Antibiotics In Milk Samples Research Articles

Koncept “Jedno zdravlje” u prevenciji pojave ostataka β-laktamskih antibiotika u mlijeku i okolišu

The One Health concept emerged with the aim of balancing the lives of humans, animals, and plants on Earth, while also preserving theenvironment. Its aim is to improve overall living conditions on Earth and one of these issues is the overuse of antibiotics for therapeutic purposes and the use of antibiotics to promote livestock breeding on farms, which has led to a rapid spread of antibiotic resistance among microorganisms. Additionally, residual antibiotics are found in food of animal origin, and in the environment where they pollute soil and water. The most widely used group of antimicrobial agents are the β-lactam antibiotics. Due to their powerful antimicrobial effect and low toxicity, they are used to treat bacterial infections in both human and animal medicine. β-lactam antibiotics are major antibiotics used for treating mastitis, the most common infection occurring in milk-producing cows. Across EU Member States, testing and identifying the residues of β-lactam antibiotics in milk samples is included in national antibiotic residue monitoring plans for food of animal origin. The development of sophisticated methods with high sensitivity and precision, based on liquid chromatography coupled to mass spectrometry, enables the simultaneous control of different antibiotic classes for the official control of residues in foods of animal origin. According to the literature, β-lactam antibiotics are frequently detected antibiotic residues in EU Member States, with penicillin G as the most common compound.

Selective luminescent detection of 5-nitroimidazole antibiotics through self-aggregates of a single non-aromatic amino acid, L-lysine

This study presents an innovative approach for the detection of 5-nitroimidazole antibiotics, namely ornidazole, secnidazole, metronidazole, and tinidazole. These antibiotics are widely used to treat microbial infections in both humans and livestock industries. Their unregulated use poses environmental and health risks due to their persistence in water bodies and potential to contribute to drug resistance. In response, this research proposes the utilisation of the self-aggregation property of a single unmodified non-aromatic amino acid, L-lysine, for the detection of these antibiotics. Lysine exhibits strong fluorescence in water in a concentration-dependent manner, and the interaction of lysine with 5-nitroimidazole antibiotics resulted in the quenching of its fluorescence. With this technique, we obtained a detection limit of 2.5 μM for metronidazole (MDZ), 2.65 μM for ornidazole (ODZ), 3.13 μM for secnidazole (SDZ), and 2.98 μM for tinidazole (TDZ). This cost-effective approach also offers practicality through visual detection on paper strips as well as successful application in detecting those antibiotics in milk samples and animal products. Taking advantage of the unique properties of lysine and its interaction with antibiotics, this method provides a robust, simplified yet efficient means of detecting 5-nitroimidazole antibiotics, which holds significant potential for real-world implementation.

Electromembrane extraction – capillary zone electrophoresis for the quantitative determination of β-lactam antibiotics in milk samples

Three penicillin-based β-lactam antibiotics (benzylpenicillin, amoxicillin, and ampicillin) were extracted by electromembrane extraction (EME) and determined in the resulting extracts by capillary zone electrophoresis (CZE) with UV–Vis detection. The EME was optimized for the simultaneous clean-up of complex samples and preconcentration of the three antibiotics and employed 1-octanol as the organic phase interface (impregnated in the pores of a hollow fiber), acidified donor solution (pH 3), and phosphate buffer (pH 5.6) as the acceptor solution. The EMEs were carried out for 20 min at 300 V and constant stirring (750 rpm) of the donor solution. At the optimized EME-CZE conditions, the sensitivity of the analytical method was sufficient for the determination of the three β-lactam antibiotics in undiluted cow's milk at concentrations below the EU maximum residue limits (4 μg/L) in foodstuffs. The method was simple, rapid, and convenient and offered extraction recoveries of 13.5 – 87.3 %, enrichment factors of 23.6 – 152.8, repeatability (RSD values) better than 7.6 %, linear analytical response in the 1 – 100 μg/L (3 – 100 μg/L for benzylpenicillin) concentration range with correlation coefficients ≥ 0.9997, and limits of detection from 0.2 to 1.2 μg/L. The proposed analytical concept was used for the rapid control of milk quality (i.e. assessment of excessive use of antibiotics in dairy animals), moreover, it was further extended to the trace determination of β-lactam antibiotics in other complex samples, such as in wastewater.

