Mass imaging of ketamine in a single scalp hair by MALDI-FTMS

Applications of MALDI mass spectrometry in forensic science

Forensic chemistry literature has grown exponentially, with many analytical techniques being used to provide valuable information to help solve criminal cases. Among them, matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), particularly MALDI MS imaging (MALDI MSI), has shown much potential in forensic applications. Due to its high specificity, MALDI MSI can analyze a wide variety of compounds in complex samples without extensive sample preparation, providing chemical profiles and spatial distributions of given analyte(s). This review introduces MALDI MS(I) to forensic scientists with a focus on its basic principles and the applications of MALDI MS(I) to the analysis of fingerprints, drugs of abuse, and their metabolites in hair, medicine samples, animal tissues, and inks in documents.

Estimation of the time of zolpidem intake and differentiation between consumption and external contamination using MALDI-MSI for investigations on single hair samples

Estimation of drug ingestion time (event time) and distinguishing between drug ingestion and external contamination are important for interpreting hair analysis results in forensics practice. Here, we present a matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) method for in situ analysis of intact hair. We applied a longitudinal cutting method for a single hair to analysis authentic hair samples from a victim of a drug-facilitated sexual assault (DFSA) case and zolpidem-soaked hair. MALDI-MSI showed that zolpidem-positive segments distributed at 4-6 mm or 6-8 mm from the root in three single hairs of a DFSA victim collected 25 days after the event, at concentrations ranging from 0.1 to 5.7 pg mm-1, in agreement with the results from segmental analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS). The estimation of drug intake time was about 20-30 days before sampling, which was consistent with the known time of drug intake. This MALDI-MS method allows imaging analysis of trace substances in a single hair and can realize the intuitive reflection of drug taking time. In addition, zolpidem applied by soaking was mainly distributed on both sides of the longitudinal hair shaft, whereas ingested zolpidem was found only in the middle of the hair shaft of the DFSA victim. The MALDI-MS images of unwashed and washed hair suggested that the amount of externally applied drug was decreased by washing, it was still present on surface layer (cuticle) sides although. Visualization using MALDI-MSI could therefore distinguish between drug ingestion and contamination by reflecting the distribution and deposition site of the drug in hair.

Morphological and chemical profiling for forensic hair examination: A review of quantitative methods

Within the past two decades, there have been many studies for quantitative analysis on human hair samples. Microscopical and chemical analysis techniques have been used to analyze various aspects of hair regarding biological, chemical, anthropological, cosmetic, and forensic applications. Studies have attempted to develop quantification methods to increase the evidentiary value of hair in forensic casework. The literature reviewed in this paper provides some of the current techniques used for forensic examinations and quantitative methods. Although microscopical analysis has been scrutinized in the past, using chemical and microscopical techniques can provide a myriad of information. The extraction of DNA from hair provides high-value evidence; however, it may not be readily available and may yield inconclusive results. Hair analysis can be used for many forensic applications such as comparison, toxicology, and exposure analysis. In this article, we will review published research material regarding chemical and microscopical techniques for human hair analysis. Aspects considered for this review were the sample size requirement for analysis and the destructive nature of the instrumental method. This review will focus on both macro and micro quantitative methods for human hair analysis.

Matrix-assisted laser-desorption/ionization-mass spectrometric imaging of psilocybin and its analogues in psychedelic mushrooms using a cesium chloride-coated target plate

