Dried blood spot sampling in combination with LC-MS/MS for quantitative analysis of small molecules

Screening of Synthetic Cathinones and Metabolites in Dried Blood Spots by UPLC-MS-MS

After its use for decades in clinical screening, dried blood spots (DBS) have recently received considerable attention for their application in various novel psychoactive substances. The goal of this study was to develop and apply a DBS-based assay for 37 synthetic cathinones and their metabolites. Thirty microliters of whole blood sample after administration was spotted onto Whatman FTA classical cards, dried and extracted, and then analyzed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS). The samples were chromatographed on a Waters Acquity UPLC®HSS T3 column (1.8 μm, 2.1 × 100 mm) and then identically packed defender guard cartridges of a Waters Acquity UPLC®HSS T3 column (1.8 μm, 2.1 × 5 mm, 3/pk). The separation was achieved via solvents of 20 mM ammonium acetate/formic acid 0.1% (A) and acetonitrile (B) at a flow rate of 0.25 mL/min. A tandem MS equipped with positive electrospray ionization mode source was used as the detector. Multiple reaction monitoring with the precursor/product ion combinations was used to quantify each analyte. The linear range of synthetic cathinones in the DBS was 2.0-200 ng/mL, and the lowest limit of quantification was 2.0 ng/mL for some synthetic cathinones and 10 ng/mL for others. The precision and accuracy of the results for the validation samples of the synthetic cathinones were within acceptable criteria. DBS sampling offers the advantages of reduced sample volume and convenient sample storage and shipment. This method can be successfully applied to the quantification of synthetic cathinones.

Steroid profiling by UHPLC-MS/MS in dried blood spots collected from healthy women with and without testosterone gel administration

The quantification of a large panel of endogenous steroids in serum by LC-MS/MS represents a powerful clinical tool for the screening or diagnosis of diverse endocrine disorders. This approach has also demonstrated excellent sensitivity for the detection of testosterone misuse in the anti-doping field, especially in female athlete population. In both situations, the use of dried blood spots (DBS) could provide a viable alternative to invasive venous blood collection. Here, the evaluation of DBS sampling for the quantification of a panel of endogenous steroids using UHPLC-MS/MS is described. The UHPLC-MS/MS method was validated for quantitative analysis of eleven free and eight conjugated steroids and was then used for the analysis of DBS samples collected in 14 healthy women during a normal menstrual cycle (control phase) followed by a 28-days testosterone gel treatment (treatment phase). Results were compared with those obtained from serum matrix. Satisfactory performance was obtained for all compounds in terms of selectivity, linearity, accuracy, precision, combined uncertainty, stability as well as extraction recovery and matrix effects. In control phase, high correlation was observed between DBS and serum concentrations for most compounds. In treatment phase, higher testosterone concentrations were observed in capillary than in venous DBS, suggesting a possible interference resulting from testosterone contamination on finger(s) used for gel application. Steroid profiling in capillary DBS represents a simple and efficient strategy for monitoring endogenous steroid concentrations and their fluctuation in clinical context of steroid-related disorders, or for the detection of testosterone abuse in anti-doping.

Microsampling Devices for Routine Therapeutic Drug Monitoring-Are We There Yet?

BACKGROUND

The use of microsampling for therapeutic drug monitoring (TDM) is increasingly feasible as sensitive methods have become more accessible. There exists an increasing interest in the use of microsampling, and new microsampling devices and techniques can potentially improve patient convenience and care, among other features. This review provides an update on currently validated methods for measuring drugs pertinent to TDM, including data from clinical samples.

METHODS

A literature record search was undertaken, including PubMed and Google Scholar. Reports that included the use of microsampling to measure concentrations of drugs associated with TDM were reviewed and included if data from patient samples were reported. The studies are described in brief, including sample preparation and analyte stability, with the most pertinent findings reported.

RESULTS

Sensitive analyses and innovative designs and materials have resulted in an increasing number of reported evaluations and validations for measuring drugs using microsamples. Novel designs largely overcome common problems associated with traditional dried blood spot sampling. Although examples of patient self-sampling are rare at present, studies that evaluated feedback found it to be largely positive, revealing the feasibility of microsampling for TDM.

CONCLUSIONS

Microsampling is suited to the TDM of numerous drugs in diverse situations, and it will play an increasingly important role. The issues with traditional dried blood spot samples have been largely overcome by employing novel methods to obtain volumetric samples.

Simultaneous Quantification of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Plasma Spots and Its Application to Clinical Sample Analysis

BACKGROUND

Recent reports highlight the importance of therapeutic drug monitoring (TDM) of BCR-ABL and Bruton tyrosine kinase inhibitors (TKIs); thus, large-scale studies are needed to determine the target concentrations of these drugs. TDM using dried plasma spots (DPS) instead of conventional plasma samples is a promising approach. This study aimed to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of BCR-ABL and Bruton TKIs for further TDM studies.

METHODS

A 20-μL aliquot of plasma was spotted onto a filter paper and dried completely. Analytes were extracted from 2 DPS using 250 μL of solvent. After cleanup by supported liquid extraction, the sample was analyzed by LC-MS/MS. Applicability of the method was examined using samples of patients' DPS transported by regular mail as a proof-of-concept study. The constant bias and proportional error between plasma and DPS concentrations were assessed by Passing-Bablok regression analysis, and systematic errors were evaluated by Bland-Altman analysis.

