Applications of a copper microparticle-modified carbon fiber microdisk array electrode for the simultaneous determination of aminoglycoside antibiotics by capillary electrophoresis

Lattice matching enables construction of CaS@NaYF4 heterostructure with synergistically enhanced water resistance and luminescence for antibiotic detection

Rare earth (RE)-doped CaS phosphors have been widely used as light-emitting components in various fields. Nevertheless, the application of nanosized CaS particles is still significantly limited by their poor water resistance and weak luminescence. Herein, a lattice-matching strategy is developed by growing an inert shell of cubic NaYF4 phase on the CaS luminescent core. Due to their similarity in crystal structure, a uniform core-shell heterostructure (CaS:Ce3+@NaYF4) can be obtained, which effectively protects the CaS:Ce3+ core from degradation in aqueous environment and enhances its luminescence intensity. As a proof of concept, a label-free aptasensor is further constructed by combining core-shell CaS:Ce3+@NaYF4 and Au nanoparticles (AuNPs) for the ultrasensitive detection of kanamycin antibiotics. Based on the efficient FRET process, the detection linear range of kanamycin spans from 100 to 1000 nM with a detection limit of 7.8 nM. Besides, the aptasensor shows excellent selectivity towards kanamycin antibiotics, and has been successfully applied to the detection of kanamycin spiked in tap water and milk samples, demonstrating its high potential for sensing applications.

Dual fluorescence-colorimetric sensor based on silver nanoparticles for determination of tobramycin in its pharmaceutical preparations

The purpose of this study is to develop a dual fluorescence-colorimetric sensor for determination of the non-chromophoric drug, tobramycin using fluorescein-modified silver nanoparticles. Fluorescein is adsorbed on the surface of silver nanoparticles resulting in quenching of the fluorescence intensity of fluorescein at 513 nm. Upon addition of tobramycin to fluorescein-bound silver nanoparticles, tobramycin can displace fluorescein from the surface of nanoparticles resulting in nanoparticles aggregation and liberation of free fluorescein restoring its fluorescence. The interaction of tobramycin with fluorescein-bound silver nanoparticles is manifested by a decrease in the surface plasmon resonance band of silver nanoparticles at 395 nm, an increase in the fluorescence intensity of fluorescein at 513 nm and color change of the colloidal solution from yellow to light pink. These spectral effects are directly proportional to the concentration of tobramycin with a linearity range of 0.10 - 0.45 μg mL-1 and 0.05 - 0.45 μg mL-1 for the spectrophotometric and spectrofluorimetric methods, respectively. The proposed methods were applied for determination of tobramycin in Tobrin® ophthalmic solution with mean %recovery ± standard deviation of 99.036 ± 1.737 for the spectrophotometric method and 101.192 ± 1.315 for the spectrofluorimetric method. The optical sensor is simple, rapid, and cost-effective and can be used for determination of tobramycin in bulk and in its pharmaceutical preparations.

A novel aptasensor for colorimetric monitoring of tobramycin: Strategy of enzyme-like activity of AuNPs controlled by three-way junction DNA pockets

In this study, a novel colorimetric sensor was introduced to detect tobramycin (TOB) based on controlling the catalytic activity of gold nanoparticles (AuNPs) by the three-way junction aptamer pockets. In the absence of TOB, the surfaces of AuNPs were masked by the three-way junction pockets that prevented their catalytic activation for the reduction of 4-Nitrophenol in the presence of NaBH₄. While the formation of the pockets was prevented in the presence of TOB that facilitated the 4-Nitrophenol access to AuNPs. Hence, the catalytic reduction of 4-Nitrophenol induced a color change of the solution from yellow to colorless, highlighting the presence of the target. The aptasensing assay provided good target specificity with a detection limit (LOD) of 1.16 µM and a linear dynamic range over 4-32 µM. The aptasensor was successfully applied to quantitatively monitor TOB in the human serum and milk samples with the LODs of 1.38 and 1.42 µM and recovery values of 94.87-105.75% and 93.75-105.31%, respectively.