Fungi with hallucinogenic properties and neurotoxicity have been listed as prohibited drugs in recent years, but there is a lack of in situ quantification of psilocybin and analogues in these samples to avoid the decomposition of these psychoactive tryptamines in time-consuming sample preparation. In this study, matrix-assisted laser-desorption/ionization (MALDI)-Fourier transform ion cyclotron resonance (FT ICR) mass spectrometric imaging (MSI) was used to analyze the distribution of psilocybin and its analogues in hallucinogenic Psilocybe mushrooms. A cesium chloride (CsCl)-coated target plate was prepared to improve the detection sensitivity and reduce the interference of other compounds or decomposition products with very similar m/z values in MALDI-FT ICR MS analysis. Psilocybin and other tryptamines with structurally similar compounds, including psilocin, baeocystin, tryptophan, tryptamine, and aeruginascin, were identified and imaged in the psilocybe tissue section; the semiquantitative analysis of the distribution of psilocybin was also investigated using a homemade 75-well CsCl-coated plate; and the target plate can be placed on the mass spectrometry target carrier along with the indium-tin oxide (ITO) conductive slide, which can simultaneously carry out matrix vapor deposition, thus ensuring the parallelism between the standards and samples in the pretreatment experiment and MSI. The contents of psilocybin and its analogues in the psilocybe tissue section can be evaluated from the color changes corresponding to different concentration standard curves. Furthermore, a comprehensive comparison between MALDI-FT ICR MS and ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q/TOF MS) analysis was performed for quantification and validation. This study reduces the decomposition in time-consuming sample pretreatment and provides a powerful tool for drug abuse control and forensic analysis.

Micro-segmental hair analysis: detailed procedures and applications in forensic toxicology

PURPOSE

Since the 1980s, the detection sensitivity of mass spectrometers has increased by improving the analysis of drugs in hair. Accordingly, the number of hair strands required for the analysis has decreased. The length of the hair segment used in the analysis has also shortened. In 2016, micro-segmental hair analysis (MSA), which cuts a single hair strand at a 0.4-mm interval corresponding to a hair growth length of approximately one day, was developed. The advantage of MSA is that the analytical results provide powerful evidence of drug use in the investigation of drug-related crimes and detailed information about the mechanism of drug uptake into hair. This review article focuses on the MSA technique and its applications in forensic toxicology.

METHODS

Multiple databases, such as SciFinder, PubMed, and Google, were utilized to collect relevant reports referring to MSA and drug analysis in hair. The experiences of our research group on the MSA were also included in this review.

RESULTS

The analytical results provide a detailed drug distribution profile in a hair strand, which is useful for examining the mechanism of drug uptake into hair in detail. Additionally, the analytical method has been used for various scenarios in forensic toxicology, such as the estimation of days of drug consumption and death.

CONCLUSIONS

The detailed procedures are summarized so that beginners can use the analytical method in their laboratories. Moreover, some application examples are presented, and the limitations of the current analytical method and future perspectives are described.

Cell and Tissue Imaging by TOF-SIMS and MALDI-TOF: An Overview for Biological and Pharmaceutical Analysis

The potential of mass spectrometry imaging (MSI) has been demonstrated in cell and tissue research since 1970. MSI can reveal the spatial distribution of a wide range of atomic and molecular ions detected from biological sample surfaces, it is a powerful and valuable technique used to monitor and detect diverse chemical and biological compounds, such as drugs, lipids, proteins, and DNA. MSI techniques, notably matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) and time of flight secondary ion mass spectrometry (TOF-SIMS), witnessed a dramatic upsurge in studying and investigating biological samples especially, cells and tissue sections. This advancement is attributed to the submicron lateral resolution, the high sensitivity, the good precision, and the accurate chemical specificity, which make these techniques suitable for decoding and understanding complex mechanisms of certain diseases, as well as monitoring the spatial distribution of specific elements, and compounds. While the application of both techniques for the analysis of cells and tissues is thoroughly discussed, a briefing of MALDI-TOF and TOF-SIMS basis and the adequate sampling before analysis are briefly covered. The importance of MALDI-TOF and TOF-SIMS as diagnostic tools and robust analytical techniques in the medicinal, pharmaceutical, and toxicology fields is highlighted through representative published studies.

Mapping the Chemistry of Hair Strands by Mass Spectrometry Imaging-A Review

Hair can record chemical information reflecting our living conditions, and, therefore, strands of hair have become a potent analytical target within the biological and forensic sciences. While early efforts focused on analyzing complete hair strands in bulk, high spatial resolution mass spectrometry imaging (MSI) has recently come to the forefront of chemical hair-strand analysis. MSI techniques offer a localized analysis, requiring fewer de-contamination procedures per default and making it possible to map the distribution of analytes on and within individual hair strands. Applying the techniques to hair samples has proven particularly useful in investigations quantifying the exposure to, and uptake of, toxins or drugs. Overall, MSI, combined with optimized sample preparation protocols, has improved precision and accuracy for identifying several elemental and molecular species in single strands of hair. Here, we review different sample preparation protocols and use cases with a view to make the methodology more accessible to researchers outside of the field of forensic science. We conclude that—although some challenges remain, including contamination issues and matrix effects—MSI offers unique opportunities for obtaining highly resolved spatial information of several compounds simultaneously across hair surfaces.

