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

Simultaneous detection of myostatin-targeting monoclonal antibodies in dried blood spots and plasma using liquid chromatography-tandem mass spectrometry with field asymmetric ion mobility spectrometry

Transforming growth factor-β superfamily members, such as myostatin, growth/differentiation factor 11, and activin A, negatively regulate skeletal muscle mass. Inhibitors targeting these cytokines or activin receptor type IIB have the potential to treat muscular diseases and enhance physical performance. However, because of their effects on muscle mass and potential misuse, they are strictly prohibited in sports. Given the high potential for misuse as a doping agent in sports, effective analytical methods for these prohibited antibodies targeting these specific cytokines or their receptor are critically needed. In this study, we aimed to develop and validate a multitarget method to detect the prohibited transforming growth factor-β superfamily-targeting monoclonal antibodies, such as landogrozumab, domagrozumab, and the activin receptor type IIB-targeting antibody, bimagrumab, in human plasma and dried blood spot (DBS) samples using liquid chromatography-tandem mass spectrometry. Antibodies were purified from both the DBS and plasma samples using protein G magnetic beads and field-asymmetric ion mobility spectrometry (FAIMS) to minimize interference, followed by liquid chromatography-tandem mass spectrometry analysis. The validation process included tests for specificity, selectivity, linearity, limit of detection (LOD), limit of identification, precision, recovery, carryover effect, and matrix effect. The LODs for the target antibodies were identical in both DBS and plasma samples at 0.1 µg/mL for landogrozumab heavy and light chains, as well as 0.25 µg/mL for the domagrozumab light chain and 0.25 µg/mL for the bimagrumab heavy chain. However, the heavy chain of domagrozumab exhibited an LOD of 0.5 µg/mL in DBS and 1 µg/mL in plasma. The analytical method demonstrated strong linearity, with R² values greater than 0.99 for both plasma and DBS, and no carryover effect. Precision (CV%) was below 15 % at both middle (1 or 5 µg/mL; specific to the heavy chain of domagrozumab in plasma) and high (10 µg/mL) concentrations and was less than 20 % at the LOD. The selectivity and specificity indicated no interference in the analysis of target mAbs in different blood samples. Recovery was 31.6-49.8 % for DBS and 51.4-85.3 % for plasma, with no significant matrix effect. This study provides an effective method for doping analysis and novel protein detection.

Evaluation of low volume sampling devices for a pharmacodynamic biomarker analysis: Challenges and solutions

Low volume sampling technologies have gained popularity as they are minimally invasive, reduce patient burden, enhance population diversity, and have the potential to facilitate decentralized clinical trials. Herein, we validated a Gyrolab assay to measure soluble Mucosal Addressin Cell Adhesion Molecule 1 (sMAdCAM-1) in dried blood samples collected using two low volume sampling devices, Mitra and Tasso-M20. This validated assay was implemented in a proof-of-concept study to compare three low volume sampling devices (Mitra, Tasso-M20 and TassoOne Plus) with serum collected via venipuncture from healthy volunteers receiving etrolizumab. We observed significantly higher concentration of sMAdCAM-1 in dried blood samples collected using Mitra and Tasso-M20 compared to serum in some paired samples, which was attributed to interference from the dried blood extraction buffer. To mitigate this interference, samples required substantial dilution into the appropriate buffer, which negatively impacted the detectability of sMAdCAM-1 with the Gyrolab assay. By employing the Quanterix single molecule array (Simoa), known for its superior assay sensitivity, the interference was minimized in the diluted samples. Both liquid blood collected in TassoOne Plus and dried blood collected using Mitra and Tasso-M20 demonstrated great concordance with serum for sMAdCAM-1 measurement. However, a bias was observed in Mitra dried blood samples, presumably due to the different sample collection sites in comparison with venipuncture and Tasso devices. Our study highlights the potential of low volume sampling technologies for biomarker analysis, and underscores the importance of understanding the challenges and limitations of these technologies before integrating them into clinical studies.

Use of a Novel Whole Blood Separation and Transport Device for Targeted and Untargeted Proteomics

BACKGROUND

There is significant interest in developing alternatives to traditional blood transportation and separation methods, which often require centrifugation and cold storage to preserve specimen integrity. Here we provide new performance findings that characterize a novel device that separates whole blood via lateral flow then dries the isolated components for room temperature storage and transport.

METHODS

Untargeted proteomics was performed on non-small cell lung cancer (NSCLC) and normal healthy plasma applied to the device or prepared neat.

RESULTS

Significantly, proteomic profiles from the storage device were more reproducible than from neat plasma. Proteins depleted or absent in the device preparation were shown to be absorbed onto the device membrane through largely hydrophilic interactions. Use of the device did not impact proteins relevant to an NSCLC clinical immune classifier. The device was also evaluated for use in targeted proteomics experiments using multiple-reaction monitoring (MRM) mass spectrometry. Intra-specimen detection intensity for protein targets between neat and device preparations showed a strong correlation, and device variation was comparable to the neat after normalization. Inter-specimen measurements between the device and neat preparations were also highly concordant.

CONCLUSIONS

These studies demonstrate that the lateral flow device is a viable blood separation and transportation tool for untargeted and targeted proteomics applications.

Advances in textile-based microfluidics for biomolecule sensing

Textile-based microfluidic biosensors represent an innovative fusion of various multidisciplinary fields, including bioelectronics, material sciences, and microfluidics. Their potential in biomedicine is significant as they leverage textiles to achieve high demands of biocompatibility with the human body and conform to the irregular surfaces of the body. In the field of microfluidics, fabric coated with hydrophobic materials serves as channels through which liquids are transferred in precise amounts to the sensing element, which in this case is a biosensor. This paper presents a condensed overview of the current developments in textile-based microfluidics and biosensors in biomedical applications over the past 20 years (2005-2024). A literature search was performed using the Scopus database. The fabrication techniques and materials used are discussed in this paper, as these will be key in various modifications and advancements in textile-based microfluidics. Furthermore, we also address the gaps in the application of textile-based microfluidic analytical devices in biomedicine and discuss the potential solutions. Advances in textile-based microfluidics are enabled by various printing and fabric manufacturing techniques, such as screen printing, embroidery, and weaving. Integration of these devices into everyday clothing holds promise for future vital sign monitoring, such as glucose, albumin, lactate, and ion levels, as well as early detection of hereditary diseases through gene detection. Although most testing currently takes place in a laboratory or controlled environment, this field is rapidly evolving and pushing the boundaries of biomedicine, improving the quality of human life.

Temporal Assessment of Protein Stability in Dried Blood Spots

The use of protein biomarkers in blood for clinical settings is limited by the cost and accessibility of traditional venipuncture sampling. The dried blood spot (DBS) technique offers a less invasive and more accessible alternative. However, protein stability in DBS has not been well evaluated. Herein, we deployed a quantitative LC-MS/MS system to construct proteomic atlases of whole blood, DBSs, plasma, and blood cells. Approximately 4% of detected proteins' abundance was significantly altered during blood drying into blood spots, with overwhelming disturbances in cytoplasmic fraction. We also reported a novel finding suggesting a decrease in the level of membrane/cytoskeletal proteins (SLC4A1, RHAG, DSC1, DSP, and JUP) and an increase in the level of proteins (ATG3, SEC14L4, and NRBP1) related to intracellular trafficking. Furthermore, we identified 19 temporally dynamic proteins in DBS samples stored at room temperature for up to 6 months. There were three declined cytoskeleton-related proteins (RDX, SH3BGRL3, and MYH9) and four elevated proteins (XPO7, RAN, SLC2A1, and SLC29A1) involved in cytoplasmic transport as representatives. The instability was governed predominantly by hydrophilic proteins and enhanced significantly with an increasing storage time. Our analyses provide comprehensive knowledge of both short- and long-term storage stability of DBS proteins, forming the foundation for the widespread use of DBS in clinical proteomics and other analytical applications.

