Solid-phase microextraction. How far are we from clinical practice?

Targeted volatolomics of human monocytes: Comparison of 2D-GC/TOF-MS and 1D-GC/Orbitrap-MS methods

Blood is a complex biological matrix providing valuable information on nutritional, metabolic, and immune status. The detection of blood biomarkers requires sensitive analytical methods because analytes are at very low concentrations. Peripheral blood monocytes play a crucial role in inflammatory processes, and the metabolites released by monocytes during these processes might serve as important signalling molecules and biomarkers of particular physiological states. Headspace solid-phase microextraction (HS-SPME) combined with two different mass spectrometric platforms, two-dimensional (2D) gas chromatography coupled to time-of-flight mass spectrometry (2D-GC/TOF-MS) and one-dimensional gas chromatography coupled to Orbitrap mass spectrometry (GC/Orbitrap-MS), were applied for the investigation of volatile organic compounds (VOCs) produced by human peripheral blood monocytes. An optimized method was subsequently applied for the characterization of changes in VOCs induced by lipopolysaccharides (LPS) and zymosan (ZYM) stimulation. Overall, the 2D-GC/TOF-MS and the 1D-GC/Orbitrap-MS analyses each yielded about 4000 and 400 peaks per sample, respectively. In total, 91 VOCs belonging to eight different chemical classes were identified. The samples were collected in two fractions, conditioned media for monitoring extracellularly secreted molecules and cell pellet samples to determine the intracellular composition of VOCs. Alcohols, ketones, and hydrocarbons were the main chemical classes of the metabolic profile identified in cell fractions. Aldehydes, acids and cyclic compounds were characteristic of the conditioned media fraction. Here we demonstrate that HS-SPME-2D-GC/TOF-MS is more suitable for the identification of specific VOC profiles produced by human monocytes than 1D-GC/Orbitrap-MS. We define the signature of VOCs occurring early after monocyte activation and characterise the signalling compounds released by immune cells into media.

Chromatographic methods development for clinical practice: requirements and limitations

Development of a chromatographic method in bioanalysis is a challenging and complex procedure with many pitfalls and often unexpected reversals that can require several months to accomplish. Even an experienced analytical team must contend many limitations mainly in connection with the strict requirements imposed on current clinical research. These restrictions typically persist throughout the whole development process, from clinical trial assignment, across optimization of extraction of biological materials and chromatographic separation, to validation and data interpretation. This paper describes questions and their possible answers raised during the pre-analytical phase such as use of modern sample preparation techniques in clinical methods, application of internal standards, as well as selection of stationary phases and detection techniques in the analytical phase. Validation problems and interpretation of results are demonstrated with three typical examples of characteristics to be considered, i.e. recovery, matrix effect, and limit of detection vs. lower limit of quantification.

Current Trends in Fully Automated On-Line Analytical Techniques for Beverage Analysis

The determination of target analytes in complex matrices such as beverages requires a series of analytical steps to obtain a reliable analysis. This critical review presents the current trends in sample preparation techniques based on solid phase extraction miniaturization, automation and on-line coupling. Techniques discussed include solid-phase extraction (SPE), solid-phase microextraction (SPME), in-tube solid-phase microextraction (in-tube SPME) and turbulent-flow chromatography (TFC). Advantages and limitations, as well as several of their main applications in beverage samples are discussed. Finally, fully automated on-line systems that involve extraction, chromatographic separation, and tandem mass spectrometry in one-step are introduced and critically reviewed.

Solid phase microextraction devices prepared on plastic support as potential single-use samplers for bioanalytical applications

This study presents new thin-film solid phase microextraction (SPME) devices prepared on plastic as potential single-use samplers for bioanalysis. Polybutylene terephthalate (PBT) was selected as a support due to its well-known chemical resistance, low cost, and suitability as a material for different medical grade components. The herein proposed samplers were prepared by applying a hydrophilic-lipophilic balanced (HLB)-polyacrylonitrile (PAN) coating on rounded and flat PBT pieces previously sanded with regular sandpaper. SPME devices prepared on PBT were evaluated in terms of robustness, chemical stability, and possible interferences upon exposure to different solvents and matrixes. Rewarding results were found when these samplers were employed for the quantitative analysis of multiple doping substances in common biological matrixes such as urine, plasma, and whole blood. Finally, the proposed thin-film SPME devices made on a PBT were evaluated by conducting multiple extractions from whole blood and plasma using the Concept 96 system. Results showed that more than 20 extractions from plasma and whole blood can be performed without observed decreases in coating performance or peeling of the extraction phase from the plastic surface. These findings demonstrate the robustness of PAN-based coatings applied on such polymeric substrate and open up the possibility of introducing new alternatives and cost-effective materials as support to manufacture SPME biocompatible devices for a wide range of applications, particularly in the clinical field.