Polydopamine- and MOFs-based molecularly imprinted microfiltration membranes in syringe filter for selective capture of thiamphenicol, florfenicol and chloramphenicol in milk samples

In this study, molecularly imprinted microfiltration membranes (MIMFMs) based on polydopamine and metal–organic framework were innovatively proposed, and successfully prepared for capturing thiamphenicol, florfenicol and chloramphenicol from milk samples through syringe filter device. The provision of PDA and coupling of MOF particles enabled the filter membranes to have great permeability and binding capacity. Cleverly, hydrophilicity and heightened rebinding selectivity (IF = 2.42) of filter membranes was provided using two functional monomers (methacrylate and acrylamide), and microfiltration-grade composite membranes were generated by adjusting the imprinting polymerization time. The combination of the selective filter membranes and the syringe filter devices can effectively simplify the operation process, minimize the extraction time and reduce the tested sample volume. The method was validated by coupling with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) and obtained a good correlation (r2 > 0.99). The limit of detection (LOD) of three analytes was 0.0800–0.6583 µg kg−1 and the mean recovery ranged from 85.5% to 91.2% within relative standard deviations (RSDs) less than 8.2%. Finally, an effective MIMFMs-UHPLC-MS/MS method was established for the recognition and detection of three amphenicol antibiotics in milk samples. The MIMFMs filtration technique offered in this work provides valuable science references and potential application prospects for complicated sample pretreatment.

Artificial networks for spectral resolution of antibiotic residues in bovine milk; solidification of floating organic droplet in dispersive liquid-liquid microextraction for sample treatment

The intensive use of antibiotics in livestock practice has a negative impact on human health and increases the antibiotic resistance. In this study feasible data interpretation algorithm along with efficient extraction protocol were combined for selective analysis of three antibiotics in milk samples. Trimethoprim, sulphamethoxazole and oxytetracycline are widely used antibiotics in veterinary pharmaceuticals. The studied antibiotics were efficiently extracted from milk samples with solidification of floating organic droplet in dispersive liquid-liquid microextraction. This extraction protocol was optimized not only to maximize extraction recoveries but also to approach the lower residue limits specified by European Union. Artificial neural networks succeeded in resolving spectral overlap between the studied drugs. The network architecture was optimized and validated for accurate and precise analysis. The proposed method outweighs the reported chromatographic methods for being simple and inexpensive and compared favorable to official methods.

Application of the novel organic network material for the detection of fluoroquinolone antibiotics in milk

<p indent=0mm>The residues of fluoroquinolone antibiotics in milk increase the risk of dietary exposure. The development of detection technology is an important guarantee of food safety. In this work, 1,3,5-triacetylbenzene and 2,4,6-triiodophenol were selected as monomers to synthesize new organic network materials based on Sonogashira coupling reaction under moderate condition of <sc>30 °C.</sc> Morphology, structure and hydrophobicity of the prepared material were characterized. Due to the π-π, hydrogen bonding and hydrophobic interaction, fluoroquinolone antibiotics in milk can be absorbed efficiently on the material. As an adsorbent of solid phase extraction (SPE), the pipette-tip SPE conditions were optimized combined with high performance liquid chromatography coupled with fluorescence detector, and the novel method for the detection of fluoroquinolone antibiotics in milk was established. The linear range was <sc>0.4–100 μg/kg,</sc> and <italic>R</italic>²<x content-type=symbol>³</x>0.9992 showed the good linear relationship. The detection limit was <sc>0.15–1.2 μg/kg.</sc> The recoveries and relative standard deviations were 89.6%–103.5% and 1.3%–5.9%, respectively. It was suitable for the determination of fluoroquinolone antibiotics in milk samples.

