In-tube solid-phase microextraction directly coupled to tandem mass spectrometry for anandamide and 2-arachidonoylglycerol determination in rat brain samples from an animal model of Parkinson's disease

Recent advance on microextraction sampling technologies for bioanalysis

The contents of target substances in biological samples are usually at low concentration levels, and the matrix of biological samples is usually complex. Sample preparation is considered a very critical step in bioanalysis. At present, the utilization of microextraction sampling technology has gained considerable prevalence in the realm of biological analysis. The key developments in this field focus on the efficient microextraction media and the miniaturization and automation of adaptable sample preparation methods currently. In this review, the recent progress on the microextraction sampling technologies for bioanalysis has been introduced from point of view of the preparation of microextraction media and the microextraction sampling strategies. The advance on the microextraction media was reviewed in detail, mainly including the aptamer-functionalized materials, molecularly imprinted polymers, carbon-based materials, metal-organic frameworks, covalent organic frameworks, etc. The advance on the microextraction sampling technologies was summarized mainly based on in-vivo sampling, in-vitro sampling and microdialysis technologies. Moreover, the current challenges and perspective on the future trends of microextraction sampling technologies for bioanalysis were briefly discussed.

SPME as a green sample-preparation technique for the monitoring of phytocannabinoids and endocannabinoids in complex matrices

The endocannabinoid system (ECS), particularly its signaling pathways and ligands, has garnered considerable interest in recent years. Along with clinical work investigating the ECS' functions, including its role in the development of neurological and inflammatory conditions, much research has focused on developing analytical protocols enabling the precise monitoring of the levels and metabolism of the most potent ECS ligands: exogenous phytocannabinoids (PCs) and endogenous cannabinoids (endocannabinoids, ECs). Solid-phase microextraction (SPME) is an advanced, non-exhaustive sample-preparation technique that facilitates the precise and efficient isolation of trace amounts of analytes, thus making it appealing for the analysis of PCs and ECs in complex matrices of plant and animal/human origin. In this paper, we review recent forensic medicine and toxicological studies wherein SPME has been applied to monitor levels of PCs and ECs in complex matrices, determine their effects on organism physiology, and assess their role in the development of several diseases.

Monitoring of age- and gender-related alterations of endocannabinoid levels in selected brain regions with the use of SPME probes

INTRODUCTION

The endocannabinoid system consists of different types of receptors, enzymes and endocannabinoids (ECs), which are involved in several physiological processes, but also play important role in the development and progression of central nervous system disorders.

OBJECTIVES

The purpose of this study was to apply precise and sensitive methodology for monitoring of four ECs, namely anandamide (AEA), 2-arachidonoyl glycerol (2-AG), N-arachidonoyl dopamine (NADA), 2-arachidonyl glyceryl ether (2-AGe) in selected brain regions of female and male rats at different stages of development (young, adult and old).

METHODS

Biocompatible solid-phase microextraction (SPME) probes were introduced into the intact (non-homogenized) brain structures for isolation of four ECs, and the extracts were subjected to LC-MS/MS analysis. Two chemometric approaches, namely hierarchical cluster analysis (HCA) and Principal Component Analysis (PCA) were applied to provide more information about the levels of 2-AG and AEA in different brain structures.

RESULTS

2-AG and AEA were extracted and could be quantified in each brain region; the level of 2-AG was significantly higher in comparison to the level of AEA. Two highly unstable ECs, NADA and 2-AGe, were captured by SPME probes from intact brain samples for the first time.

CONCLUSION

SPME probes were able to isolate highly unstable endogenous compounds from intact tissue, and provided new tools for precise analysis of the level and distribution of ECs in different brain regions. Monitoring of ECs in brain samples is important not only in physiological conditions, but also may contribute to better understanding of the functioning of the endocannabinoid system in various disorders.

Direct coupling of fiber-in-tube solid-phase microextraction with tandem mass spectrometry to determine amyloid beta peptides as biomarkers for Alzheimer's disease in cerebrospinal fluid samples

Current research efforts at neurological diseases have focused on identifying novel biomarkers to aid in diagnosis, to provide accurate prognostic information, and to monitor disease progression. This study presents the direct coupling of fiber-in-tube solid-phase microextraction to tandem mass spectrometry as a reliable method to determine amyloid beta peptides (Aβ38, Aβ40, and Aβ42) as biomarkers for Alzheimer's disease in cerebrospinal fluid (CSF) samples. To obtain the biocompatible fiber-in-tube SPME capillary, a PEEK tube segment was longitudinally packed with fine fibers [nitinol wires coated with a zwitterionic polymeric ionic liquid], to act as selective extraction medium. The fiber-in-tube SPME-MS/MS method integrated analyte extraction/enrichment and sample cleanup (exclusion of interferents) into one step. The method provided lower limits of quantification (LLOQ: 0.2 ng mL^-1 for Aβ38 and 0.1 ng mL^-1 for Aβ40 and Aβ42), high precision (CV lower than 11.6%), and high accuracy (relative standard deviation lower than 15.1%). This method was successfully applied to determine Aβ peptides in CSF samples obtained from AD patients (n = 8) and controls (healthy volunteers, n = 10). Results showed that Aβ42 levels in the CSF samples obtained from AD patients were significantly lower compared to healthy controls (p < 0.05). On the basis of the ROC analysis results, the Aβ42/Aβ40 ratio (AUC = 0.950, p < 0.01; 95%) performed significantly better than Aβ42 alone (AUC = 0.913, p < 0.01; 95%) in discriminating between AD patients and healthy controls and presented better diagnostic ability for AD. The novelties of this study are not only related to evaluating Aβ peptides as AD biomarkers, but also to demonstrating direct online coupling of fiber-in-tube SPME with MS/MS as a quantitative high-throughput method for bioanalysis.

