Magnetic aluminum-based metal organic framework as a novel magnetic adsorbent for the effective removal of minocycline from aqueous solutions.

In this paper, Fe3O4@MIL-68 (Al), a magnetic aluminum-based metal organic framework, was synthesized by a simple method and used as a novel and effective adsorbent for the removal of minocycline (MC) from aqueous solutions. The material was thoroughly characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and N2 adsorption isotherms. The characterization results showed that the original structure of MIL-68(Al) was unchanged by the addition of Fe3O4 nanoparticles, and that the obtained material had a strong magnetic response which also promoted its adsorption. Batch adsorption experiments were conducted by the varying the adsorption time, temperature, initial MC concentration and pH. The maximum adsorption amount of MC onto Fe3O4@MIL-68 (Al) was 248.05 mg g-1 (t = 160 min, pH = 6, Co = 60 mg L-1), and the adsorption kinetics followed a pseudo-second-order model, and the adsorption isotherms conformed to the Freundlich equation. The adsorption mechanism of the magnetic metal organic framework materials were determined to involve complex interactions, including Al-N and Fe-N covalent bonds, hydrogen bonding, electrostatic adsorption, and π-π stacking. Combined the results indicate that Fe3O4@MIL-68 (Al) is an outstanding adsorbent for the removal of MC from water.

Easy-Assessment of Levofloxacin and Minocycline in Relevant Biomimetic Media by HPLC-UV Analysis.

Simple, economic and environmental friendly high-performance liquid chromatography methods for levofloxacin and minocycline quantification in biomimetic media were developed and validate including their stability at body temperature, an often neglected evaluation parameter. Both methods are similar only differing in the wavelength setting, i.e., for levofloxacin and minocycline quantification the UV detection was set at 284 and at 273 nm, respectively. The separation of both antibiotics was achieved using a reversed-phase column and a mobile phase consisting of acetonitrile and water (15:85) with 0.6% triethylamine, adjusted to pH 3. As an internal standard for levofloxacin quantification, minocycline was used and vice versa. The calibration curves for both methods were linear (r = 0.99) over a concentration range of 0.3-16 µg/mL and 0.5-16 µg/mL for levofloxacin and minocycline, respectively, with precision, accuracy and recovery in agreement with international guidelines requirement. Levofloxacin revealed stability in all media and conditions, including at 37°C, with exception to freeze-thaw cycle conditions. Minocycline presented a more accentuated degradation profile over prolonged time courses, when compared to levofloxacin. Reported data is of utmost interest for pharma and biomaterials fields regarding the research and development of new local drug-delivery-systems containing either of these two antibiotics, namely when monitoring the in vitro release studies of those systems.

Rapid turbidimetric assay to potency evaluation of tigecycline in lyophilized powder.

Tigecycline, a first-in-class glycylcycline and an analog of the semisynthetic antibiotic minocycline, is a potent, broad-spectrum antibiotic that acts by the inhibition of protein translation in bacteria. This glycylcycline inhibits Gram-positive, Gram-negative, atypical, anaerobic and antibiotic-resistant organisms. There is no microbiological analytical method for tigecycline in lyophilized powder reported yet. Thus, this paper reports the development and validation of a simple, sensitive, accurate and reproducible turbidimetric method to quantify tigecycline in lyophilized powder, using Staphylococcus aureus as microorganism test and 3×3 parallel line assay design, with twenty tubes for each assay. The validated method showed good results of linearity in the concentration range from 3 to 4.32µg/mL (r(2)=0.9999), selectivity, precision, robustness and accuracy of 99.74%. The results demonstrated the validity of the proposed bioassay, which allows reliable quantitation of tigecycline in pharmaceutical samples and therefore can be used as a useful alternative methodology for the routine quality control of this medicine.

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline.

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (∼25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 µg for colorimetric detection and from 10 ng to 1.0 µg for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

Determination of atypical nonlinear plasma−protein-binding behavior of tigecycline using an in vitro microdialysis technique.

