Dual-ligand lanthanide metal-organic framework based ratiometric fluorescent platform for visual monitoring of aminoglycoside residues in food samples

Herein, a dual-emission Eu metal-organic framework (Eu-MOF) is prepared and used as the ratiometric fluorescence probe for ultrasensitive detection of aminoglycoside antibiotics (AGs). Due to the strong hydrogen bond interactions between AGs and Eu-MOF, the blue emission is enhanced while the red emission has little fluctuation in Eu-MOF with the addition of AGs, thus a good linear relationship with the logarithm of AGs concentrations from 0.001 to 100 μg/mL can be established for quantitative analysis. Good sensitivity with the detection limit of 0.33 ng/mL for apramycin, 0.32 ng/mL for amikacin and 0.30 ng/mL for kanamycin is achieved. The proposed assay demonstrates good selectivity and applicability for determination of AGs in real milk and honey samples. The Eu-MOF materials are further fabricated as fluorescent test papers for facile visual detection. The as-established ratio fluorescence platform offers a portable and economical way for rapid monitoring AGs residues in complex food samples.

High-pH mobile phase in reversed-phase liquid chromatography-tandem mass spectrometry to improve the separation efficiency of aminoglycoside isomers

In chromatography, the use of extreme conditions can often lead to unique separation selectivity. In this study, a highly basic mobile phase (pH > 11), which is not typically employed for reversed-phase liquid chromatography (RPLC), was utilized in RPLC-tandem mass spectrometry (MS/MS) to achieve effective separation between electrically neutral bases of aminoglycosides (AGs). A mixture of AGs was simultaneously analyzed using 500 mmol L-1 ammonia aqueous solution (pH 11.8) as the mobile phase. A total of 11 AGs, including 2 stereoisomers of neomycin (B and C) and 5 structurally similar components of gentamicin (C1, C1a, C2, C2a, and C2b), were completely separated for the first time. The high separation performance for AGs was mainly due to two factors: First, slight differences in hydrophobicity among the AGs were significantly enhanced at a high pH by the complete acid dissociation of amines. Second, the high pH of the mobile phase minimized any electrostatic interactions between the AGs and residual silanol groups in the stationary phase, resulting in extremely sharp peaks for the AGs. The sensitivity of spectinomycin decreased by more than 20% when using the highly basic mobile phase (pH 11.8) due to its degradation, therefore, a mixture of 10 AGs was analyzed with 250 mmol L-1 ammonia aqueous solution (pH 11.5) with less degradation as the optimum condition. The developed analytical method could be used to determine the concentrations of trace AGs in milk with high accuracy and precision. Thus, RPLC-MS/MS using a high-pH mobile phase has great potential for the efficient separation of basic compounds containing amino sugars such as AGs.

Residue analysis of 10 aminoglycoside antibiotics in aquatic products by multiwalled carbon nanotubes combined with mixed-mode ion exchange liquid chromatography-tandem mass spectrometry

An ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for simultaneous determination of 10 kinds of aminoglycosides in edible parts of aquatic products. The samples were extracted with 10 mmol/L potassium dihydrogen phosphate buffer solution, then the pH value of the extract was adjusted to neutral by sodium hydroxide. Half volume of the extract was loaded onto multiwalled carbon nanotubes cartridge. All the target compounds were separated on a mixed-mode ion exchange column and detected by ultra-high-performance liquid chromatography-tandem mass spectrometry with electrospray in the positive ionization mode. Under optimized conditions, this method had a good linearity with a squared correlation coefficient > 0.999. For neomycin, the limit of detection and limit of quantification were 5.0 μg/kg and 10.0 μg/kg, respectively; for hygromycin B and apramycin, values were 2.0 μg/kg and 5.0 μg/kg, respectively; for the other seven kinds of aminoglycosides, values were 1.0 μg/kg and 2.0 μg/kg, respectively. The average recoveries presented 75.8%-107.2% with intra- and interday reproducibility ranging between 3.8% and 12.5%. The method was rapid with good separation and sharp peak shapes, had the characteristicsis of high accuracy and good precision, and was suitable for simultaneous determination of 10 kinds of aminoglycosides in aquatic products.

