Evaluation of swabs from 15 commercially available oral fluid sample collection devices for the analysis of commonly abused substances: doping agents and drugs of abuse

Quantification of prohibited substances and endogenous corticosteroids in saliva using traditional, alternative microextraction-based, and novel 3D printed sample-preparation methods coupled with LC-MS

Oral fluid has gained significant interest as an alternative matrix for drug testing due to its easy and non-invasive collection. Despite these advantages, achieving suitably low limits of detection remains a clear challenge in the use of oral fluids for drug screening. In this study, we demonstrate that the application of commercially available SPME fibers followed by liquid chromatography tandem mass spectrometry can enable the comprehensive detection and confirmation of drugs in oral fluid samples. To this end, we develop and test a sample-preparation protocol for a panel of 46 drugs covering the most popular drugs of abuse and doping agents available worldwide. Human saliva samples were collected using a Salivette® device (CE IVD certified) and sampled using SPME devices coated with a C18 extraction phase. The proposed protocol was validated with respect to its lower limits of quantification (LLOQ), linearity, matrix effects, precision, and extraction recovery. Linearity was confirmed for all compounds (R2 > 0.97), except for testosterone (R2 = 0.953) and metandrostenolon (R2 = 0.958). Furthermore, 4 compounds suffered from matrix effects, with less than 10 % deviation from acceptance criteria. After analytical validation, saliva samples from volunteers were analyzed to determine free concentrations of cortisol at different times after awaking. Finally, a 3D-printed prototype device was designed and successfully applied to extract small molecules, thus demonstrating a new modern low-cost approach for bioanalysis.

Mixed-mode cationic exchange sorptive tapes combined with direct infusion mass spectrometry for determining opioids in saliva samples

This article describes the synthesis of mixed-mode cationic exchange (MCX) tapes as sorptive phases in bioanalysis, and it faces the determination of methadone and tramadol in saliva as the model analytical problem. The tapes are synthesized using aluminum foil as substrate, which is subsequently covered with double-sided adhesive tape where the MCX particles (ca. 1.4 ± 0.2 mg) finally adhere. MCX particles allow the extraction of the analytes at the physiological pH, where both drugs are positively charged, minimizing the potential co-extraction of endogenous matrix compounds. The extraction conditions were studied considering the main variables (e.g. ionic strength, extraction time, sample dilution). Under the optimum conditions and using direct infusion mass spectrometry as the instrumental technique, detection limits as low as 3.3 μg·L^-1 were obtained. The precision calculated at three different levels, and expressed as relative standard deviation, was better than 3.8%. The accuracy, expressed as relative recoveries, ranged from 83 to 113%. The method was finally applied to determine tramadol in saliva samples from patients under medical treatment. This approach opens the door to easily preparing sorptive tapes based on commercial (or ad-hoc synthesized) sorbent particles.

Innovative, simple, and green: A sample preparation method based on 3D printed polymers

The present study evaluates the capability of fifteen 3D printed thermoplastic polymers as novel stationary phases for the extraction of forty-three physicochemically diverse analytes from fortified human oral fluid samples. Prototype extraction devices were prepared in 96-well plate-compatible format using fused deposition modeling 3D printer. The sample preparation was performed with 5-step protocol utilizing 96-well plates and semiautomated benchtop shaker. All resulting extracts were analyzed via high-performance liquid chromatography (operated in reversed-phase gradient elution mode) and tandem mass spectrometry (with electrospray ionization and triple quadrupole mass spectrometer). Exceptionally favorable results were observed for three polymer types: polyamide 6 (reinforced with 15% carbon fiber), LAYFOMM-60 (polyurethane with water-soluble polyvinyl alcohol), and S-FLEX 90A (thermoplastic polyurethane). Furthermore, this study also introduces an automated and repeatable 3D printing method for the fast fabrication of high-throughput, and highly selective sample preparation devices, most of which are ready-to-use without any additional processing or chemical functionalization. As such, the proposed printing method represents a significant step towards the introduction of novel polymeric stationary phases for analytical sample preparation, thus providing laboratory personnel with a method that is safer and more convenient, while minimizing negative environmental impacts.