Tigecycline, a novel glycylcycline antibiotic, shows atypical nonlinear plasma-protein-binding behavior using ultrafiltration and ultracentrifugation techniques. The mechanism of such counterintuitive behavior is currently unknown. Ultrafiltration and ultracentrifugation cause fractional change in protein concentration and therefore may influence plasma-protein binding. Microdialysis (MD), a novel technique, can sample unbound drugs without any change in fractional protein concentration. To determine whether the atypical nonlinear plasma-protein-binding behavior is not related to measurement technique, the plasma-protein binding of tigecycline was determined using MD. A sensitive liquid chromatography-mass spectrometry method was developed and validated for the bioanalysis of tigecycline in the dialysate. The probe recoveries and plasma-protein binding of tigecycline at four different concentration levels 0.1, 1, 10, and 100 µg/mL were determined. Similar to ultracentrifugation and ultrafiltration, MD also showed atypical nonlinear plasma-protein-binding behavior of tigecycline up to 10 µg/mL, but unbound fraction increased at 100 µg/mL indicating saturation of mechanism responsible for atypical nonlinear behavior. This study concludes that the atypical nonlinear binding behavior of tigecycline is not technique-dependent, rather it is a true behavior of tigecycline. Further investigations are necessary to elucidate the mechanism.

Validation of a stability-indicating RP-LC method for the determination of tigecycline in lyophilized powder.

A reversed-phase liquid chromatography (RP-LC) method was validated for the determination of tigecycline in lyophilized powder. The LC method was conducted on a Luna C18 column (250 × 4.6 mm i.d.), maintained at room temperature. The mobile phase consisted of buffer containing sodium phosphate monobasic (0.015M) and oxalic acid (0.015M) (pH 7.0)-acetonitrile (75:25, v/v), run at a flow rate of 1.0 mL/min and using ultraviolet detection at 280 nm. The chromatographic separation was obtained with a retention time of 8.6 min, and was linear in the range of 40-100 µg/mL (r(2) = 0.9997). The specificity and stability-indicating capability of the method was proven through forced degradation studies, which also showed no interference of the excipients. The accuracy was 99.01% with a bias lower than 1.81%. The limits of detection and quantitation were 1.67 and 5.05 µg/mL, respectively. Moreover, method validation demonstrated satisfactory results for precision and robustness. The proposed method was applied for the analysis of the lyophilized powder formulation, contributing to improve the quality control and to assure the therapeutic efficacy.

[Simultaneous determination of 6 antibiotics and metronidazole in acne removal products bt high performance liquid chromatography].

An analytical method for the simultaneous determination of 6 antibiotics (minocycline, oxytetracycline, tetracycline hydrochloride, chlorotetracycline hydrochloride, doxycycline hydrochloride and chloramphenicol) and metronidazole in acne removal products of cosmetic was established using high performance liquid chromatography (HPLC). The drugs in the sample were extracted with methanol. The separation was performed on an Agilent ZORBAX SB-C18 column (250 mm x 4.6 mm, 5 microm) at 20 degrees C with methanol, acetonitrile and 0.002 mol/L oxalic acid solution as mobile phases with gradient elution at a flow rate of 0.8 mL/min. The detection was performed by a diode array detector (DAD) at 268 nm. The injection volume was 10 microL. The quantification was performed by external standard method. The calibration curves showed good linearity within the range of 1 - 30 mg/L with the correlation coefficients no less than 0.997 0. The detection limits were in the range of 1.1 - 1.2 microg/g. The recoveries were between 91.9% and 107.7% in three spiked levels of 5, 10 and 20 mg/L with the relative standard deviations (RSDs) of 0.13% - 1.74%. The method was used in the analysis of acne removal products, and metronidazole was found in 15% of the total test samples. The method is rapid, sensitive, accurate, effective in separation, and can be used in the determination of the six antibiotics and metronidazole in acne removal products.

[Simultaneous determination of six antibiotics in disinfection products by high performance liquid chromatography tandem mass spectrometry].