Criteria for the selection of antibacterial drugs in the treatment of bovine mastitis

Relevance . The work is devoted to the study of the therapeutic efficacy of the drug Enroflon® gel on cows of the Holstein-Friesian breed, as well as the Holsteinized black-and-white breed during lactation. The aim of the research was to determine the therapeutic efficacy of Enroflon ® gel in the treatment of subclinical and clinical mastitis of bacterial etiology, as well as determination of the residual presence of antibiotics in milk samples from animals subjected to treatment. Methodology. Production experience to determine the therapeutic effectiveness of clinical (experience 1) and subclinical (experience 2) mastitis was carried out in the conditions of the farm of LLC “Babaevo” of Vladimir region. Two experimental groups of cows with clinical and subclinical mastitis were formed. An industrial experiment to determine the residual amount of enrofloxacin in milk (experiment 3) was carried out in the conditions of the livestock complex of LLC “Lesnye Polyany», Moscow region. An experimental group (experiment 3) of cows with subclinical mastitis was formed. The diagnosis of subclinical mastitis was made on the basis of a diagnostic test for the determination of somatic cells using the Kenotest system. The presence of a residual amount of antibiotic was determined in the Research Laboratory “Milk” of the Federal State Scientific Institution “All-Russian Research Institute of the Dairy Industry”. The complex preparation Enroflon ® gel was injected intracisternally into the inflamed lobe of the udder with clinical and subclinical mastitis during lactation. The drug was administered 2 times a day with an interval of 12 hours for 3 days. The investigated drug was produced at LLC “VIC Animal Health”. Results . In the treatment of clinical (experiment 1) and subclinical (experiment 2) mastitis in cows using Enroflon ® gel the therapeutic effect was 80% and 100% respectively. In laboratory studies of milk samples using the RANDOX matrix biochip technology (experiment 3) no active ingredient, enrofloxacin, was detected in all treated animals 72 hours after the last injection of the drug.

Preparation of Magnetic Dummy Template Molecularly Imprinted Polymers for the Determination of Aminoglycosides Antibiotics in Milk

In this paper, the efficient magnetic dummy molecular imprinted polymers were firstly synthesized by dummy template (raffinose). The dummy molecularly imprinted layer was polymerized on the surface of Fe3O4 nanoparticles modified with NH2 group. The micromorphology and chemical composites of prepared polymers were detailed characterized. Their adsorption and desorption conditions including extraction time, adsorbent dosage, solution pH, washing solvent, and elution solvent were carefully evaluated. The results showed that the obtained magnetic dummy template molecularly imprinted polymers showed uniform sizes, high magnetic responsivity, core–shell structure, and selectively recognition capacity towards five aminoglycoside antibiotics. Under optimum conditions, magnetic solid-phase extraction coupled high performance liquid chromatography-tandem mass spectrometry for enriching and determining aminoglycoside antibiotics in milk samples was developed. This method showed good linearity (50–1000 μg/kg) with r2 larger than 0.9923. The limits of detection (S/N = 3) were from 3.6 to 9.6 μg/kg. With spiked at three different concentration levels, the recoveries fell into 82.6–114.1% with relative standard deviation from 2.8 to 13.2%. The established method based on magnetic dummy molecular imprinted polymers proved to be highly sensitive and repeatable, providing the promising adsorbent for aminoglycoside antibiotics analysis in the complex samples.

Highly selective magnetic dual template molecularly imprinted polymer for simultaneous enrichment of sulfadiazine and sulfathiazole from milk samples based on syringe–to–syringe magnetic solid–phase microextraction

Antibiotics, such as sulfadiazine and sulfathiazole, are widely used in veterinary applications which can result in remains in edible animal products. Therefore, there is an immense need for a reliable, selective, sensitive, and simple analytical technique for monitoring the concentration of sulfadiazine (SDZ) and sulfathiazole (STZ) in edible animal products. In this regard, we developed a magnetic dual template molecularly imprinted polymer (MMIP) to determine the SDZ and STZ in milk samples. For the sensitive and selective extraction and determination of target analytes, MMIPs have been combined with the syringe–to–syringe magnetic solid–phase microextraction (SS–MSPME) method. In addition, we used central composite design (CCD) for the extraction of SDZ and STZ. With optimum conditions, an efficient, rapid, and convenient technique for the preconcentration and determination of SDZ and STZ in milk samples by SS–MSPME coupling with HPLC–UV was developed. Using our combined approach, the limits of detection are 0.9 and 1.3 ng mL−1 for SDZ and STZ, respectively, along with good linearity and determination coefficients higher than 0.98. Our method demonstrates a practical approach for the deduction of antibiotics in milk samples with high recoveries and selectivity.