In vivo and ex vivo SPME: a low invasive sampling and sample preparation tool in clinical bioanalysis

Solid phase microextraction (SPME) is well-established technology in bioanalysis. Current review discusses the features of SPME, which determine the non- or low-invasiveness of the method in biomedical analysis. In the first section we analyze the factors, which have significant influence on the SPME sampling device performance in the view of sampling safety and efficiency. In the later sections applicability of various SPME approaches for analysis of easily accessible samples routinely used for analysis (e.g., urine, blood) as well as limited availability samples (tissues) is discussed. Moreover, the examples of sampling alternative matrices such as hair, saliva, sweat or breath are presented. The advantages and limitation of the technology in the view of future development of SPME are also reviewed.

Chemical analysis of whale breath volatiles: a case study for non-invasive field health diagnostics of marine mammals

We explored the feasibility of collecting exhaled breath from a moribund gray whale (Eschrichtius robustus) for potential non-invasive health monitoring of marine mammals. Biogenic volatile organic compound (VOC) profiling is a relatively new field of research, in which the chemical composition of breath is used to non-invasively assess the health and physiological processes on-going within an animal or human. In this study, two telescopic sampling poles were designed and tested with the primary aim of collecting whale breath exhalations (WBEs). Once the WBEs were successfully collected, they were immediately transferred onto a stable matrix sorbent through a custom manifold system. A total of two large volume WBEs were successfully captured and pre-concentrated onto two Tenax^®-TA traps (one exhalation per trap). The samples were then returned to the laboratory where they were analyzed using solid phase micro extraction (SPME) and gas chromatography/mass spectrometry (GC/MS). A total of 70 chemicals were identified (58 positively identified) in the whale breath samples. These chemicals were also matched against a database of VOCs found in humans, and 44% of chemicals found in the whale breath are also released by healthy humans. The exhaled gray whale breath showed a rich diversity of chemicals, indicating the analysis of whale breath exhalations is a promising new field of research.

Low invasive in vivo tissue sampling for monitoring biomarkers and drugs during surgery

The techniques currently used for drug, metabolite, and biomarker determination are based on sample collection, and therefore they are not suitable for repeated analysis because of the high invasiveness. Here, we present a novel method of biochemical analysis directly in organ during operation without need of a separate sample collection step: solid-phase microextraction (SPME). The approach is based on flexible microprobe coated with biocompatible extraction phase that is inserted to the tissue with no damage or disturbance of the organ. The method was evaluated during lung and liver transplantations using normothermic ex vivo liver perfusion (NEVLP) and ex vivo lung perfusion (EVLP). The study demonstrated feasibility of the method to extract wide range of endogenous compounds and drugs. Statistical analysis allowed observing metabolic changes of lung during cold ischemic time, perfusion, and reperfusion. It was also demonstrated that the level of drugs and their metabolites can be monitored over time. Based on the methylprednisolone as a selected example, the impairment of enzymatic properties of liver was detected in the injured organs but not in healthy control. This finding was supported by changes in pathways of endogenous metabolites. The SPME probe was also used for analysis of perfusion fluid using stopcock connection. The evaluation of biochemical profile of perfusates demonstrated potential of the approach for monitoring organ function during ex vivo perfusion. The simplicity of the device makes it convenient to use by medical personnel. With the microprobe, different areas of the organ or various organs can be sampled simultaneously. The technology allows assessment of organ function by biochemical profiling, determination of potential biomarkers, and drug monitoring. The use of this method for preintervention analysis could enhance the decision-making process for the best possible personalized approach, whereas post-transplantation monitoring would be used for graft assessments and fast response in case of organ failure.