OBJECTIVE: To develop a method for determination of the Metronidazole, Chlortetracycline hydrochloride, Oxytetracycline dihydrate, Minocycline hydrochloride, Erythromycin and Tetracycline hydrochloride in disinfection products by high performance liquid chromatography tandem mass spectrometry(LC-MS/MS). METHODS: Samples were extracted by methanol and filtered through 0.45 microm PTFE membrane filter, then analyzed by LC-MS/MS using Waters Symmetry C18 (2.1 mm x 150 mm, 3.5 microm) column in positive ion scan mode. The mobile phase was 5 mmol/L ammonium acetate, methanol and acetonitrile. RESULTS: The linear range was 0-2000 ng/ml and the correlation coefficients were more than 0.998, the average recoveries ranged from 74.7% to 114% with the relative standard deviations between 1.6%-20.2%. The method was successfully used to detect the content of antibiotics in 115 disinfection products. CONCLUSION: The method is simple, sensitive, selective and suitable for the analysis of residual content of antibiotics in cream formulations of disinfection products.

Tigecycline for the treatment of severe Clostridium difficile infection.

OBJECTIVE: To evaluate the evidence for the use of tigecycline in the treatment of Clostridium difficile infection (CDI). DATA SOURCES: Searches were performed (2004 to June 2011), using the EMBASE and MEDLINE databases, with the terms tigecycline, Tygacil, Clostridium difficile, C. difficile, Clostridium difficile infection, and CDI. STUDY SELECTION: Six case reports that described the use of tigecycline for treatment of CDI were included for review. No clinical trials were identified. DATA SYNTHESIS: In all case reports except 1, tigecycline (alone or in combination with other CDI therapies) was used for the treatment of CDI that was refractory to metronidazole and/or vancomycin. In 6 of the cases, treatment success was reported following initiation of tigecycline therapy; 1 patient died following a complicated hospitalization. The treatment duration with tigecycline was 2-4 weeks. In the cases with successful outcomes, symptoms began to improve within 1 week. None of these patients experienced recurrence during follow-up of various lengths. In vitro studies demonstrated a 90% minimum inhibitory concentration range for tigecycline of 0.016-0.25 mg/L for all C. difficile isolates. Tigecycline exhibited good fecal penetration because of primary biliary excretion of unchanged drug. Up to 59% of the dose is recovered in feces following administration over 4 days in healthy volunteers. CONCLUSIONS: Case reports have suggested that tigecycline may be successful for treatment of severe or severe complicated CDI, when prior therapy has failed. Data demonstrating tigecycline use as initial therapy for CDI are limited; therefore, this option should be reserved for patients in whom other therapeutic options, including metronidazole and vancomycin, have failed. A randomized controlled trial is needed to assess the safety and efficacy of tigecycline in this patient population and better define the drug's role in the treatment of CDI.

Determination of tigecycline in human skin using a novel validated LC-MS/MS method.

BACKGROUND: To develop and validate a sensitive and novel bioanalytical method for measuring tigecycline concentrations in human skin using LC-MS/MS. RESULTS: The method utilizes addition of a stabilizing agent to the human skin or surrogate (human liver or rat skin), homogenization of human skin in a strong acidic-methanol extraction solvent, centrifugation of the skin suspension, filtration of the skin suspension supernatant, separation by LC (Polaris™ C18-A 50 × 2.0 mm), and detection of tigecycline by MS/MS. Linearity was 50-20,000 ng/g, using a sample size of 100 mg. The intra-and inter-day accuracy and precision of the assay met acceptance criteria. CONCLUSION: This method has been successfully applied to 17 incurred human skin samples from volunteers with surgical infections who received intravenous doses of tigecycline (100 mg initial loading dose and 50 mg every 12 h for at least 2 days). Tigecycline concentrations in these samples ranged from 185 to 2853 ng/g.

Local delivery of minocycline hydrochloride: a therapeutic paradigm in periodontal diseases.