RESULTS

The method was successfully validated over the following calibration ranges: 1-200 ng/mL for dasatinib and ponatinib, 2-400 ng/mL for ibrutinib, 5-1000 ng/mL for bosutinib, and 20-4000 ng/mL for imatinib and nilotinib. TKI concentrations were successfully determined for 93 of 96 DPS from clinical samples. No constant bias between plasma and DPS concentrations was observed for bosutinib, dasatinib, nilotinib, and ponatinib, whereas there were proportional errors between the plasma and DPS concentrations of nilotinib and ponatinib. Bland-Altman plots revealed that significant systematic errors existed between both methods for bosutinib, nilotinib, and ponatinib.

CONCLUSIONS

An LC-MS/MS method for the simultaneous quantification of 6 TKIs in DPS was developed and validated. Further large-scale studies should be conducted to assess the consistency of concentration measurements obtained from plasma and DPS.

Measurement of Dabigatran Concentration Using Finger Prick Dried Blood Spot Sample Collection

Background and Purpose: Real-world laboratory monitoring of dabigatran activity is challenging. The purpose of the present study was to demonstrate the feasibility and accuracy of finger prick sampling with dried blood spot (fpDBS) cards in measuring the dabigatran concentration.

Material and Methods: Patients >20 years of age with atrial fibrillation and receiving dabigatran therapy for more than 7 days were included in the study. Peak and trough dabigatran concentrations were collected by simultaneous finger prick and venous puncture. The dabigatran concentration was measured by ultra-high performance liquid chromatography with tandem mass spectrometry. Our previously developed post-column infused internal standard (PCI-IS) method was applied to estimate the blood spot volume on fpDBS and to calibrate the drug concentration. Deming regression was used to analyze the correlation between dabigatran concentration on fpDBS cards and in plasma samples, followed by Bland–Altman analysis to compare the bias between two sampling techniques.

Results: A total of 33 patients were enrolled and contributed 66 plasma and 55 fpDBS dabigatran samples. The average patient age was 74.6 ± 7.9 years, mean creatinine clearance 58.1 ± 18.3 mL/min, and CHA₂DS₂-VASc score 3.5 ± 1.6 points. The dabigatran concentration ranged from 41.8–1421.7 ng/mL. The plasma and DBS dabigatran concentrations correlated well (r = 0.98), and the conversion factor for fpDBS to plasma dabigatran concentration was 1.28. The Bland–Altman analysis showed that 94.5% of the fpDBS-predicted concentration fell within 20% of bias.

Conclusions: The study showed that fpDBS measurement of dabigatran concentration is reliable and can be applied in clinical scenarios.

Iron oxide xerogels for improved water quality monitoring of arsenic(III) in resource-limited environments via solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT)

Arsenic is a widespread trace groundwater contaminant that presents a range of health risks and has an acceptable level of only 10 μg L-1 in drinking water. However, in many countries arsenic quantification in water is limited to centralized laboratories because it requires the use of elemental analysis techniques with high capital cost. As a result, routine water samples are frequently not tested for trace contaminants such as arsenic. In order to facilitate improved arsenic monitoring, we present the use of iron oxide xerogels for adsorption of arsenic(iii) from water samples at neutral pH, dry storage for over 120 days, and desorption of stored arsenic at elevated pH. Iron oxide xerogels offer high surface area (340 m2 g-1) and an As(iii) adsorption capacity of 165 mg g-1. Using an extraction solution of 100 mM sodium hydroxide and 1 mM sodium phosphate, As(iii) is reliably eluted from iron oxide xerogels for initial As(iii) concentrations from 10 μg L-1 to 1000 μg L-1, with a calculated detection limit of less than 4 μg L-1 and less than 17% difference in recovered As(iii) between test solutions with low and high interfering ion concentrations. By demonstrating the ability for iron oxide xerogels to reliably adsorb, store, and release arsenic, we enable the development of protocols for solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT), where arsenic would be adsorbed from water samples onto xerogel-based sorbents and shipped to centralized laboratories for recovery and quantification.

Sildenafil 4.0-Integrated Synthetic Chemistry, Formulation and Analytical Strategies Effecting Immense Therapeutic and Societal Impact in the Fourth Industrial Era

Sildenafil is a potent selective, reversible inhibitor of phosphodiesterase type 5 (PDE5) approved for the treatment of erectile dysfunction and pulmonary arterial hypertension. Whilst twenty years have passed since its original approval by the US Food and Drug Administration (USFDA), sildenafil enters the fourth industrial era catalyzing the treatment advances against erectile dysfunction and pulmonary hypertension. The plethora of detailed clinical data accumulated and the two sildenafil analogues marketed, namely tadalafil and vardenafil, signify the relevant therapeutic and commercial achievements. The pharmacokinetic and pharmacodynamic behavior of the drug appears complex, interdependent and of critical importance whereas the treatment of special population cohorts is considered. The diversity of the available formulation strategies and their compatible administration routes, extend from tablets to bolus suspensions and from per os to intravenous, respectively, inheriting the associated strengths and weaknesses. In this comprehensive review, we attempt to elucidate the multi-disciplinary elements spanning the knowledge fields of chemical synthesis, physicochemical properties, pharmacology, clinical applications, biopharmaceutical profile, formulation approaches for different routes of administration and analytical strategies, currently employed to guide the development of sildenafil-based compositions.

