous amoxicillin and clavulanic acid in a single dose one hour after birth. We rated most of the domains for risk of bias as high risk, with the exception of reporting bias and other potential bias.The quality of evidence ranged from low to very low, based on the GRADE quality assessment, given very serious design limitations of the included studies, few events and wide confidence intervals (CIs) of effect estimates.We found a decrease in the risk of endometritis (RR 0.28, 95% CI 0.09 to 0.83, two trials, 1364 women,very low quality). However, one trial reported zero events for this outcome and we rate the evidence as very low quality. There was little or no difference between groups for the risk of urinary tract infection (RR 0.25, 95% CI 0.05 to 1.19, two trials, 1706 women,low quality), wound infection after episiotomy (reported as wound dehiscence in the included trials) (RR 0.78, 95% CI 0.31 to 1.96, two trials, 1364 women, very low quality) and length of maternal hospital stay in days (MD -0.15, 95% CI -0.31 to 0.01, one trial, 1291 women, very low quality). Cost of care in US dollar equivalent was 2½ times higher in the control group compared to the group receiving antibiotics prophylaxis (USD 3600: USD 9000, one trial, 1291 women). There were few or no differences between treated and control groups for adverse effects of antibiotics (skin rash) reported in one woman in each of the two trials (RR 3.03, 95% CI 0.32 to 28.95, two trials, 1706 women, very low quality). The incidence of severe maternal infectious morbidity, antimicrobial resistance or women's satisfaction with care were not addressed by any of the included studies. AUTHORS' CONCLUSIONS: Routine administration of antibiotics may reduce the risk of endometritis after uncomplicated vaginal birth. The small number and nature of the trials limit the interpretation of the evidence for application in practice, particularly in settings where women may be at higher risk of developing endometritis. The use of antibiotics did not reduce the incidence of urinary tract infections, wound infection or the length of maternal hospital stay. Antibiotics are not a substitute for infection prevention and control measures around the time of childbirth and the postpartum period. The decision to routinely administer prophylactic antibiotics after normal vaginal births needs to be balanced by patient features, childbirth setting and provider experience, including considerations of the contribution of indiscriminate use of antibiotics to raising antimicrobial resistance. Well-designed and high-powered randomised controlled trials would help to evaluate the added value of routine antibiotic administration as a measure to prevent maternal infections after normal vaginal delivery.

Quantum chemical investigation on photodegradation mechanisms of sulfamethoxypyridazine with dissolved inorganic matter and hydroxyl radical.

Sulfamethoxypyridazine (SMP) is one of the commonly used sulfonamide antibiotics (SAs). SAs are mainly studied to undergo triplet-sensitized photodegradation in water under natural sunlight with other coexisting aquatic environmental organic pollutants. In this work, SMP was selected as a representative of SAs. We studied the mechanisms of triplet-sensitized photodegradation of SMP and the influence of selected dissolved inorganic matter, i.e., anions (Br-, Cl-, and NO3-) and cations ions (Ca2+, Mg2+, and Zn2+) on SMP photodegradation mechanism by quantum chemical methods. In addition, the degradation mechanisms of SMP by hydroxyl radical (OH) were also investigated. The creation of SO2 extrusion product was accessed with two different energy pathways (pathway-1 and pathway-2) by following two steps (step-I and step-II) in the triplet-sensitized photodegradation of SMP. Due to low activation energy, the pathway-1 was considered as the main pathway to obtain SO2 extrusion product. Step-II of pathway-1 was measured to be the rate-limiting step (RLS) of SMP photodegradation mechanism and the effect of the selected anions and cations was estimated for this step. All selected anions and cations promoted photodegradation of SMP by dropping the activation energy of pathway-1. The estimated low activation energies of different degradation pathways of SMP with OH radical indicate that OH radical is a very powerful oxidizing agent for SMP degradation via attack through benzene derivative and pyridazine derivative ring.

Development of amino- and dimethylcarbamate-substituted resorcinol as programmed cell death-1 (PD-1) inhibitor.

Blockading the interaction of programmed death-1 (PD-1) protein with its ligands (PD-Ls, such as PD-L1) was proved to be a pathway for suppressing the development of tumors and other degradations of biological species. Thus, finding PD-1 inhibitors situated at the convergence point of drug discovery. In addition to some monoclonal antibodies applied to treat cancers clinically, the screening of organic molecules for hindering the interaction of PD-1 with PD-L1 became an efficient strategy in the development of PD-1 inhibitors. We herein applied resorcinol and 3-hydroxythiophenol as the core to link with N,N-dimethylcarbamate and other alkyl-substituted amines to afford 13 amine-appended phenyl dimethylcarbamates (AAPDs). The test for blockading the combination of PD-1 with PD-L1 revealed that abilities of 13 AAPDs were higher than that of sulfamethizole, a successful PD-1 inhibitor. In particular, large hydrophobic substituents at amine moiety or a nitro at resorcinol skeleton enhanced the inhibitory effect of AAPD even higher than that of sulfamethoxypyridazine, another successful PD-1 inhibitor. The present results may provide valuable information for further investigation on synthetic PD-1 inhibitors.