An optimized method for the detection and spatial distribution of aminoglycoside and vancomycin antibiotics in tissue sections by mass spectrometry imaging

Suboptimal antibiotic dosing has been identified as one of the key drivers in the development of multidrug-resistant (MDR) bacteria that have become a global health concern. Aminoglycosides and vancomycin are broad-spectrum antibiotics used to treat critically ill patients infected by a variety of MDR bacterial species. Resistance to these antibiotics is becoming more prevalent. In order to design proper antibiotic regimens that maximize efficacy and minimize the development of resistance, it is pivotal to obtain the in situ pharmacokinetic-pharmacodynamic profiles at the sites of infection. Mass spectrometry imaging (MSI) is the ideal technique to achieve this. Aminoglycosides, due to their structure, suffer from poor ionization efficiency. Additionally, ion suppression effects by endogenous molecules greatly inhibit the detection of aminoglycosides and vancomycin at therapeutic levels. In the current study, an optimized method was developed that enabled the detection of these antibiotics by MSI. Tissue spotting experiments demonstrated a 5-, 15-, 35-, and 54-fold increase in detection sensitivity in the washed samples for kanamycin, amikacin, streptomycin, and vancomycin, respectively. Tissue mimetic models were utilized to optimize the washing time and matrix additive concentration. These studies determined the improved limit of detection was 40 to 5 μg/g of tissue for vancomycin and streptomycin, and 40 to 10 μg/g of tissue for kanamycin and amikacin. The optimized protocol was applied to lung sections from mice dosed with therapeutic levels of kanamycin and vancomycin. The washing protocol enabled the first drug distribution investigations of aminoglycosides and vancomycin by MSI, paving the way for site-of-disease antibiotic penetration studies.

Aptamer-based ellipsometric sensor for ultrasensitive determination of aminoglycoside group antibiotics from dairy products

BACKGROUND

Residual antibiotics taken along with food consumed through the food chain are the main cause of the super-bacteria and may damage organs such as liver and kidney. Therefore, monitoring residual antibiotic levels of products in the food chain is both important and a requirement. Maximum residual limits for kanamycin and neomycin are 150 ng mL^-1 and 500 ng mL^-1 respectively, which are challenging for most sensor platforms. In this paper, a novel method is presented for the determination of antibiotics residues in animal-derived foods.

RESULTS

Aptamer-based kanamycin and neomycin biosensors based on the spectroscopic ellipsometer and the surface plasmon resonance-enhanced total internal reflection ellipsometer methods as transducing element were developed. Detection limits of both sensor platforms were in the 0.1-1 nmol L^-1 ranges, and the detection range was between the detection limit and 1000 nmol L^-1 .

CONCLUSION

Both ellipsometry-based aptasensors can be used as an alternative to the existing enzyme-linked immunosorbent assay-based method in terms of assay time (10 min), detection limit (0.22 ng mL^-1 for neomycin and 0.048 ng mL^-1 for kanamycin), and detection range. © 2020 Society of Chemical Industry.

Simultaneous Determination of 11 Aminoglycoside Residues in Honey, Milk, and Pork by Liquid Chromatography with Tandem Mass Spectrometry and Molecularly Imprinted Polymer Solid Phase Extraction

An analytical method was developed for the simultaneous determination of 11 aminoglycoside (AG) antibiotics, including amikacin, paromomycin, dihydrostreptomycin, gentamicin C1a, hygromycin, kanamycin, netilmicin, spectinomycin, sisomicin, streptomycin, and tobramycin in honey, milk, and pork samples by LC with tandem MS and molecularly imprinted polymer (MIP) SPE. The AG antibiotics in milk and homogenated meat samples were extracted with a solution composed of 10 mmol/L potassium dihydrogen phosphate, 0.4 mmol/L EDTA-Na2, and 2% trichloroacetic acid. For honey samples, the extractant was 50 mmol/L potassium dihydrogen phosphate. The extracts were cleaned up with MIP SPE cartridges. The separation was performed on a zwitter ionic-HILIC column (50 × 2.1 mm, 3.5 μm), with the mobile phase consisting of methanol, 0.3% formic acid, and 175 mmol/L ammonium formate at 0.50 mL/min in gradient elution. A triple-quadrupole mass spectrometer equipped with an electrospray ionization source, which was operated in positive mode, was used for detection. The quantification was based on matrix-matched calibration curves. The method was applied to real samples with three different matrixes. The LODs of the method were 2–30 μg/kg and the LOQs were 7–100 μg/kg; the average recovery ranged from 78.2 to 94.8%; intraday RSDs and interday RSDs were ≤15 and ≤18%, respectively; and the absolute values of matrix effect for all AGs were RSDs ≤23%.