A Status Update on Pharmaceutical Analytical Methods of Aminoglycoside Antibiotic: Amikacin

Amikacin (AMK) is one of the commonly used aminoglycoside antibiotics, introduced for clinical use in patients suffering from bacterial infections especially life-threatening gram-negative infections. Due to lack of chromophore in the molecule, the detection of AMK during analysis is a challenge. Thus, pre and post-column derivatization techniques are generally used for AMK estimation. This review focuses on different analytical methods used for detection and quantification of AMK in pure or fixed dose combination pharmaceutical formulations and biological samples. Various reported methods described in the literature include high-performance liquid chromatography techniques, pulsed electrochemical detection techniques, Chemiluminescence techniques, Capillary electrophoresis and immunological methods. High-performance-liquid-chromatography based methods with UV/Vis spectrophotometric, fluorescence and mass spectrometric detection are the most prevailing methods employed for the analysis of AMK. This review could be of significant importance in the area of future AMK analytical method development studies.

The Supramolecular Self-Assembly of Aminoglycoside Antibiotics and their Applications

Aminoglycosides, a class of antibiotics that includes gentamicin, kanamycin, neomycin, streptomycin, tobramycin and apramycin, are derived from various streptomyces species. Despite the significant increase in the antibacterial resistant pathogens, aminoglycosides remain an important class of antimicrobial drugs due to their unique chemical structure which offers a broad spectrum of activity. The modification of antibiotics and their subsequent use in supramolecular chemistry is rarely reported. Given the importance of aminoglycosides, here we give a brief overview on the modification of 4,5- and 4,6-disubstituted deoxystreptamine classes of aminoglycosides through supramolecular chemistry and their potential for real world applications. We also make the case that the work in this area is gaining momentum, and there are significant opportunities to meet the challenges of modern antibiotics through the modification of aminoglycosides by harnessing the advantages of supramolecular chemistry.

Simple, rapid, sensitive, selective and label-free lincomycin detection by using HAuCl4and NaOH

A simple, rapid, sensitive, selective and label-free method is presented for the colorimetric determination of lincomycin (Lin) by using HAuCl₄and NaOH.

Bimetallic cerium/copper organic framework-derived cerium and copper oxides embedded by mesoporous carbon: Label-free aptasensor for ultrasensitive tobramycin detection

We reported a novel bimetallic cerium/copper-based metal organic framework (Ce/Cu-MOF) and its derivatives pyrolyzed at different temperatures, followed by exploiting them as the scaffold of electrochemical aptamer sensors for extremely sensitive detection of trace tobramycin (TOB) in human serum and milk. After the calcination at high temperature, the meal coordination centers (Ce and Cu) were transferred to metal oxides containing various chemical valences, such as Ce(III), Ce(IV), Cu(II) and Cu(0), which were embedded within the mesoporous carbon network originated from the organic ligands (represented by CeO₂/CuO_x@mC). Owning to the strong synergistic effect among the metal oxides, mesoporous carbon, and small cavities and open channels of MOF, the as-prepared CeO₂/CuO_x@mC nanocomposites not only possess good electrochemical activity but also exhibit strong bioaffinity toward the aptamer strands. By comparing the electrochemical biosensing peroformances using on the Ce/Cu-MOF- and the series of CeO₂/CuO_x@mC-based aptasensors, the constructed CeO₂/CuO_x@mC₉₀₀-based (calcinated at 900 °C) aptasensor exhibits an extremely low detection limit of 2.0 fg mL^-1 within a broad linear TOB concentration range from 0.01 pg mL^-1 to 10 ng mg L^-1. It demonstrates that the proposed aptasensor is substantially superior to those previously reported in the literature, along with high selectivity, good stability and reproducibility, and acceptable applicability in human serum and milk. Thereby, the newly fabricated aptasensing approach based on bimetallic CeO₂/CuO_x@mC has a considerable potential for the quantitative detection of antibiotics in the food safety and biomedical field.

