Dried matrix spots and clinical elemental analysis. Current status, difficulties, and opportunities

Direct multi-elemental analysis of cerebrospinal fluid samples by LA-ICP-MS employing an aerosol local extraction cryogenic ablation cell

A novel method for direct high-throughput analysis of multi-elements in cerebrospinal fluid (CSF) samples by laser ablation inductively coupled plasma mass spectrometry with an aerosol local extraction cryogenic ablation cell (ALEC-LA-ICP-MS) was developed. Microliter-level CSF samples were frozen by a designed cryogenic ablation cell and directly analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) without time-consuming pretreatment. Compared with the precision obtained at room temperature (20℃), that obtained at low temperature (- 25℃) was significantly improved; the RSDs were reduced from 8.3% (Zn) to 32.6% (Mn) to 2.2% (Pb) to 6.5% (Mn) with six times parallel determination. To meet the analytical requirement of the micro-volume CSF samples, the laminar flow aerosol local extraction strategy was adopted to improve the transmission efficiency of aerosols, and the signal intensity was increased by four times compared with the standard commercial ablation cell. The standard solution with 0.4% bovine serum albumin (BSA) matrix was used as matrix-match external standard, and Rh was added into the samples as internal standard. The limits of detection (LODs) ranged from 0.17 μg·L-1 (Mn) to 8.67 μg·L-1 (Mg). Standard addition recovery experiments and the determination of CRM serum L-1 and L-2 were carried out to validate the accuracy of the method; all results indicated there were excellent accuracy and precision in the proposed method. The matrix-scanning function in the GeoLas software combined with the microwell plate realizes the high-throughput automatic analysis. Twenty-four CSF samples from different patients were determined; the results showed that there might be a correlation between the metal elements in CSF and the diseases, which means that the proposed method has potential in the diagnosis of neurological diseases.

Biological Fluid Microsampling for Therapeutic Drug Monitoring: A Narrative Review

Therapeutic drug monitoring (TDM) is a specialized area of laboratory medicine which involves the measurement of drug concentrations in biological fluids with the aim of optimizing efficacy and reducing side effects, possibly modifying the drug dose to keep the plasma concentration within the therapeutic range. Plasma and/or whole blood, usually obtained by venipuncture, are the "gold standard" matrices for TDM. Microsampling, commonly used for newborn screening, could also be a convenient alternative to traditional sampling techniques for pharmacokinetics (PK) studies and TDM, helping to overcome practical problems and offering less invasive options to patients. Although technical limitations have hampered the use of microsampling in these fields, innovative techniques such as 3-D dried blood spheroids, volumetric absorptive microsampling (VAMS), dried plasma spots (DPS), and various microfluidic devices (MDS) can now offer reliable alternatives to traditional samples. The application of microsampling in routine clinical pharmacology is also hampered by the need for instrumentation capable of quantifying analytes in small volumes with sufficient sensitivity. The combination of microsampling with high-sensitivity analytical techniques, such as liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), is particularly effective in ensuring high accuracy and sensitivity from very small sample volumes. This manuscript provides a critical review of the currently available microsampling devices for both whole blood and other biological fluids, such as plasma, urine, breast milk, and saliva. The purpose is to provide useful information in the scientific community to laboratory personnel, clinicians, and researchers interested in implementing the use of microsampling in their routine clinical practice.

Advances in testing for sample manipulation in clinical and forensic toxicology - Part A: urine samples

In many countries, adherence testing is used to monitor consumption behavior or to prove abstinence. Urine and hair are most commonly used, although other biological fluids are available. Positive test results are usually associated with serious legal or economic consequences. Therefore, various sample manipulation and adulteration strategies are used to circumvent such a positive result. In these critical review articles on sample adulteration of urine (part A) and hair samples (part B) in the context of clinical and forensic toxicology, recent trends and strategies to improve sample adulteration and manipulation testing published in the past 10 years are described and discussed. Typical manipulation and adulteration strategies include undercutting the limits of detection/cut-off by dilution, substitution, and adulteration. New or alternative strategies for detecting sample manipulation attempts can be generally divided into improved detection of established urine validity markers and direct and indirect techniques or approaches to screening for new adulteration markers. In this part A of the review article, we focused on urine samples, where the focus in recent years has been on new (in)direct substitution markers, particularly for synthetic (fake) urine. Despite various and promising advances in detecting manipulation, it remains a challenge in clinical and forensic toxicology, and simple, reliable, specific, and objective markers/techniques are still lacking, for example, for synthetic urine.