Detection of transgenes in equine dried blood spots using digital PCR and qPCR for gene doping control

Due to the ease of collection, transport and storage, the use of dried blood spots (DBS) offers an attractive alternative matrix for detection of the abuse of gene therapy, otherwise known as gene doping. This study evaluated the recovery, extraction efficiency and resulting detection capability of DNA from DBS by evaluating different target types, DNA extraction kits, the number of punches and blood tube preservatives. The long-term storage stability of low-copy-number transgene targets in DBS was not assessed in this study but would be noteworthy to investigate further. DNA was quantified using two detection methods: qPCR and digital PCR (dPCR). Using six punches with the Qiagen Investigator kit gave the best overall DNA yield compared with other extraction methods. Including three punches, however, gave better DNA extraction efficiency. Reference material could be detected using qPCR and dPCR in DBS spiked with 5000 copies/mL of blood (approximately 15 copies per 3 mm of punch). The optimal DNA extraction protocol was used on DBS samples from a custom recombinant adeno-associated virus administration study and showed successful detection of vector targets in DBS samples.

Identification of Benzodiazepine Use Based on Dried Blood Stains Analysis

Biological matrices are typically used in forensic toxicological or pharmacological analysis: mainly blood, vitreous humor or urine. However, there are many cases in which crimes are a consequence of drug intoxication or drug abuse and they are not closed because over the months or years the samples become altered or decomposed. A dried blood stains test (DBS-MS) has recently been proposed to be used in drug toxicology when blood is found at a crime scene. This test could help an investigator to reveal what a person had consumed before the perpetration of the crime. In order to check the possibilities of this test, we analyzed several dried blood stains located on a cotton fabric. Therefore, the aim of this study was to determine if the analysis of a dried blood spot located on a cotton fabric could be an alternate source of obtaining toxicological results, particularly regarding benzodiazepines. We splashed blood stains on cotton fabric with different concentrations of the following benzodiazepines: alprazolam, bromazepam, clonazepam, diazepam and lorazepam, which were dried for 96 h and subsequently quantified by high-performance liquid chromatography coupled mass spectrometry (HPLC-MS). Our results show that it is possible to identify several benzodiazepines contained in a cotton fabric blood stain; consequently, this method may add another sample option to the toxicological analysis of biological vestiges found at a crime scene.

Maternal and neonatal IgG against Klebsiella pneumoniae are associated with broad protection from neonatal sepsis: a case-control study of hospitalized neonates in Botswana

Sepsis is the leading postnatal cause of neonatal mortality worldwide. Globally Klebsiella pneumoniae is the leading cause of sepsis in hospitalized neonates. This study reports development and evaluation of ELISA for anti-Klebsiella IgG using dried blood spot samples and evaluates the association of anti-Klebsiella IgG (anti-Kleb IgG) antibodies in maternal and neonatal samples and the risk of neonatal sepsis. Neonates and their mothers were enrolled at 0-96 hours of life in the neonatal unit of a tertiary referral hospital in Gaborone, Botswana and followed until death or discharge to assess for episodes of blood culture-confirmed neonatal sepsis. Neonates with sepsis had significantly lower levels of Kleb-IgG compared to neonates who did not develop sepsis (Mann-Whitney U, p=0.012). Similarly, samples from mothers of neonates who developed sepsis tended to have less Kleb-IgG compared to mothers of controls (p=0.06). The inverse correlation between Kleb-IgG levels and all-cause bacteremia suggests that maternal Kleb-IgG is broadly protective through cross-reactivity with common bacterial epitopes. These data support the continued use of immunoglobulin assays using DBS samples to explore the role of passive immunity on neonatal sepsis risk and reaffirm the critical need for research supporting the development of maternal vaccines for neonatal sepsis.

A Mathematical Algorithm for Dried Blood Spot Quality Assessment and Results concerning Quality from a Newborn Screening Program

BACKGROUND

In addition to newborn screening, dried blood spots (DBSs) are used for a wide variety of analytes for clinical, epidemiological, and research purposes. Guidelines on DBS collection, storage, and transport are available, but it is suggested that each laboratory should establish its own acceptance criteria.

METHODS

An optical scanning device was developed to assess the quality of DBSs received in the newborn screening laboratory from 11 maternity wards between 2013 and 2018. The algorithm was adjusted to agree with the visual examination consensus of experienced laboratory personnel. Once validated, the algorithm was used to categorize DBS specimens as either proper or improper. Improper DBS specimens were further divided based on 4 types of specimen defects.

RESULTS

In total, 27 301 DBSs were analyzed. Compared with an annual DBS rejection rate of about 1%, automated scanning rejected 26.96% of the specimens as having at least one defect. The most common specimen defect was multi-spotting (ragged DBS, 19.13%). Among maternity wards, improper specimen rates varied greatly between 5.70% and 49.92%.

CONCLUSIONS

Improper specimen rates, as well as the dominant type of defect(s), are mainly institution-dependent, with various maternity wards consistently showing specific patterns of both parameters over time. Although validated in agreement with experienced laboratory personnel consensus, automated analysis rejects significantly more specimens. While continuous staff training, specimen quality monitoring, and problem-reporting to maternities is recommended, a thorough quality assessment strategy should also be implemented by every newborn screening laboratory. An important role in this regard may be played by automation in the form of optical scanning devices.

Single Cell mass spectrometry: Towards quantification of small molecules in individual cells

Studying cell heterogeneity can provide a deeper understanding of biological activities, but appropriate studies cannot be performed using traditional bulk analysis methods. The development of diverse single cell bioanalysis methods is in urgent need and of great significance. Mass spectrometry (MS) has been recognized as a powerful technique for bioanalysis for its high sensitivity, wide applicability, label-free detection, and capability for quantitative analysis. In this review, the general development of single cell mass spectrometry (SCMS) field is covered. First, multiple existing SCMS techniques are described and compared. Next, the development of SCMS field is discussed in a chronological order. Last, the latest quantification studies on small molecules using SCMS have been described in detail.

Detection of 26 Drugs of Abuse and Metabolites in Quantitative Dried Blood Spots by Liquid Chromatography-Mass Spectrometry

A method was developed for the determination of 26 drugs of abuse from different classes, including illicit drugs in quantitative dried blood spots (qDBSs), with the aim to provide a convenient method for drug testing by using only 10 μL of capillary blood. A satisfactory limit of quantification (LOQ) of 2.5 ng/mL for 9 of the compounds and 5 ng/mL for 17 of the compounds and a limit of detection (LOD) of 0.75 ng/mL for 9 of the compounds and 1.5 ng/mL for 17 of the compounds were achieved for all analytes. Reversed-phase liquid chromatography was applied on a C18 column coupled to MS, providing selective detections with both +ESI and -ESI modes. Extraction from the qDBS was performed using AcN-MeOH, 1:1 (v/v), with recovery ranging from 84.6% to 106%, while no significant effect of the hematocrit was observed. The studied drugs of abuse were found to be stable over five days under three different storage conditions (at ambient temperature 21 °C, at -20 °C, and at 35 °C), thus offering a highly attractive approach for drug screening by minimally invasive sampling for individuals that could find application in forensic toxicology analysis.

Ready-to-use nanopore platform for label-free small molecule quantification: Ethanolamine as first example

In recent decades, nanopores have become a promising diagnostic tool. Protein and solid-state nanopores are increasingly used for both RNA/DNA sequencing and small molecule detection. The latter is of great importance, as their detection is difficult or expensive using available methods such as HPLC or LC-MS. DNA aptamers are an excellent detection element for sensitive and specific detection of small molecules. Herein, a method for quantifying small molecules using a ready-to-use sequencing platform is described. Taking ethanolamine as an example, a strand displacement assay is developed in which the target-binding aptamer is displaced from the surface of magnetic particles by ethanolamine. Non-displaced aptamer and thus the ethanolamine concentration are detected by the nanopore system and can be quantified in the micromolar range using our in-house developed analysis software. This method is thus the first to describe a label-free approach for the detection of small molecules in a protein nanopore system.