Aptamer based voltammetric determination of ampicillin using a single-stranded DNA binding protein and DNA functionalized gold nanoparticles

An aptamer based method is described for the electrochemical determination of ampicillin. It is based on the use of DNA aptamer, DNA functionalized gold nanoparticles (DNA-AuNPs), and single-stranded DNA binding protein (ssDNA-BP). When the aptamer hybridizes with the target DNA on the AuNPs, the ssDNA-BP is captured on the electrode surface via its specific interaction with ss-DNA. This results in a decreased electrochemical signal of the redox probe Fe(CN)₆^3- which is measured best at a voltage of 0.188 mV (vs. reference electrode). In the presence of ampicillin, the formation of aptamer-ampicillin conjugate blocks the further immobilization of DNA-AuNPs and ssDNA-BP, and this leads to an increased response. The method has a linear reposne that convers the 1 pM to 5 nM ampicillin concentration range, with a 0.38 pM detection limit (at an S/N ratio of 3). The assay is selective, stable and reproducible. It was applied to the determination of ampicillin in spiked milk samples where it gave recoveries ranging from 95.5 to 105.5%. Graphical abstract Schematic of a simple and sensitive electrochemical apta-biosensor for ampicillin detection. It is based on the use of gold nanoparticles (AuNPs), DNA aptamer, DNA functionalized AuNPs (DNA-AuNPs), and single-strand DNA binding protein (SSBP).

Anodic Voltammetric Behavior of Lincomycin and its Electroanalytical Determination in Pharmaceutical Dosage form and Urine at Gold Electrode

The anodic voltammetric behavior of an antibiotic drug, lincomycin hydrochloride (LIN) at gold electrode (GE) has been investigated using cyclic and linear sweep voltammetry. The dependence of the current on pH, concentration and scan rate were investigated to optimize the experimental conditions for the determination of lincomycin. The anodic peak was characterized and the process was adsorption-controlled. The number of electrons transferred in the oxidation process was calculated. In the range of 8.0×10−6 to 1.0×10−4 M, the current measured by linear sweep voltammetry presents a good linear property as a function of the concentration of lincomycin with a detection limit of 1.7×10−7 M with good selectivity and sensitivity. The proposed method was successfully applied to lincomycin determination in pharmaceutical dosage form and in urine as a real sample. This method can be employed in clinical analysis, quality control and routine determination of drugs in pharmaceutical formulations.

Study of the post separation pH adjustment by a microchip for the analysis of aminoglycoside antibiotics

A simple microfluidic technique was developed with the ability to adjust the pH after separation for the electrochemical detection of aminoglycoside antibiotics.

[Determination of netilmicin in rat serum using high performance liquid chromatography and resonance Rayleigh scattering]

A method was developed for the direct determination of netilmicin in rat serum using high performance liquid chromatography and resonance Rayleigh scattering (RRS). The separation was carried out on a C18 column with the isocratic elution of the mixture of 20 mmol/L sodium acetate aqueous solution and methanol containing 0.22% trifluoroacetic acid (92:8, v/v). With the molecular recognition probe of pontamine sky blue, netilmicin formed an ion-association complex and enhanced the intensity of RRS. The RRS signal was detected by a commercial fluorescence detector at 365 nm of both excitation wavelength (lambda ex) and emission wavelength (lambda em). Under the optimized conditions, the limit of detection (LOD, S/N = 3) for the netilmicin was 0.7 mg/L. With the internal standard (IS) of tobramycin, a linear calibration curve ranged from 1.2 mg/L to 30 mg/L was obtained. The presented method can be used for the pharmacokinetics study of netilmicin in rat serum, and can be a new choice for the determination of aminoglycoside antibiotics in biological samples.