From the literature we can draw conclusions regarding the local use of minocycline in periodontal diseases. This review article attempts to evaluate the role of local delivery of minocycline HCl in the management of periodontal diseases. The efficacies of several local delivery devices of minocycline like minocycline films, strips, gels/ointment, microspheres and nanoparticles are discussed. The functional characteristics of local delivery devices of minocycline, their effectiveness as monotherapy, and comparison with scaling and root planning (SRP) are discussed in detail. Methods for the analysis of minocycline in various biological fluids, clinical trials and patents relevant to the local use of minocycline HCl in dental diseases have also been addressed in the article, conceptualizing the fact that direct application of minocycline into the diseased periodontal sulcus is an attractive treatment approach.

An HPTLC method for the determination of minocycline in human plasma, saliva, and gingival fluid after single step liquid extraction.

A rapid, sensitive and specific high-performance thin-layer chromatographic (HPTLC) method was developed and validated for determination of minocycline in human plasma, saliva, and gingival fluid samples. Densitometric analysis of minocycline was carried out at 345 nm after single step extraction with methanol. The method uses TLC aluminium plates pre-coated with silica gel 60F-254 as a stationary phase and methanol-acetonitrile-isopropyl alcohol-water (5:4:0.5:0.5, v/v/v/v) as mobile phase. In all the three matrices, the calibration curve was linear (r(2) >/= 0.9958) in the tested range of 100 - 1200 ng spot(-1) with a limit of quantification of 15.4 ng spot(-1). Drug recovery from plasma, saliva and gingival fluid averaged 97.7%. Intra- and inter-day accuracies, determined at three different concentrations, were 95.08 to 100.6% and the corresponding precision (% CV) values were < 4.61%. In all the three matrices, rapid degradation of drug occurred and the half-life of drug ranged from 9.9 to 16.1 h at 4 degrees C and from 6.3 to 11.5 h at 20 degrees C. Frozen at -20 degrees C, this drug was stable for at least 2 months and can tolerate two freeze-thaw cycles without losses higher than 10%. The method's ability to quantify minocycline with precision, accuracy and sensitivity makes it useful in pharmacokinetic studies.

A sensitive human bone assay for quantitation of tigecycline using LC/MS/MS.

Tigecycline (Tygacil,Wyeth) is a first-in-class, broad spectrum antibiotic with activity against multiple-resistant organisms. In order to address the unexpectedly low tigecycline concentrations in human bone samples analyzed using a LC/MS/MS method developed elsewhere, we have developed and validated a new and sensitive human bone assay for the quantitation of tigecycline using LC/MS/MS. The new method utilizes the addition of a stabilizing agent to the human bone sample, homogenization of human bone in a strong acidic-methanol extraction solvent, centrifugation of the bone suspension, separation by liquid chromatography, and detection of tigecycline by mass spectrometry. Linearity was demonstrated over the concentration range from 50 to 20,000 ng/g using a 0.1g human bone sample. The intra- and inter-day accuracy of the assay was within 100+/-15%, and the corresponding precision (CV) was <15%. The stability of tigecycline was evaluated and shown to be acceptable under the assay conditions. The extraction recovery of tigecycline with the current method was 79% when using radio-labeled rat bone samples as a substitute for human bone samples. Twenty-four human bone samples collected previously from volunteers without infections who had elective orthopedic surgery after receiving a single dose of tigecycline were re-analyzed using the current validated method. Tigecycline concentrations in these samples ranged from 238 to 794 ng/g with a mean value 9 times higher than the mean concentration previously reported. The data demonstrated that the current method has significantly higher extraction efficiency than the previously reported method.

Validated stability-indicating densitometric thin-layer chromatography: application to stress degradation studies of minocycline.