Polyvinyl alcohol-based hydrogel sorbent for extraction of parabens in human milk samples by in-tube SPME–LC–UV

In this work, we developed an in-tube solid-phase microextraction (SPME) device consisting of a fused silica capillary modified with a polyvinyl alcohol (PVOH) hydrogel. Methylparaben, ethylparaben, propylparaben, and butylparaben were determined in human milk samples by using the in-tube SPME device coupled with liquid chromatography with spectrophotometric detection in the ultraviolet region (LC-UV). The inner surface of the fused silica capillary was silanized to allow covalent modification with the PVOH-hydrogel, using glutaraldehyde as cross-linking agent. The developed device was used up to 250 times with no reduction in the analytes' peak areas or carryover effect, besides having a low production cost. The human milk samples showed a significant matrix effect for parabens with higher logKo/w. Low limits of quantification (LLOQ) between 10.0 and 15.0 ng mL-1 were obtained with RSD values in the range of 1.18 to 18.3%. For the intra- and inter-day assays, RSD values from 5.6 to 16.5% and accuracy from 74.5 to 128.8% were achieved. The PVOH-based hydrogel sorbent allowed the use of water as desorption solvent, eliminating the use of organic solvents, which follows the principles of green chemistry. The results showed a great application potential of the PVOH-based hydrogel sorbent for the extraction of organic compounds from high-complexity samples.

In-Tube Solid-Phase Microextraction Directly Coupled to Mass Spectrometric Systems: A Review

Since it was introduced in 1997, in-tube solid-phase microextraction (in-tube SPME), which uses a capillary column as extraction device, has been continuously developed as online microextraction coupled to LC systems (in-tube SPME-LC). In the last decade, new couplings have been evaluated on the basis of state-of-the-art LC instruments, including direct coupling of in-tube SPME to MS/MS systems, without chromatographic separation, for high-throughput analysis. In-tube SPME coupling to MS/MS has been possible thanks to the selectivity of capillary column coatings and MS/MS systems (SRM mode). Different types of capillary columns (wall-coated open-tubular, porous-layer open-tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with selective stationary phases have been developed to increase the sorption capacity and selectivity of in-tube SPME. This review focuses on the in-tube SPME principle, extraction configurations, current advances in direct coupling to MS/MS systems, experimental parameters, coatings, and applications in different areas (food, biological, clinical, and environmental areas) over the last years.

A novel porphyrin-based conjugated microporous nanomaterial for solid-phase microextraction of phthalate esters residues in children's food

A novel porphyrin-based conjugated microporous polymer (PCMP) with microporous structure and nitrogen-rich pyrrole building blocks was synthesized. The PCMP was used as a coating material to prepare solid-phase microextraction (SPME) fibers by sol-gel technique. Due to the toxicity of the phthalate esters (PAEs) and the necessity for their sensitive determinations in some food samples, the SPME fiber was investigated for the extraction of eleven PAEs from six different children's milk beverages prior to their detection by gas chromatography-mass spectrometry. Under the optimal conditions, the linear response range for the PAEs was in the range from 0.03 to 200 µg L^-1 and the limits of detection (S/N = 3) for the analytes were 0.01-3.00 μg L^-1. The method recoveries for the PAEs were between 80% and 120%, with the relative standard deviations varying from 1.3% to 9.8%. The method was successfully applied for the determination of PAEs in children's milk beverages.

Lipidomics of Bioactive Lipids in Alzheimer's and Parkinson's Diseases: Where Are We?

Lipids are not only constituents of cellular membranes, but they are also key signaling mediators, thus acting as “bioactive lipids”. Among the prominent roles exerted by bioactive lipids are immune regulation, inflammation, and maintenance of homeostasis. Accumulated evidence indicates the existence of a bidirectional relationship between the immune and nervous systems, and lipids can interact particularly with the aggregation and propagation of many pathogenic proteins that are well-renowned hallmarks of several neurodegenerative disorders, including Alzheimer’s (AD) and Parkinson’s (PD) diseases. In this review, we summarize the current knowledge about the presence and quantification of the main classes of endogenous bioactive lipids, namely glycerophospholipids/sphingolipids, classical eicosanoids, pro-resolving lipid mediators, and endocannabinoids, in AD and PD patients, as well as their most-used animal models, by means of lipidomic analyses, advocating for these lipid mediators as powerful biomarkers of pathology, diagnosis, and progression, as well as predictors of response or activity to different current therapies for these neurodegenerative diseases.