Meire Ribeiro da Silva

Kisspeptin modulates sexual and emotional brain processing in humans

BACKGROUND. Sex, emotion, and reproduction are fundamental and tightly entwined aspects of human behavior. At a population level in humans, both the desire for sexual stimulation and the desire to bond with a partner are important precursors to reproduction. However, the relationships between these processes are incompletely understood. The limbic brain system has key roles in sexual and emotional behaviors, and is a likely candidate system for the integration of behavior with the hormonal reproductive axis. We investigated the effects of kisspeptin, a recently identified key reproductive hormone, on limbic brain activity and behavior. METHODS. Using a combination of functional neuroimaging and hormonal and psychometric analyses, we compared the effects of kisspeptin versus vehicle administration in 29 healthy heterosexual young men. RESULTS. We demonstrated that kisspeptin administration enhanced limbic brain activity specifically in response to sexual and couple-bonding stimuli. Furthermore, kisspeptin’s enhancement of limbic brain structures correlated with psychometric measures of reward, drive, mood, and sexual aversion, providing functional significance. In addition, kisspeptin administration attenuated negative mood. CONCLUSIONS. Collectively, our data provide evidence of an undescribed role for kisspeptin in integrating sexual and emotional brain processing with reproduction in humans. These results have important implications for our understanding of reproductive biology and are highly relevant to the current pharmacological development of kisspeptin as a potential therapeutic agent for patients with common disorders of reproductive function. FUNDING. National Institute for Health Research (NIHR), Wellcome Trust (Ref 080268), and the Medical Research Council (MRC).

New materials for sample preparation techniques in bioanalysis

The analysis of biological samples is a complex and difficult task owing to two basic and complementary issues: the high complexity of most biological matrices and the need to determine minute quantities of active substances and contaminants in such complex sample. To succeed in this endeavor samples are usually subject to three steps of a comprehensive analytical methodological approach: sample preparation, analytes isolation (usually utilizing a chromatographic technique) and qualitative/quantitative analysis (usually with the aid of mass spectrometric tools). Owing to the complex nature of bio-samples, and the very low concentration of the target analytes to be determined, selective sample preparation techniques is mandatory in order to overcome the difficulties imposed by these two constraints. During the last decade new chemical synthesis approaches has been developed and optimized, such as sol-gel and molecularly imprinting technologies, allowing the preparation of novel materials for sample preparation including graphene and derivatives, magnetic materials, ionic liquids, molecularly imprinted polymers, and much more. In this contribution we will review these novel techniques and materials, as well as their application to the bioanalysis niche.

Unified chromatography: Fundamentals, instrumentation and applications†

The concept of unified chromatography has been in existence for 50 years after the work of Giddings proposing that all modes of chromatography (gas chromatography, liquid chromatography, supercritical fluid chromatography and so on) may be treated together under a single unified theory. His idea was partially fulfilled 23 years later by Ishii, Takeuchi and colleagues, who demonstrated for the first time the possibility to analyze a complex sample containing substances with a wide range of boiling points and polarities in the same instrument and column, just by varying the mobile phase pressure and temperature to change from one chromatographic mode to another. This approach has been demonstrated through application to the separation of complex mixtures in several areas including crude oil, edible oils and polymers. Still, unified chromatography has not yet been fully developed. In the present work, we will review the fundamentals, instrumentation and several applications of the technique. Also discussed are the drawbacks that still hinder development, as well as the recent developments and trends in instrumentation and columns that suggest the most feasible ways forward to the full development of unified chromatography.

SPME determination of low concentration levels of monoaromatic chemical markers in soils after remediation by supercritical fluid extraction

Soil contamination by organic compounds has been a serious concern over the years. Among the various forms of pollutant release, gas station contamination has been widely emphasized. The presence of simple aromatic compounds in soils sampled near gas stations may indicate contamination, considering that such compounds are frequently found in petroleum-derived products. The present paper reports on the development of a process that uses pressurized fluids for the remediation of contaminated soils. Supercritical fluid extraction (SFE) employing CO2 as the solvent and an 11.0 g capacity extraction cell was utilized. In order to demonstrate the efficiency of the process, an analytical procedure employing headspace-solid phase micro extraction (HS-SPME) as the sample preparation method and GC-MS as the separation technique was optimized and validated. Limits of quantification and detection obtained were in agreement with the values established by national and international regulatory agencies. The linear range obtained was from 10 to 260 μg kg−1, with determination coefficients r2 > 0.98 for all analyses. Different removal rates were observed for the contaminants studied, the best results being achieved by employing CO2 in a supercritical state.

Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples

Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively.

An automated and self-cleaning nano liquid chromatography mass spectrometry platform featuring an open tubular multi-hole crystal fiber solid phase extraction column and an open tubular separation column

An open tubular (OT) sample preparation/separation platform was developed. A multi-channel polymer layer open tubular (mPLOT) solid phase extraction (SPE) column was prepared by wall-coating the 126 channels (8μm inner diameter (ID) each) of a crystal fiber capillary with an organic polymer, namely poly(styrene-co-octadecene-co-divinylbenzene) (PS-OD-DVB). The mPLOT SPE was coupled on-line with a 10μm×2m poly(styrene-co-divinylbenzene) (PS-DVB) OT liquid chromatography column with nanospray mass spectrometry (OTLC-MS). Compared to using monolithic/particle-packed SPEs, mPLOT-SPE-OTLC allowed both fast loading and sufficient refocusing on the OT analytical column of small model compounds (sulfonamides≈300Da). Using automatic filtration/filter back-flushing (AFFL) plumbing, the mPLOT SPE column gave a constant and low back-pressure ≈35bar at 0.5μL/min. Surprisingly large sample volumes (10μL) were possible to be injected using a 12cm mPLOT.

Miniaturized Column Liquid Chromatography

Abstract Miniaturization in liquid chromatography (LC) has received considerable attention from analysts since the demonstration of its advantageous applicability in diverse fields including the OMICS arena (proteomics, metabolomics, foodomics, lipodomics, etc.) as well as several other niches such as environmental, biological, foodstuff, and pharmaceutical analysis. Although the first attempts to miniaturize modern LC systems started around 1967, these efforts have not yet been completed, with several practical problems still to be solved. Therefore, this is still an open and exciting area for research involving new instrumentation, columns improvement, novel sorbent materials, smaller volume detectors, lower dead volume connections, multidimensional systems, and so on. Among the main difficulties still hindering the wide implementation of miniaturized LC, particularly in routine labs, a major one relates to the absence of appropriate and robust commercial instrumentation designed and dedicated to mini-LC, instead of rough adaptation from conventional high-performance LC instrumentation. Removing this obstacle will facilitate the expansion of this exciting research area involving new instrumentation, columns improvement, novel sorbent materials, smaller volume detectors, lower dead volume connections, multidimensional systems, and robust miniaturized columns available with a large range of stationary phases prepared with distinct chemical (sorbents) and physical (length, internal diameter, and film thickness) characteristics. In this chapter, the main topics related to the recent advances and prospects for miniaturization of LC are discussed including the following: (1) instrumentation (pumps, column heater, tubing and connectors, sample introduction, and detectors); (2) column technology, including both filled (monolithic and packed capillary/nano-LC columns) and open-tubular columns (wall-coated open-tubular and porous layer open-tubular columns); and (3) simplified theory of micro- and nano-LC. Furthermore, the recent development of nanomaterials fully compatible with the principles of micro- and nano-LC are presented and discussed, including monoPLOT columns and molecularly imprinted polymer monolithic columns. Selected applications of miniaturized LC as well as the coupling of capillary and nano-LC columns with mass spectrometry are also addressed.