Development and validation of an LC-MS/MS method for relevant drugs in epilepsy patients using dried blood spots

Epilepsy is one of the most common diseases of the central nervous system globally. To ensure the correct dosage of antiepileptic treatment, it is helpful to check the blood levels of the administered substances regularly. The analysis of the capillary dried blood samples provides a promising and less-invasive alternative to venous blood collection. Therefore, the aim of the present study was to develop an LC-MS method for the quantification of 22 commonly used drugs in patients with an epileptic syndrome and 5 drug metabolites in one dried blood spot (DBS). The calibration ranges were selected in such a way that the therapeutic reference ranges in serum for the respective substances were completely covered. The analytical validation was successfully performed according to relevant guidelines with a consideration of requirements for DBS analysis. Proof of concept of the developed method was obtained by the analysis of DBSs from 282 authentic leftover ethylenediaminetetraacetic acid blood samples, which were compared with the corresponding serum concentrations. Altogether, the results show a dependency on the blood/plasma (b/p) ratios of the respective analytes so that for drugs with b/p ratios close to one, for example, lacosamide, levetiracetam, brivaracetam, and sertraline, a good accordance was observed.

The Development of a Liquid Chromatography High-Resolution Mass Spectrometric Method for Apixaban Quantification in Dried Plasma Spots in Parallel Reaction Monitoring Mode

This work aimed at developing and validating a rapid, sensitive, and robust method of liquid chromatography with high-resolution mass spectrometry (LC–HRMS) in parallel reaction monitoring (PRM) mode for apixaban quantification in dried plasma spots (DPSs) with a simple extraction procedure. A 25 µL sample of human plasma was placed onto Whatman 903 Protein Saver Cards and allowed to dry; 3.2 mm diameter disks were cut out from DPSs using a puncher, and 100 µL of a working internal standard solution was added to each sample. After this, they were vortexed on a shaker for 15 min at 800 rpm and 40 °C and quick centrifugation (10,000× g, 10 s), and then the extracts were transferred into a 300 µL vial for LC–HRMS. Data were acquired in PRM mode via detection of all target product ions with 10 ppm tolerance. Total analysis time was 5 min. The LC–HRMS method was validated for the 10–400 ng/mL range with R2 > 0.99. Within this range, intra- and interday variability of precision and accuracy was <10%, and recovery was 69.7–85.1%. Apixaban was stable after brief storage at room temperature, and at 4 °C for up to a month. The method development and validation results proved that this LC–HRMS assay of apixaban in DPSs is selective and robust.

Validation of a simple liquid chromatography coupled to tandem mass spectrometry method for the simultaneous determination of tacrolimus, sirolimus, everolimus and cyclosporin A in dried matrix on paper discs

INTRODUCTION

Due to its high specificity and sensitivity, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is the gold standard method for immunosuppressant quantification in therapeutic drug monitoring. In this context, dried blood spots (DBS) have become a promising strategy as a sample collection procedure. Although the advantages of DBS over venipuncture are well known, this approach has limitations that strongly influence the acceptance of analytical results. Among them, the most important is hematocrit (Ht). The easiest way of overcoming this problem is by analyzing complete spots. In this strategy, called dried matrix on paper discs (DMPD), blood is volumetrically applied on pre-punched discs.

OBJECTIVES

To validate an LC-MS/MS method for the quantification of tacrolimus, sirolimus, everolimus and cyclosporin A using DMPD.

METHODS

The procedure was validated according to international guidelines using a commercial kit. The following performance parameters were evaluated: selectivity, carryover, linearity, accuracy, precision, lower limit of quantitation, relative recovery, commutability and stability. In addition, a method comparison study was performed to evaluate the clinical influence of Ht on the results.

RESULTS

All performance parameters were within acceptance criteria and, hence, it was determined that the validated method is fit for the intended purpose. Likewise, calculated bias values on medical decision levels showed that there was no clinical influence of Ht on the results.

CONCLUSION

Unlike other similar methodologies that have been published, here, a simple method has been fully validated. This is the first LC-MS/MS methodology adapting a commercial kit to use DMPD as a sampling strategy.

Stability of Plasma Protein Composition in Dried Blood Spot during Storage

Dried blood spot (DBS) technology has become a promising utility for the transportation and storage of biological fluids aimed for the subsequent clinical analysis. The basis of the DBS method is the adsorption of the components of a biological sample onto the surface of a membrane carrier, followed by drying. After drying, the molecular components of the biosample (nucleic acids, proteins, and metabolites) can be analyzed using modern omics, immunological, or genomic methods. In this work, we investigated the safety of proteins on a membrane carrier by tryptic components over time and at different temperatures (+4, 0, 25 °C) and storage (0, 7, 14, and 35 days). It was shown that the choice of a protocol for preliminary sample preparation for subsequent analytical molecular measurements affects the quality of the experimental results. The protocol for preliminary preparation of a biosample directly in a membrane carrier is preferable compared to the protocol with an additional stage of elution of molecular components before the sample preparation procedures. It was revealed that the composition of biosamples remains stable at a temperature of −20 and +4 °C for 35 days of storage, and at +25 °C for 14 days.

Technological advancement in dry blood matrix microsampling and its clinical relevance in quantitative drug analysis

In the past few decades, dried blood matrix biosampling has witnessed a marvelous interest among the researcher due to its user-friendly operation during blood sampling in preclinical and clinical applications. It also complies with the basic 3Rs (reduce, reuse and recycle) philosophy. Because of comparative simplicity, a huge number of researchers are paying attention to its technological advancements for widespread application in the bioanalysis and diagnosis arena. In this review, we have explained different approaches to be considered during dried blood matrix based microsampling including their clinical relevance in therapeutic drug monitoring. We have also discussed various strategies for avoiding and minimizing major unwanted analytical interferences associated with this technique during drug quantification. Further, various recent technological advancement in microsampling devices has been discussed correlating their clinical applications.