Comparison of Dried Blood Spot and Microtube Techniques for Trace Element Quantification by ICP-MS

Microsampling techniques became more popular in the last decades, and their use for common analyses such as trace element quantification by inductively coupled plasma mass spectrometry (ICP-MS) has been investigated. We decided to compare two of these techniques (dried blood spots and microtubes) to evaluate their potential for the analysis of 12 trace elements in human whole blood: aluminum (Al), total arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), selenium (Se) and zinc (Zn). Signal contributions from blank filter paper and instability at room temperature for several elements in the dried blood spot samples restrained our enthusiasm for the use of this technique. Conversely, microtube samples presented low background contamination and good stability under different temperature conditions. Therefore, our results demonstrate that the use of microtubes is more suitable than dried blood spots for trace element quantification in human blood, both in research and routine analysis.

In-vial dried urine spot collection and processing for quantitative analyses

Analysis of dried urine spots (DUSs) is becoming an emerging technique in clinical, toxicological, and forensic chemistry due to the fully non-invasive collection, facile transportation, and simple storage of DUS samples. Correct DUS collection and elution is of the utmost importance because inadequate DUS sampling/processing may have direct consequences on quantitative DUS analyses and these aspects were, for the first time, comprehensively investigated in this contribution. Various groups of endogenous and exogenous species were selected as model analytes and their concentrations were monitored in DUSs collected on standard cellulose-based sampling cards. Strong chromatographic effects were observed for most analytes having a crucial impact on their distribution within the DUSs during sampling. Concentrations of target analytes were up to 3.75-fold higher in the central DUS sub-punch in comparison to the liquid urine. Consequently, substantially reduced concentrations of these analytes were determined in peripheral DUS sub-punches demonstrating that sub-punching, often applied to dried material spots, is not acceptable for quantitative DUS analyses. Hence, a simple, rapid, and user-friendly procedure was suggested, which employed an in-vial collection of a known urine volume on a pre-punched sampling disc (using a low-cost micropipette designed for patient-centric clinical sampling) and in-vial processing of the whole DUS. Excellent accuracy (0.20%) and precision (0.89%) of liquid transfers were achieved by the micropipette, which was also applied to remote DUS collection by laic and expert users. The resulting DUS eluates were analysed by capillary electrophoresis (CE) for the determination of endogenous urine species. The CE results demonstrated no significant differences between the two user groups, elution efficiencies of 88-100% (in comparison to the liquid urine), and precision better than 5.5%.

Facile Lego-Spinner Pretreatment Device for Analysis of Arsenic Species in Dried Blood Spots by Ion Chromatography-Inductively Coupled Plasma-Mass Spectrometry

Dried blood spot (DBS) detection has the advantages of small blood collection, convenience, and reliability, which provides a possibility for large-scale evaluation of arsenic exposure in human population. Herein, a facile Lego-spinner pretreatment device is rationally designed for speciation analysis of arsenic in DBSs by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). In the mixing mode of the Lego-spinner, the magnetic stir bar in the centrifuge tube rotates under a magnetic field to assist the dispersive extraction of arsenic species in the DBS with reagents. In the centrifugation mode of the Lego-spinner, the arsenic extract is separated from the blood matrix for the subsequent IC-ICP-MS analysis. For the DBS prepared from 80 μL of whole blood, the whole pretreatment operation can be completed within 25 min. The detection limits of arsenobetaine, arsenite, dimethylarsenate, monomethylarsonate, and arsenate in the DBS are 0.09-0.15 μg L^-1, and precisions are <11%. The concentrations of these five arsenic species are highly correlated between whole blood and the DBS (r² > 0.97), and Bland-Altman analysis indicates that the concentration difference of arsenic species between whole blood and the DBS is within ±20%. The DBS sampling approach can effectively preserve arsenic species for at least 30 days at 4 °C, and the contents of arsenic species in the DBS prepared from capillary blood are in a reasonable agreement with those of venous whole blood (gold standard). This Lego-spinner provides a handy and efficient tool for fast extraction of arsenic species in DBSs, facilitating the in-depth study of arsenic migration and transformation in the human body.

Potential use of a dried saliva spot (DSS) in therapeutic drug monitoring and disease diagnosis

In recent years, scientific researchers have increasingly become interested in noninvasive sampling methods for therapeutic drug monitoring and disease diagnosis. As a result, dried saliva spot (DSS), which is a sampling technique for collecting dried saliva samples, has been widely used as an alternative matrix to serum for the detection of target molecules. Coupling the DSS method with a highly sensitive detection instrument improves the efficiency of the preparation and analysis of biological samples. Furthermore, dried blood spots, dried plasma spots, and dried matrix spots, which are similar to those of the DSS method, are discussed. Compared with alternative biological fluids used in dried spot methods, including serum, tears, urine, and plasma, saliva has the advantage of convenience in terms of sample collection from children or persons with disabilities. This review aims to provide integral strategies and guidelines for dried spot methods to analyze biological samples by illustrating several dried spot methods. Herein, we summarize recent advancements in DSS methods from June 2014 to March 2021 and discuss the advantages and disadvantages of the key aspects of this method, including sample preparation and method validation. Finally, we outline the challenges and prospects of such methods in practical applications.