A simple, stability-indicating high-performance thin-layer liquid chromatographic (HPTLC) method for analysis of minocycline was developed and validated. The densitometric analysis was carried out at 345 nm using methanol-acetonitrile-isopropyl alcohol-water (5:4:0.5:0.5, v/v/v/v) as mobile phase. The method employed TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase. To achieve good result, plates were sprayed with a 10% (w/v) solution of disodium ethylene diaminetetraacetic acid (EDTA), the pH of which was adjusted to 9.0. Compact spots of minocycline were found at R(f) = 0.30+/-0.02. For proposed procedure, linearity (r = 0.9997), limit of detection (3.7 ng spot(-1)), recovery (99.23-100.16%), and precision (% R.S.D. < or = 0.364) was found to be satisfactory. The drug undergoes acidic and basic degradation, oxidation and photodegradation. All the peaks of degradation products were well resolved from the pure drug with significantly different R(f) values. The acidic and alkaline degradation kinetics of minocycline, evaluated using this method, is found to be of first order.

A novel antibiotic bone assay by liquid chromatography/tandem mass spectrometry for quantitation of tigecycline in rat bone.

Tigecycline (Tygacil) is a first-in-class, broad spectrum antibiotic with activity against antibiotic-resistant organisms. In rats and humans, tigecycline readily distributes to bone tissue but its accuracy of quantitation via liquid chromatography/mass spectrometry (LC/MS/MS) is hindered by a low extraction recovery when using a conventional plasma extraction method. To overcome this issue, we have identified an effective extraction solvent for quantitation of tigecycline in rat bone. The current LC/MS/MS bone assay is novel, simple, and sensitive, and has a wide linear range of 50-10,000 ng/g. The assay requires homogenization of the rat bone in a strong acidic-methanol extraction solvent, centrifugation of the bone suspension, separation of the supernatant with liquid chromatography, and detection of tigecycline with tandem mass spectrometry. The incurred pooled rat bone samples obtained from rats given 3mg/kg/day of [(14)C]-tigecycline and non-radio-labeled tigecycline were analyzed with the current method. The absolute extraction recovery of the bone assay for tigecycline was 77.1%. The intra-day accuracy ranged from 91.7 to 106% with precision (CV) of 1.9-10.7%, and inter-day accuracy ranged from 96.1 to 100% with a precision of 6.3-8.7%. In addition, biological activity was demonstrated for the tigecycline extracted from incurred rat bone. This bone assay provides an important analytical tool for the determination of drug concentrations (especially, antimicrobials) in rodent bone tissues and has served as the foundation of development and validation of a similar bone assay for tigecycline in human bone tissues.

Improved LC of minocycline drug substance.

An isocratic liquid chromatographic method is described for the separation of minocycline and its impurities. This method uses XTerra RP-18, 5 microm (25 cm x 4.6 mm I.D.), a silica-based stationary phase with reduced silanol activity. A mobile phase composed of acetonitrile-0.2 M tetrabutylammonium hydrogen sulphate pH 6.5-0.2 M ethylenediaminetetraacetic acid pH 6.5-water (20:20:20:40; v/v/v/v) was used at a flow rate of 1 ml/min. The column temperature was set at 35 degrees C. UV detection was performed at 280 nm. Optimisation of the separation method and a robustness study were performed by means of a central composite experimental design. The method allows to separate minocycline from known impurities. Some unidentified impurities are also separated. The total time of analysis is less than 20 min.

Determination of minocycline by oxidative coupling and diazocoupling reactions in pharmaceutical formulations.

Simple and sensitive spectrophotometric methods (M(1)-M(4)) by the application of oxidative coupling and diazocoupling reactions for the assay of minocycline (MC) in pure form and pharmaceutical formulations have been described. Methods M(1) and M(2) involve the oxidative coupling reactions of MC with 3-methyl-2-benzothiozolinone hydrazone (MBTH) (method M(1), lambda(max) 440 nm) or 4-aminophenazone (4-AP) (method M(2), lambda(max) 520 nm) in the presence of periodate. Methods M(3) and M(4) are based on the formation of diazocoupling products of MC with diazotised p-nitroaniline (DPNA) (method M(3), lambda(max) 420 nm) or diazotised sulfanilic acid (DSAC) (method M(4), lambda(max) 420 nm). Regression analysis of Beer's law plot showed good correlation in the concentration range of 8-48, 20-120, 4-20 and 8-40 microg ml(-1) for methods A, B, C and D, respectively. The molar absorptivities fell within the range of 2.23 x 10(3)-1.51 x 10(4) l mol(-1) cm(-1). The recoveries range from 99.02 to 100.61%.