Current status of hair analysis in forensic toxicology in China

Hair analysis has been mainly used to document drug use history in abusers, drug-facilitated crime cases, doping control analysis and postmortem toxicology in the fields of forensic toxicology, clinical toxicology, and doping control. Hair analysis has also gained more attention in the last 30 years in China. Relevant technology has been promoted as more research has appeared concerning hair analysis, and consensus has been sought among forensic toxicologists regarding aspects such as hair decontamination treatment, detection of abused substances in hair, segmental hair analysis and interpretation of analytical results. However, there are still some limitations in the estimation of drug intake time and frequency by segmental hair analysis due to the different growth cycles evident within a bundle of hairs, the drug incorporation mechanism and sampling errors. Microsampling and imaging mass spectrometry (IMS) technology based on a single hair may be a good choice to estimate drug intake time more accurately. Analysis of hair root samples may also be used to document acute poisoning in postmortem toxicology, and the analysis of the hair shaft can document long-term use of drugs depending on the length of the hair being evaluated.

Ocfentanil testing in hair from a fatality case: Comparative analysis of a lock of hair versus a single hair fiber

In clinical and forensic toxicology, hair analysis offers a larger window for detecting drug exposure than blood or urine. Drug measurements are generally carried out using a segmented lock of hair, but few articles report the use of a single hair to document drug exposure. Nevertheless, single hair analysis can be very useful, particularly if only small amounts of biological matrices are available. More data on analyzing new synthetic opioids (NSOs) in hair are needed to help interpretation in future cases. In this study, segmental single hair analysis is compared with segmental hair lock analysis to document an ocfentanil-related death. The hair lock and single hair analyses were performed using the LC-MS/MS method after decontamination and incubation. Ocfentanil (OcF) concentrations ranged from 42 to 150 pg/mg in the segmented hair lock, depending on the segments. The hair lock and single hair analyses showed similar results: the highest concentrations were measured in the first two centimeters and decreased from root to tip. The similar profiles obtained from both the lock of hair and the single hair demonstrate the relevance of single hair analysis in cases where very few data are available. This article describes OcF concentrations in an authentic hair sample after a documented intake of this molecule in a fatality.

Single hair analysis: Validation of a screening method for over 150 analytes and application on documented single-dose cases

Hair is the matrix of choice in forensic toxicology when retrospective analysis is needed. Nonetheless, due to misalignment, different growth stages and segmentation lengths of 0.5-1 cm, resolution of time is limited. By segmental analysis of single hairs, most of these factors can be compensated and resolution of time is enhanced. A method for manually segmenting single hairs in 2-mm sections and screening for 156 analytes by liquid chromatography coupled to tandem mass spectrometry has been developed and validated. The method was applied to 15 single-dose cases concerning different pharmaceuticals by analyzing 10 hairs each, sampled 1 and 2 months after ingestion in most cases. The validation showed a lower limit of quantification of ≤1.25 pg/segment for ~90% of analytes and good accuracy. Many substances could be detected in the presented cases, whereas detection of benzodiazepines and low dosed opioids remains challenging. In positive cases, characteristic peak-shaped concentration profiles across the hairs were obtained. The segment with most coinciding peak maxima can be allocated to the time of ingestion. A method for the determination of individual hair growth rate was applied and revealed a gap between expected and actual position of peak maxima. Additionally, different localization of simultaneously administered substances was observed. These findings were tried to be explained by different routes of incorporation and may contribute to current knowledge. The presented method may directly be applied to similar questions in hair analysis, and the findings are considered important for interpreting further results in single hair analysis.