Colorimetric analysis based on solid-phase extraction with sedimentable dispersed particulates: demonstration of concept and application for on-site environmental water analysis

A novel simple and functional colorimetric methodology for on-site environmental water analysis was proposed. This method combines coloration of the analyte and extraction of the colored species on dispersed particulates during their sedimentation in the same container. The whole analysis can be performed within 15 min by comprising the addition of 1 mL of sample solution into a 1.5-mL microtube containing the powders of coloring reagents and the sedimentable fine particulates as an adsorbent. The analyte is determined by comparing the sediment color with the standard color by visual inspection or the color information of the photo image. The potential of this methodology was demonstrated through developing colorimetry for Fe²⁺ with o-phenanthroline, NO₂^- by azo-dye formation, HCHO by the MBTH method, and PO₄^3- by the 4-aminoantipyrine method based on the enzyme reactions. The material, size, amount of the adsorbent particles, and other conditions were optimized for each analytes. The advantages of the methodology were as follows: high sensitivity, easy controllability of the sensitivity over the wide range by the amount, size, and material of the particulates, lower interference from the colored matrix components due to obtaining the color data from not the aqueous phase but the sedimented particulates, and acceleration of the color development rate by the particulates as seen in NO₂^- determination as consequence shorten the operation time. A simple device equipped with twin cells was proposed for on-site analysis which contains two successive different coloring operations. The developed methods were successfully applied to the environmental water samples with the good agreement of the results with those by the usual instrumental methods.

Living in a transient world: ICP-MS reinvented via time-resolved analysis for monitoring single events

After 40 years of development, inductively coupled plasma-mass spectrometry (ICP-MS) can hardly be considered as a novel technique anymore. ICP-MS has become the reference when it comes to multi-element bulk analysis at (ultra)trace levels, as well as to isotope ratio determination for metal(loid)s. However, over the last decade, this technique has managed to uncover an entirely new application field, providing information in a variety of contexts related to the individual analysis of single entities (e.g., nanoparticles, cells, or micro/nanoplastics), thus addressing new societal challenges. And this profound expansion of its application range becomes even more remarkable when considering that it has been made possible in an a priori simple way: by providing faster data acquisition and developing the corresponding theoretical substrate to relate the time-resolved signals thus obtained with the elemental composition of the target entities. This review presents the underlying concepts behind single event-ICP-MS, which are needed to fully understand its potential, highlighting key areas of application (e.g., single particle-ICP-MS or single cell-ICP-MS) as well as of future development (e.g., micro/nanoplastics).

Mercury biomonitoring in German adults using volumetric absorptive microsampling

Mercury (Hg) is a global pollutant and a danger to human health. Human biomonitoring of Hg using a dried blood matrix instead of venous blood sampling for exposure assessment is of growing interest. This study aims to develop, validate, and evaluate the application of volumetric absorptive microsampling (VAMS) for Hg biomonitoring in humans. Sampling, drying, and storage conditions were evaluated during method development. Storage in pre-cleaned glass vials after drying for 2 h in a desiccator ensured analyte stability for at least 4 weeks. Sixty-eight paired capillary VAMS and venous blood samples from volunteers in Munich, Germany, were used for method validation. Hg levels in VAMS and venous blood samples were determined by direct mercury analysis. The limits of detection and quantitation for VAMS were 0.18 and 0.61 µg/l, respectively. However, sensitivity could be improved by using two microsamples for analysis instead of one. Hg levels in VAMS samples correlated very well with Hg levels in venous blood samples (R² = 0.958). Furthermore, VAMS showed a high accuracy (median recovery: 117%) and precision (median relative standard deviation: 8.7%), especially for Hg concentrations above 1.0 µg/l. In fact, accuracy and precision of VAMS improved with increasing Hg concentrations. In conclusion, VAMS in combination with direct mercury analysis is an accurate and viable alternative for human biomonitoring of Hg.