High-performance liquid chromatographic assay for minocycline in human plasma and parotid saliva.

A sensitive and specific high-performance liquid chromatographic (HPLC) method with UV detection was developed for the determination of minocycline in human plasma and parotid saliva samples. Samples were extracted using an Oasis HLB cartridge and were injected into a C8 Nucleosil column. The HPLC eluent contained acetonitrile-methanol-distilled water-0.1% trifluoroacetic acid (25:2:72.9:0.1, v/v). Demeclocycline was used as internal standard. The assay showed linearity in the tested range of 0.1-25 microg/ml. The limit of quantitation was 100 ng/ml. Recovery from plasma or parotid saliva averaged 95%. Precision expressed as %CV was in the range 0.2-17% (limit of quantitation). Accuracy ranged from 93 to 111%. In the two matrices studied at 20 and 4 degrees C, rapid degradation of the drug occurred. Frozen at -30 degrees C, this drug was stable for at least 2 months, the percent recovery averaged 90%. The method's ability to quantify minocycline with precision, accuracy and sensitivity makes it useful in pharmacokinetic studies.

Concentration of 3 tetracyclines in plasma, gingival crevice fluid and saliva.

BACKGROUND: Systemically-administered tetracyclines have been used widely for treatment of periodontal diseases with little understanding of their delivery characteristics to periodontal tissues. This study was designed to measure concentrations of 3 tetracyclines in gingival crevice fluid (GCF), plasma and saliva of following systemic administration. METHOD: The concentration of tetracycline (TC), minocycline (MN) and doxycycline (DX) was measured in gingival crevice fluid (GCF), plasma and saliva of 20 subjects following single sequential standard oral systemic doses. Gingival crevice fluid concentration was measured at 4 sites (2 shallow and 2 deep) before administration, and at 1 h and 2 h following administration. Plasma and saliva concentrations were measured from in samples at the same time points. No antibacterial activity was detected before administration. The highest concentrations were measured 2 h after administration. RESULTS: The average concentrations at 2 h were highest in plasma (TC = 1.02, MN=2.18, DX=2.35 microg/ml). Intermediate concentrations were measured in GCF (TC=0.61, MN= 1.49, DX= 1.65 microg/ml). Saliva concentrations (TC=0.09 MN=0.31, DX=0.47 microg/ml) were the lowest of the 3 fluids monitored. Data are presented indicating that the average GCF concentration of systemically administered tetracyclines is less than the that of plasma concentration. The concentration of tetracyclines in GCF was strongly associated with plasma concentration, indicating a primary role of drug absorption in the delivery of these systemically administered antibiotics to the site of action in periodontal therapy. The average GCF concentration in individuals varied widely (between 0 and 8 microg/ml) with approximately 50% of samples not achieving levels of 1 microg/ml. CONCLUSION: These observations suggest that poor absorption of orally-administered tetracyclines in many individuals may account for much of the variability in clinical response to antibiotics observed in practice.

Analysis of minocycline by high-performance liquid chromatography in tissue and serum.

A sensitive and rapid reversed-phase high-performance liquid chromatography assay can be used to accurately determine serum and tissue minocycline concentrations. Minocycline is a broad spectrum tetracycline derivative with many applications. Tissue and serum samples were obtained from guinea pigs that had received either topical or intravenous minocycline. Samples were extracted using a Sep-Pak C18 cartridge and were injected into a microBondapak C18 column with an isocratic methanol mobile phase. Samples were analyzed using UV detection and produced sharp peaks with a retention time of 2.5 min. The lower limit of detection was 100 ng and drug recovery was 61%. This method greatly facilitated the analysis of minocycline while allowing for sensitivity.