Development of SPME method for concomitant sample preparation of rocuronium bromide and tranexamic acid in plasma

A high-throughput method using solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry (SPME-LC-MS/MS) for determination of tranexamic acid and rocuronium bromide in human plasma was developed and validated. Standard analytical approaches employ acidification of the sample due to the instability of rocuronium bromide in collected plasma samples. However, acidification affects the binding equilibrium of the drug and consequently no information on the free/bound concentration can be obtained. Contrary to these protocols, the proposed method requires minimum sample handling and no ion pairing and/or derivatization procedure. A weak cation exchange coating was chosen as the best extracting phase for selected drugs, guaranteed a good recovery, minimum carry-over, reusability and reproducibility. SPME procedure met all Food and Drug Administration acceptance criteria for bioanalytical assays at three concentration levels, for both selected drugs. Post-extraction addition experiments showed that matrix effect was less than ±3%. Here, a weak cation exchange thin-film solid-phase microextraction (WCX TF-SPME) approach is presented, offering effective cleanup procedure and full quantitation of the drugs in plasma, undoubtedly one the most challenging matrices with regards to its complexity. In addition, the 96-well plate format of WCX TF-SPME system provides considerable advantages, such as high throughput analysis for up to 96 samples in 35min (22s/sample), requirement of small amounts of plasma samples (0.8mL), and a simple sample preparation protocol, all of which shows a promise for possible on-site application in hospitals to monitor concentrations of the drugs in close to real time.

Microextraction by Packed Sorbent (MEPS) and Solid-Phase Microextraction (SPME) as Sample Preparation Procedures for the Metabolomic Profiling of Urine

For a long time, sample preparation was unrecognized as a critical issue in the analytical methodology, thus limiting the performance that could be achieved. However, the improvement of microextraction techniques, particularly microextraction by packed sorbent (MEPS) and solid-phase microextraction (SPME), completely modified this scenario by introducing unprecedented control over this process. Urine is a biological fluid that is very interesting for metabolomics studies, allowing human health and disease characterization in a minimally invasive form. In this manuscript, we will critically review the most relevant and promising works in this field, highlighting how the metabolomic profiling of urine can be an extremely valuable tool for the early diagnosis of highly prevalent diseases, such as cardiovascular, oncologic and neurodegenerative ones.

Sampling and analysis of metabolomes in biological fluids

Metabolome analysis involves the study of small molecules that are involved in the metabolic responses that occur through patho-physiological changes caused by genetic stimuli or chemical agents.

Is SPME a destination or just another station for bioanalysis?

This article reviews the solid-phase microextraction technique and its potential to revolutionize bioanalysis in terms of combining sampling, sample preparation and extraction in one step with no blood withdrawal. Possible hurdles facing the technology when implemented in a pharmaceutical setting will be covered and the author will provide an outlook on the future of solid-phase microextraction as a novel microsampling technique for bioanalysis.

Overcoming the challenges of studying conservation physiology in large whales: a review of available methods

Large whales are subjected to a variety of conservation pressures that could be better monitored and managed if physiological information could be gathered readily from free-swimming whales. However, traditional approaches to studying physiology have been impractical for large whales, because there is no routine method for capture of the largest species and there is presently no practical method of obtaining blood samples from free-swimming whales. We review the currently available techniques for gathering physiological information on large whales using a variety of non-lethal and minimally invasive (or non-invasive) sample matrices. We focus on methods that should produce information relevant to conservation physiology, e.g. measures relevant to stress physiology, reproductive status, nutritional status, immune response, health, and disease. The following four types of samples are discussed: faecal samples, respiratory samples ('blow'), skin/blubber samples, and photographs. Faecal samples have historically been used for diet analysis but increasingly are also used for hormonal analyses, as well as for assessment of exposure to toxins, pollutants, and parasites. Blow samples contain many hormones as well as respiratory microbes, a diverse array of metabolites, and a variety of immune-related substances. Biopsy dart samples are widely used for genetic, contaminant, and fatty-acid analyses and are now being used for endocrine studies along with proteomic and transcriptomic approaches. Photographic analyses have benefited from recently developed quantitative techniques allowing assessment of skin condition, ectoparasite load, and nutritional status, along with wounds and scars from ship strikes and fishing gear entanglement. Field application of these techniques has the potential to improve our understanding of the physiology of large whales greatly, better enabling assessment of the relative impacts of many anthropogenic and ecological pressures.