A flow injection chemiluminescence method for the determination of lincomycin in serum using a diperiodato-cuprate (III)-luminol system

In this paper, the novel trivalent copper-periodate complex {K₅[Cu(HIO₆)₂], DPC} has been applied in a luminol-based chemiluminescence (CL) reaction. Coupled with flow injection (FI) technology, the FI-CL method was proposed for the determination of lincomycin hydrochloride. The CL reaction between luminol and DPC occurred in an alkaline medium. The CL intensity could be greatly enhanced by lincomycin hydrochloride. The relative CL intensity was proportional to the concentration of lincomycin hydrochloride in the range of 1 × 10⁻⁸ to 5 × 10⁻⁶ g mL⁻¹ and the detection limit was at the 3.5 × 10⁻⁹ g mL⁻¹ level. The relative standard deviation at 5 × 10⁻⁸ g mL⁻¹ was 1.7% (n = 9). The sensitive method was successfully applied to the direct determination of lincomycin hydrochloride (ng mL⁻¹) in serum. A possible mechanism of the lumonol-DPC CL reaction was discussed by the study of the CL kinetic characteristics and the spectra of CL reaction. The oxidability of DPC was studied by means of its electrochemical response.

Trace analysis of aminoglycoside antibiotics in bovine milk by MEKC with LIF detection

This work describes a straightforward and sensitive method for the multi-residue analysis of aminoglycoside antibiotics (kanamycin B, amikacin, neomycin B and paromomycin I) in bovine milk samples. The method involves the pre-capillary derivatization of antibiotics with sulfoindocyanine succinimidyl ester (Cy5) and their separation and determination by MEKC with LIF detection. The optimum procedure includes a derivatization step of the antibiotics at 25 degrees C for 30 min and direct injection for MEKC analysis, which is performed in about 20 min by using borate buffer (35 mM; pH 9.2) with 55 mM SDS as an anionic surfactant and 20% ACN as the organic modifier. Under these conditions, dynamic ranges of 10-500 microg/L and RSDs (within-day precision) from 3.8 to 5.3% were obtained. These results indicate that the proposed MEKC-LIF method is useful as a selective and sensitive tool for the determination of these antibiotics and surpasses other reported electrophoretic alternatives. Finally, the method was successfully applied to bovine milk samples after a simple solid-phase extraction clean-up and preconcentration procedure. The aminoglycosides were readily detected at 0.5-1.5 microg/kg levels with average recoveries ranging from 89.4 to 93.3%.

Determination of amikacin in body fluid by high-performance liquid-chromatography with chemiluminescence detection

A simple and sensitive method was developed for the quantification of amikacin in human plasma and urine samples. The method involves centrifugation of body fluid plasma after dilution with an ethanol/sodium carbonate mixture, and then an aliquot of the supernatant is directly injected into the chromatograph. After separation on a reversed-phase C18 column (runtime 20 min), aminoglycoside is detected on the basis of its complex formation reaction with Cu(II), the catalyst of the luminol/hydrogen peroxide chemiluminescence system. Using a volume of 500 microl biological sample, linearity is established over the concentration range 0.15-2.0 microg/ml and the limit of detection (LOD) is ca. 50 microg/l in plasma or urine. The intra-day and inter-day precision (measured by relative standard deviation, R.S.D.%) are always less than 9%, and relative recoveries are found to be over 92%.

Electrochemical study of lincomycin on a multi-wall carbon nanotubes modified glassy carbon electrode and its determination in tablets

Multi-wall carbon nanotubes (MWNTs) were dispersed in dihexadecylphosphate (DHP), sodium dodecylbenzenesulfonate (SDBS), and Nafion to give a homogeneous and stable suspension, respectively. MWNTs film in different solvents was fabricated onto a glassy carbon electrode (GCE) with an easy and convenient method. It was found that on MWNTs-DHP film lincomycin exhibited a well-defined oxidation peak. The electrochemical behavior of lincomycin at coated GCE was investigated by cyclic voltammetry and chronocoulometry. The MWNTs-DHP film modified glassy carbon electrode shows obvious electrocatalytic activity to the oxidation of lincomycin, since it greatly enhances the oxidation peak current of lincomycin as well as lowers its oxidation overpotential. Based on this, a very sensitive and simple voltammetric method was developed for the measurement of lincomycin. A sensitive linear voltammetric response for lincomycin was obtained in the concentration range of 4.5x10(-7) to 1.5x10(-4) mol/l, and the detection limit is 2.0x10(-7) mol/l using linear sweep voltammetry. Compared with other methods, this proposed method possesses many advantages such as very low detection limit, fast response, low cost and simplicity. The practical application was demonstrated to determine lincomycin in tablets with good result.