Facile synthesis of magnetic hypercrosslinked polystyrene and its application in the magnetic solid-phase extraction of sulfonamides from water and milk samples before their HPLC determination.

In this study, a novel magnetic solid-phase extraction (MSPE) sorbent, magnetic hypercrosslinked polystyrene (HCP/Fe3O4), was prepared and used for preconcentration of four sulfonamides (sulfamethoxypyridazine, sulfamethazine, sulfamethoxazole and sulfachloropyridazine) from natural water and milk samples. This material was prepared by sorption of pre-synthesized Fe3O4 nanoparticles (NPs) onto HCP. A number of sorbents with varying Fe3O4NPs content were prepared, and their structural, magnetic and sorption properties were studied. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, pH of the sample solution and desorption conditions were studied and optimized. Under the optimal conditions, a convenient and efficient method for the determination of sulfonamides in water and milk samples was developed by combining MSPE and high-performance liquid chromatography with amperometric detection. The results showed that the recoveries of these compounds were in the range of 84-105% with the relative standard deviations ranging between 3% and 10%; the limit of detection were in the range of 0.21-0.33 ng mL(-1) for water and 2.0-2.5 ng mL(-1) for milk.

Fabrication of 2D nanosheet through self assembly behavior of sulfamethoxypyridazine inclusion complexes with α- and ß-cyclodextrins.

A 2D nanosheet was fabricated through the supramolecular self assembly of sulfamethoxypyridazine (SMP) and ß-cyclodextrin (ß-CD) inclusion complexes. HRTEM image exhibited 2D nanosheet morphology with a length of 1200mm and the sheet thickness of 60mm. It is noted that the nanosheet did not form a single layer aggregation but a bulk aggregation of SMP/ß-CD inclusion complex. The formation of this multilayer 2D nanosheet based on the self assembly of SMP/ß-CD inclusion complexes is proposed by the topological transformation as well as molecular modeling calculations. But, nanorods are formed in SMP/α-CD inclusion complex indicated that the nature of the CD determined the shape of the self assembled supramolecular architecture. The formation of nanomaterial was characterized by using FT-IR, DSC, PXRD, (1)H NMR, absorption, fluorescence and lifetime measurements.

Photolysis of sulfamethoxypyridazine in various aqueous media: aerobic biodegradation and identification of photoproducts by LC-UV-MS/MS.

Sulfonamides are one of the most frequently used antibiotics worldwide. Therefore, mitigation processes such as abiotic or biotic degradation are of interest. Photodegradation and biodegradation are the potentially significant removal mechanisms for pharmaceuticals in aquatic environments. The photolysis of sulfamethoxypyridazine (SMP) using a medium pressure Hg-lamp was evaluated in three different media: Millipore water pH 6.1 (MW), effluent from sewage treatment plant pH 7.6 (STP), and buffered demineralized water pH 7.4 (BDW). Identification of transformation products (TPs) was performed by LC-UV-MS/MS. The biodegradation of SMP using two tests from the OECD series was studied: Closed Bottle test (OECD 301 D), and Manometric Respirometry test (OECD 301 F). In biodegradation tests, it was found that SMP was not readily biodegradable so it may pose a risk to the environment. The results showed that SMP was removed completely within 128 min of irradiation in the three media, and the degradation rate was different for each investigated type of water. However, dissolved organic carbon (DOC) was not removed in BDW and only little DOC removal was observed in MW and STP, thus indicating the formation of TPs. Analysis by LC-UV-MS/MS revealed new TPs formed. The hydroxylation of SMP represents the main photodegradation pathway.

Occurrence and source apportionment of sulfonamides and their metabolites in Liaodong Bay and the adjacent Liao River basin, North China.