Towards wearable and implantable continuous drug monitoring: A review

Continuous drug monitoring is a promising alternative to current therapeutic drug monitoring strategies and has a strong potential to reshape our understanding of pharmacokinetic variability and to improve individualised therapy. This review highlights recent advances in biosensing technologies that support continuous drug monitoring in real time. We focus primarily on aptamer-based biosensors, wearable and implantable devices. Emphasis is given to the approaches employed in constructing biosensors. We pay attention to sensors' biocompatibility, calibration performance, long-term characteristics stability and measurement quality. Last, we discuss the current challenges and issues to be addressed in continuous drug monitoring to make it a promising, future tool for individualised therapy. The ongoing efforts are expected to result in fully integrated implantable drug biosensing technology. Thus, we may anticipate an era of advanced healthcare in which wearable and implantable biochips will automatically adjust drug dosing in response to patient health conditions, thus enabling the management of diseases and enhancing individualised therapy.

Giving patients choices: AstraZeneca's evolving approach to patient-centric sampling

This paper shares experiences and learning from introducing patient-centric sampling (PCS) into AstraZeneca trials. Through two case studies we show how modeling approaches can assist pharmacokinetic (PK) bridging studies accounting for blood partitioning and hematocrit and how reduced PK sampling schedules, profiles constructed from composite data (plasma & dry blood) and combined assays (PK & pharmacodynamic) can all reduce patient sampling burden without impacting study outcomes. Following sharing some clinical operational challenges, we finally highlight some key requirements for implementing a patient-centric sampling strategy such as collaborative working across organizational silos, continuous patient engagement throughout the study life cycle and accepting that if the aim is to give patient choice, then one solution (device, procedure and design) will not fit all.

Combining lipidomics and machine learning to measure clinical lipids in dried blood spots

INTRODUCTION

Blood-based sample collection is a challenge, and dried blood spots (DBS) represent an attractive alternative. However, for DBSs to be an alternative to venous blood it is important that these samples are able to deliver comparable associations with clinical outcomes. To explore this we looked to see if lipid profile data could be used to predict the concentration of triglyceride, HDL, LDL and total cholesterol in DBSs using markers identified in plasma.

OBJECTIVES

To determine if DBSs can be used as an alternative to venous blood in both research and clinical settings, and to determine if machine learning could predict 'clinical lipid' concentration from lipid profile data.

METHODS

Lipid profiles were generated from plasma (n = 777) and DBS (n = 835) samples. Random forest was applied to identify and validate panels of lipid markers in plasma, which were translated into the DBS cohort to provide robust measures of the four 'clinical lipids'.

RESULTS

In plasma samples panels of lipid markers were identified that could predict the concentration of the 'clinical lipids' with correlations between estimated and measured triglyceride, HDL, LDL and total cholesterol of 0.920, 0.743, 0.580 and 0.424 respectively. When translated into DBS samples, correlations of 0.836, 0.591, 0.561 and 0.569 were achieved for triglyceride, HDL, LDL and total cholesterol.

CONCLUSION

DBSs represent an alternative to venous blood, however further work is required to improve the combined lipidomics and machine learning approach to develop it for use in health monitoring.

Simple and Sensitive Analysis for Dried Blood Spot Proteins by Sodium Carbonate Precipitation for Clinical Proteomics

Dried blood spots (DBS) are widely used for screening biomolecular profiles, including enzymatic activities. However, detection of minor proteins in DBS by liquid chromatography-mass spectrometry (LC-MS/MS) without pre-enrichment remains challenging because of the coexistence of large quantities of hydrophilic proteins. In this study, we address this problem by developing a simple method using sodium carbonate precipitation (SCP). SCP enriches hydrophobic proteins from DBS, allowing substantial removal of soluble proteins. In combination with SCP, we used quantitative LC-MS/MS proteome analysis in a data-independent acquisition mode (DIA) to enhance the sensitivity and quantification limits of proteome analysis. As a result, identification of 1977 proteins in DBS is possible, including 585 disease-related proteins listed in the Online Mendelian Inheritance in Man.

Emerging trends in paper spray mass spectrometry: Microsampling, storage, direct analysis, and applications

Recent advancements in the sensitivity of chemical instrumentation have led to increased interest in the use of microsamples for translational and biomedical research. Paper substrates are by far the most widely used media for biofluid collection, and mass spectrometry is the preferred method of analysis of the resultant dried blood spot (DBS) samples. Although there have been a variety of review papers published on DBS, there has been no attempt to unify the century old DBS methodology with modern applications utilizing modified paper and paper-based microfluidics for sampling, storage, processing, and analysis. This critical review will discuss how mass spectrometry has expanded the utility of paper substrates from sample collection and storage, to direct complex mixture analysis to on-surface reaction monitoring.

