Tissue distribution of pretomanid in rat brain via mass spectrometry imaging.

1. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) combines the sensitivity and selectivity of mass spectrometry with spatial analysis to provide a new dimension for histological analyses of the distribution of drugs in tissue. Pretomanid is a pro-drug belonging to a class of antibiotics known as nitroimidizoles, which have been proven to be active under hypoxic conditions and to the best of our knowledge there have been no studies investigating the distribution and localisation of this class of compounds in the brain using MALDI MSI. 2. Herein, we report on the distribution of pretomanid in the healthy rat brain after intraperitoneal administration (20 mg/kg) using MALDI MSI. Our findings showed that the drug localises in specific compartments of the rat brain viz. the corpus callosum, a dense network of neurons connecting left and right cerebral hemispheres. 3. This study proves that MALDI MSI technique has great potential for mapping the pretomanid distribution in uninfected tissue samples, without the need for molecular labelling.

Rapid and widespread distribution of doxycycline in rat brain: a mass spectrometric imaging study.

1. The penetration of tetracyclines into the brain has been widely documented. The aim of this work was to develop a matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI MSI) method for the molecular histology of doxycycline (DOX) in the healthy rat brain. 2. The time-dependent distribution was investigated after an i.p. dose of 25 mg/kg at 0, 5, 30, 120, 240, 360 and 480 min postdose. LCMS/MS was used to quantify the drug in plasma and brain homogenates and MALDI MSI was used to determine the distribution of the analyte. 3. Within the first-hour postdose, the drug showed slow accumulation into the plasma and brain tissues. DOX brain concentration gradually increased and reached a peak (Cmax) of 1034.9 ng/mL at 240 min postdose, resulting in a brain plasma ratio of 31%. The images acquired by MSI matched the quantification results and clearly showed drug distribution over the entire rat brain coronal section from 5 min and its slow elimination after 360-min postdose. 4. Our findings confirm that MALDI MSI provides an advanced, label-free and faster alternative technique for xenobiotic distribution such as DOX in tissues, making it an essential drug discovery tool for other possible neuroprotective agents.

Development and validation of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of tigecycline in rat brain tissues.

Tigecycline (TIG), a derivative of minocycline, is the first in the novel class of glycylcyclines and is currently indicated for the treatment of complicated skin structure and intra-abdominal infections. A selective, accurate and reversed-phase high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the determination of TIG in rat brain tissues. Sample preparation was based on protein precipitation and solid phase extraction using Supel-Select HLB (30 mg/1 mL) cartridges. The samples were separated on a YMC Triart C18 column (150 mm x 3.0 mm. 3.0 µm) using gradient elution. Positive electrospray ionization (ESI+) was used for the detection mechanism with the multiple reaction monitoring (MRM) mode. The method was validated over the concentration range of 150-1200 ng/mL for rat brain tissue. The precision and accuracy for all brain analyses were within the acceptable limit. The mean extraction recovery in rat brain was 83.6%. This validated method was successfully applied to a pharmacokinetic study in female Sprague Dawley rats, which were given a dose of 25 mg/kg TIG intraperitoneally at various time-points. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of different imidazolium supported ionic liquid polymeric phases with strong anion-exchange character for the extraction of acidic pharmaceuticals from complex environmental samples.

Two imidazolium supported ionic liquid phases (SILPs) containing different anions, trifluoromethanesulphonate [CF(3)SO(3)(-)], and tetrafluoroborate [BF(4)(-)], were synthesized and evaluated as solid-phase extraction sorbents for extracting acidic pharmaceuticals from aqueous samples under strong anion-exchange conditions, which include an effective cleanup of the sample. The best SILP material [MI(+)][CF(3)SO(3)(-) ] was selected and successfully applied to the determination of acidic pharmaceuticals in different types of water samples (river water and effluent wastewater). The results were then compared to the previously synthesized SILP material based on [MI(+)][CF(3)COO(-)] and the commercially available Oasis MAX sorbent.

Hypercrosslinked strong anion-exchange resin for extraction of acidic pharmaceuticals from environmental water.