A simple and rapid external standard calibration HPLC method for determination of lumefantrine in dried blood spot samples from malaria patients in Botswana

A simple external calibration liquid chromatography-diode array detector method was developed, validated, and applied for the determination of lumefantrine (Lum) in dried blood spot (DBS) samples collected from malaria patients in Botswana. The samples were validated in accordance with the United States Food and Drug Administration guidelines for bioanalytical methods after sample preparation using solid-liquid extraction. Separation was achieved using an XTerra C18 column (50 × 4.6 mm, 5 μm), and a binary solvent system of acetonitrile and water adjusted to pH 2.3 was used as the mobile phase. The validated method was applied for the determination of Lum in DBS samples collected from malaria patients infected with Plasmodium falciparum in Botswana. The calibration curve was linear between 0.5 and 12 μg/mL with a coefficient of determination (R2 ) of 0.9996. The limit of detection and the lower limit of quantification were 0.5 and 1.4 μg/mL, respectively. The efficiency of extraction measured as percentage recovery ranged between 84.2% and 107.8% at the three quality control (QC) levels, that is, low QC, mid QC, and high QC. In conclusion, data suggest that the method is suitable for the determination of trace Lum in biofluids and can also be used for therapeutic drug monitoring and pharmacokinetic profiling.

Development and evaluation of serological screening based on one dried plasma spot for HIV, syphilis, and HCV

BACKGROUND

In the effort to prevent and control HIV/AIDS, China has established a national sentinel surveillance system. However, some sentinel sites face limitations in environmental resources and accessibility, prompting the exploration of alternative sample strategies. Dried plasma spots (DPS) samples are viewed as promising alternatives to traditional plasma samples due to their advantages, including sample stability, easy storage, and convenient transport. This study aims to develop a method for screening HIV, Treponema pallidum (TP), and Hepatitis C Virus (HCV) using DPS samples and assess their performance.

METHODS

Based on existing commercial assay kits, a detection method was established through the optimization of experimental parameters, including the amount of plasma on filter paper, the volume of elution solution applied to dried plasma spots, the size of dried plasma spots, elution solution volume, elution solution components, elution temperature, and elution time. A series of laboratory evaluation panels were constructed for laboratory assessments, including the laboratory basic panel, laboratory interference panel, and laboratory precision panel. Additionally, clinical samples were used for evaluation.

RESULTS

Optimal conditions for DPS sample extraction were: plasma volume, 100 µL; DPS size, whole spot; eluent volume, 500 µL; eluent, PBS with 1‰ Tween20; elution time, 2 h; elution temperature, room temperature. A total of 619 paired plasma/DPS samples were tested by both methods. The DPS-based ELISA method exhibited 100% sensitivity/specificity for HIV, 98.6%/100% for TP, and 99.6%/100% for HCV. Kappa values between the plasma samples and DPS samples were 100% for HIV, 99% for TP, and 100% for HCV. The DPS-based ELISA method failed to detect 1 HCV mono-infected sample and TP in 1 HIV/HCV/TP co-infected sample. For the HIV/HCV/TP co-infected sample, the S/CO in the plasma sample was 2.143 and in the DPS sample was 0.5. For HCV, the S/CO (sample OD/cut-off) was 3.049 in the plasma sample and 0.878 in the DPS sample.

CONCLUSIONS

A single DPS, following one-time standardized processing, can be used to detect HIV, HCV, and TP. Researching and establishing laboratory testing methods better suited for China's sentinel surveillance have significant practical applications in improving HIV testing in resource-constrained environments.

Validation of low-volume sampling devices for pharmacokinetic analysis: technical and logistical challenges and solutions

While low-volume sampling technologies offer numerous advantages over venipuncture, implementation in clinical trials poses technical and logistical challenges. Bioanalytical methods were validated for measuring the concentration of crenezumab and etrolizumab in dried blood samples collected using Mitra and Tasso-M20. The data generated demonstrate that the concentrations of crenezumab and etrolizumab in dried blood collected by either device could be determined using calibrators prepared in serum. Drug concentrations from dried blood were converted to serum concentrations using patient hematocrit levels. Contract Research Organization experience in sample handling and analysis allowed us to compare differences between various low-volume sampling technologies. This study evaluated challenges and presented potential solutions for use of different low-volume sampling technologies for pharmacokinetic analysis.

Dried Blood Spots-A Platform for Therapeutic Drug Monitoring (TDM) and Drug/Disease Response Monitoring (DRM)

This review provides an overview on the current applications of dried blood spots (DBS) as matrices for therapeutic drug (TDM) and drug or disease response monitoring (DRM). Compared with conventional methods using plasma/serum, DBS offers several advantages, including minimally invasiveness, a small blood volume requirement, reduced biohazardous risk, and improved sample stability. Numerous assays utilising DBS for TDM have been reported in the literature over the past decade, covering a wide range of therapeutic drugs. Several factors can affect the accuracy and reliability of the DBS sampling method, including haematocrit (HCT), blood volume, sampling paper and chromatographic effects. It is crucial to evaluate the correlation between DBS concentrations and conventional plasma/serum concentrations, as the latter has traditionally been used for clinical decision. The feasibility of using DBS sampling method as an option for home-based TDM is also discussed. Furthermore, DBS has also been used as a matrix for monitoring the drug or disease responses (DRM) through various approaches such as genotyping, viral load measurement, assessment of inflammatory factors, and more recently, metabolic profiling. Although this research is still in the development stage, advancements in technology are expected to lead to the identification of surrogate biomarkers for drug treatment in DBS and a better understanding of the correlation between DBS drug levels and drug responses. This will make DBS a valuable matrix for TDM and DRM, facilitating the achievement of pharmacokinetic and pharmacodynamic correlations and enabling personalised therapy.

Ultra-High Performance Liquid Chromatography Method for Bioanalysis of Fampridine Using Dried Blood Spot (DBS) Methodology: Application to Pharmacokinetic Study in Albino Rats

Fampridine (dalfampridine) is used to improve walking in people who have multiple sclerosis (a disease in which the nerves do not function properly and may cause weakness, numbness, loss of muscle coordination and problems with vision, speech and bladder control). Measurement of fampridine plasma concentrations is not practical at sites lacking the facilities to prepare and process blood samples. A dried blood spot (DBS) sampling method, in which a few drops of blood, drawn by lancet from the finger, are applied onto specially manufactured absorbent filter paper, can be used as an alternative to plasma monitoring and would allow for simplified sample storage and transport. Using blood samples from pharmacokinetic studies, an ultra-high performance liquid chromatography assay method for quantification of fampridine in DBS is developed and validated for specificity, selectivity, accuracy, precision, reproducibility and stability. Method was specific and selective relative to endogenous compounds, with required process efficiency, and no matrix effect. Inaccuracy and precision for intra-day and inter-day analyses were tested at all concentrations. Quantification of fampridine in DBS assay was not affected by blood deposit volume and punch position within spot, and hematocrit level had a limited but acceptable effect on measurement accuracy. Fampridine was stable for at least 2 months at room temperature. The correlation between DBS and plasma concentrations with an average blood-to-plasma ratio is determined. DBS sampling is a simple and practical method for monitoring fampridine concentrations. The method is completely validated as per ICH guidelines and extended to the in vivo determination of fampridine in male albino rats.

Liquid chromatography with tandem mass spectrometric method for determination of 425 drugs and poisons in dried blood spots and application to forensic cases

PURPOSE

An analytical method using liquid chromatography with tandem mass spectrometry (LC-MS/MS) was established and validated for screening 425 drugs and poisons in dried blood spots (DBSs).

METHODS

Blood (20 μL) was spotted on Whatman FTA™ classic card to prepare DBS sample, then extracted with 150 μL methanol and analyzed by LC-MS/MS using a multiple reaction monitoring method.

RESULTS

The limit of detection of the compounds were 0.1-10 ng/mL. The values for recovery and matrix effect were 40.3-114.9% and 40.2-118.4%, respectively. This method was successfully applied to DBS samples from 105 humans suspected of drug poisoning, which was stored for 3-5 years at room temperature. Thirty-three kinds of drugs, including benzodiazepines, antipsychotics, antidepressants, antipyretic analgesics, non-steroidal anti-inflammatory drugs, antibiotics, antiepileptic drugs, new psychoactive drugs were confirmed in 102 cases, while no compound was detected in the other 3 cases. Estazolam, a benzodiazepine widely used in clinical practice as a sedative, hypnotic, and anti-anxiety drug, was the most frequently detected substance, occurring in 34.2% of the cases.