Evaluation of the presence of antibiotics in milk samples sold in the region of Campinas - SP

Abstract Milk is considered one of the most complete sources of health nutrients and is quite susceptible to contamination by antimicrobial residues due to the indiscriminate use of veterinary drugs to treat dairy cattle, mainly in the treatment of mastitis in cows. Antibiotic residues are considered chemical contaminants, arising from the treatment of pathologies of the dairy herd without adequate control of the disposal period provided by each medication. Milk may also contain residues of other substances from agricultural products and / or inputs and environmental residues, such as: antiparasitic agents, growth promoters, milking hygiene products, heavy metals and mycotoxins. The present study aimed to qualitatively evaluate the presence of antibiotics in raw milk samples, being 2 samples of bovine milk and one sample of goat milk. The samples of raw, bovine and goat milk were purchased from local stores and were kept at approximately 5 ºC for 8 hours and subsequently frozen at - 6 ºC for conservation purposes. The tests were carried out at the premises of Hexis Científica, Av. Antonieta Piva Barranqueiros, 385 - Distrito Industial - Jundiaí-SP, which provided training and use of the laboratory. Kit Charm QUAD-1, Test LF-BRPAC-100K, interpretation of the EZ System test (HX0066-00205) which detects the presence of Beta-lactams, Quimolones, Sulfa drugs, Tetraciclynes, Macrolides, Gentamicin, Aminoglycosides and Amphenicols, covering the drugs required in the National Contaminant Waste Plan-PNCRC. According to the analyzes, the samples studied did not show residues of antibiotics, which demonstrates the responsibility of producers with current legislation and consumers. Key messages As for the public health issue, different types of risks are associated with the presence of antimicrobials in milk, such as microbiological, immunopathological and toxic-pharmacological. The carrying out of information actions, in the production chain, regarding the risks arising from the ingestion of food contaminated by antimicrobial agents is essential for consumer safety.

Rapid and sensitive determination of trace fluoroquinolone antibiotics in milk by molecularly imprinted polymer-coated stainless steel sheet electrospray ionization mass spectrometry

Rapid analysis of trace analytes in complex biological samples is a great challenge for direct mass spectrometry, which suffers from low detection sensitivity. In this study, molecular imprinting technology was explored on the stainless steel sheet and integrated with the electrospray ionization method for direct sample analyses. The molecularly imprinted polymer-coated stainless steel sheet (MIPCS) was prepared and used as a solid-phase microextraction tip for rapid sampling of trace fluoroquinolone antibiotics in milk samples and then applied as an electrospray ionization tip to couple MS for sensitive detection. Our results shown that MIPCS could significantly enrich the trace fluoroquinolone antibiotics in milk samples. In our study, the extraction process of milk sample was completed within 30 min and the direct MS analysis was accomplished within 1 min. In addition, this proposed MIPCS-ESI-MS method showed a good linearity (R2>0.99) ranged from 1 to 1000 ng mL−1. The limits of detection (LODs) and limits of quantitation (LOQs) for the analytes range from 0.1 to 5 ng mL−1. The recoveries were in a range of 78.84%–103.04%. The relative standard deviation (RSD%) of inter-day and intra-day precision ranged from 7.00% to 10.4% and 4.46%–11.44% respectively. Overall, the proposed MIPCS-ESI-MS method could be feasibly used as a rapid and sensitive method for determination of trace analytes in complex food samples.