Study of matrix effects for liquid chromatography-electrospray ionization tandem mass spectrometric analysis of 4 aminoglycosides residues in milk

Matrix effect (ME) is always a major issue for the development of LC-MS/MS method. ME resulting from co-eluting residual matrix components can affect the ionization efficiency of target analytes, leading to quantification errors of the analytes of interest. The present work evaluates MEs of milk samples on simultaneous analysis of four aminoglycosides residues via LC-ESI/MS/MS including streptomycin, dihydrostreptomycin, spectinomycin and kanamycin. Approaches to reduce MEs were examined: optimization of the sample preparation, sample dilution and lower flow rate used. Three commercial sorbents were tested including Oasis MCX, Oasis HLB and Oasis WCX. WCX behaved better for all analytes, but high MEs (80.8-134.9%) were obtained. Therefore, a consecutive SPE of tC18-WCX was found to effectively reduce ME. Milk samples from different manufacturers were analyzed and low MEs (85.6-112.9%) were obtained.

Development of spectrofluorimetric method for determination of certain aminoglycoside drugs in dosage forms and human plasma through condensation with ninhydrin and phenyl acetaldehyde

A simple and sensitive spectrofluorimetric method has been developed and validated for determination of amikacin sulfate, neomycin sulfate and tobramycin in pure forms, pharmaceutical formulations and human plasma. The method was based on condensation reaction of cited drugs with ninhydrin and phenylacetaldehyde in buffered medium (pH 6) resulting in formation of fluorescent products which exhibit excitation and emission maxima at 395 and 470nm, respectively. The different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The calibration plots were constructed with good correlation coefficients (0.9993 for tobramycin and 0.9996 for both neomycin and amikacin). The proposed method was successfully applied for the analysis of cited drugs in dosage forms with high accuracy (98.33-101.7)±(0.80-1.26)%. The results show an excellent agreement with the reference method, indicating no significant difference in accuracy and precision. Due to its high sensitivity, the proposed method was applied successfully for determination of amikacin in real human plasma.

Validated spectrofluorimetric method for determination of selected aminoglycosides

New, sensitive, and selective spectrofluorimetric method was developed for determination of three aminoglycoside drugs in different dosage forms, namely; neomycin sulfate (NEO), tobramycin (TOB) and kanamycin sulfate (KAN). The method is based on Hantzsch condensation reaction between the primary amino group of aminoglycosides with acetylacetone and formaldehyde in pH 2.7 yielding highly yellow fluorescent derivatives measured emission (471 nm) and excitation (410 nm) wavelengths. The fluorescence intensity was directly proportional to the concentration over the range 10-60, 40-100 and 5-50 ng/mL for NEO, TOB and KAN respectively. The proposed method was applied successfully for determination of these drugs in their pharmaceutical dosage forms.

[Inducible specific lux-biosensors for the detection of antibiotics: construction and main parameters]

Based on Escherichia coli, highly sensitive specific lux-biosensors for the detection of tetracycline and beta-lactam antibiotics, quinolones, and aminoglycosides have been obtained. To make biosensors, bacteria were used that contained fungal plasmids pTetA'::lux, pAmpC'::lux, pColD'::lux, and plbpA'::lux, in which transcription of the reporter Photorhabdus luminescens luxCDABE genes occurred from the inducible promoters of the tetA, ampC, cda, and ibpA genes, respectively. The main parameters (threshold sensitivity and response time) of lux-biosensors were measured. The high specificity of biosensors responding only to antibiotics of a certain type was demonstrated.

DNA-aptamers binding aminoglycoside antibiotics

Aptamers are short, single stranded DNA or RNA oligonucleotides that are able to bind specifically and with high affinity to their non-nucleic acid target molecules. This binding reaction enables their application as biorecognition elements in biosensors and assays. As antibiotic residues pose a problem contributing to the emergence of antibiotic-resistant pathogens and thereby reducing the effectiveness of the drug to fight human infections, we selected aptamers targeted against the aminoglycoside antibiotic kanamycin A with the aim of constructing a robust and functional assay that can be used for water analysis. With this work we show that aptamers that were derived from a Capture-SELEX procedure targeting against kanamycin A also display binding to related aminoglycoside antibiotics. The binding patterns differ among all tested aptamers so that there are highly substance specific aptamers and more group specific aptamers binding to a different variety of aminoglycoside antibiotics. Also the region of the aminoglycoside antibiotics responsible for aptamer binding can be estimated. Affinities of the different aptamers for their target substance, kanamycin A, are measured with different approaches and are in the micromolar range. Finally, the proof of principle of an assay for detection of kanamycin A in a real water sample is given.