MASS SPECTROMETRY ANALYSIS OF DRUGS OF ABUSE: CHALLENGES AND EMERGING STRATEGIES

Mass spectrometry has been the "gold standard" for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography-mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future. © 2020 Periodicals, Inc. Mass Spec Rev.

Variability associated with interpreting drugs within forensic hair analysis: A three-stage interpretation

Hair analysis is capable of determining both an individual's long-term drug history and a single exposure to a drug, which can be particularly important for corroborating incidents of drug-facilitated crimes. As a source of forensic evidence that may be used in a court of law, it must be credible, impartial and reliable, yet the pathways of drug and metabolite entry into hair are still uncertain. Many variables may influence drug analysis results, most of which are outside of the control of an analyst. An individual's pharmacokinetic and metabolic responses, hair growth rates, drug incorporation routes, axial migration, ethnicity, age and gender, for example, all display interpersonal variability. At present there is little standardization of the analytical processes involved with hair analysis. Both false positives and negative results for drugs are frequently encountered, regardless of whether a person has consumed a drug or not. In this regard, we have categorized these variables and proposed a three-stage analytical approach to facilitate forensic toxicologists, hair analysis experts, judiciaries and service users in the analytical and interpretation process.

Protein identification strategies in MALDI imaging mass spectrometry: a brief review

Matrix assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) is a powerful technology used to investigate the spatial distributions of thousands of molecules throughout a tissue section from a single experiment. As proteins represent an important group of functional molecules in tissue and cells, the imaging of proteins has been an important point of focus in the development of IMS technologies and methods. Protein identification is crucial for the biological contextualization of molecular imaging data. However, gas-phase fragmentation efficiency of MALDI generated proteins presents significant challenges, making protein identification directly from tissue difficult. This review highlights methods and technologies specifically related to protein identification that have been developed to overcome these challenges in MALDI IMS experiments.

Micro-segmental hair analysis for proving drug-facilitated crimes: Evidence that a victim ingested a sleeping aid, diphenhydramine, on a specific day

Sleeping aids are often abused in the commission of drug-facilitated crimes. Generally, there is little evidence that a victim ingested a spiked drink unknowingly because the unconscious victim cannot report the situation to the police immediately after the crime occurred. Although conventional segmental hair analysis can estimate the number of months since a targeted drug was ingested, this analysis cannot determine the specific day of ingestion. We recently developed a method of micro-segmental hair analysis using internal temporal markers (ITMs) to estimate the day of drug ingestion. This method was based on volunteer ingestion of ITMs to determine a timescale within individual hair strands, by segmenting a single hair strand at 0.4-mm intervals, corresponding to daily hair growth. This study assessed the ability of this method to estimate the day of ingestion of an over-the-counter sleeping aid, diphenhydramine, which can be easily abused. To model ingestion of a diphenhydramine-spiked drink unknowingly, each subject ingested a dose of diphenhydramine, followed by ingestion of two doses of the ITM, chlorpheniramine, 14days apart. Several hair strands were collected from each subject's scalp several weeks after the second ITM ingestion. Diphenhydramine and ITM were detected at specific regions within individual hair strands. The day of diphenhydramine ingestion was estimated from the distances between the regions and the days of ITM ingestion. The error between estimated and actual ingestion day ranged from -0.1 to 1.9days regardless of subjects and hair collection times. The total time required for micro-segmental analysis of 96 hair segments (hair length: 3.84cm) was approximately 2days and the cost was almost the same as in general drug analysis. This procedure may be applicable to the investigation of crimes facilitated by various drugs.