Magnetic solid phase extraction employing a novel restricted access material based on mesoporous polyaniline coated with hydrophilic monomers and casein for determination of antibiotics in milk samples

In this study was developed a new analytical method for the simultaneous determination of several antibiotics used in cows. For this, the technique of determination of doxycycline (DOX), oxytetracycline (OXY), trimethoprim (TPM) and penicillin G (PC-G) in milk samples was using the magnetic solid phase extraction (MSPE) and analyzing by high performance liquid chromatography (HPLC). Then, the adsorbent material developed was a novel restricted access material based on magnetic mesoporous polyaniline coated with hydrophilic monomers and casein (RA-MMPAni-HM-CAS). The materials of each step of the synthesis were characterized by thermogravimetric analysis, scanning electron microscopy with energy dispersive spectroscopy, X-Rays diffraction and Fourier transform infrared spectroscopy. The chromatographic method developed was using the mobile phase composed by methanol: 50 mM phosphate buffer solution pH 6.6 (45: 55, v/v) in isocratic mode and reverse phase with flow rate at 1.25 mL min−1, temperature at 25 °C, injection volume of 20 μL and ultraviolet detection in 240 nm. The optimized parameters conditions, for the sample preparation were 500 μL of water as washing solvent, 800 μL acetonitrile: acetic acid (7: 3, v/v) as eluent solvent, 1 mL of sample at pH 12.5, 40 mg of RA-MMPAni-HM-CAS of and 1 min stirring on vortex. The method shown to be linear over the concentration range from 8 to 1000 ng mL−1 with coefficients of determination (R2) ≥0.99 for all analytes and recoveries proximity to 100% for TPM, DOX and OXY, and recovery to 93.16% for PC-G. The method developed and validated was applied in real milk samples from various local supermarkets. In conclusion, the results showed that RA-MMPAni-HF-CAS coupled to HPLC was low cost technique, simple and easy to perform.

Chemiluminescence imaging immunoassay for multiple aminoglycoside antibiotics in cow milk

SummaryA simple and rapid multiplexed direct competitive chemiluminescent (CL) imaging immunoassay had been developed for the simultaneous detection of kanamycin (KAN) and streptomycin (STR), which were widely used against bacterial infections in animals. To achieve the multiplexed detection of the two targets, a microarray format based on nitrocellulose membranes (NCMs) has been designed. Then, the peroxidase activity of the captured HRP‐labelled immunocomplex in each channel was measured by an enhanced luminol‐based chemiluminescent solution using a cooled low‐light CCD with high resolution. For qualitative analysis, the limit of detection (LOD) was 0.5 ng mL−1 for KAN and 3.13 ng mL−1 for STR by the naked eye. Through the CL data collected, KAN and STR could be detected quantitatively at the LOD of 0.03 and 0.33 ng mL−1, respectively. This method can be utilised as a screening test to evaluate the presence of antibiotics in milk samples.

Surface plasmon resonance based sensor for the detection of glycopeptide antibiotics in milk using rationally designed nanoMIPs

Glycopeptide antibiotics are known as the last resort for the treatment of serious infections caused by Gram-positive bacteria. The use of milk products contaminated with these antibiotic residues leads to allergic reactions and sensitivity in human. Also, long-term consumption of milk products containing low levels of these antibiotics may cause the relevant bacteria to build up resistance to these last resort antibiotics. Sensitive, rapid and effective quantification and monitoring systems play a key role for their determination in milk products. Hence, molecularly imprinted nanostructures were rationally designed in this work to produce high affinity synthetic receptors to be coupled with a surface plasmon resonance sensor for the analysis of glycopeptide antibiotics in milk samples. The nanoMIP-SPR sensor enabled vancomycin quantification with the LODs of 4.1 ng mL−1 and 17.7 ng mL−1 using direct and competitive assays, respectively. The recoveries rates for two sensor methods ranged in 85–110% with RSDs below 7%. The affinity between the nanoMIP receptors and the target molecule (dissociation constant: 1.8 × 10−9 M) is mostly superior to natural receptors and other synthetic receptors. Unlike other methods commonly employed for the detection of milk contaminants this approach is extremely simple, fast and robust, and do not require pre-sample treatment.