Residues and dynamics of kasugamycin in chilli and soil

A simple and efficient method for determination of kasugamycin in chilli and soil was developed, and the fate of kasugamycin in chilli field ecosystem was also studied. Kasugamycin residues were extracted from sample, cleaned up by solid phase extraction and chromatographic column and then determined by ultra performance liquid chromatography with tandem mass spectrometry detection. The method got recoveries ranged from 77.82% to 83.35% with relative standard deviations of 2.20%-6.54%. As far as the accuracy and precision was concerned, the method met certain standard. The LODs of kasugamycin calculated as a sample concentration (S/N ratio of 3) was 2.50 μg kg(-1). The degradation of kasugamycin in chilli and soil was determined. The results showed that kasugamycin degradation in chilli plant and soil followed the first-order kinetics. The half-lives of kasugamycin in chilli and soil was 2.76-3.77 and 3.07-3.91 days, respectively. The final kasugamycin residues in chilli and soil were undetectable at levels of recommended and 1.5 times recommended dosage with an interval of 21 days.

Sensitive fluorescence detection of etimicin based on derivatives of formaldehyde and acetylacetone

A novel fluorescence method for the determination of etimicin is described. Etimicin reacts with acetylacetone and formaldehyde in pH 4.0 Britton-Robinson (B.R.) buffer solution to from a fluorescent substance [I]. Emission spectra of [I] and the reagent blank were overlapped, so the arithmetic emission spectra of the fluorescent substance were obtained by subtracted form the spectra of [I] to the spectra of the reagent blank using the Fluorescence Data Software. There is a linear relationship between the intensity of the arithmetic emission spectra and the concentration of etimicin. Effects of pH, amount of acetylacetone-formaldehyde, and heating time on the determination of etimicin have been examined. Etimicin can be determined over the concentration range of 1.0 to 10.0 μg mL(-1) with a correlation coefficient of 0.9991. The relative standard deviation (RSD) for 11 repetitive determinations of 5.0 μg mL(-1) etimicin is 0.22%. The utility of this method was demonstrated by determining etimicin in commercial samples.

Toggled RNA aptamers against aminoglycosides allowing facile detection of antibiotics using gold nanoparticle assays

We have used systematic evolution of ligands by exponential enrichment (SELEX) to isolate RNA aptamers against aminoglycoside antibiotics. The SELEX rounds were toggled against four pairs of aminoglycosides with the goal of isolating reagents that recognize conserved structural features. The resulting aptamers bind both of their selection targets with nanomolar affinities. They also bind the less structurally related targets, although they show clear specificity for this class of antibiotics. We show that this lack of aminoglycoside specificity is a common property of aptamers previously selected against single compounds and described as "specific". Broad target specificity aptamers would be ideal for sensors detecting the entire class of aminoglycosides. We have used ligand-induced aggregation of gold-nanoparticles coated with our aptamers as a rapid and sensitive assay for these compounds. In contrast to DNA aptamers, unmodified RNA aptamers cannot be used as the recognition ligand in this assay, whereas 2'-fluoro-pyrimidine derivatives work reliably. We discuss the possible application of these reagents as sensors for drug residues and the challenges for understanding the structural basis of aminoglycoside-aptamer recognition highlighted by the SELEX results.

Multiresidue analysis of antibiotics in food of animal origin using liquid chromatography-mass spectrometry

Antibiotics are the most important drugs administered in veterinary medicine. Their use in food-producing animals may result in antibiotic residues in edible tissues, which are monitored to protect human and animal health, support the enforcement of regulations, provide toxicological assessment data, and resolve international trade issues. This chapter provides basic characterization of the most important classes of antibiotics used in food-producing animals (aminoglycosides, amphenicols, β-lactams, macrolides and lincosamides, nitrofurans, quinolones, sulfonamides, and tetracyclines), along with examples of practical liquid chromatographic-(tandem) mass spectrometric methods for analysis of their residues in food matrices of animal origin. The focus is on multiresidue methods that are favored by regulatory and other food testing laboratories for their ability to analyze residues of multiple compounds in a time- and cost-effective way.