Saliva as Blood Alternative in Therapeutic Monitoring of Teriflunomide-Development and Validation of the Novel Analytical Method

Therapeutic drug monitoring (TDM) is extremely helpful in individualizing dosage regimen of drugs with narrow therapeutic ranges. It may also be beneficial in the case of drugs characterized by serious side effects and marked interpatient pharmacokinetic variability observed with leflunomide and its biologically active metabolite, teriflunomide. One of the most popular matrices used for TDM is blood. A more readily accessible body fluid is saliva, which can be collected in a much safer way comparing to blood. This makes it especially advantageous alternative to blood during life-threatening SARS-CoV-2 pandemic. However, drug’s saliva concentration is not always a good representation of its blood concentration. The aim of this study was to verify whether saliva can be used in TDM of teriflunomide. We also developed and validated the first reliable and robust LC-MS/MS method for quantification of teriflunomide in saliva. Additionally, the effect of salivary flow and swab absorptive material from the collector device on teriflunomide concentration in saliva was evaluated. Good linear correlation was obtained between the concentration of teriflunomide in plasma and resting saliva (p < 0.000016, r = 0.88), and even better between plasma and the stimulated saliva concentrations (p < 0.000001, r = 0.95) confirming the effectiveness of this non-invasive method of teriflunomide’s TDM. The analyzed validation criteria were fulfilled. No significant influence of salivary flow (p = 0.198) or type of swab in the Salivette device on saliva’s teriflunomide concentration was detected. However, to reduce variability the use of stimulated saliva and synthetic swabs is advised.

Polydopamine inner wall-coated hypodermic needle as microextraction device and electrospray emitter for the direct analysis of illicit drugs in oral fluid by ambient mass spectrometry

In this article, polydopamine inner wall-coated hypodermic needles (PDA-HNs) are evaluated as both microextraction devices and electrospray ionization (ESI) emitters for determining selected illicit drugs (methamphetamine, cocaine, and methadone) in oral fluid samples. The PDA film, located in the inner wall of the needle, allows the extraction of the analytes at alkaline pH, where their hydrophobic character is promoted. The extracted analytes are finally eluted in a methanol/formic acid mixture that also acts as ESI solution. For this purpose, a dedicated interface based on the connection of a PEEK tube with the needle hub is proposed. This assembly allows delivering the ESI solution by the infusion syringe pump of the mass spectrometer, providing an efficient ESI on the tip of the needle. The double use of the PDA-HNs as microextraction devices and ESI emitters permits the determination of the target analytes with limits of detection and precision (expressed as relative standard deviation) values better than 2.4 μg/L and 17.6%, respectively. The accuracy was evaluated by analyzing independent spiked oral fluid samples, obtaining good results.

Potential of hydrophobic paper-based sorptive phase prepared by in-situ thermal imidization for the extraction of methadone from oral fluid samples

Paper-based sorptive phases (PSPs) are functional planar materials with a demonstrated potential in analytical sample preparation. This article describes the synthesis of a polyimide coated paper by an in-situ imidization at a high temperature. Polyimides (PI) are synthesized in two subsequent steps where a hydrophilic polymer, in this case, poly(amic acid) (PAA), is formed as an intermediate product. PAA is finally transformed into hydrophobic PI by thermal curing at 180 °C. The synthesis of PI-paper takes advantage of this two-step procedure. In the first stage, a segment of filter paper is immersed into an aqueous PAA solution. After the solvent evaporation, the paper is heated at 180 °C for 1 h inducing the formation of the hydrophobic PI over the cellulose fibers. Infrared spectroscopy has been used to characterize the synthesized materials by defining a coverage factor F. The hydrophobicity of the materials has been studied using an aqueous methylene blue solution as a marker. To fully demonstrate the usefulness of the material in the sample preparation field, the extraction of methadone from oral fluid (OF) samples has been considered as a model analytical problem. The main variables affecting the synthesis (PAA concentration on the precursor solution and number of dips) and the extraction (elution and extraction times) have been fully evaluated. Working under the optimum conditions, a limit of quantification of 9 µg/L, intraday and interday precision better than 14.6%, and accuracy in the range of 87-108% were obtained.

Pre-cleaned bare wooden toothpicks for the determination of drugs in oral fluid by mass spectrometry

This article deepens the potential of pre-cleaned bare wooden toothpicks (pb-WTs) for extracting drugs (antidepressants and acetaminophen) from oral fluid samples. The leaching of the intrinsic compounds from the wood matrix is identified as the main challenge for the final determination of the targets, even when a very selective instrumental technique, such as mass spectrometry, is employed. The pre-cleaning of the WTs is proposed for improving the analytical performance. The number of cleaning cycles depends on the injection mode (direct infusion or chromatography) into the mass spectrometer. The different variables affecting the extraction of selected antidepressant drugs were studied in detail, and the optimum procedure was validated using the two mentioned injection modes. The limits of detection were in the ranges 0.1–0.5 ng/mL and 0.1–0.3 ng/mL for direct infusion and liquid chromatography, respectively. The intra-day precision (expressed as relative standard deviation) was better than 12.1% and 8.6%, for direct infusion and liquid chromatography, respectively. Single-blind samples were used to study the applicability of the method. Finally, as a proof-of-concept, the potential of pb-WTs for in vivo sampling was outlined.