GENETIC INDIVIDUAL IDENTIFICATION FROM DRIED URINE SPOTS (DUS): A COMPLEMENTARY TOOL TO DRUG MONITORING AND ANTI DOPING TESTING

The collection of liquid biological matrices onto paper cards (dried matrix spots [DMS]) is becoming an alternative sampling strategy. The stability over time of molecules of interest for therapeutic, sport drug monitoring, and forensic toxicology on DMS has been recently investigated representing a reliable alternative to conventional analytical techniques. When a tampering of a urine sample in drug monitoring or doping control cases is suspected, it could be relevant to know whether genetic profiles useful for individual identification could be generated from urine samples spotted onto paper (dried urine spot [DUS]). To understand the influence of sex, storage conditions, and time on the quality and quantity of the DNA, five female and ten male urine samples were dispensed onto Whatman 903 paper and sampled after different storage conditions over time, from 1 to 12 weeks. Direct PCR was performed starting from 2‐mm punches collected from each spot amplifying a panel of markers useful for individual identification. The female DUS stored in different conditions produced genetic profiles fully matching the reference samples. The same result was obtained for the male DUS but using urine 30X concentrated by centrifugation instead of the original samples. Our data show that this approach is valid for genetic individual identification of urine samples spotted onto paper cards up to 12 weeks after deposition and could be easily incorporated in anti‐doping or drug screening protocols to help on the suspicion of evidence tampering or to solve questions on the reliability of samples collection.

Precise sample metering method by coordinated burst action of hydrophobic burst valves applied to dried blood spot collection

Dried blood spot (DBS) sampling by finger-pricking has recently gained a lot of interest as an alternative sample collection method. The reduced invasiveness, requirement of lower sample volumes and suitability for long-term storage at room temperature make DBS ideal for use in home settings or low-resource environments. However, traditional protocols often suffer from biased analysis data due to variable and not exactly known blood volumes present in the samples. In this work, a novel device has been developed to split-off precisely metered volumes from a blood drop and load them on pre-cut filter paper. Hereto, hydrophobic burst valves (HBV) were developed to temporarily retain a fluid flow, configurable to burst at pressures within a range of 175-600 Pa. By combining HBVs with different burst pressures, a volume metering system was developed to allow parallel metering of multiple pre-defined sample volumes. The system was shown to be accurate and consistent for blood volumes between 5-15 μL and for hematocrit levels spanning the range of 25-70%. Finally, a point-of-care DBS sampling device was developed combining the self-powered microfluidic SIMPLE technology. To evaluate the system's practical applicability, a validation study in the context of therapeutic drug monitoring of biologicals was performed using adalimumab-spiked blood samples. Microfluidic DBS samples showed good performance compared to the traditional DBS method with improved recovery rates (86% over 62%). This innovative metering system, allowing for parallelization and integration with complex liquid manipulations, will greatly impact the field of robust sampling, sample preparation, storage and analysis at the point-of-care.

Microsampling with a Solid-Phase Extraction Cartridge: Storage and Online Mass Spectrometry Analysis

This study aims to introduce the concept of utilizing a solid-phase extraction (SPE) cartridge for remote biofluid collection, followed by direct sample analysis at a later time. For this, a dried matrix spot was prepared in a syringe, in the form of SPE cartridge for the first time to enable small biofluid collection (microsampling), storage, shipment, and online electrospray ionization (ESI) mass spectrometry (MS) analysis of the stored dried samples. The SPE sorbents were packed into an ESI syringe and the resultant cartridge was used for sampling small volumes (<20 μL) of different complex biological fluids including blood, plasma, serum, and urine. The collected sample was stored in the dry state within the confinement of the SPE sorbent at room temperature, and analyte stability (e.g., diazepam) was maintained for more than a year. Direct coupling of the SPE cartridge to MS provides excellent accuracy, precision, and sensitivity for analyzing illicit drugs present in the biofluid. The corresponding mechanism of wrong-way positive ion generation from highly basic elution solvents was explored. Without chromatography, our direct SPE-ESI-MS analysis technique afforded detection limits as low as 26 and 140 pg/mL for raw urine and untreated plasma, respectively. These promising results proved that the new syringe-based SPE cartridge can serve as a good alternative to conventional microsampling techniques in terms of analyte stability, ease of operation and versatility, and analytical sensitivity and speed.

Methylmercury Measurements in Dried Blood Spots from Electronic Waste Workers Sampled from Agbogbloshie, Ghana

Biomonitoring methylmercury (MeHg) exposure is problematic in resource-limited settings and with difficult-to-access populations where traditional biomarker approaches present logistical, economic, and ethical issues. The present study aimed to validate the use of dried blood spots (DBS) to assess MeHg exposure in a real-world contaminated field setting. Whole-blood and DBS samples were collected from electronic waste workers (n = 20) from Agbogbloshie (Ghana) in 2017, and DBS were also artificially created in the laboratory using the field-collected blood. Whole-blood MeHg concentrations averaged 0.84 µg/L, which was not different from levels measured in the corresponding DBS samples (field-collected or artificially created). Whole-blood MeHg comprised 61% of the blood total Hg concentrations. Linear regression analysis revealed no differences in MeHg concentrations between whole-blood samples and field-collected DBS (slope 0.89, R²  = 0.94) and between field and laboratory DBS (slope 0.89, R²  = 0.96). The MeHg content in DBS punch blanks averaged 0.86 pg and thus was not of concern. These findings indicate that DBS are a suitable tool for assessing MeHg exposure in real-world environmental settings that may be heavily contaminated.  Environ Toxicol Chem 2021;40:2183-2188. © 2021 SETAC.