Determination of tobramycin in human serum by capillary electrophoresis with contactless conductivity detection

A study on the determination of the antibiotic tobramycin by CE with capacitively coupled contactless conductivity detection is presented. This method enabled the direct quantification of the non-UV-absorbing species without incurring the disadvantages of the indirect approaches which would be needed for optical detection. The separation of tobramycin from inorganic cations present in serum samples was achieved by optimizing the composition of the acetic acid buffer. Field-amplified sample stacking was employed to enhance the sensitivity of the method and a detection limit of 50 microg/L (S/N = 3) was reached. The RSDs obtained for migration time and peak area using kanamycin B as internal standard were typically 0.12 and 4%, respectively. The newly developed method was validated by measuring the concentration of tobramycin in serum standards containing typical therapeutic concentrations of 2 and 10 mg/L. The recoveries were 96 and 97% for the two concentrations, respectively.

Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde

A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0 x 10(-3) g ml(-1) formaldehyde, netilmicin exhibits a sensitive cathodic peak at -1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton-Robinson buffer (pH 8.7) with a scan rate of 100 mV s(-1) after a preconcentration period of 120 s at -1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2 x 10(-9)-1.0 x 10(-7) g ml(-1). The achieved limits of detection and quantitation were 1.0 x 10(-10) and 3.3 x 10(-10) g ml(-1) netilmicin, respectively. It was deduced from the experiments that the amine-aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.

Capillary electrophoresis assay of netilmicin sulphate

An effective method based on capillary electrophoresis (CE) for the determination of netilmicin sulphate in commercial ophthalmic formulations was developed and validated. The use of a polymer-coated capillary and a non-absorbing running buffer permitted the elution of netilmicin in cationic mode at pH 3.0 and with direct UV detection at lambda=195 nm. Since pre-treatment of the samples is not required, this procedure may be straightforwardly applied to the other aminoglycosides provided that their extinction coefficient is not too low.

Direct electrochemical detection of glucose in human plasma on capillary electrophoresis microchips

We developed an electrochemical detector on a hybrid chip for the determination of glucose in human plasma. The microchip system described in this paper consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate. The copper microelectrode is fabricated by selective electroless deposition. The fabrication of the decoupler is performed by platinum electrochemical deposition on the metal film formed by electroless deposition. Factors influencing the performance, including detection potential, separation field strength, and buffer concentration, were studied. The electrodes exhibited good stability and durability in the analytical procedures. Under optimized detection conditions, glucose responded linearly from 10 microM to 1 mM. Finally, glucose in human plasma from three healthy individuals and two diabetics was successfully determined, giving a good prospect for a new clinical diagnostic instrument.

Selective kinetic determination of amikacin in serum using long-wavelength fluorimetry

A simple and rapid method for the determination of the antibiotic amikacin, involving the use of a long-wavelength fluorophor, namely indocyanine green, (ICG) is presented. The dye is oxidised by cerium(IV) in acidic medium, resulting in a sharp decrease of the fluorescence, but this fluorescence quenching is inhibited in the presence of amikacin, which can be ascribed to the formation of an ion pair between the fluorophor and the analyte. The initial rate of the system is monitored at lambda(ex): 765 nm and lambda(em): 812 nm as excitation and emission wavelengths, respectively, using the stopped-flow mixing technique, which makes the method applicable to automatic routine analysis. Each measurement is obtained in only 2-3s. The method presents a detection limit of 0.02 microg m1(-1) in standard solutions, which corresponds to 2.5 microg ml(-1) in serum samples. The precision is in the range 4.8-6%. The good selectivity of the method allows amikacin to be determined in the presence of other antibiotics, including other aminoglycoside antibiotics, in serum. The recoveries obtained from the analysis of different samples were in the range 89.4-104.7%.