CONCLUSIONS

Most drugs in DBS could still be detected after storage for 3-5 years, but ambroxol, zopiclone, carbofuran, chlorpyrifos, and valproic acid were not detectable after 3-5 years of storage at room temperature. The components measured in DBS were consistent with those measured in whole blood at the collection time, thereby confirming that DBS samples have the advantage of stable storage at room temperature.

Microneedle Patch for Painless Intradermal Collection of Interstitial Fluid Enabling Multianalyte Measurement of Small Molecules, SARS-CoV-2 Antibodies, and Protein Profiling

Blood sampling is a common practice to monitor health, but it entails a series of drawbacks for patients including pain and discomfort. Thus, there is a demand for more convenient ways to obtain samples. Modern analytical techniques enable monitoring of multiple bioanalytes in smaller samples, opening possibilities for new matrices, and microsampling technologies to be adopted. Interstitial fluid (ISF) is an attractive alternative matrix that shows good correlation with plasma concentration dynamics for several analytes and can be sampled in a minimally invasive and painless manner from the skin at the point-of-care. However, there is currently a lack of sampling devices compatible with clinical translation. Here, to tackle state-of-the-art limitations, a cost-effective and compact single-microneedle-based device designed to painlessly collect precisely 1.1 µL of dermal ISF within minutes is presented. The fluid is volume-metered, dried, and stably stored into analytical-grade paper within the microfluidic device. The obtained sample can be mailed to a laboratory, quantitatively analyzed, and provide molecular insights comparable to blood testing. In a human study, the possibility to monitor various classes of molecular analytes is demonstrated in ISF microsamples, including caffeine, hundreds of proteins, and SARS-CoV-2 antibodies, some being detected in ISF for the first time.

New Trend in Toxicological Screening Using Volumetric Absorptive Microsampling (VAMS) and High-Resolution Mass Spectrometry (HR/MS) Combination

In toxicology, screenings are routinely performed using chromatographic methods coupled to detection systems such as high-resolution mass spectrometry (HR/MS). The increase in specificity and sensitivity of HRMS is responsible for the development of methods for alternative samples such as Volumetric Adsorptive Micro-Sampling. Whole blood overloaded with 90 drugs was sampled with 20 µL Mitra^TM to optimize the pre-analytical step as well as to determine the identification limits of drugs. Elution of chemicals was carried out in a solvent mixture through agitation and sonication. After dissolution, 10 μL was injected into the chromatographic system coupled to the Orbitrap^TM HR/MS. Compounds were confirmed against the laboratory library. The clinical feasibility was assessed in fifteen poisoned patients using the simultaneous sampling of plasma, whole blood and Mitra^TM. The optimized extraction procedure allowed us to confirm 87 compounds out of the 90 present in the spiked whole blood. Cannabis derivatives were not detected. For 82.2% of the investigated drugs, the identification limits were below 12.5 ng·mL^-1, with the extraction yields ranging from 80.6 to 108.7%. Regarding the patients' analysis, 98% of the compounds in plasma were detected in Mitra^TM compared to whole blood, with a satisfying concordance (R² = 0.827). Our novel screening approach opens new insights into different toxicologic fields appropriate for pediatrics, forensics or to perform mass screening.

Applications of Volumetric Absorptive Microsampling Technique: A Systematic Critical Review

METHODS

A novel microsampling device called Volumetric Absorptive microsampling (VAMS), developed in 2014, appears to have resolved the sample inhomogeneity inherent to dried blood spots, with improved precision in the volume of sample collected for measuring drug concentration. A literature search was conducted to identify several analytical and pharmacokinetic studies that have used VAMS in recent years.

RESULTS

The key factors for proper experimental design and optimization of the extraction of drugs and metabolites of interest from the device were summarized. This review focuses on VAMS and elaborates on bioanalytical factors, method validation steps, and scope of this technique in clinical practice.

CONCLUSIONS

The promising microsampling method VAMS is especially suited for conducting pharmacokinetic studies with very small volumes of blood, especially in special patient populations. Clinical validation of every VAMS assay must be conducted prior to the routine practical implementation of this method.

Microsampling tools for collecting, processing, and storing blood at the point-of-care

In the wake of the COVID-19 global pandemic, self-administered microsampling tools have reemerged as an effective means to maintain routine healthcare assessments without inundating hospitals or clinics. Finger-stick collection of blood is easily performed at home, in the workplace, or at the point-of-care, obviating the need for a trained phlebotomist. While the initial collection of blood is facile, the diagnostic or clinical utility of the sample is dependent on how the sample is processed and stored prior to transport to an analytical laboratory. The past decade has seen incredible innovation for the development of new materials and technologies to collect low-volume samples of blood with excellent precision that operate independently of the hematocrit effect. The final application of that blood (i.e., the test to be performed) ultimately dictates the collection and storage approach as certain materials or chemical reagents can render a sample diagnostically useless. Consequently, there is not a single microsampling tool that is capable of addressing every clinical need at this time. In this review, we highlight technologies designed for patient-centric microsampling blood at the point-of-care and discuss their utility for quantitative sampling as a function of collection material and technique. In addition to surveying methods for collecting and storing whole blood, we emphasize the need for direct separation of the cellular and liquid components of blood to produce cell-free plasma to expand clinical utility. Integrating advanced functionality while maintaining simple user operation presents a viable means of revolutionizing self-administered microsampling, establishing new avenues for innovation in materials science, and expanding access to healthcare.

Quantification of 25-hydroxyvitamin D2 and D3 in Mitra® devices with volumetric absorptive microsampling technology (VAMS®) by UHPLC-HRMS for regular vitamin D status monitoring

The numbers of vitamin D inadequacies has reportedly increased in the general population, especially in the Northern hemisphere. However, routine measurement of 25(OH) vitamin D is usually associated with a substantial effort due to the requirement of a venous blood sample taken by medical professionals. Thus, the objective of this work is to develop and validate an easy and minimal-invasive method, using a microsampling technique for autonomous blood collections by medically untrained individuals. The assay enables a simplified monitoring of the vitamin D-status in both, risk group and normal population throughout the year. For this purpose, a simple methanol extraction without derivatization combined with a UHPLC-HRMS method was developed to quantify 25(OH)D2 and 25(OH)D3 in capillary blood. For sample collection, a 20 μl Mitra® device with VAMS® technology is used. By employing the six-fold deuterium-labelled 25(OH)D3 as internal standard, the validated assay provides accurate (<10%) and precise (<11%) results. With a LOQ of 5 ng/ml, the approach also proved sensitive enough to adequately identify potential vitamin D deficiencies (< 12 ng/ml), and proof-of-concept analyses of authentic VAMS® samples (n = 20) yielded test results in the expected blood concentration range. Implementing VAMS® sampling for vitamin D-status monitoring enables a higher frequency due to a simplified, straightforward, and time-effective sample collection. VAMS® assures accurate sample volumes because of its absorptive capacities and, thus, area bias and homogeneity issues associated with conventional DBS are avoided. Regular monitoring of 25(OH)D status throughout the year supports people in high-risk groups for vitamin D-deficiency by early identifying inadequacies and, thus, preventing adverse health consequences.

Dried blood microsampling-assisted therapeutic drug monitoring of immunosuppressants: An overview

In the field of solid organ transplantation, chemotherapy and autoimmune disorders, treatment with immunosuppressant drugs requires intensive follow-up of the blood concentrations via therapeutic drug monitoring (TDM) because of their narrow therapeutic window and high intra- and inter-subject variability. This requires frequent hospital visits and venepunctures to allow the determination of these analytes, putting a high burden on the patients. In the context of patient-centric thinking, it is becoming increasingly established that at least part of these conventional blood draws could be replaced by microsampling, allowing home-sampling and increasing the quality of life for these patients. In this review we discuss the published methods - mostly using liquid chromatography coupled to tandem mass spectrometry - that have utilized (volumetric) dried blood samples as an alternative for conventional liquid whole blood for the TDM of immunosuppressant drugs. Furthermore, some pre-analytical considerations using DBS or volumetric alternatives are considered, as well as the applicability on clinical samples. The implementation status in clinical practice is also discussed, including (1) the cost-effectiveness of this approach compared to venepuncture, (2) the availability of multiplexed methods, (3) the status of harmonization and (4) patient perception. A brief perspective on potential future developments for the dried blood-based TDM of immunosuppressant drugs is provided, by considering how obstacles for the implementation of these strategies into clinical practice might be overcome.