Removal of antibiotics from water and waste milk by ozonation: kinetics, byproducts, and antimicrobial activity

The use of antibiotics in the dairy farming for curing and growth promotion results in the production of massive quantities of non-recyclable wastewater by the conventional purification techniques. Additionally, waste milk is produced during the drug withholding periods, which is not suitable for human or animal consumption and cause huge economic loss as well as present serious environmental waste. This study was designed to investigate the decomposition of various antibiotic compounds in un-buffered aqueous solutions and milk samples by ozonation process. Commonly administered broad-spectrum antibiotics such as amoxicillin, doxycycline, ciprofloxacin, and sulphadiazine were selected as model examples in the current investigation. Gradual exposure of these antibiotics to increasing ozone gas concentration induced increasing removal percentages of the antibiotics in spiked water and milk samples. The removal reached 95% across all the tested treated antibiotics with ozone dose as low as 75 mg L−1. It was noted that the removal of antibiotics in milk samples is more efficient with faster rate constants. This was attributed to the self-buffering characteristic of milk that maintains the neutral pH, keeping the amine groups un-protonated and more reactive towards the electrophilic attack by the molecular ozone. 1H NMR as well as HPLC experiments support the near complete removal of antibiotics and indicated the break down to simpler and more soluble fragments of acidic nature. Bacterial growth experiments, conducted with E. coli, and milk ageing experiments provided clear evidences that the resulting decomposition byproducts lack both toxicity effect and antimicrobial activity. This study provides a viable route to remove hazardous materials, which contribute to a growing issue of antibiotic resistance of pathogenic bacteria.

Evaluation of a multiresidue capillary electrophoresis-quadrupole-time-of-flight mass spectrometry method for the determination of antibiotics in milk samples

A selective and rapid method has been developed to determine 15 antibiotic residues (eight tetracyclines and seven quinolones) in milk samples by capillary zone electrophoresis coupled with quadrupole time-of-flight mass spectrometry (CZE-Q-TOF-MS). The use of this hybrid mass spectrometer allowed obtaining full scan and full MS/MS spectra for quantification/confirmation purposes in a single run. In addition, solid phase extraction (SPE) using the new Oasis PRiME HLB cartridge was proposed for the extraction, achieving excellent results in terms of sample throughput. The proposed method was validated using whole cow milk as representative matrix. Good linearity was obtained (R2>0.99) for all the studied compounds. The precision, expressed as relative standard deviation (%, RSD), at two concentration levels (50 and 100μgkg−1) was below 13%. Recoveries obtained from goat milk, whole cow milk and semi-skimmed cow milk, at two concentration levels, ranged from 76 to 106%, while limits of quantification ranged from 1.5 to 9.6μgkg−1, being lower than the established maximum residue limits in the European legislation. Matrix effect was negligible in all cases, showing that with this new SPE sorbent cleanest extracts were obtained with a minimum number of steps in the sample treatment. Thus, the proposed SPE-CZE-Q-TOF-MS method is suitable for multiclass multiresidue monitoring in different types of milk samples.

Screening food-borne and zoonotic pathogens associated with livestock practices in the Sumapaz region, Cundinamarca, Colombia

Hazardous practices regarding antibiotics misuse, unsanitary milking procedures, and the commercial sales of raw milk and unpasteurized dairy products are currently being practiced by livestock farmers in the Sumapaz region (Colombia). The purpose of this study was to screen for food-borne and zoonotic pathogens associated with local livestock practices. We evaluated 1098 cows from 46 livestock farms in the Sumapaz region that were selected by random. Of the total population of cattle, 962 animals (88%) were tested for bovine TB using a caudal-fold tuberculin test and 546 (50%) for brucellosis by a competitive ELISA. In the population tested, 23 cows were positive for Brucella sp. representing a 4.2% seroprevalence and no cases of bovine tuberculosis were found. In addition, food-borne contamination with Escherichia coli and Staphylococcus aureus was assessed together with antibiotic susceptibility for ten different antibiotics in milk samples from 16 livestock farms. We found that 12 of the farms (75%) were contaminated with these food-borne pathogens. Noteworthy, all of the isolated pathogenic strains were resistant to multiple antibiotics, primarily to oxytetracycline and erythromycin. Our findings suggest that livestock products could be a source of exposure to Brucella and multidrug-resistant E. coli and S. aureus strains as a result of unhygienic livestock practices in the Sumapaz region. Training in good farming practices is the key to improving safety in food production.

Ultrasensitive Self-Powered Aptasensor Based on Enzyme Biofuel Cell and DNA Bioconjugate: A Facile and Powerful Tool for Antibiotic Residue Detection.