Quantitative analysis of lincomycin in animal tissues and bovine milk by liquid chromatography electrospray ionization tandem mass spectrometry

A sensitive method for determining lincomycin in bovine milk, animal muscles and organs using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) is presented. Milk and homogenized animal tissues were extracted with acetonitrile twice after addition of an appropriate amount of clindamycin, a lincosamide analogue as the internal standard. The combined extracts were finally made up to 10 ml with distilled water and partitioned with hexane to remove the animal fats prior to analysis. Analytes in the extracts were separated on a reversed phase C18 column (250 mm x 2.1 mm, 5 microm) using a mobile phase of a 3:7 (v/v) mixture of 0.1% formic acid in acetonitrile and an ammonium formate buffer (ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v/v/v) running at a flow rate of 0.2 ml min(-1). Presence of lincomycin was confirmed by the presence of two characteristic product ions at m/z 126.1 and 359.2 within a defined retention time window from the precursor ion at m/z 407.2, whilst quantification was based on the relative ratio of the sum of the peak areas at m/z 126.1 and 359.2 for lincomycin to that of the internal standard (peaks at m/z 126.1 and 377.2) with reference to the respective ratios of the calibration standards. The validated method that was found to have linear responses in the calibration range from 25 to 3000 microg kg(-1) and satisfactory intra-day and inter-day accuracy (94.4-107.8%) and precision (1.3-7.8%) at concentrations ranging from 100 to 1500 microg kg(-1) has been applied to real samples and matrix spiked samples. It is considered robust and suitable for analysis of lincomycin in milk and animal tissues.

Lincomycin, cultivation of producing strains and biosynthesis

Lincomycin and its derivatives are antibiotics exhibiting biological activity against Gram-positive bacteria. The semi-synthetic chlorinated lincomycin derivative is used in clinical practice. The chemical structure of lincosamide antibiotics, cultivation of producing strains and analytical procedures used for separation and isolation of these compounds are described in this review. Biosynthesis of lincomycin and related compounds and its genetic control are briefly discussed.

Reversed-phase liquid chromatographic method for the analysis of aminoglycoside antibiotics using pre-column derivatization with phenylisocyanate

A pre-column derivatization liquid chromatographic method has been developed for the analysis of aminoglycoside antibiotics using phenylisocyanate as a derivatization reagent. Derivatives including kanamycin, neomycin and gentamicin were formed by reaction of the analytes with phenylisocyanate in the presence of triethylamine. Phenylisocyanato groups were attached to corresponding amino groups of aminoglycoside and their molecular mass was confirmed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The experimental conditions for derivatization and separation of aminoglycoside derivatives were optimized and validated. A simple liquid chromatographic method for the determination of aminoglycoside antibiotics was demonstrated.

Modeling and optimization of the chiral selectivity of basic analytes in chiral capillary electrophoresis with negatively charged cyclodextrins using electrochemical detection

A mathematical model concerning the separation selectivity of basic analytes in chiral capillary electrophoresis (CE) modified with negatively charged cyclodextrins (CDs) has been presented to describe the dependence of chiral selectivity on the buffer pH and the chiral selector concentration. The electrophoretic method to determine the parameters of the model has also been developed. The model has been tested with racemic epinephrine and isoproterenol as target analytes and sulfonated beta-CD as chiral selector. The agreements have been found between the calculated and the measured values. Some significant conclusions to optimize chiral CE separation have been derived from the model and proven by the experiments. Electrochemical detection was used to meet the requirement of the low introduced concentration of analytes.