A simple and rapid HPLC-MS/MS method for therapeutic drug monitoring of amikacin in dried matrix spots

Individualized treatment of amikacin under the guidance of therapeutic drug monitoring (TDM) is important to reduce the occurrence of toxicity and improve clinical efficacy. In the present study, we developed and validated a simple and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine the concentration of amikacin in dried matrix spots (DMS) which the matrix is serum. DMS samples were obtained by spotting volumetric blood onto Whatman 903® cards. Samples were punched into 3 mm diameter discs and extracted with 0.2 % formic acid in water. The HILIC column (2.1 mm × 100 mm, 3.0 µm) under gradient elution was applied, and the analysis time was 3 min per injection. The mass spectrometry transitions were m/z 586.3 → 163.0 for amikacin and m/z 591.4 → 163.1 for D5-amikacin. Full validation was conducted for DMS method, and the method was applied for the amikacin TDM and compared with serum method. The linearity was ranged from 0.5 to 100 mg/L. Both within-run and between-run accuracy and precision of DMS ranged from 91.8 % to 109.6 % and 3.6 % to 14.2 %, respectively. The matrix effect was 100.5 %-106.5 % of DMS method. Amikacin remained stable in DMS for at least 6 days at room temperature, 16 days at 4 °C, 86 days at -20 °C and -70 °C. A good agreement between the DMS method and serum method has been shown in Bland-Altman plots and Passing-Bablok regression. All of the results demonstrated that the DMS methods can be a favorable replacement for amikacin TDM.

Hemoglobin normalization outperforms other methods for standardizing dried blood spot metabolomics: A comparative study

Dried blood spot (DBS) metabolomics has numerous applications in newborn health screening, exposomics, and biomonitoring of environmental chemicals in pregnant women and the elderly. However, accurate metabolite quantification is hindered by several challenges: notably the "hematocrit effect" and unknown blood-spotting volumes. Different techniques have been employed to overcome these issues but there is no consensus on the optimal normalization method for DBS metabolomics, and in some cases no normalization is used. We compared five normalization methods (hemoglobin (Hb), specific gravity (SG), protein, spot weight, potassium (K+)) to unnormalized data, and assessed sex-related differences in the DBS metabolome in 21 adults (group 1, n = 10 males, n = 11 females). The performance of each normalization method was evaluated using multiple criteria: (a) reduction of intragroup variation (pooled median absolute deviation, pooled estimate of variance, pooled coefficient of variation, NMDS and principal component analysis), (b) effect on differential metabolic analysis (dendrogram, heatmap, p-value distribution), and (c) influence on classification accuracy (partial least squares discriminant analysis, sparse partial least squares discriminant analysis error rates, receiver operating curve, random forest out of bag error rate). Our results revealed that Hb normalization outperformed all the other methods based on the three criteria and 13 different parameters; the performance of Hb was further demonstrated in an independent group of DBS from 18 neonates (group 2, n = 9 males, n = 9 females). Furthermore, we showed that SG and Hb are correlated in adults (rs = 0.86, p < 0.001), and validated this relationship in an independent group of 18 neonates and infants (group 3) (rs = 0.84, p < 0.001). Using the equation, SG = -0.4814Hb2 + 2.44Hb + 0.005, SG can be used as a surrogate for normalization by Hb. This is the first comparative study to concurrently evaluate multiple normalization methods for DBS metabolomics which will serve as a robust methodological platform for future environmental epidemiological studies.

Stabilization and quantitative measurement of nicotinamide adenine dinucleotide in human whole blood using dried blood spot sampling

Nicotinamide adenine dinucleotide (NAD⁺) is a coenzyme essential for energy production. Recently, associations between NAD⁺ and aging-related diseases have been reported, and NAD⁺ precursors that increase NAD⁺ concentration in the body have been acknowledged as anti-aging supplements. However, there have been only a few studies on the link between aging or aging-related diseases and human blood NAD⁺ concentration because NAD⁺ and its precursors are unstable in blood and difficult to measure. Therefore, we aimed to construct a quantitative NAD⁺ measurement method that is simpler than the existing methods. The calibration standards of NAD⁺ showed good linearity (0.9936 to 0.9990) in the range of 0.25 to 200 μM, and the lower limit of quantification was 0.5 to 2 μM. We found that QIAcard FTA DMPK-B maintained NAD⁺ stability of 85% or more for at least 2 weeks at 4 °C and 1 week at room temperature using the dried blood spot method. Additionally, NAD⁺ stability in the blood extraction solution was more than 90% for 2 months. To our knowledge, there has been no report on a quantitative NAD⁺ measurement method in human whole blood that can be performed with as little as 5 μL of blood and can be easily implemented at both medical clinics and private homes. Our simple and convenient method has the potential to become the gold standard for NAD⁺ measurement in blood. It is expected to contribute to the acceleration of research on the correlation between aging or aging-related diseases and NAD⁺ concentration in human blood.

Internal standard metabolites for estimating origin blood volume of bloodstains

The volume of blood leaked from blood vessels may change due to evaporation of water under the natural influence of the external environment. Bloodstains and dried blood spots (DBS), which describes blood dried in the external environment, are similar in their production and their metabolite quantification profiles. In both bloodstain metabolite analysis in the forensic science field and DBS metabolite analysis in the clinical field, it is important to determine the volume of the origin blood as this affects metabolite quantification results. Therefore, the purpose of this study is to discover the internal standard metabolites that have quantitatively proportional relationships with origin blood volume and maintain constant concentrations even as the age of the bloodstain increases. As a result, the concentrations of L-isoleucine and L-phenylalanine increased in proportion to the origin blood volume of the bloodstain. The differences in concentration of L-isoleucine were significant in all volume comparisons except in the comparison between 65 μL and 85 μL. The differences in concentration of L-phenylalanine were significant in all volume comparisons except between 65 μL and 45 μL and between 65 μL and 85 μL. In addition, it was confirmed that both metabolites tended to maintain constant concentrations without being affected by bloodstain age as the volume became smaller. These internal standard metabolites can be used for estimating the origin blood volume of bloodstains during metabolite analysis of bloodstains and DBS and could provide a volume criterion for standardization when comparing metabolite quantification between samples.

Development and Validation of a Simple Method for Simultaneously Measuring the Concentrations of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Blood Spot (DBS): A Pilot Study to Obtain Candidate Conversion Equations for Predicting Plasma Concentration Based on DBS Concentration

BACKGROUND

Dried blood spots (DBSs) are promising candidates for therapeutic drug monitoring. In this study, a simple method for the simultaneous measurement of tyrosine kinase inhibitors (TKIs), including bosutinib, dasatinib, ibrutinib, imatinib, nilotinib, and ponatinib, using DBS was developed and validated. The prediction of the plasma concentration of TKIs based on the TKI concentrations in the DBS was assessed using the developed measurement method.

METHODS

DBS was prepared using venous blood on Whatman 903 cards. One whole DBS sample containing the equivalent of 40 μL of blood was used for the analysis. The analytical method was validated according to the relevant guidelines. For clinical validation, 96 clinical samples were analyzed. The regression equation was derived from a weighted Deming regression analysis, and correction factors for calculating the estimated plasma concentrations (EPCs) of the analytes from their concentrations in the DBS and the predictive performance of EPC were evaluated using 2 conversion equations.

RESULTS

This method was successfully validated. Hematocrit had no significant effect on the method's accuracy or precision. Ibrutinib was stable in the DBS for up to 8 weeks at room temperature, whereas all BCR-ABL TKIs were stable for 12 weeks. All BCR-ABL TKIs exhibited similar predictive performance for EPCs using both calculation methods. Good agreement between EPCs and the measured plasma concentrations of bosutinib, imatinib, and ponatinib was observed with both conversion equations. However, Bland-Altman analysis showed that blood sampling time affected the EPC accuracy for dasatinib and nilotinib.

CONCLUSIONS

A simple method for the simultaneous determination of BCR-ABL and Bruton TKI concentrations in DBS was developed and validated. Owing to the small clinical sample size, further clinical validation is needed to determine the predictive performance of EPCs for the 6 TKIs.