Optimization of Sample Preparation and Instrumental Parameters for the Rapid Analysis of Drugs of Abuse in Hair samples by MALDI-MS/MS Imaging

Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) has been employed to rapidly screen longitudinally sectioned drug user hair samples for cocaine and its metabolites using continuous raster imaging. Optimization of the spatial resolution and raster speed were performed on intact cocaine contaminated hair samples. The optimized settings (100 × 150 μm at 0.24 mm/s) were subsequently used to examine longitudinally sectioned drug user hair samples. The MALDI-MS/MS images showed the distribution of the most abundant cocaine product ion at m/z 182. Using the optimized settings, multiple hair samples obtained from two users were analyzed in approximately 3 h: six times faster than the standard spot-to-spot acquisition method. Quantitation was achieved using longitudinally sectioned control hair samples sprayed with a cocaine dilution series. A multiple reaction monitoring (MRM) experiment was also performed using the 'dynamic pixel' imaging method to screen for cocaine and a range of its metabolites, in order to differentiate between contaminated hairs and drug users. Cocaine, benzoylecgonine, and cocaethylene were detectable, in agreement with analyses carried out using the standard LC-MS/MS method. Graphical Abstract ᅟ.

Matrix-assisted laser desorption/ionization mass spectrometric imaging for the rapid segmental analysis of methamphetamine in a single hair using umbelliferone as a matrix

Segmental hair analysis offers a longer period for retrospective drug detection than blood or urine. Hair is a keratinous fiber and is strongly hydrophobic. The embedding of drugs in hydrophobic hair at low concentrations makes it difficult for extraction and detection with matrix-assisted laser desorption/ionization (MALDI) coupled with mass spectrometric imaging (MSI). In this study, a single scalp hair was longitudinally cut with a cryostat section to a length of 4 mm and fixed onto a stainless steel MALDI plate. Umbelliferone was used as a new hydrophobic matrix to enrich and assist the ionization efficiency of methamphetamine in the hair sample. MALDI-Fourier transform ion cyclotron resonance (FTICR)-MS profiling and imaging were performed for direct detection and mapping of methamphetamine on the longitudinal sections of the single hair sample in positive ion mode. Using MALDI-MSI, the distribution of methamphetamine was observed throughout five longitudinally sectioned hair samples from a drug abuser. The changes of methamphetamine were also semi-quantified by comparing the ratios of methamphetamine/internal standard (I.S). This method improves the detection sensitivity of target drugs embedded in a hair matrix for imaging with mass spectrometry. The method could provide a detection level of methamphetamine down to a nanogram per milligram incorporated into hair. The results were also compared with the conventional high performance liquid chromatography -tandem mass spectrometry (HPLC-MS/MS) method. Changes in the imaging results over time by the MSI method showed good semi-quantitative correlation to the results from the HPLC-MS/MS method. This study provides a powerful tool for drug abuse control and forensic medicine analysis in a narrow time frame, and a reduction in the sample amount required.

Mass Spectrometry Imaging of Drugs of Abuse in Hair

Hair testing is a powerful tool routinely used for the detection of drugs of abuse. The analysis of hair is highly advantageous as it can provide prolonged drug detectability versus that in biological fluids and chronological information about drug intake based on the average growth of hair. However, current methodology requires large amounts of hair samples and involves complex time-consuming sample preparation followed by gas or liquid chromatography coupled with mass spectrometry. Mass spectrometry imaging is increasingly being used for the analysis of single hair samples, as it provides more accurate and visual chronological information in single hair samples.Here, two methods for the preparation of single hair samples for mass spectrometry imaging are presented.The first uses an in-house built cutting apparatus to prepare longitudinal sections, the second is a method for embedding and cryo-sectioning hair samples in order to prepare cross-sections all along the hair sample.

Critical comparison of mass analyzers for forensic hair analysis by ambient ionization mass spectrometry

RATIONALE

Recently, several direct and/or ambient mass spectrometry (MS) approaches have been suggested for drugs of abuse imaging in hair. The use of mass spectrometers with insufficient selectivity could result in false-positive measurements due to isobaric interferences. Different mass analyzers have been evaluated regarding their selectivity and sensitivity for the detection of Δ9-tetrahydrocannabinol (THC) from intact hair samples using direct analysis in real time (DART) ionization.

METHODS

Four different mass analyzers, namely (1) an orbitrap, (2) a quadrupole orbitrap, (3) a triple quadrupole, and (4) a quadrupole time-of-flight (QTOF), were evaluated. Selectivity and sensitivity were assessed by analyzing secondary THC standard dilutions on stainless steel mesh screens and blank hair samples, and by the analysis of authentic cannabis user hair samples. Additionally, separation of isobaric ions by use of travelling wave ion mobility (TWIM) was investigated.