Application of tail vein serial microsampling for plasma or dried plasma spots in toxicokinetic assessment in rats using acetaminophen as the model compound

In the current study, two groups of rats (five per group) were administered a single oral dose of 500 mg/kg acetaminophen. For toxicokinetic assessment, the Group 1 animals were bled via conventional sparse (two animals/time point) sublingual vein bleeding (~0.5 ml) with anesthesia, while the Group 2 animals were bled via serial tail vein microsampling (~0.075 ml) without anesthesia. All collected blood was processed for plasma. Each Group 2 plasma sample (~30 μl) was divided into 'wet' and 'dried' (dried plasma spots). All plasma samples were analyzed by LC-MS/MS for acetaminophen and its major metabolites acetaminophen glucuronide and acetaminophen sulfate. In addition, plasma and urine samples were collected for analysis of corticosterone and creatinine to assess stress levels. Comparable plasma exposure to acetaminophen and its two metabolites was observed in the plasma obtained via conventional sparse sublingual vein bleeding and serial tail vein microsampling and between the 'wet' and 'dried' plasma obtained by the latter. Furthermore, comparable corticosterone levels or corticosterone/creatinine ratios between the two groups suggested that serial microsampling without anesthesia did not increase the levels of stress as compared with conventional sampling with anesthesia, confirming the utility of microsampling for plasma or dried plasma spots in rodent toxicokinetic assessment.

Dried Blood Spot in Laboratory: Directions and Prospects

Over the past few years, dried blood spot (DBS) technology has become a convenient tool in both qualitative and quantitative biological analysis. DBS technology consists of a membrane carrier (MC) on the surface of which a biomaterial sample becomes absorbed. Modern analytical, immunological or genomic methods can be employed for analysis after drying the sample. DBS has been described as the most appropriate method for biomaterial sampling due to specific associated inherent advantages, including the small volumes of biomaterials required, the absence of a need for special conditions for samples’ storage and transportation, improved stability of analytes and reduced risk of infection resulting from contaminated samples. This review illustrates information on the current state of DBS technology, which can be useful and helpful for biomedical researchers. The prospects of using this technology to assess the metabolomic profile, assessment, diagnosis of communicable diseases are demonstrated.

Hematocrit, blood volume, and surface area of dried blood spots - a quantitative model

The use of the dried blood spot (DBS) sampling technique has extended the scope of clinical research, particularly in children. The effects of different hematocrit levels (25-55%) and different blood volumes (7.5-30 μL) on the surface area of the blood spots were investigated using ImageJ® software. Variation in hematocrit levels between patients and inaccuracies in blood volumes applied to Guthrie cards can have a marked effect on analyte concentrations measured in DBS samples. The current study presents a validated model that links blood volume and hematocrit to the surface area of the blood spot. The final model showed that both factors affect the blood spot surface area, however, the positive effect of blood volume is higher than the negative effect of hematocrit. The measurement of surface area could be added as an additional quality control step in clinical studies that have adopted fixed volume DBS sampling for the quantification of the analytes. This approach can be used in estimating the hematocrit if this is not known for a patient or estimating the volume in spots that are visually different in size from the norm, i.e. technical error.

Targeted Host Cell Protein Quantification by LC-MRM Enables Biologics Processing and Product Characterization

Multiple reaction monitoring (MRM) is a liquid chromatography-mass spectrometry (LC-MS) based quantification platform with high sensitivity, specificity, and throughput. It is extensively used across the pharmaceutical industry for the quantitative analysis of therapeutic molecules. The potential of MRM analysis for the quantification of specific host cell proteins (HCPs) in bioprocess, however, has yet to be well established. In this work, we introduce a multiplex LC-MRM assay that simultaneously monitors two high risk lipases known to impact biologics product quality, Phospholipase B-like 2 protein (PLBL2) and Group XV lysosomal phospholipase A2 (LPLA2). Quantitative data generated from the LC-MRM assay were used to monitor the clearance of these lipases during biologics process development. The method is linear over a dynamic range of 1 to 500 ng/mg. To demonstrate the fitness for use and robustness of this assay, we evaluate a comprehensive method qualification package that includes intra- and inter-run precision and accuracy across all evaluated concentrations, selectivity, recovery and matrix effect, dilution linearity, and carryover. Additionally, we illustrate that this assay provides a rapid and accurate means of monitoring high risk HCP clearance for in-process support and can actively guide process improvement and optimization. Lastly, we compare direct digestion platforms and affinity depletion platforms to demonstrate the impact of HCP-mAb interaction on lipase quantification.

Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection for Quantitative Analysis of Dried Blood Spots with Unknown Blood Volume

Blood volume in dried blood spot (DBS) analysis is assumed to be constant for DBS punches with a fixed area. However, blood volume in the punch is dependent on several factors associated with the blood composition and is preferentially normalized by off-line analysis for quantitative purposes. Instead of using external instrumentation, we present an all-in-one approach for the simultaneous determination of exact blood volume in the DBS punch and the quantitation of target analytes. A DBS is eluted with 500 μL of elution solvent in a sample vial, and the eluate is directly subjected to an automated analysis by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D). The capillary blood volume in the eluate is calculated from the concentrations of the inorganic blood constituents (K⁺, Na⁺, or Cl^-) determined by CE-C⁴D, which are linearly proportional to the blood volume originally sampled onto the DBS card. Alternatively, conductivity of the DBS eluate can be used for the blood volume determination by using C⁴D in a nonseparation flow-through mode. The methods are suitable for the determination of blood volume in unknown DBS samples by punching out the entire DBS or by subpunching a small section of a large DBS with variations of the true vs the determined volume ≤5.5%. Practical suitability was demonstrated by the simultaneous CE-C⁴D determination of K⁺ and Na⁺ (for DBS volume calculation) and amino acids (target analytes) in unknown DBS samples. Quantitative analysis of selected amino acids (related to inborn metabolic disorders) in the unknown DBS was compared with a standard analytical procedure using wet-blood chemistry, and an excellent fit was obtained. The use of CE-C⁴D represents an important milestone in quantitative DBS analysis since the detection technique is universal, and the separation technique enables the determination of cations and/or anions and the use of multiple detectors, which further enhance selectivity/sensitivity of the analysis and the range of detectable analytes.