The presence of antibiotics in the environment is of great concern because of their potential for resistance selection among pathogens. In the present study we investigated the occurrence of 19 sulfonamides, five N-acetylated sulfonamide metabolites, and trimethoprim in the Liao River basin and adjacent Liaodong Bay, China, as well as 10 human/agricultural source samples. Within the 35 river samples, 12 sulfonamides, four acetylated sulfonamides, and trimethoprim were detected, with the dominant being sulfamethoxazole (66.6 ng/L), N-acetylsulfamethoxazole (63.1 ng/L), trimethoprim (29.0 ng/L), sulfadiazine (14.0 ng/L), and sulfamonomethoxine (8.4 ng/L); within the 36 marine samples, 10 chemicals were detected, with the main contributions from sulfamethoxazole (25.2 ng/L) and N-acetylsulfamethoxazole (28.6 ng/L). Sulfamethoxazole (25.9%), N-acetylsulfamethoxazole (46.6%), trimethoprim (22.9%), and sulfapyridine (1.4%) were the main chemicals from human sources, while sulfamonomethoxine, sulfamethazine, sulfaquinoxaline, sulfaguanidine, sulfadiazine, sulfanilamide, and sulfamethoxypyridazine were dominant in the animal husbandry sources, specifically, swine and poultry farms, and sulfamethoxazole (91%) was dominant in the mariculture source. A principal component analysis with multiple linear regression was performed to evaluate the source apportionment of total sulfonamides in Liaodong Bay. It was found that animal husbandry contributed 15.2% of total sulfonamides, while human sources contributed 28.5%, and combined human and mariculture sources contributed 56.3%. In addition, the mariculture contribution was 24.1% of total sulfonamides into the sea based on mass flux estimation. The present study is the first report that the environmental levels of sulfonamide metabolites were comparable to the corresponding parents; therefore, we should pay attention to their environmental occurrence. Source apportionment showed human discharge (60.7%) significantly contributed to these antibiotics in Liaodong Bay, which provides important information for environmental management.

[Enzyme immunoassay for determination of sulfamethoxypyridazine in honey].

An enzyme immunoassay technique for the detection of sulfamethoxypyridazine in honey, developed using rabbit polyclonal antibodies raised against N-sulfonyl-4-aminobutyric acid, which contains a structural group characteristic of sulfonamides, is proposed. Under the optimized conditions, the sulfamethoxypyridazine detection limit was 0.05 ng/ml, with the entire analysis procedure taking 2 h. In total, 24 honey samples were tested using the protocol based on tenfold dilutions of samples without their preliminary treatment.

Advantages of soybean peroxidase over horseradish peroxidase as the enzyme label in chemiluminescent enzyme-linked immunosorbent assay of sulfamethoxypyridazine.

An indirect competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) of sulfamethoxypyridazine (SMP) was developed. The conjugates of streptavidin with cationic horseradish peroxidase (HRP) and anionic soybean peroxidase (SbP) were used in CL-ELISA for the detection of biotinylated anti-SMP antibodies. For streptavidin-HRP conjugate-catalyzed chemiluminescence measured 20 s after the initiation of the enhanced chemiluminescence reaction (ECR), the limit of detection (IC(10)), the IC(50) value, and the working range in CL-ELISA of SMP are 0.3, 12.4, and 1.2-85.0 ng/mL, respectively. An increase in the time interval between the ECR initiation and the luminescence measurement results in the loss in the quality of analytical measurements because of the time-dependent quenching of chemiluminescence typical of the HRP-catalyzed ECR. In the case of SbP-based CL-ELISA of SMP, the limit of detection, the IC(50) value, and the working range (0.025, 0.17, and 0.045-0.63 ng/mL, respectively) are better than those for HRP-based CL-ELISA. Furthermore, the analytical parameters of SbP-based CL-ELISA remain unchanged during a long period of time (for at least 30 min). The recovery values from four spiked milk samples with different concentrations of SMP in SbP-based CL-ELISA vary from 70 to 130%.

[Simultaneous determination of nine sulfonamide residues in milk using solid phase extraction and high performance liquid chromatography].

A simple, rapid, sensitive and reliable high performance liquid chromatographic method for the simultaneous determination of nine sulfonamides (SAs) (sulfadiazine, sulfathiazole, sulfamethazine, sulfamethoxypyridazine, sufamonomethoxine, sulfachloropyridazine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline) in milk was developed. The method includes the shaking of the milk with phosphate buffer, centrifugation, and cleaning up on a C18 solid-phase extraction cartridge. The C18 cartridge was washed with water, and the SAs were eluted with methanol. After the evaporation, the residue was dissolved in ethyl acetate, and cleaned up on an amino solid-phase extraction column. Analytical separation was performed on an Inertsil ODS-3 column with photodiode-array detection at 270 nm under the gradient condition. The mean recoveries of SAs at the spiked levels of 10, 20, 40 microg/L were between 72.1% and 88.3%. The relative standard deviations were between 2.3% and 5.0%. The detection limits were 1.7 - 2.8 microg/L, and the quantification limits wer 5.7 - 9.2 microg/L.

[Use of soybean peroxidase for the enzyme immunoassay of sulfamethoxipyridazine in milk].

An enzyme immunoassay with colorimetric detection of sulfamethoxipyridazine (SMP), the most widely used sulfamide, was developed with the soybean anionic peroxidase as an enzyme marker. The range of SMP detection is 1.3-63.0 ng/ml with a detection limit of 0.4 ng/ml. The root square deviation of detection results did not exceed 6%. It was demonstrated that 0.15% casein added to the working buffer prevented the effect of the milk matrix on the detection. The results obtained demonstrate that the assay developed is promising, displaying a sensitivity that exceeds the maximum permissible concentration of sulfamides in milk (100 microg/l) by several orders of magnitude.