RESULTS

The use of a triple quadrupole instrument resulted in the highest sensitivity; however, transitions used for multiple reaction monitoring were only found to be specific when using high mass resolution product ion measurements. A mass resolution of at least 30,000 FWHM at m/z 315 was necessary to avoid overlap of THC with isobaric ions originating from the hair matrix. Even though selectivity was enhanced by use of TWIM, the QTOF instrument in resolution mode could not indisputably differentiate THC from endogenous isobaric ions in drug user hair samples.

CONCLUSIONS

Only the high resolution of the (quadrupole) orbitrap instruments and the QTOF instrument in high-resolution mode distinguished THC in hair samples from endogenous isobaric interferences. As expected, enhanced selectivity compromises sensitivity and THC was only detectable in hair from heavy users. Copyright © 2016 John Wiley & Sons, Ltd.

MALDI-MS drug analysis in biological samples: opportunities and challenges

Drug analysis represents a large field in different disciplines. Plasma is commonly considered to be the biosample of choice for that purpose. However, concentrations often do not represent the levels present within deeper compartments and therefore cannot sufficiently explain efficacy or toxicology of drugs. MALDI-MS in drug analysis is of great interest for high-throughput quantification and particularly spatially resolved tissue imaging. The current perspective article will deal with challenges and opportunities of MALDI-MS drug analysis in different biological samples. A particular focus will be on hair samples. Recent applications were included, reviewed for their instrumental setup and sample preparation and pros and cons as well as future perspectives are critically discussed.

MALDI Imaging Mass Spectrometry Spatially Maps Age-Related Deamidation and Truncation of Human Lens Aquaporin-0

PURPOSE

To spatially map human lens Aquaporin-0 (AQP0) protein modifications, including lipidation, truncation, and deamidation, from birth through middle age using matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS).

METHODS

Human lens sections were water-washed to facilitate detection of membrane protein AQP0. We acquired MALDI images from eight human lenses ranging in age from 2 months to 63 years. In situ tryptic digestion was used to generate peptides of AQP0 and peptide images were acquired on a 15T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Peptide extracts were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and database searched to identify peptides observed in MALDI imaging experiments.

RESULTS

Unmodified, truncated, and fatty acid-acylated forms of AQP0 were detected in protein imaging experiments. Full-length AQP0 was fatty acid acylated in the core and cortex of young (2- and 4-month) lenses. Acylated and unmodified AQP0 were C-terminally truncated in older lens cores. Deamidated tryptic peptides (+0.9847 Da) were mass resolved from unmodified peptides by FTICR MS. Peptide images revealed differential localization of un-, singly-, and doubly-deamidated AQP0 C-terminal peptide (239-263). Deamidation was present at 4 months and increases with age. Liquid chromatography-MS/MS results indicated N246 undergoes deamidation more rapidly than N259.

CONCLUSIONS

Results indicated AQP0 fatty acid acylation and deamidation occur during early development. Progressive age-related AQP0 processing, including deamidation and truncation, was mapped in human lenses as a function of age. The localization of these modified AQP0 forms suggests where AQP0 functions may change throughout lens development and aging.

(Un)targeted Scanning of Locks of Hair for Drugs of Abuse by Direct Analysis in Real Time-High-Resolution Mass Spectrometry

Forensic hair evidence can be used to obtain retrospective timelines of drug use by analysis of hair segments. However, this is a laborious and time-consuming process, and mass spectrometric (MS) imaging techniques, which show great potential for single-hair targeted analysis, are less useful due to differences in hair growth rate between individual hairs. As an alternative, a fast untargeted analysis method was developed that uses direct analysis in real time-high-resolution mass spectrometry (DART-HRMS) to longitudinally scan intact locks of hair without extensive sample preparation or segmentation. The hair scan method was validated for cocaine against an accredited liquid chromatography/tandem mass spectrometry (LC/MS/MS) method. The detection limit for cocaine in hair was found to comply with the cutoff value of 0.5 ng/mg recommended by the Society of Hair Testing; that is, the DART hair scan method is amenable to forensic cases. Under DART conditions, no significant thermal degradation of cocaine occurred. The standard DART spot size of 5.1 ± 1.1 mm could be improved to 3.3 ± 1.0 mm, corresponding to approximately 10 days of hair growth, by using a high spatial resolution exit cone. By use of data-dependent product ion scans, multiple drugs of abuse could be detected in a single drug user hair scan with confirmation of identity by both exact mass and MS/HRMS fragmentation patterns. Furthermore, full-scan high-resolution data were retrospectively interrogated versus a list of more than 100 compounds and revealed additional hits and temporal profiles in good correlation with reported drug use.