Analysis of antibiotic fungicide kasugamycin in irrigation water by high performance liquid chromatography

A high performance liquid chromatographic (HPLC) analysis method with an ultraviolet (UV) detector and an Aqua C18 (250 x 4.6 mm, Phenomenex) column were applied to analyze the antibiotic fungicide kasugamycin in water. An aromatic sulfonic acid spe column (Backerbond, J. T. Backer) was used to remove the interfering materials from irrigation water. A good linear relation existed between the concentration of the fungicide and the peak area, and correlation coefficient of linearity from 0.1 to 10.2 microg/mL was 0.998. The accuracies expressed as the recoveries of kasugamycin from irrigation water ranged from 112.2 to 111.7 %. The precisions expressed as relative standard deviations (RSD) were found to be below 7.0 %. The quantitative detection limit (LOQ) of kasugamycin in irrigation water was set at 2.2 microg/mL which was 2-times higher than the method detection limit (MDL) 1.03 microg/mL. Electrospray ionization-mass (ESI-MS) and fast-atom bombardment-mass (FAB-MS) were applied to compare the ability of identifying the component of the eluent peak from HPLC, and the result indicated that electrospray ionization-mass (ESI-MS) was more sensitive than fast-atom bombardment-mass (FAB-MS) in the detection of kasugamycin. There was no kasugamycin residue detected in irrigation water samples collected from paddyfields at Wufong, indicated that the residues of kasugamycin in water were less than 2.2 microg/mL, and the risk of water contamination was very low.

Multiclass, multiresidue drug analysis, including aminoglycosides, in animal tissue using liquid chromatography coupled to tandem mass spectrometry

A multiresidue, multiclass semiquantitative screening analysis of 39 drug residues covering 8 drug classes, including aminoglycosides in veal muscle, based on a single multiresidue extraction routine and using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), is presented. Sample preparation involves extraction of a 5 g diced tissue sample with 10 mL of acetonitrile/ water (86:14), incubated at 60 degrees C for 1 h, and then cooled for 10 min in ice. Formic acid is added to the suspension, then mixed, and centrifuged. The supernatant is retained, and the pellet is extracted with 10 mL of water for aminoglycosides and again centrifuged. Approximately 9.5 mL of each of the supernatants from both extracts is combined and diluted with water to 25 mL. The final solution is then defatted with 20 mL of hexane prior to analysis. Liquid chromatography for the aminoglycosides is carried out with ZIC-HILIC and for the remainder of the compounds with an Atlantis dC18 minicolumn. LC-ESI-MS/MS in positive and negative ionization modes (three injections total) is carried out, and two ion transitions per analyte are monitored. The method provides semiquantitative analysis to identify incurred positive drug classes in a rapid and cost-effective manner. Of particular interest is the detection of numerous compounds in the low nanograms per gram concentration range, which are not typically detected using receptor-based screening methods. All identified drugs were confirmed using internationally recognized regulatory methods, with no apparent false positives.

Immunoassays for the rapid detection of gentamicin and micronomicin in swine muscle

A monoclonal antibody (mAb)-based ELISA and strip test for gentamicin (GEN) and its analogue micronomicin (MIN), are reported in this study. The conjugate gentamicin-glutaraldehyde-bovine serum albumin (GEN-GDA-BSA) was used as an immunogen. The produced anti-GEN mAB exhibited high cross-reactivity with micronomicin (MIN; 131.2%) and slight or negligible crossreactivity with other aminoglycosides. Based on this mAB, an ELISA and a strip test for GEN and MIN were developed and evaluated. The ELISA showed a 50% inhibition concentration (IC50) of 0.75 ng/mL for GEN and 0.58 ng/mL for MIN. For GEN, the average recoveries at 25-200 microg/kg ranged from 73 to 91%, with intraday CVs of 9-16% and interday CVs of 8-15%. For MIN, the average recoveries ranged from 108 to 131%, with intraday CVs of 10-16% and interday CVs of 8-15%. In contrast, the strip test for GEN or MIN had a detection limit of 5 ng/mL in phosphate-buffered saline and 50 microg/kg in muscle (n=24), and the results could be judged within 10 min. The detection results of incurred samples analyzed by the strip test, ELISA, and HPLC indicated that the two immunoassays correlated well with the HPLC method and could be used as convenient tools for the rapid screening of GEN and MIN residues in swine muscle.

Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe

In pH 6.6 Britton-Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (DeltaI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3 sigma) were 1.7 ng mL(-1) (NEO) and 4.4 ng mL(-1) (STP) by RRS method, were 5.2 ng mL(-1) (NEO) and 20.9 ng mL(-1) (STP) by SOS method and were 4.4 ng mL(-1) (NEO) and 25.7 ng mL(-1) (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.