Study of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) extraction FROM dried oral fluid spots (DOFS) and LC-MS/MS detection

Background

Oral fluid is a widely studied matrix able to isolate the primary Cannabis constituent THC, facilitating its detection via mass spectrometry, and in most cases link these findings to recent drug use. As an alternative to liquid oral fluid, dried oral fluid spots (DOFS) is a simple and a low-cost sampling technique. It has shown improved stability compared to liquid samples, allowing for the possibility to preserve the specimens under various temperature and humidity conditions. The sampling strategy is straightforward and involves the application of a small quantity of oral fluid aliquot to a paper substrate that is set to air dry allowing for on-site collection at a large-scale demand. The goal of this study is to study THC and CBD extraction from DOFS, applying a previous established protocol for a LC–MS/MS qualitative method validation. Although other drugs of abuse have been included in DOFS methods, this is the first method validation including cannabinoids. An alternative oral fluid extraction method (WAX-S tips) is demonstrated to improve the recovery of the analytes.

Methods

A pool of blank oral fluid was used to prepare THC and CBD spiked DOFS samples for method validation and application. Spiked oral fluid was used to demonstrate WAX-S tips THC and CBD extraction. All samples were analyzed on a LC–MS/MS instrument.

Results

The qualitative method validation for THC and CBD confirmation in DOFS included method selectivity, matrix effects (< 20%), recovery (average of 25%), process efficiency (average of 21%), LOD (2 ng/mL for THC and 4 ng/mL for CBD), absence of carryover, and DOFS stability (70% in 35 days) as figures of merit. The method application in blindly prepared samples demonstrated the method capability to identify THC and CBD. WAX-S tips extraction showed an average of 91% recovery of THC and CBD from liquid oral fluid.

Conclusions

THC and CBD extraction from DOFS showed low recoveries. However, the LC–MS/MS qualitative confirmation of THC and CBD in DOFS could improve cannabinoids screening in oral fluid, as it shows adequate LOD and stability over time. This method has potential for assisting the screening of drivers under possible drug influence by facilitating sample transportation and temporary storage in dried spot form. Additional research is suggested for WAX-S tips extraction and quantitative method validation.

Current applications and future perspectives on elemental analysis of non-invasive samples for human biomonitoring

Humans are continuously exposed to numerous environmental pollutants including potentially toxic elements. Essential elements play an important role in human health. Abnormal elemental levels in the body, in different forms that existed, have been reported to be correlated with different diseases and environmental exposure. Blood is the conventional biological sample used in human biomonitoring. However, blood samples can only reflect short-term exposure and require invasive sampling, which poses infection risk to individuals. In recent years, the number of research evaluating the effectiveness of non-invasive samples (hair, nails, urine, meconium, breast milk, placenta, cord blood, saliva and teeth) for human biomonitoring is increasing. These samples can be collected easily and provide extra information in addition to blood analysis. Yet, the correlation between the elemental concentration in non-invasive samples and in blood is not well established, which hinders the application of those samples in routine human biomonitoring. This review aims at providing a fundamental overview of analytical methods of non-invasive samples in human biomonitoring. The content covers the sample collection and pretreatment, sample preparation and instrumental analysis. The technical discussions are separated into solution analysis and solid analysis. In the last section, the authors highlight some of the perspectives on the future of elemental analysis in human biomonitoring.

Enzyme activity in dried blood spot as a diagnostic tool for adenosine deaminase 2 deficiency

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by mutations in the adenosine deaminase 2 (ADA2) gene. Loss of functional ADA2 activity results in vasculitis syndrome, immunodeficiency, and hematopoietic disorders. Early diagnosis is required for effective treatment.

METHODS

We developed a dried blood spot (DBS)-based ADA2 activity colorimetric assay. Heparin-affinity purification was used during sample preparation to improve the assay more efficiently. The stability of ADA2 during DBS storage and ADA2 activity of DADA2 patients and healthy controls were examined.

RESULTS

Active ADA2 was extracted from the DBS of healthy controls. ADA2 activity in DBS, stored either frozen or refrigerated, remained stable for at least 90 days. A significant difference in ADA2 activity was observed between healthy controls and patients. No ADA2 activity was detected in DBS from patients.