Analysis of Antiretrovirals in Single Hair Strands for Evaluation of Drug Adherence with Infrared-Matrix-Assisted Laser Desorption Electrospray Ionization Mass Spectrometry Imaging

Adherence to a drug regimen can be a strong predictor of health outcomes, and validated measures of adherence are necessary at all stages of therapy from drug development to prescription. Many of the existing metrics of drug adherence (e.g., self-report, pill counts, blood monitoring) have limitations, and analysis of hair strands has recently emerged as an objective alternative. Traditional methods of hair analysis based on LC-MS/MS (segmenting strands at ≥1 cm length) are not capable of preserving a temporal record of drug intake at higher resolution than approximately 1 month. Here, we evaluated the detectability of HIV antiretrovirals (ARVs) in hair from a range of drug classes using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mass spectrometry imaging (MSI) with 100 μm resolution. Infrared laser desorption of hair strands was shown to penetrate into the strand cortex, allowing direct measurement by MSI without analyte extraction. Using optimized desorption conditions, a linear correlation between IR-MALDESI ion abundance and LC-MS/MS response was observed for six common ARVs with estimated limits of detection less than or equal to 1.6 ng/mg hair. The distribution of efavirenz (EFV) was then monitored in a series of hair strands collected from HIV infected, virologically suppressed patients. Because of the role hair melanin plays in accumulation of basic drugs (like most ARVs), an MSI method to quantify the melanin biomarker pyrrole-2,3,5-tricarboxylic acid (PTCA) was evaluated as a means of normalizing drug response between patients to develop broadly applicable adherence criteria.

Applications of MALDI Mass Spectrometry in Clinical Chemistry

BACKGROUND

MALDI-TOF mass spectrometry (MS) is set to make inroads into clinical chemistry because it offers advantages over other analytical platforms. These advantages include low acquisition and operating costs, ease of use, ruggedness, and high throughput. When coupled with innovative front-end strategies and applied to important clinical problems, it can deliver rapid, sensitive, and cost-effective assays.

CONTENT

This review describes the general principles of MALDI-TOF MS, highlights the unique features of the platform, and discusses some practical methods based upon it. There is substantial potential for MALDI-TOF MS to make further inroads into clinical chemistry because of the selectivity of mass detection and its ability to independently quantify proteoforms.

SUMMARY

MALDI-TOF MS has already transformed the practice of clinical microbiology and this review illustrates how and why it is now set to play an increasingly important role in in vitro diagnostics in particular, and clinical chemistry in general.

High resolution mass spectrometry imaging reveals the occurrence of phenylphenalenone-type compounds in red paracytic stomata and red epidermis tissue of Musa acuminata ssp. zebrina cv. 'Rowe Red'

The banana epidermis and in particular their stomata are conducive sites for the penetration of pathogenic fungi which can severely limit global banana production. The red pseudostem of the ornamental banana Musa acuminata ssp. zebrina cv. 'Rowe Red' was used to study the chemical constituents of the epidermal cell layer using matrix-free laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric imaging (LDI-FT-ICR-MSI). The high resolution of this technique allowed phenylphenalenone-type compounds to be located in single plant cells. Some of these secondary metabolites were identified as constitutive compounds and found in specialized epidermal cells in banana pseudostem tissue. Especially the red paracytic stomata revealed higher signal intensities of certain phenylphenalenones than normal epidermis cells. The ease of detection of polycyclic aromatic compounds on the cellular level is discussed with regard to future investigations of plant-pathogen interactions.