Polyamide Noncoated Device for Adsorption-Based Microextraction and Novel 3D Printed Thin-Film Microextraction Supports

Polyamide noncoated device for adsorption-based microextraction (PANDA microextraction) is a brand new, easy to prepare, environmentally friendly, inexpensive, and efficient sample preparation method created entirely with the use of 3D printing. The proposed method is based on the extractive proprieties of the unmodified polyamide and carbon fiber blends and is compared with the highly selective thin-film microextraction (TFME). In addition, 3D printing was used to simplify the process of TFME. Prototype sample preparation devices were evaluated by the extraction of oral fluid spiked with 38 small molecules with diverse chemical natures, such as lipophilicity in the log P range of 0.2–7.2. The samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. The results indicate that chemically and thermally resistant 3D printed supports can be successfully used as a cost-saving, environmentally friendly solution for the preparation of TFME devices, alternative to the conventional metal supports, with only marginal differences in the extraction yield (mean = 4.0%, median = 1.8%, range = 0.0–22.3%, n = 38). Even more remarkably, in some cases, the newly proposed PANDA microextraction method exceeded the reference TFME in terms of the extraction efficacy and offered excellent sample cleanup as favorable matrix effects were observed (mean = −8.5%, median = 7.5%, range = −34.7–20.0%, n = 20). This innovative approach paves the road to the simplified sample preparation with the use of emerging extractive 3D printing polymers.

Modifying current thin-film microextraction (TFME) solutions for analyzing prohibited substances: Evaluating new coatings using liquid chromatography

For identifying and quantifying prohibited substances, solid-phase microextraction (SPME) continues to arouse interest as a sample preparation method. However, the practical implementation of this method in routine laboratory testing is currently hindered by the limited number of coatings compatible with the ubiquitous high-performance liquid chromatography (HPLC) systems. Only octadecyl (C₁₈) and polydimethylsiloxane/divinylbenzene ligands are currently marketed for this purpose. To address this situation, the present study evaluated 12 HPLC-compatible coatings, including several chemistries not currently used in this application. The stationary phases of SPME devices in the geometry of thin film-coated blades were prepared by applying silica particles bonded with various functional ligands (C₁₈, octyl, phenyl-hexyl, 3-cyanopropyl, benzenesulfonic acid, and selected combinations of these), as well as unbonded silica, to a metal support. Most of these chemistries have not been previously used as microextraction coatings. The 48 most commonly misused substances were selected to assess the extraction efficacy of each coating, and eight desorption solvent compositions were used to optimize the desorption conditions. All samples were analyzed using an HPLC system coupled with triple quadrupole tandem mass spectrometry. This evaluation enables selection of the best-performing coatings for quantifying prohibited substances and investigates the relationship between extraction efficacy and the physicochemical characteristics of the analytes. Ultimately, using the most suitable coatings is essential for trace-level analysis of chemically diverse prohibited substances.

•

12 HPLC-compatible TFME coatings were evaluated for extraction of small molecules.

•

8 desorption solvent compositions were used to optimize the desorption conditions.

•

48 prohibited substances (drugs of abuse and doping agents) were used as analytes.

•

A mixed coating comprising octyl/3-cyanopropyl (50/50) provided the best results.

Overview, consequences, and strategies for overcoming matrix effects in LC-MS analysis: a critical review

The high-performance liquid chromatography-mass spectrometry (LC-MS) technique is widely applied to routine analysis in many matrices. Despite the enormous application of LC/MS, this technique is subjected to drawbacks called matrix effects (MEs) that could lead to ion suppression or ion enhancement. This phenomenon can exert a deleterious impact on the ionization efficacy of an analyte and subsequently on the important method performance parameters. LC-MS susceptibility to MEs is the main challenge of this technique in the analysis of complex matrices such as biological and food samples. Nowadays, the assessment, estimation, and overcoming of the MEs before developing a method is mandatory in any analysis. Two main approaches including the post-column infusion and post-extraction spike are proposed to determine the degree of MEs. Different strategies can be adopted to reduce or eliminate MEs depending on the complexity of the matrix. This could be done by improving extraction and clean-up methods, changing the type of ionization employed, optimization of liquid chromatography conditions, and using corrective calibration methods. This review article will provide an overview of the MEs as the Achilles heel of the LC-MS technique, the causes of ME occurrence, their consequences, and systemic approaches towards overcoming MEs during LC-MS-based multi-analyte procedures.