CONCLUSIONS

Our new DBS ADA2 activity assay is experimentally simple, highly adaptable, and requires no special equipment except for a microplate reader. A low background was achieved with heparin-affinity purification. The method differentiates clearly between healthy controls and patients. ADA2 activity can be reliably measured in DBS, providing an opportunity to diagnose DADA2 at an early stage.

Next-Generation Dried Blood Spot Samplers for Protein Analysis: Describing Trypsin-Modified Smart Sampling Paper

This paper describes smart sampling paper to be used for bottom-up protein analysis. Four different manners to immobilize trypsin on cellulose were evaluated. Untreated paper, potassium-periodate-functionalized paper (with and without post-immobilization reduction) and 2-hydroxyethyl methacrylate (HEMA)/2-vinyl-4,4-dimethylazlactone (VDM)-functionalized paper were all used to immobilize trypsin. For the evaluation, Coomassie Brilliant Blue staining of proteins on paper and the BAEE trypsin activity assay needed to be modified. These methods allowed, together with data from mass spectrometric analysis of cytochrome C digestions, us to acquire fundamental insight into protein binding, and trypsin action and activity on paper. All functionalized discs bind more protein than the untreated discs. Protein binding to functionalized discs is based on both adsorption and covalent binding. Trypsin immobilized on potassium-periodate-functionalized discs exhibits the highest trypsin activity when using cytochrome C as substrate. It is proven that it is trypsin attached to paper (and not desorbed trypsin) which is responsible for the enzyme activity. The use of discs on complex biological samples shows that all functionalized discs are able to digest diluted serum; for the best-performing disc, HEMA-VDM functionalized, up to 200 high-confidence proteins are qualified, showing its potential.

Trace elements in dried blood spots as potential discriminating features for metabolic disorder diagnosis in newborns

Trace elements in dried blood spots (DBSs) from newborns were determined by laser ablation coupled with inductively coupled plasma mass spectrometry, and data were subjected to chemometric evaluation in an attempt to classify healthy newborns and newborns suffering from metabolic disorders. Unsupervised [principal component analysis (PCA) and cluster analysis (CA)] and supervised [linear discriminant analysis (LDA) and soft independent modeling by class analogy (SIMCA)] pattern recognition techniques were used as classification techniques. PCA and CA have shown a clear tendency to form two groups (healthy newborns and newborns suffering from metabolic disorders). LDA and SIMCA have predicted that 90.5% and 83.9% of originally grouped healthy newborn cases were correctly classified by LDA and SIMCA, respectively. In addition, these percentages were 97.6% (LDA) and 80.6% (SIMCA) for DBSs from newborns suffering from metabolic disorders. However, SIMCA has only detected one misclassified DBS from the healthy group, and the lower percentage is attributed to four DBSs from the healthy newborn group and five DBSs from newborns with disorders that were found as belonging to both categories (healthy newborns and newborns with disorders) in the training set. LDA also gave a percentage of grouped maple syrup urine disease (MSUD) cases correctly classified of 100%, although the percentage fells to 66.7% when classifying phenylketonuria (PKU) cases. Finally, essential elements such as Fe, K, Rb, and Zn were found to be matched (correlated) with the concentration of amino acids such as phenylalanine, valine, and leucine, biomarkers linked with MSUD and PKU diseases.

Feasibility of Lead Exposure Assessment in Blood Spots using Energy-Dispersive X-ray Fluorescence

Collecting blood spots from newborns is a common procedure used to diagnose multiple health conditions. Fingerstick blood samples are routinely collected from children to diagnose elevated blood lead levels. In our study, we wanted to test the feasibility of using a high-power energy-dispersive X-ray fluorescence (EDXRF) device to accurately measure the concentration of lead in blood spots. We created spotted standards of a known concentration of lead on a filter paper at different volumes and concentrations. We determined the detection limit for lead through repeated measurements of our standards and calibration line slopes. We also tested the variability of the measured lead concentration across procedures and spotted blood volumes and found no significant additions to uncertainty in measurements. Finally, we compared blood lead concentrations measured by EDXRF and atomic absorption spectroscopy (AAS) and found EDXRF to be a significant predictor of blood lead (n = 22, R = 0.98, p value <0.001) with an average detection limit of 1.7 μg/dL of blood lead. This detection limit is similar to that of the AAS technique, which is commonly used in clinical testing laboratories for blood lead surveillance. These findings provide a proof of concept that blood spots measured by EDXRF may be used as a surveillance tool for lead exposure, even at elevated blood lead levels of 2-3 μg/dL.