Herein, we reported a novel ultrasensitive one-compartment enzyme biofuel cells (EBFCs)-based self-powered aptasensing platform for antibiotic residue detection. By taking full advantage of the unique features of both EBFCs-based self-powered sensors and aptamers, the as-proposed aptasensing platform has the merits of simple instrumentation, anti-interference ability, high selectivity, and low cost. In this study, DNA bioconjugate, i.e., SiO2@gold nanoparticles-complementary strand of aptamer (SiO2@AuNPs-csDNA), was elaborately designed and played a key role in blocking the mass transport of glucose to the bioanode. While in the presence of the target antibiotic, SiO2@AuNPs-csDNA bioconjugate broke away from the bioanode due to the aptamer recognition of the target. Without the blocking of glucose by the DNA bioconjugate, a significantly elevated open circuit voltage of the EBFCs-based aptasensor was obtained, whose amplitude was dependent on the antibiotic concentration. In addition, this proposed aptasensor was the first reported self-powered aptasensing platform for antibiotic determination and featured high sensitivity owing to the elaborate design of the DNA bioconjugate modified bioanode of EBFC, which was superior to those previously reported in the literature. Furthermore, due to the anti-interference ability and the excellent selectivity of the aptasensor, no special sample pretreatment was needed for the detection of antibiotics in milk samples. Therefore, the proposed EBFCs-based self-powered aptasensor has a great promise to be applied as a powerful tool for on-site assay in the field of food safety.

Luminescent determination of quinolones in milk samples by liquid chromatography/post-column derivatization with terbium oxide nanoparticles

The usefulness of terbium oxide nanoparticles (Tb4O7NPs) as post-column derivatizing reagent for the liquid chromatographic determination of residues of quinolone antibiotics in milk samples has been studied. Seven quinolones of veterinary use have been chosen as model analytes to develop this method. The derivatization step is based on the formation of luminescent chelates of quinolones with Tb4O7NPs, which are monitored at λex=340nm and λem=545nm. Another relevant feature of the method is that the use of a 10-cm column and a ternary mixture of methanol, acetonitrile and acetic acid as mobile phase in gradient elution mode allow the chromatographic separation of the quinolones in about 13min, whereas previously described chromatographic methods require about 20min.The dynamic ranges of the calibration graphs and limits of detection are, respectively: 65–900ngmL−1 and 35ngmL−1 for marbofloxacin, 7.2–900ngmL−1 and 2.5ngmL−1 for ciprofloxacin, 6–900ngmL−1 and 2ngmL−1 for danofloxacin, 50–900ngmL−1 and 20ngmL−1 for enrofloxacin, 35–900ngmL−1 and 12ngmL−1 for sarafloxacin, 5–900ngmL−1 and 2ngmL−1 for oxolinic acid, and 7–900ngmL−1 and 2.5ngmL−1 for flumequine. The precision, established at two concentration levels of each analyte and expressed as the percentage of the relative standard deviation is in the range of 1.9–8.1% using standards, and of 3.4–10.7% in the presence of milk samples. The method has been satisfactorily applied to the analysis of skimmed, semi-skimmed and whole milk samples, with recoveries ranging from 89.0 to 106.5%.

Electrochemical detection of fluoroquinolone antibiotics in milk using a magneto immunosensor.

An amperometric magneto-immunosensor (AMIS) for the detection of residues of fluoroquinolone antibiotics in milk samples is described for the first time. The immunosensor presented combines magnetic beads biomodified with an antibody with a broad recognition profile of fluoroquinolones, a haptenized enzyme and a magnetic graphite–epoxy composite (m-GEC) electrode. After the immunochemical reaction with specific enzyme tracer, the antibody biomodified magnetic beads are easily captured by an electrode made of graphite-epoxy composite containing a magnet, which also acts as transducer for the electrochemical detection. In spite of the complexity of milk, the use of magnetic beads allows elimination of potential interferences caused by the matrix components; hence the AMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. The immunosensor is able to detect up to seven different fluoroquinolones far below the MRLs defined by the UE for milk; for example ciprofloxacin is detected directly in milk with an IC50 of 0.74 μg/L and a LOD of 0.009 μg/L. This strategy offers great promise for rapid, simple, cost-effective, and on-site analysis fluoroquinolones in complex samples.