Development of robust isothermal RNA amplification assay for lab-free testing of RNA viruses

Simple tests of infectiousness that return results in minutes and directly from samples even with low viral loads could be a potential game-changer in the fight against COVID-19. Here, we describe an improved isothermal nucleic acid amplification assay, termed the RICCA (RNA Isothermal Co-assisted and Coupled Amplification) reaction, that consists of a simple one-pot format of ‘sample-in and result-out’ with a primary focus on the detection of low copy numbers of RNA virus directly from saliva without the need for laboratory processing. We demonstrate our assay by detecting 16S rRNA directly from E. coli cells with a sensitivity as low as 8 CFU/μL and RNA fragments from a synthetic template of SARS-CoV-2 with a sensitivity as low as 1740 copies/μL. We further demonstrate the applicability of our assay for real-time testing at the point of care by designing a closed format for paper-based lateral flow assay and detecting heat-inactivated SARS-COV-2 virus in human saliva at concentrations ranging from 28,000 to 2.8 copies/μL with a total assay time of 15–30 min.

Benefits of Innovative and Fully Water-Compatible Stationary Phases of Thin-Film Microextraction (TFME) Blades

Octadecyl (C₁₈) groups are arguably the most popular ligands used for preparation of solid phase microextraction (SPME) devices. However, conventional C₁₈-bonded silica particles are not fully compatible with the nearly 100% aqueous composition of typical biological samples (e.g., plasma, saliva, or urine). This study presents the first evaluation of thin-film SPME devices coated with special water-compatible C₁₈-bonded particles. Device performance was assessed by extracting a mixture of 30 model compounds that exhibited various chemical structures and properties, such as hydrophobicity. Additionally, nine unique compositions of desorption solvents were tested. Thin-film SPME devices coated with C₁₈-bonded silica particles with polar end-capping groups (10 µm) were compared with conventional trimethylsilane end-capped C₁₈-bonded silica particles of various sizes (5, 10, and 45 µm) and characteristics. Polar end-capped particles provided the best extraction efficacy and were characterized by the strongest correlations between the efficacy of the extraction process and the hydrophobicity of the analytes. The results suggest that the original features of octadecyl ligands are best preserved in aqueous conditions by polar end-capped particles, unlike with conventional trimethylsilane end-capped particles that are currently used to prepare SPME devices. The benefits associated with this improved type of coating encourage further implementation of microextractraction as greener alternative to the traditional sample preparation methods.

Polydopamine coated hypodermic needles as a microextraction device for the determination of tricyclic antidepressants in oral fluid by direct infusion MS/MS

In-needle microextraction consists of the confinement of the sorbent, by coating or packing, inside a metallic needle. The size of the needles reduces the eluent requirements providing an efficient preconcentration of the analytes. In this work, hypodermic needles coated with polydopamine (PDA) are presented as microextraction devices to isolate six tricyclic antidepressants from oral fluid samples. The coating consists of the in-surface polymerization of dopamine at pH 8.5 and mild conditions (room temperature and water as solvent). The PDA coating over the stainless-steel surface confers the needles with a high extraction ability towards the target analytes. After the extraction, the eluates were analyzed by direct infusion MS spectrometry, working in multiple reaction monitoring (MRM) mode, which provided a sample throughput of 30 samples per hour. The variables affecting the synthesis (number of coating cycles, the concentration of dopamine, and needle surface pre-treatment) and the extraction (sample salinity, sample loading cycles, and the number of elution strokes) were studied in depth. Under the optimum conditions, a matrix-matched calibration model was built. The limits of quantification are between 2 and 5 ng mL⁻¹ with linear ranges up to 1000 ng mL⁻¹ for all analytes. The precision, expressed as relative standard deviation (RSD), is better than 10% for all analytes. Accuracy was calculated as recovery, and the obtained values are between 84% and 107%. A single-blind assay was also performed to evaluate the suitability of the method for real application.

Hypodermic needles coated with polydopamine for the extraction of antidepressants.