Dried urine spots as sampling technique for multi-mycotoxin analysis in human urine

A simple and effective approach for HPLC-MS/MS based multi-mycotoxin analysis in human urine samples was developed by application of dried urine spots (DUS) as alternative on-site sampling strategy. The newly developed method enables the detection and quantitation of 14 relevant mycotoxins and mycotoxin metabolites, including citrinin (CIT), dihydrocitrinone (DH-CIT), deoxynivalenol (DON), fumonisin B₁ (FB₁), T-2 Toxin (T-2), HT-2 Toxin (HT-2), ochratoxin A (OTA), 2′R-ochratoxin A (2′R-OTA), ochratoxin α (OTα), tenuazonic acid and allo-tenuazonic acid (TeA + allo-TeA), zearalenone (ZEN), zearalanone (ZAN), α-zearalenol (α-ZEL), and β-zearalenol (β-ZEL). Besides the spotting procedure, sample preparation includes enzymatic cleavage of glucuronic acid conjugates and stable isotope dilution analysis. Method validation revealed low limits of detection in the range of pg/mL urine and excellent apparent recovery rates for most analytes. Stability investigation of DUS displayed no or only slight decrease of the analyte concentration over a period of 28 days at room temperature. The new method was applied to the analysis of a set of urine samples (n = 91) from a Swedish cohort. The four analytes, DH-CIT, DON, OTA, and TeA + allo-TeA, could be detected and quantified in amounts ranging from 0.06 to 0.97 ng/mL, 3.03 to 136 ng/mL, 0.013 to 0.434 ng/mL and from 0.36 to 47 ng/mL in 38.5%, 70.3%, 68.1%, and 94.5% of the samples, respectively. Additional analysis of these urine samples with an established dilute and shoot (DaS) approach displayed a high consistency of the results obtained with both methods. However, due to higher sensitivity, a larger number of positive samples were observed using the DUS method consequently providing a suitable approach for human biomonitoring of mycotoxin exposure.

A review of recent advances in microsampling techniques of biological fluids for therapeutic drug monitoring

Conventional sampling of biological fluids often involves a bulk quantity of samples that are tedious to collect, deliver and process. Miniaturized sampling approaches have emerged as promising tools for sample collection due to numerous advantages such as minute sample size, patient friendliness and ease of shipment. This article reviews the applications and advances of microsampling techniques in therapeutic drug monitoring (TDM), covering the period January 2015 - August 2020. As whole blood is the gold standard sampling matrix for TDM, this article comprehensively highlights the most historical microsampling technique, the dried blood spot (DBS), and its development. Advanced developments of DBS, ranging from various automation DBS, paper spray mass spectrometry (PS-MS), 3D dried blood spheroids and volumetric absorptive paper disc (VAPD) and mini-disc (VAPDmini) are discussed. The volumetric absorptive microsampling (VAMS) approach, which overcomes the hematocrit effect associated with the DBS sample, has been employed in recent TDM. The sample collection and sample preparation details in DBS and VAMS are outlined and summarized. This review also delineates the involvement of other biological fluids (plasma, urine, breast milk and saliva) and their miniaturized dried matrix forms in TDM. Specific features and challenges of each microsampling technique are identified and comparison studies are reviewed.

Development of a new method for drug detection based on a combination of the dried blood spot method and capillary electrophoresis

The aim of this study was to develop a new approach to sample preparation of biological material based on a combination of the Dried Blood Spot (DBS) method and capillary electrophoresis coupled with mass spectrometry (CE-MS) for the analysis of blood samples collected in vivo or post-mortem. The proposed approach allowed the identification of typical drugs from different groups, such as tricyclic antidepressants (amitriptyline, imipramine), selective serotonin reuptake inhibitors (citalopram), benzodiazepines (tetrazepam) and hypnotics (zolpidem). In this study, a blood sample was spotted on FTA DMPK C cards, then dried, and 6-mm discs were cut out. The sample preparation procedure involved microwave-assisted extraction (MAE). Various extraction agents, temperatures and durations of extraction were examined in order to achieve the highest efficiency of the process. The method was subjected to a validation procedure. Limits of detection (LOD = 1.76 - 14.7 ng/mL) and quantification (LOQ = 5.25 - 49.0 ng/mL), inter- (CV = 1.31 - 9.43%) and intra- (CV = 3.26 - 18.52%) day precision of the determinations, recovery (RE = 85.0-105.4%) and matrix effect on ionization of analytes (ME = 98.6-105.5%) were determined. Furthermore, the developed DBS/MAE/CM-MS method was selective and analytes present in the blood applied on DBS cards were found to be stable after 7 and after 14 days. Moreover, the developed method was successfully applied to the analysis of both post-mortem samples and blood samples taken from patients treated with the analyzed drugs.