Analysis of the Heterogeneous Distribution of Amiloride and Propranolol in Dried Blood Spot by UHPLC-FLD and MALDI-IMS

Dried blood spot (DBS) has lately experienced an increase in its use in bioanalysis due to its several advantages compared with traditional blood sampling methods. Nevertheless, the use of DBS with quantitative purposes is hindered by the heterogeneous distribution of some compounds in the supporting matrix and the dependence of the response on different factors, such as the hematocrit, blood volume, and sampling position. In this study the effect of those factors in the analytical response was investigated by ultra high performance liquid chromatography coupled to fluorescence detection, using amiloride and propranolol as model compounds. The results showed a heterogeneous and drug-dependent distribution of the compounds in the blood spot. While amiloride concentration was higher in the center, propranolol concentration was higher in the periphery of the spot. Besides, the influence of the hematocrit on the quantitative results was observed. MALDI mass spectrometry imaging (MALDI-IMS) has allowed study of the distribution of the two cardiovascular drugs when they were placed in the DBS card using water:methanol solutions, demonstrating that they followed a similar distribution pattern as in blood. This work has showed the potentiality of the MALDI-IMS technique to predict the distribution of the drugs in the DBS card.

Microsampling: considerations for its use in pharmaceutical drug discovery and development

There is growing interest in the implementation of microsampling approaches for the quantitation of circulating concentrations of analytes in biological samples derived from nonclinical and clinical studies involved in drug development. This interest is partly due to the ethical advantages of taking smaller blood volumes, particularly for studies in rodents, children and the critically ill. In addition, these technologies facilitate sampling to be performed in previously intractable locations and occasions. Further, they enable the collection of samples for additional purposes (extra time points, biomarkers, sampling during a clinical event, etc). This article gives a comprehensive insight to the utilization of these approaches in drug discovery and development, and provides recommendations for best practice for nonclinical, clinical and bioanalytical aspects.

Urea Cycle Related Amino Acids Measured in Dried Bloodspots Enable Long-Term In Vivo Monitoring and Therapeutic Adjustment

BACKGROUND

Dried bloodspots are easy to collect and to transport to assess various metabolites, such as amino acids. Dried bloodspots are routinely used for diagnosis and monitoring of some inherited metabolic diseases.

METHODS

Measurement of amino acids from dried blood spots by liquid chromatography-tandem mass spectrometry.

RESULTS

We describe a novel rapid method to measure underivatised urea cycle related amino acids. Application of this method enabled accurate monitoring of these amino acids to assess the efficacy of therapies in argininosuccinate lyase deficient mice and monitoring of these metabolites in patients with urea cycle defects.

CONCLUSION

Measuring urea cycle related amino acids in urea cycle defects from dried blood spots is a reliable tool in animal research and will be of benefit in the clinic, facilitating optimisation of protein-restricted diet and preventing amino acid deprivation.

Presoaking dried blood spot with water improves efficiency for small-molecule analysis

The current method of extracting small molecules from dried blood spots (DBSs) and liquid blood is similar. However, owing to their different physical characteristics, a modification of the extraction process for DBS is required. We propose a modified method involving presoaking in water that results in better extraction efficiency for small-molecule analysis than the conventional protein precipitation method. Using blood and DBSs from eight subjects, the similarities, recovery rates and extraction efficiencies of both methods were compared. Quantitative analysis showed that seven and six out of ten conditions for the modified method group exhibited almost 100% recovery and extraction efficiency rates, respectively, compared with the conventional method group. Taken together, the results suggest that a presoaking step is needed for efficient DBS analysis.

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.

Using dried blood spots to facilitate therapeutic drug monitoring of antiretroviral drugs in resource-poor regions

Objectives

We evaluated whether dried blood spots (DBS) are suitable to monitor combined ART when samples are collected in rural Tanzania and transported over a long distance to a specialized bioanalytical laboratory.

Methods

Plasma and DBS samples were collected in Tanzania from study patients treated with nevirapine, efavirenz or lopinavir. In addition, plasma, whole blood and DBS samples were obtained from a cohort of HIV patients at the site of the bioanalytical laboratory in Switzerland. DBS samples were analysed using a fully automated LC-MS/MS method.

Results

Comparison of DBS versus plasma concentrations of samples obtained from the bridging study in Switzerland indicated an acceptable bias only for nevirapine (18.4%), whereas for efavirenz and lopinavir a pronounced difference of -47.4% and -48.1% was found, respectively. Adjusting the DBS concentrations by the haematocrit and the fraction of drug bound to plasma proteins removed this bias [efavirenz +9.4% (-6.9% to +25.7%), lopinavir +2.2% (-20.0% to +24.2%)]. Storage and transportation of samples from Tanzania to Switzerland did not affect the good agreement between plasma and DBS for nevirapine [-2.9% (-34.7% to +29.0%)] and efavirenz [-9.6% (-42.9% to +23.8%)]. For lopinavir, however, adjusted DBS concentrations remained considerably below [-32.8% (-70.4% to +4.8%)] corresponding plasma concentrations due to decay of lopinavir in DBS obtained under field conditions.