Rapid diagnosis of malaria by chemometric peak-free LIBS of trace biometals in blood

Laser Induced Breakdown Spectroscopy (LIBS) trace atomic species of diseased biofluids are subtle (peak-free) in complex spectra. Trace analysis requires a considerable push in analytical strategy. Enabling LIBS with chemometrics can help identify, extract, analyze and interpret the trace species' spectral signatures to give an insight on the biophysiological status of the bodies from which the biofluids originate. We report on the trace quantitative performance of peak-free LIBS enabled by chemometrics modelling using principal components analysis (PCA) for direct artificial neural network (ANN)-based analysis of Cu, Zn, Fe and Mg in Plasmodium falciparum-infected blood in the context of rapid spectral diagnosis of malaria utilizing the biometals as the disease biomarkers. Only one standard is required in this method-to delineate the analyte spectral regions (feature selection) and to test for accuracy. Based on the alteration of the biometal levels and their multivariate and correlational patterns in cultured blood, peripheral finger blood drops dried directly on Nucleopore membrane filters was accurately discriminated as either malaria-infected or healthy. Further the morphological evolution of Plasmodium was accurately predicted using spectral features of the biometals wherein high negative correlations between Fe (- 0.775) and Zn (- 0.881) and high positive correlations between Cu (0.892) and Mg (0.805) with parasitemia were observed. During the first 96 h of malaria infection Cu increases profoundly (from 328 to 1999 ppb) while Fe, Zn and Mg decrease (from 1206 to 674 ppb), (from 1523 to 499 ppb) and (from 23,880 to 19,573 ppb) respectively. Compared with healthy, Plasmodium falciparum-infected blood has high Cu but low levels of Fe, Zn and Mg. Cu and Zn are highly (≥ 0.9) positively correlated while Fe and Cu as well as Zn and Cu are highly (≥ 0.9) negatively correlated. Chemometric peak-free LIBS showed the potential for direct rapid malaria diagnostics in blood based on the levels, alterations and multivariate associations of the trace biometals which are used as biomarkers of the disease.

Toxicokinetics in preclinical drug development of small-molecule new chemical entities

Toxicokinetics (TK) is an integral part of nonclinical (preclinical) safety assessment of small-molecule new chemical entities in drug development. It is employed to describe the systemic exposure of a drug candidate and/or its important metabolite(s) achieved in study animals and elucidate the relationship (proportional, over-proportional, or under-proportional) between systemic exposure and dose administered and the associated differences/similarities between male and female animals along with the possible accumulation/induction. TK data and the derived parameters are employed to propose safe starting doses for clinical use of the new drug candidate through proper extrapolation of findings in study animals to humans. This review has attempted to highlight the health authority expectations on TK assessment in supporting preclinical safety profiling of new chemical entities. A robust TK assessment requires good understanding of absorption, distribution, metabolism, and elimination processes of drug candidate, adequate TK sampling (e.g., controls where relevant), implementation of fit-for-purpose bioanalytical methods (validated or scientifically qualified) along with necessary measures to prevent mis-dosing or ex vivo contamination, and establishment of stability of the drug candidate and/or its metabolite(s) in the intended species matrix to ensure the reliability of bioanalytical and TK data. The latter provides a vital link between animal experiments and human safety.

Developmental pharmacokinetics of indomethacin in preterm neonates: Severely decreased drug clearance in the first week of life

Indomethacin is used commonly in preterm neonates for the prevention of intracranial hemorrhage and closure of an abnormally open cardiac vessel. Due to biomedical advances, the infants who receive this drug in the neonatal intensive care unit setting have become younger, smaller, and less mature (more preterm) at the time of treatment. To develop a pharmacokinetics (PK) model to aid future dosing, we designed a prospective cohort study to characterize indomethacin PK in a dynamically changing patient population. A population PK base model was created using NONMEM, and a covariate model was developed in a primary development cohort and subsequently was tested for accuracy in a validation cohort. Postnatal age was a significant covariate for hepatic clearance (CL_H ) and renal clearance (CL_R ). The typical value of the total clearance (CL, the sum of CL_R and CL_H ) was 3.09 ml/h and expressed as CL/WT_median  = 3.96 ml/h/kg, where WT_median is the median body weight. The intersubject variability of CL_R and CL_H were 61% and 207%, respectively. The typical value of the volume of distribution V_p  = 366 ml (V_p /WT_median  = 470 ml/kg), and its intersubject variability was 38.8%. Half-life was 82.1 h. Compared with more mature and older preterm populations studied previously, indomethacin CL is considerably lower in this contemporary population. Model-informed precision dosing incorporating important covariates other than weight alone offers an opportunity to individualize dosing in a susceptible patient undergoing rapid change.

Rapid Detection of Amitriptyline in Dried Blood and Dried Saliva Samples with Surface-Enhanced Raman Spectroscopy

There is growing demand for rapid, nondestructive detection of trace-level bioactive molecules including medicines, toxins, biomolecules, and single cells, in a variety of disciplines. In recent years, surface-enhanced Raman scattering has been increasingly applied for such purposes, and this area of research is rapidly growing. Of particular interest is the detection of such compounds in dried saliva spots (DSS) and dried blood spots (DBS), often in medical scenarios, such as therapeutic drug monitoring (TDM) and disease diagnosis. Such samples are usually analyzed using hyphenated chromatography techniques, which are costly and time consuming. Here we present for the first time a surface-enhanced Raman spectroscopy protocol for the detection of the common antidepressant amitriptyline (AMT) on DBS and DSS using a test substrate modified with silver nanoparticles. The validated protocol is rapid and non-destructive, with a detection limit of 95 ppb, and linear range between 100 ppb and 1.75 ppm on the SERS substrate, which covers the therapeutic window of AMT in biological fluids.

Quantitation of Phenylalanine in Dried Blood Spot Using Liquid Chromatography Tandem Mass Spectrometry for Monitoring of Patients with Phenylketonuria (PKU)

Newborn screening for phenylketonuria (PKU) is performed by analysis of phenylalanine in dried blood spot (DBS). Once diagnosed by a definitive method, a patient's dietary control is performed by repeated analysis of phenylalanine in venous blood or DBS. Since venipuncture is time consuming, painful, and may often be difficult to achieve in newborns, the use of DBS for analysis of phenylalanine is becoming a preferred method for dietary monitoring of patients with PKU. Using a lancet, patients or their guardians collect finger capillary blood on an approved filter paper. Once collected, the filter paper with DBS is sent to the laboratory for phenylalanine analysis. In the laboratory, phenylalanine is extracted from the DBS using organic solvents. Here, we describe an LC-MS/MS method for the analysis of phenylalanine from DBS with an approximation to serum levels.

Thalidomide measurement in plasma and dried plasma spot by SPE combined with UHPLC-MS/MS for therapeutic drug monitoring

Aims: To validate an SPE-ultra-HPLC-MS/MS method for thalidomide (THD) measurement in dried plasma spot (DPS). Methods: Extraction included acetonitrile/water clean-up and online SPE. The LOD, LLOQ, linearity, precision, accuracy, recovery, matrix effect, process efficiency, carryover, stability, drug interference and dilution integrity were assessed. Results: The method was linear from 50 to 2000 ng/ml with a LOD of 20 ng/ml and LLOQ of 50 ng/ml. The coefficient of variation for precision was 0.4-7.9% for intra-assay and 1.3-8.9% for interassay and accuracy was 81.4-97.1%. Adequate matrix effect (100.6-107.0%), recovery (88.7-105.0%) and process efficiency (91.3-109.3%) were registered. DPS was stable for 14 days at room temperature and 45°C and for 4 months at -80°C. The method was applied to quantify THD in both wet plasma and DPS from patients with cutaneous lupus receiving THD treatment. The difference between THD wet plasma and DPS concentration was <15%. Conclusion: The method is suitable to quantify THD in DPS.

Clinical validation of a liquid chromatography-tandem mass spectrometry method for the quantification of calcineurin and mTOR inhibitors in dried matrix on paper discs

Introduction

Advances in liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) have enabled the quantification of immunosuppressants using microsampling techniques. In this context, dried matrix on paper discs (DMPD) could be a useful alternative to conventional venipuncture. Although analytical validation is necessary to establish the suitability of method performance, it is not sufficient to proceed with its implementation into routine clinical practice. Also necessary is that equivalence between sampling methods be demonstrated in a clinical validation study.