Simultaneous identification and quantitative determination of selected aminoglycoside antibiotics by thin-layer chromatography and densitometry

A TLC-densitometric method has been developed for simultaneous identification and quantitative determination of amikacin, gentamicin, kanamycin, neomycin, netilmicin, and tobramycin. This separation of antibiotics was achieved on silica gel TLC plates without a fluorescent indicator and with methanol-25% ammonia-chloroform (3 + 2 + 1, v/v/v) as the mobile phase. The densitometric measurements were made at 500 nm after detection with a 0.2% ninhydrin solution in ethanol. Under these conditions, good separation of the chosen aminoglycosides was obtained. The method is distinguished by high sensitivity, with the LOD from 0.25 microg for amikacin to 1.00 microg for gentamicin and the LOQ from 0.5 microg for amikacin to 1.65 microg for gentamicin, and a wide linearity range 0.75-6.25 microg/spot for amikacin and netilmicin and 1.5-12.50 microg/spot for other antibiotics. The precision of the determination was very good; RSD varied in the range 0.3-0.6%.

sanN encoding a dehydrogenase is essential for Nikkomycin biosynthesis in Streptomyces ansochromogenes

Nikkomycins are a group of peptidyl nucleoside antibiotics with potent fungicidal, insecticidal, and acaricidal activities. sanN was cloned from the partial genomic library of Streptomyces ansochromogenes 7100. Gene disruption and complementation analysis demonstrated that sanN is essential for nikkomycin biosynthesis in S. ansochromogenes. Primer extension assay indicated that sanN is transcribed from two promoters (sanN-P1 and sanN-P2), and sanN-P2 plays a more important role in nikkomycin biosynthesis. Purified recombinant SanN acts as a dehydrogenase to convert benzoate-CoA to benzaldehyde in a random-order mechanism in vitro, with respective Kcat/Km values of 3.8 mM-1s-1 and 12.0 mM-1s-1 toward benzoate-CoA and NADH, suggesting that SanN catalyzes the formation of picolinaldehyde during biosynthesis of nikkomycin X and Z components in the wild-type stain. These data would facilitate us to understand the biosynthetic pathway of nikkomycins and to consider the combinatorial synthesis of novel antibiotic derivatives.

Micellar electrokinetic chromatography of aminoglycosides

The components of the aminoglycosides, e.g., gentamicin, sisomicin, netilmicin, kanamycin, amikacin, and tobramycin, and related impurities of these antibiotics can be separated by means of micellar electrokinetic chromatography (MEKC). Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for all antibiotics. The background electrolyte was composed of sodium tetraborate (100 mM), sodium deoxycholate (20 mM), and beta-cyclodextrin (15 mM) and has a pH value of 10.0. This method is valid for evaluation of gentamicin, kanamycin, and tobramycin. It has yet to be adopted for amikacin, paramomycin, neomycin, and netilmicin.

Analytical Profiling of Biosynthetic Intermediates Involved in the Gentamicin Pathway of Micromonospora echinospora by High-Performance Liquid Chromatography Using Electrospray Ionization Mass Spectrometric Detection

In the present study, we developed a sensitive and highly selective method of detecting the biosynthetic intermediates involved in the gentamicin pathway from a cell culture of Micromonospora echinospora. A novel extraction method utilizing a dual solid-phase extraction (SPE) technique was employed to purify and recover all of the gentamicin-related components from the cell culture broth, and high-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS/MS) was used to analyze the extractant for gentamicin intermediates. The pH of the culture broth was adjusted to an acidic condition of pH 2 prior to the extraction. The samples were first cleaned with a reversed-phase AccuBOND C(18) cartridge, and then the aminoglycosidic components were purified using a cationic exchanger OASIS MCX cartridge. The detection limit of a gentamicin standard spiked in blank medium processed by this method was found to be approximately 5 ng for each component of the gentamicin C complex, and the mean recovery for each component of standard gentamicin was above 91% when analyzed by HPLC-ESI-MS/MS. We further demonstrated that this method enables the analytical profiling of the gentamicin-related compounds produced by wild-type M. echinospora ATCC 15835, which mainly produces the gentamicin C complex, and the UV-induced mutant strain KCTC 10506BP, which produces gentamicin B as the major product. Seven intermediates (paromamine, gentamicin A2, B, X2, A, JI-20A, and JI-20B) besides the gentamicin C complex were detected in the culture broth of both M. echinospora strains when analyzed by MS/MS for the distinct fragmentation patterns of each gentamicin component. This report displays the first example of the HPLC profiling in a wide range of structurally related biosynthetic intermediates involved in the gentamicin pathway.