Conclusions

Our field study shows that the DBS technique is a suitable tool for therapeutic drug monitoring in resource-poor regions; however, sample stability remains an issue for certain analytes and therefore needs special consideration.

An overview of the current progress, challenges, and prospects of human biomonitoring and exposome studies

Human Biomonitoring (HB), the process for determining whether and to what extent chemical substances penetrated our bodies, serves as a useful tool to quantify human exposure to pollutants. In cases of nutrition and physiologic status, HB plays a critical role in the identification of excess or deficiency of essential nutrients. In pollutant HB studies, levels of substances measured in body fluids (blood, urine, and breast milk) or tissues (hair, nails or teeth) aid in the identification of potential health risks or associated adverse effects. However, even as a widespread practice in several countries, most HB studies reflect exposure to a single compound or mixtures which are measured at a single time point in lifecycle. On the other hand, throughout an individual's lifespan, the contact with different physical, chemical, and social stressors occurs at varying intensities, differing times and durations. Further, the interaction between stressors and body receptors leads to dynamic responses of the entire biological system including proteome, metabolome, transcriptome, and adductome. Bearing this in mind, a relatively new vision in exposure science, defined as the exposome, is postulated to expand the traditional practice of measuring a single exposure to one or few chemicals at one-time point to an approach that addresses measures of exposure to multiple stressors throughout the lifespan. With the exposome concept, the science of exposure advances to an Environment-Wide Association Perspective, which might exhibit a stronger relationship with good health or disease conditions for an individual (phenotype). Thus, this critical review focused on the current progress of HB and exposome investigations, anticipating some challenges, strategies, and future needs to be taken into account for designing future surveys.

Development and validation of a dried blood spot test for thiamine deficiency among infants by HPLC-fluorimetry

Thiamine deficiency, if detected early in infancy, can be treated with thiamine supplementation and can prevent seizures, other disabilities and death. The dried blood spot (DBS) sampling technique is an attractive sample collection technique for infants. The present study reports the development and validation of a highly sensitive and precise method for quantification of thiamine diphosphate from DBS. The method utilizes full-spot analysis of a volumetrically deposited 40 μl DBS. The analyte was extracted from the DBS using 50% methanol and then derivatized using potassium ferricyanide to thiochrome. Separation was achieved with the help of an Inertsil ODS C₁₈ column (5.0 μm, 250 × 4.6 mm) using 150 mm phosphate buffer pH 7-acetonitrile (90:10, % v/v) as the mobile phase. The use of a fluorimetric detector gave a good response to the thiochrome derivative offering good sensitivity for the method. The excitation and emission wavelengths were 367 and 435 nm, respectively. The limit of detection and lower limit of quantification were 5 and 10 ng/ml, respectively. Linearity was demonstrated from 10 to 1000 ng/ml, and precision (CV) was <12.08%, at all tested quality control levels. The method accuracy was 89.34-118.89% with recoveries >80%. Bland-Altman analysis of DBS sampling vs. whole blood demonstrated a mean bias of only 1.16 ng/ml, with a majority of the 60 investigated patient samples lying within 7.2% of the corresponding concentration measured in blood, thereby meeting the clinical desirable biological specification criterion and showing that the two methods are comparable.

Spreading and Imbibition of Vesicle Dispersion Droplets on Porous Substrates

Vesicles have recently found widespread use in applications such as conditioning of textiles, paper and hair, as well as transdermal drug delivery. The mode of treatment in several such cases involves the application of droplets of aqueous dispersions of vesicles onto dry porous substrates like paper and textiles. One of the factors which affects the performance of such treatments is the rate at which the droplets spread and imbibe on the porous substrate. Depending upon the specific purpose of the treatment either a fast or slow droplet spreading kinetics could be desired. Therefore, it is important to have a good understanding of the droplet spreading process and the factors which influence it. In this work, an experimental investigation of the simultaneous spreading and imbibition of vesicle dispersion droplets on cellulose filter papers is carried out. Two different types of vesicles which are composed of similar lipid molecules but exhibit contrasting lipid bilayer phase behavior are used. Two different grades of filter papers with comparable porosities but different thicknesses are used as porous substrate. It is found that the droplet spreading behavior is of the “complete wetting” type on the thicker porous substrate, whereas it is of the “partial wetting” type on the thinner substrate. Furthermore, it is observed that the spreading of droplets containing vesicles with liquid-crystalline phase bilayers occurs faster than that of vesicles with solid-gel phase bilayers. The secondary radial penetration which commences after the initial droplet spreading is complete is also investigated and discussed.

Dried blood spots sampling in case samples deprived of hematocrit level information - Investigation and calculation strategy

The application of a new calculation strategy for the psychotropic drug concentration in blood and bone marrow samples in the form of dried blood spots (DBS) was the main aim of the study. The standard DBS method consists of the deposition of the capillary blood onto the dedicated paper cards. Nowadays, the DBS technique is seen as a fast and partly superior microsampling alternative methodology replacing the conventional venous blood and plasma collection. The calculation approach to drug concentration in the limited volume of the case sample, where the hematocrit level cannot be determined, constitutes an important step of this method. The method has been validated and the results of the determination of alprazolam and diazepam previously spiked in the post-mortem blood and bone marrow sample have been satisfactory.