Objetives

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

Methods

According to the recommendations of international guidelines, at least 40 whole blood (WB) and DMPD paired samples for each analyte were collected by skilled technicians and analyzed using LC-MS/MS. Results were evaluated in terms of statistical agreement and bias values at medical decision points.

Results

For all analytes, Passing-Bablok regression analysis revealed that confidence intervals (CIs) for slopes and intercepts included 1 and 0, respectively. It also showed that biases at medical decision points were not clinically relevant. No statistically significant differences between DMPD and WB were found using difference plots and agreement analysis. In this regard, CIs for bias estimators included 0, and more than 95% of the results fell within the limits of agreement.

Conclusion

The feasibility of the clinical application of simultaneous quantification of tacrolimus, sirolimus, everolimus and cyclosporin A in DMPD was demonstrated. Results showed that this microsampling technique is interchangeable with conventional WB sampling when specimens are collected by trained personnel.

Fentanyl Assay Derived from Intermolecular Interaction-Enabled Small Molecule Recognition (iMSR) with Differential Impedance Analysis for Point-of-Care Testing

Rapid and effective differentiation and quantification of a small molecule drug, such as fentanyl, in bodily fluids are major challenges for diagnosis and personal medication. However, the current toxicology methods used to measure drug concentration and metabolites require laboratory-based testing, which is not an efficient or cost-effective way to treat patients in a timely manner. Here, we show an assay for monitoring fentanyl levels by combining the intermolecular interaction-enabled small molecule recognition (iMSR) with differential impedance analysis of conjugated polymers. The differential interactions with the designed anchor interface were transduced through the perturbance of the electric status of the flexible conducting polymer. This assay showed excellent fentanyl selectivity against common interferences, as well as in variable body fluids through either testing strips or skin patches. Directly using the patient blood, the sensor provided 1%-5% of the average deviation compared to the "gold" standard method LC-MS results in the medically relevant fentanyl range of 20-90 nM. The superior sensing properties, in conjunction with mechanical flexibility and compatibility, enabled point-of-care detection and provided a promising avenue for applications beyond the scope of biomarker detection.

Parallel Reaction Monitoring Mode for Atenolol Quantification in Dried Plasma Spots by Liquid Chromatography Coupled with High-Resolution Mass Spectrometry

In this study, we reported a rapid, sensitive, robust, and validated method for atenolol quantification in dried plasma spots (DPS) by liquid chromatography with high-resolution mass spectrometry (LC-HRMS) using parallel reaction monitoring mode (PRM). Aliquots of 25 µL human plasma were placed onto Whatman 903 Cards and air-dried. Disks (3.2 mm internal diameter) were punched, and a 100 µL working internal standard solution was added to each sample and then incubated on a shaker for 15 min at 40 °C, followed by rapid centrifugation (10,000× g, 10 s). The supernatant was transferred into 300 µL vials for subsequent LC–HRMS analysis. After chromatographic separation, atenolol and the internal standard were quantified in positive-ion parallel reaction monitoring mode by detection of all target product ions at 10 ppm tolerances. The total time of the analysis was 5 min. The calibration curve was linear in the range of 5–1000 ng/mL with interday and intraday precision levels and biases of <14.4%, and recovery was 62.9–81.0%. The atenolol in DPS was stable for ≥30 days at 25 and 4 °C. This fully validated method is selective and suitable for atenolol quantitation in DPS using LC–HRMS.

Multi-omics analysis from archival neonatal dried blood spots: limitations and opportunities

Newborn screening (NBS) programs operate in many countries, processing millions of dried bloodspot (DBS) samples annually. In addition to early identification of various adverse health outcomes, these samples have considerable potential as a resource for population-based research that could address key questions related to child health. The feasibility of archival DBS samples for emerging targeted and untargeted multi-omics analysis has not been previously explored in the literature. This review aims to critically evaluate the latest advances to identify opportunities and challenges of applying omics analyses to NBS cards in a research setting. Medline, Embase and PubMed databases were searched to identify studies utilizing DBS for genomic, proteomic and metabolomic assays. A total of 800 records were identified after removing duplicates, of which 23 records were included in this review. These papers consisted of one combined genomic/metabolomic, four genomic, three epigenomic, four proteomic and 11 metabolomic studies. Together they demonstrate that the increasing sensitivity of multi-omic analytical techniques makes the broad use of NBS samples achievable for large cohort studies. Maintaining the pre-analytical integrity of the DBS sample through storage at temperatures below -20 °C will enable this important resource to be fully realized in a research capacity.

Determination of clozapine and norclozapine in dried plasma spot and dried blood spot by liquid chromatography-tandem mass spectrometry

The use of alternative blood sampling strategies in clozapine (CLZ) therapeutic drug monitoring (TDM) aims to facilitate collection and improve drug therapy and adherence. This study aimed to develop and validate two methods for the determination CLZ and norclozapine (NOR) in dried blood spots (DBS) and dried plasma spots (DPS) by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The analytes were extracted from one 10 microliter volumetric DBS disc punch and from one 6 mm DPS disc punch with methyl tert-butyl ether: methanol (1:9, v/v) and injected into the HPLC-MS/MS with Atmospheric pressure chemical ionization (APCI) source. Separation was performed in a phenyl column, with mobile phase ammonium formate 1 mM pH 4.0 with methanol in gradient mode. The method was linear from 50 to 1500 ng/ml (r > 0.99), with accuracy between 98% and 105% in DBS and 91-101% in DPS, and intra- and inter-assay CV% from 5.23% to 9.35% in DBS and 2.22-11.36% in DPS for both analytes. The matrix effect was compensated by the internal standard, between - 5.1-6.89% in DBS and - 2.45-5.74% in DPS. The average extraction efficiency was 63-67% for CLZ and 58-69% for NOR with no significant impact of hematocrit (HCT). The analytes were stable in the dried matrices stored up to 42 °C for 26 days. The method was applied in the evaluation of clozapine therapy in 13 schizophrenic patients with mean serum levels of 401 ng/ml (43-914 ng/ml). Only 38% were within the therapeutic range, 46% below and 23% above. CLZ and NOR concentrations in dried samples were highly correlated to serum levels, with greater accuracy for DPS compared to DBS (97 versus 89%, and 99 versus 131%, for CLZ and NOR, respectively). Our data support the use of DBS and DPS as alternative sampling strategies in CLZ therapeutic drug monitoring, with satisfactory performance and logistics advantages.

Development of an LC-MS/MS method to simultaneously quantify therapeutic mAbs and estimate hematocrit values in dried blood spot samples

Recently, monoclonal antibody (mAb) therapy has gained increasing attention in the medical field due to its high specificity. Dried blood spots (DBSs) have been used in various clinical fields due to their unique characteristics, such as easy transportation, low invasiveness, and home sampling. However, hematocrit (HCT)-associated issues may lead to inaccurate quantification; moreover, the HCT value is required for converting the drug concentration from DBS to plasma. To simultaneously measure HCT levels and quantify mAb concentrations in DBS samples, this study used volumetrically applied 15 μL DBS, and combined protein G purification and ethanol precipitation approaches as the sample preparation method. Sixty-two clinical samples were used to investigate the HCT estimation ability by using hemoglobin (Hb) peptides. Four mAbs, bevacizumab, trastuzumab, nivolumab and tocilizumab, were selected to demonstrate our method, and pembrolizumab was used as the internal standard. The optimized method could measure four mAbs and Hb peptides simultaneously within 11 min. Moreover, a correlation study revealed that the correlation coefficient for the Hb peptides and the HCT value was larger than 0.9. The HCT estimation results revealed that for over 90% of the real DBS samples the HCT could be obtained within ±20% estimation error acceptance criteria. The method was validated in terms of accuracy and precision for the four mAbs. The developed method was further applied to simultaneously quantify mAb concentrations and estimate HCT values in six patient DBS samples to demonstrate its clinical applicability. It is believed that this newly developed method could facilitate various clinical studies and provide benefits for mAb therapies in clinical fields.

