Direct imaging of elemental distributions in tissue sections by laser ablation mass spectrometry.

We present a strategy for imaging of elements in biological tissues using laser ablation (LA) mass spectrometry (MS), which was compared to laser ablation inductively coupled plasma (LA-ICP) MS. Both methods were adopted for quantitative imaging of elements in mouse kidney, as well as traumatic brain injury model tissue sections. MS imaging (MSI) employing LA provides quantitative data by comparing signal abundances of sodium from tissues to those obtained by imaging quantitation calibration standards of the target element applied to adjacent control tissue sections. LA-ICP MSI provided quantitative data for several essential elements in both brain and kidney tissue sections using a dried-droplet approach. Both methods were used to image a rat model of traumatic brain injury, revealing accumulations of sodium and calcium in the impact area and its peripheral regions. LA MSI is shown to be a viable option for quantitative imaging of specific elements in biological tissue sections.

Hydrazide-based reactive matrices for the sensitive detection of aldehydes and ketones by MALDI mass spectrometry imaging.

A one-step, on-tissue chemical derivatisation method for MALDI mass spectrometry imaging was found to improve the detectability of aldehydes and ketones by charge-tagging. The developed reactive matrices, containing a UV-chromophore, ionisable moiety and hydrazide group, showed an equal or higher detection efficiency than Girard's reagent P, enabling improved imaging of brain metabolites without the need for additional co-matrices.

Quantitative determination of salbutamol in tablets by multiple-injection capillary zone electrophoresis.

A multiple-injection capillary zone electrophoresis (MICZE) method has been developed for the assay of salbutamol in Ventoline Depot tablets (GlaxoSmithKline). In the developed method, seven sample sets, each consisting of three samples, were sequentially injected into the capillary and analyzed within a single run. This enabled a total of twenty-one sequential injections, i.e., six standards and fifteen samples, containing salbutamol and the injection marker oxprenolol. The injected sample plugs were separated by plugs of background electrolyte, through application of a short-term voltage (30kV) over the capillary for different time periods, i.e., t(PE1) and t(PE2). The samples in each set were isolated from each other by partial electrophoresis for 2.35min (t(PE1)), while the sample sets were separated for 10.50min (t(PE2)). After the final injection, all the applied samples were subjected to electrophoresis for a time period corresponding to that in conventional single-injection CZE. The method was validated regarding linearity, accuracy, precision and robustness before it was applied to the determination of salbutamol in 15 tablets of Ventoline Depot with a labeled content of 8mg salbutamol. The average salbutamol content was determined to 7.8mg (+/-0.3mg) from simultaneous analyses of the 15 different tablets.

Peptide ion channel toxins from the bootlace worm, the longest animal on Earth.

Polypeptides from animal venoms have found important uses as drugs, pharmacological tools, and within biotechnological and agricultural applications. We here report a novel family of cystine knot peptides from nemertean worms, with potent activity on voltage-gated sodium channels. These toxins, named the α-nemertides, were discovered in the epidermal mucus of Lineus longissimus, the 'bootlace worm' known as the longest animal on earth. The most abundant peptide, the 31-residue long α-1, was isolated, synthesized, and its 3D NMR structure determined. Transcriptome analysis including 17 species revealed eight α-nemertides, mainly distributed in the genus Lineus. α-1 caused paralysis and death in green crabs (Carcinus maenas) at 1 µg/kg (~300 pmol/kg). It showed profound effect on invertebrate voltage-gated sodium channels (e.g. Blattella germanica Nav1) at low nanomolar concentrations. Strong selectivity for insect over human sodium channels indicates that α-nemertides can be promising candidates for development of bioinsecticidal agents.

An introduction to MS imaging in drug discovery and development.

A vital process in drug discovery and development is to assess the absorption, distribution, metabolism, excretion and toxicology of potentially therapeutic compounds in the body. The potential utility of MS imaging has been demonstrated in many studies focusing on molecules including peptides, proteins and lipids. However, MS imaging also permits the direct analysis of drugs and drug metabolites in tissue samples without requiring the use of target-specific labels or reagents. Here, a brief technical description of the technique is presented along with examples of its usefulness at different stages of the drug discovery and development process including absorption, distribution, metabolism, excretion and toxicology, and blood-brain barrier drug penetration investigations.

Development of a chiral non-aqueous capillary electrophoretic system using the partial filling technique with UV and mass spectrometric detection.

A chiral non-aqueous CE system with UV and mass spectrometric detection has been developed. The enantioseparation was promoted by diastereomeric complex (ion-pair) formation between the amines (e.g. salbutamol, atenolol) and the chiral selector, (-)-2,3:4,6-di-O-isopropylidene-2-keto-L-gulonic acid [(-)-DIKGA]. Different solvent mixtures were studied, as well as different concentrations of (-)-DIKGA and ammonium acetate in the background electrolyte. A partial filling technique was developed with a selector plug composed of (-)-DIKGA and ammonium acetate in a solvent mixture of methanol and 2-propanol. The separated enantiomers of pronethalol were detected by a Q-TOF MS system equipped with a sheath-flow electrospray ionization interface.

Principles for different modes of multiple-injection CZE.

This paper introduces four different modes of multiple-injection CZE (MICZE). The validity of these MICZE models was evaluated by the experimental data. Prior to the application of MICZE, the electrophoretic conditions are developed in the single-injection mode by adjusting different experimental parameters such as pH, type and concentration of buffer additives and temperature. Based on the migration time difference (Deltatmig) between the analyte and the internal standard or injection marker, one or more MICZE modes can be employed. The injection marker is added to the sample to compensate for injection-volume fluctuations. The inter-plug distance is regulated by applying an electrical field over the capillary for a short period of time between each injection. After the final injection, the separation is completed by electrophoresis for a time period corresponding to that in the single-injection mode.

Quantification of buserelin in a pharmaceutical product by multiple-injection CZE.

An efficient and rapid separation method based on reversed-polarity multiple-injection CZE (MICZE), has been developed for the quantification of buserelin in a pharmaceutical product. The determinations were performed by serially injecting five standard solutions of buserelin (50-300 microg/mL) and one reference analyte into a Polybrene-coated capillary. All the samples contained goserelin, an analog peptide to buserelin, as internal standard (IS). Immediately after pressure injection, the applied sample plugs were subjected to electrophoresis for 2 min at -25 kV. Consequently, each sample plug became isolated from its neighboring plugs by the BGE, composed of 100 mM phosphate-triethanolamine buffer at pH 3.0 containing 10% v/v ACN. During separation the individual sample components migrated at similar velocities and as distinct zones through the capillary giving 24 peaks, 12 from the analyte and the IS and 12 from the sample matrix. The buserelin content of the pharmaceutical product was determined to be 0.94 +/- 0.05 mg/mL, which is only a slight deviation from the declared concentration (1 mg/mL).