Rapid electrophoretic recovery of DNA from dried blood spots

Large-scale genetic screening of neonatal dried blood spots for episomal DNA has a great potential to lower patient mortality and morbidity through early diagnosis of primary immunodeficiencies. However, DNA extraction from the surface of dried blood spots remains one of the most time consuming, costly, and labor-intensive parts of DNA analysis. In the present study, we developed and optimized a rapid methodology using only 50 V and heat to extract episomal DNA from dried blood spots prepared from diagnostic cord blood samples. This electric field DNA extraction is the first methodology to use an electric field to extract episomal DNA from a dried blood spot. This 25-minute procedure has one of the lowest times for the extraction of episomal DNA found within the literature and this novel procedure not only negates the need for costly treatment and wash steps, but reduces the time of manual procedures by more than 30 min while retaining the 75-80% of the yield. Combined with real-time PCR, this novel method of electric field extraction not only provides an effective tool for the large scale genetic analysis of neonates, but a key step forward in the simplification and standardization of diagnostic testing.

Dried blood samples can support monitoring of infliximab concentrations in patients with inflammatory bowel disease: A clinical validation

Aims

Therapeutic drug monitoring (TDM) can optimize the efficacy of infliximab (IFX) in patients with inflammatory bowel disease (IBD). Because of the delay between blood samples taken at trough and availability of results, dose adjustments can only be carried out at the next infusion, typically 8 weeks later. Dried blood samples (DBS) performed at home to measure IFX concentrations can reduce the time to adapt dose/dosing interval. Here, we aimed to validate the clinical application of DBS for IFX in IBD patients and to evaluate the feasibility of home sampling.

Methods

DBS results from 40 IBD patients on IFX treatment were compared to serum sample results at trough, peak, and 3–5 weeks after IFX infusion. Subsequently, patients performed DBS home sampling one week before the next IFX infusion. These were compared to serum concentrations as predicted by Bayesian analysis.

Results

IFX concentrations from finger prick and venous puncture correlate well. DBS IFX concentrations showed high correlation with serum IFX concentrations (Spearman correlation: ≥0.965), without bias. Passing‐Bablok regression for IFX concentrations in DBS from home sampling also showed no bias (intercept: 1.02 mg L⁻¹ (95% CI −1.77–2.04 mg L⁻¹), slope: 0.82 (95% CI 0.63–1.40)), with reasonable correlation (Spearman correlation: 0.671).

Conclusions

Timely adjustment of IFX dose/dosing interval can be facilitated by IFX concentration measurement in home‐sampled DBS. DBS is a reliable method to measure IFX and can be used to predict IFX trough concentrations.

Simultaneous Determination of Selegiline, Desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine on Dried Urine Spots by LC/MS/MS: Application to a Pharmacokinetic Study in Urine

Objective: Chiral analysis is a crucial method to differentiate selegiline intake from drug abuse. A dried urine spot (DUS) analytical method based on spotting urine samples (10 μL) onto dried spot collection cards, and followed by air-drying and extraction, was developed and validated for the determination of selegiline, desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine. Methods: Methanol (0.5 mL) was found to be the ideal extraction solvent for target extraction from DUSs under orbital-horizontal stirring on a lateral shaker at 1,450 rpm for 30 min. Determinations were performed by direct electrospray ionization tandem mass spectrometry (ESI-MS/MS) under positive electrospray ionization conditions using multiple reaction monitoring mode. The chromatographic system consisted of a ChirobioticTM V2 column (2.1 × 250 mm, 5 μm) and a mobile phase of methanol containing 0.1% (v/v) glacial acetic acid and 0.02% (v/v) ammonium hydroxide. Results and conclusions: The calibration curves were linear from 50 to 5,000 ng/mL, with r > 0.995 for all analytes, imprecisions ≤ 15% and accuracies between -11.4 and 11.7%. Extraction recoveries ranged from 48.6 to 105.4% with coefficients of variation (CV) ≤ 13.7%, and matrix effects ranged from 45.4 to 104.1% with CV ≤ 10.3%. The lower limit of quantification was 50 ng/mL for each analyte. The present method is simple, rapid (accomplished in 12 min), sensitive, and validated by a pharmacokinetic study in human urine collected after a single oral administration of SG.

In-Transit Electroextraction of Small-Molecule Pharmaceuticals from Blood

An electrokinetic platform was developed for extracting small-molecule pharmaceuticals from a dried blood spot. Through the exclusion of liquid reagents and use of low field strength (6 V cm^-1 ), the electroextraction of a drug from a dried blood spot, deposited on a polymer inclusion membrane (PIM), could be realised while in transit in the mail. In transit sample preparation provides a potential solution to in situ sample degradation and may accelerate the workflow upon arrival of a patient sample at the analytical facility. The electroextraction method was enabled through our discovery of the use of 15-20 μm thin PIMs as electrophoretic separation medium in absence of liquid reagents. Here, a PIM consisting of cellulose triacetate as polymer base, 2-nitrophenyl octyl ether as plasticizer and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as carrier was used. The PIM, was packaged with two 12 V batteries to supply the separation voltage. A blood spot containing berberine chloride was deposited and dried before the applying the separation potential, allowing for the electroextraction while the packaged device was shipped in internal mail. Upon arrival in the analytical laboratory, the PIM was analysed using a fluorescence microscope with photon multiplier tube, quantifying the berberine extracted away from the sample matrix. This platform represents a new opportunity for processing clinical samples during transport to the laboratory, saving time and manual handling to accelerate the time to result.