The Imprinted PARAFILM as a New Carrier Material for Dried Plasma Spots (DPSs) Utilizing Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) in Phospholipidomics

The application of desorption electrospray ionization mass spectrometry (DESI-MS) and dried blood spot (DBS) sampling has been successfully implemented several times. However, the difficulty of combining DBS sampling with DESI-MS is still the carrier material used for the blood samples. In this study, a new, easily obtained, and cost-effective carrier substrate for dried plasma spot (DPS) sampling and DESI-MS analysis and its application in phospholipidomics studies was described. First, the effects of several carrier materials, including cellulose-based materials (31 ET paper and filter paper) and non-cellulose-based materials (PARAFILM and its shape-modified material, PTFE-printed glass slide and polyvinylidene fluoride film), were tested. Second, a method combining DPS sampling with DESI-MS for phospholipidomics analysis was established, and parameters affecting compound signal intensities, such as sample volume and sprayer solvent system, were optimized. In conclusion, the total signal intensity obtained from shape-modified PARAFILM was the strongest. The suitable plasma sample volume deposited on PARAFILM carriers was 5 μl, and acetonitrile (ACN) was recommended as the optimal spray solvent for phospholipid (PL) profiling. Repeatability (87.5% of compounds with CV < 30%) and stability for data acquisition (48 h) were confirmed. Finally, the developed method was applied in phospholipidomics analysis of schistosomiasis, and a distinguished classification between control mice and infected mice was observed by using multivariate pattern recognition analysis, confirming the practical application of this new carrier material for DPS sampling and DESI-MS analysis. Compared with a previously reported method, the rapid metabolomics screening approach based on the implementation of DPS sampling coupled with the DESI-MS instrument developed in this study has increased analyte sensitivity, which may promote its further application in clinical studies.

Pharmacokinetics, oral bioavailability and metabolic analysis of solasodine in mice by dried blood spot LC-MS/MS and UHPLC-Q-Exactive MS

Solasodine, a major ingredient in Solanaceae family, has various biological functions such as inducing neurogenesis, anticonvulsant and anti-tumor. Its risk assessment has also drawn public attention. However, little is known about its oral bioavailability and metabolic process. In this study, an liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of solasodine in mice dried blood spot (DBS) samples. To block nonspecific adsorption, DBS samples were pretreated with bovine serum albumin (BSA) and then extracted with ethyl acetate. This method was applied to a pharmacokinetic and bioavailability study of solasodine. The absolute bioavailability was only 1.28%. Thereafter, its metabolites in mice were characterized using an ultra-performance liquid chromatography Q-Exactive high-resolution mass spectrometer (UHPLC-QE-HRMS). Several isomeric metabolites were well separated and differentiated using their retention time, fragmentation pathways and correspondingly fragmentation rules of solasodine. As a result, 21 metabolites were characterized including 16 phase I and 5 phase II metabolites. The proposed metabolic pathways showed that solasodine mainly experienced oxidation, dehydration, dehydrogenation and sulfation. These results could help us to better understand the efficacy and safety of solasodine.

Data-Independent Acquisition Mass Spectrometry-Based Deep Proteome Analysis for Hydrophobic Proteins from Dried Blood Spots Enriched by Sodium Carbonate Precipitation

Dried blood spots (DBS) are widely used for screening molecular profiles, including enzymatic activity. However, hydrophilic proteins present in large amounts in blood inhibit detection of other proteins in DBS by liquid chromatography-mass spectrometry (LC-MS/MS) without preenrichment. Sodium carbonate precipitation (SCP) can concentrate hydrophobic proteins from DBS and effectively remove soluble hydrophilic proteins. Furthermore, SCP combination with data-independent acquisition (DIA) for quantitative LC-MS/MS enhanced the proteome analysis sensitivity and quantification limits. In this protocol, we have described in detail a simple preenrichment method using SCP and a deep proteome analysis method for LC-MS/MS data using DIA.

Quantitative analysis of galactose using LDI-TOF MS based on a TiO2 nanowire chip

A novel method for quantifying galactose was developed to serve as a newborn screening test for galactosemia using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a TiO2 nanowire chip. Herein, phosphate citrate buffer, serum, and dried blood spot (DBS) were employed for the quantitative analysis of galactose. To quantitatively analyze galactose, its reduction potential was used to oxidize o-phenylene diamine (OPD) into 2,3-diaminophenazine (DA), which were both detected using LDI-TOF MS with a TiO2 nanowire chip according to the concentration of galactose. The reproducibility and the interference of glucose were determined to demonstrate the applicability of this method. Moreover, mixtures of galactose, phenylalanine, and 17 α-OHP were analyzed to determine the interference induced by other biomarkers of metabolic disorders. The OPD oxidation of galactose was found to be selectively achieved under high-glucose conditions, similar to human blood, thereby showing good reproducibility. The intensities of the mass peaks of OPD and DA based on LDI-TOF MS with a TiO2 nanowire chip were linearly correlated in the galactose concentration range of 57.2–220.0 μg/mL (r2 = 0.999 and 0.950, respectively) for serum samples and 52.5–220.0 μg/mL (r2 = 0.993 and 0.985, respectively) for DBS after methanol precipitation/extraction. The enzyme immunoassay and LDI-TOF MS analysis results were statistically analyzed, and a mixture of phenylalanine, 17 α-OHP, and galactose was simultaneously investigated quantitatively at the cutoff level.

A simplified method for bortezomib determination using dried blood spots in combination with liquid chromatography/tandem mass spectrometry

Bortezomib, a proteinase inhibitor currently used to treat multiple myeloma and mantle cell lymphoma, has a high incidence of adverse reactions and large inter-individual differences in plasma concentrations. A simple, validated LC-MS/MS method for the quantitative analysis of bortezomib in dried blood spot (DBS) samples was developed to provide support for determining the effective concentration range of bortezomib for clinical use. Fifty (i50) μL of spiked blood were added onto Whatman protein saver cards to prepare the DBS samples. Circular cards of 6 mm diameter were punched, extracted by methanol containing the internal standard (apatinib), and injected into the LC-MS/MS system. The method validation included selectivity, linearity, accuracy and precision, stability, matrix effect, recovery and hematocrit. The calibration curve showed correlation coefficient values higher than 0.999 in the range of 0.2 - 20.0 ng/mL for bortezomib. The acceptance criteria of accuracy (relative error < 12.5%) and precision (coefficient of variation < 10.7%) were met in all cases. The matrix effect was<13.2%, and the recovery was between 87.3 and 100.2%. DBS samples were shown to be stable when stored in cold conditions or at room temperature. Different hematocrit values did not significantly affect the accuracy of the measured concentrations. And there are no significant differences between bortezomib concentrations in DBS samples and plasma samples. This new method was successfully used for clinical concentration determinations of bortezomib and can be applied in future therapeutic drug monitoring and pharmacokinetic studies of bortezomib especially in pediatric patients.

Cell Analysis from Dried Blood Spots: New Opportunities in Immunology, Hematology, and Infectious Diseases

Blood cell analysis is a major pillar of biomedical research and healthcare. These analyses are performed in central laboratories. Rapid shipment from collection site to the central laboratories is currently needed because cells and biomarkers degrade rapidly. The dried blood spot from a fingerstick allows the preservation of cellular molecules for months but entire cells are never recovered. Here leucocyte elution is optimized from dried blood spots. Flow cytometry and mRNA expression profiling are used to analyze the recovered cells. 50-70% of the leucocytes that are dried on a polyester solid support via elution after shaking the support with buffer are recovered. While red blood cells lyse upon drying, it is found that the majority of leucocytes are preserved. Leucocytes have an altered structure that is improved by adding fixative in the elution buffer. Leucocytes are permeabilized, allowing an easy staining of all cellular compartments. Common immunophenotyping and mRNAs are preserved. The ability of a new biomarker (CD169) to discriminate between patients with and without Severe Acute Respiratory Syndrome induced by Coronavirus 2 (SARS-CoV-2) infections is also preserved. Leucocytes from blood can be dried, shipped, and/or stored for at least 1 month, then recovered for a wide variety of analyses, potentially facilitating biomedical applications worldwide.