Kidney transplant recipient's perceptions of blood testing through microsampling and venepuncture

A survey of kidney transplant recipients receiving two innovative microsampling methods, dried blood spot and volumetric absorptive microsampling using patient reported methodology. A total of 39 adult transplant patients underwent venepuncture and finger prick-based blood draws on two occasions. They completed a survey of blood test understanding, tolerability, preferences and the burden associated with venepuncture compared with microsampling. A total of 85% of participants (n = 33) preferred finger prick-based sampling and 95% (n = 37) were interested in blood collection using self sampling by finger prick at home; 33% (n = 13) of participants experienced blood test anxiety. To quantify time burden of providing venous samples a total of 44% (n = 17) spent greater than 1 hour to travel and provide venous samples. This study observed a patient preference for microsampling for blood sampling as an alternative to venepuncture in the management of their kidney transplant.

Determination of Antidepressants and Antipsychotics in Dried Blood Spots (DBSs) Collected from Post-Mortem Samples and Evaluation of the Stability over a Three-Month Period

An LC-MS/MS method for the identification and quantification of antidepressants and antipsychotics was developed on dried blood spots (DBSs). Moreover, analyte stability on DBSs within a 3-month period was monitored. Aliquots of 85 µL of blood from autopsy cases were pipetted onto DBS cards, which were dried and stored at room temperature. DBSs were analyzed in triplicate immediately, within the following 3 weeks, and after 3 months. For each analysis, a whole blood stain was extracted in phosphate buffer and purified using Solid Phase Extraction (SPE) cartridges in order to avoid matrix effects and injected in the LC-MS/MS system. Thirty-nine molecules were screened. Limits of detection (LODs) ranged between 0.1 and 3.2 ng/mL (g) and 0.1 and 5.2 ng/mL (g) for antidepressants and antipsychotics, respectively. Limits of quantification (LOQs) varied from 5 to 10.0 ng/mL for both. Sixteen cases among the 60 analyzed resulted positive for 17 different analytes; for 14 of these the method was fully validated. A general good agreement between the concentrations on DBSs and those measured in conventional blood samples (collected concurrently and stored at -20 °C) was observed. The degradation/enhancement percentage for most of the substances was lower than 20% within the 3-month period. Our results, obtained from real post-mortem cases, suggest that DBSs can be used for routine sample storage.

The use of dried matrix spot for determination of Pb and Ni in automotive gasoline by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

In this work a simple and practical method for the determination of Pb and Ni in automotive gasoline by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry was investigated. In the proposed method, disks of filter paper were used to pre-concentrate and store Pb, Ni and other trace elements from automotive gasoline samples. For this, a volume of sample was deposited and dried out on a filter paper disk previously adapted into a polytetrafluoroethylene mold, and then the gasoline-embedded filter paper was either cut into small pieces or pulverised and introduced directly into the graphite furnace for trace element determination. Temperature program, use of chemical modifier, chromatographic effect and volume of sample were investigated. Calibration curves using organic and inorganic standards of the analytes as well as external and internal calibration methods were evaluated. Using optimised conditions, characteristic masses and limits of detection of 6 and 11 pg, and 0.5 and 2.1 μg L^-1 were found for Pb and Ni, respectively. The accuracy of the method was evaluated with spike-recovery tests and a certified reference material of wear lubricant oil. The spike-recovery tests were accomplished for 9 samples and the best results were obtained with the pulverised filter paper. A second method that employs a transversely heated filter atomiser was applied as a comparative one. The filter paper was shown to be a simple and inexpensive tool for storage and transportation of gasoline samples, and it allowed the pre-concentration of the analytes, since a larger volume of sample can be dried out on it.

Quantitative dried blood spot analysis for metallodrugs by laser ablation-inductively coupled plasma-mass spectrometry

A quantitative dried blood spot (DBS) method based on direct sampling by means of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is presented. Gadolinium-based contrast agents were used as model metallodrugs with a significant relevance for pharmaceutical applications. Challenges regarding the ablation of the complex blood-filter matrix were characterized and successfully addressed by a thorough adaption of the laser ablation conditions. Especially the laser fluence was optimized with respect to the particle size distribution of the generated aerosol as monitored by an optical particle counter. Thus, generation of micrometer-sized particles could be minimized in favor of smaller particles increasing the transport efficiency of the DBS ablation aerosol to the plasma and the recorded signal stability. Inhomogeneous blood drying on the porous filter paper could be compensated by the addition of an internal standard prior to blood spotting. To preserve the advantages of DBS sampling, such as small blood volumes and minimal invasiveness, the combined use of DBS and a capillary blood sampling system is demonstrated. By placing the internal standard into the capillary prior to blood sampling, a simple workflow usable for clinical application was implemented. The applicability of the developed method, achieving limits of detection and quantification in the low μg L^-1 range and covering a linear range of over four orders of magnitude, was demonstrated for blood samples containing different concentrations of the gadolinium contrast agents gadopentetate and gadoterate.