Two novel high-specific surface area polymeric sorbents (HXLPP-SAXa and HXLPP-SAXb) were synthesised and evaluated as solid-phase extraction sorbents. The novel sorbents under study are based on hypercrosslinked polymer microspheres and designed specifically to offer ion-exchange properties; the specific polymers of interest in the current work have been chemically modified in such a way as to impart a tuneable level of strong anion-exchange character onto the sorbents. The novel sorbents were applied as strong anion-exchange sorbents in solid-phase extraction studies, with the goal being to selectively extract a group of acidic compounds from complex environmental samples in an efficient manner. Out of two HXLPP-SAX resins evaluated in this study, it was found that the sorbent with the lower ion-exchange capacity (HXLPP-SAXa) gave rise to the best overall performance characteristics and, indeed, was found to compare favourably to the solid-phase extraction performance of commercial strong anion-exchange sorbents. When the HXLPP-SAXa sorbent was applied to the solid-phase extraction of environmental water samples, the result showed quantitative and selective extraction of low levels of acidic pharmaceuticals from 500 mL of river water and 100 mL of effluent wastewater.

MALDI MSI and LC-MS/MS: Towards preclinical determination of the neurotoxic potential of fluoroquinolones.

Fluoroquinolones are broad-spectrum antibiotics with efficacy against a wide range of pathogenic microbes associated with respiratory and meningeal infections. The potential toxicity of this class of chemical agents is a source of major concern and is becoming a global issue. The aim of this study was to develop a method for the brain distribution and the pharmacokinetic profile of gatifloxacin in healthy Sprague-Dawley rats, via Multicenter matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) and quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed a sensitive LC-MS/MS method to quantify gatifloxacin in plasma, lung, and brain homogenates. A pharmacokinetic profile was observed where there is a double peak pattern; a sharp initial increase in the concentration soon after dosing followed by a steady decline until another increase in concentration after a longer period post dosing in all three biological samples was observed. The imaging results showed the drug gradually entering the brain via the blood brain barrier and into the cortical regions from 15 to 240 min post dose. As time elapses, the drug leaves the brain following the same path as it followed on its entry and finally concentrates at the cortex. Copyright © 2015 John Wiley & Sons, Ltd.

Visualization of Time-Dependent Distribution of Rifampicin in Rat Brain Using MALDI MSI and Quantitative LCMS/MS.

Rifampicin (RIF) is a major component for short-course chemotherapy against tuberculosis, since it is active against rapidly metabolizing as well as dormant bacteria. According to the Lipinski rules, RIF should not enter the blood-brain barrier. Visualization of tissue drug distribution is of major importance in pharmacological studies; thus, far imaging of RIF in the brain has been limited to positron emission tomography. We propose using matrix-assisted laser desorption/ionization mass spectrometry imaging techniques as a suitable alternative for the visualization and localization of drug tissue distribution. Using the liquid chromatography mass spectrometric (LCMS) technique, we were able to quantify the concentrations of RIF in the uninfected rat brain; we paired this with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) to show the time-dependent manner in which RIF is able to enter the brain. Our results show that even at the minute concentrations measured with LCMS/MS we were able visualize the drug and show its exact distribution in the rat brain. Other available methods require nuclear labeling and the detection of gamma rays produced by labeled compounds to visualize the compound and its localization; MALDI MSI is a more recently developed technique, which can provide detailed information on drug distribution in tissues when compared to other imaging techniques. This study shows that without any requirement for complex preprocessing we are able to produce images with a relatively improved resolution and localization than those acquired using more complex imaging methods, showing MALDI MSI to be an invaluable tool in drug distribution studies.

Determination of the antitubercular drug PA-824 in rat plasma, lung and brain tissues by liquid chromatography tandem mass spectrometry: application to a pharmacokinetic study.

A selective, sensitive and high performance liquid chromatography-tandem mass spectrometry (LC-(ESI)MS/MS) method has been developed and validated for the quantification of the potent antitubercular drug candidate, PA-824, in rat plasma, lung and brain tissues. Sample clean-up involved protein precipitation and solid-phase extraction. Chromatographic separation was performed on YMC Triart C18 column (150 mm × 3.0 mm, 3.0 µm). The method was validated over the concentration range of 75-1500 ng/mL for plasma, 50-1200 ng/g for lungs and 100-1500 ng/g for brain tissue. Evaluation of the pharmacokinetic properties of PA-824 utilized Sprague Dawley rats with a dosage of 20mg/kg at various time points. The new method was applied successfully for the determination of PA-824 with liquid desorption followed by liquid chromatography with ultra-high resolution quadrupole time-of-flight mass spectrometry in the different biological samples.