Lipid changes within the epidermis of living skin equivalents observed across a time-course by MALDI-MS imaging and profiling

© 2015 Mitchell et al. Abstract Background: Mass spectrometry imaging (MSI) is a powerful tool for the study of intact tissue sections. Here, its application to the study of the distribution of lipids in sections of reconstructed living skin equivalents during their development and maturation is described. Methods: Living skin equivalent (LSE) samples were obtained at 14 days development, re-suspended in maintenance medium and incubated for 24 h after delivery. The medium was then changed, the LSE re-incubated and samples taken at 4, 6 and 24 h time points. Mass spectra and mass spectral images were recorded from 12 μm sections of the LSE taken at each time point for comparison using matrix assisted laser desorption ionisation mass spectrometry. Results: A large number of lipid species were identified in the LSE via accurate mass-measurement MS and MSMS experiments carried out directly on the tissue sections. MS images acquired at a spatial resolution of 50 μm × 50 μm showed the distribution of identified lipids within the developing LSE and changes in their distribution with time. In particular development of an epidermal layer was observable as a compaction of the distribution of phosphatidylcholine species. Conclusions: MSI can be used to study changes in lipid composition in LSE. Determination of the changes in lipid distribution during the maturation of the LSE will assist in the identification of treatment responses in future investigations

Detection and mapping of illicit drugs and their metabolites in fingermarks by MALDI MS and compatibility with forensic techniques

Despite the proven capabilities of Matrix Assisted Laser Desorption Ionisation Mass Spectrometry (MALDI MS) in laboratory settings, research is still needed to integrate this technique into current forensic fingerprinting practice. Optimised protocols enabling the compatible application of MALDI to developed fingermarks will allow additional intelligence to be gathered around a suspect’s lifestyle and activities prior to the deposition of their fingermarks while committing a crime. The detection and mapping of illicit drugs and metabolites in latent fingermarks would provide intelligence that is beneficial for both police investigations and court cases. This study investigated MALDI MS detection and mapping capabilities for a large range of drugs of abuse and their metabolites in fingermarks; the detection and mapping of a mixture of these drugs in marks, with and without prior development with cyanoacrylate fuming or Vacuum Metal Deposition, was also examined. Our findings indicate the versatility of MALDI technology and its ability to retrieve chemical intelligence either by detecting the compounds investigated or by using their ion signals to reconstruct 2D maps of fingermark ridge details

The forensic exploitation of fingermark chemistry: a review

There is evidence that the use of fingerprints for the identification of an individual, either for civil or criminal purposes, has been considered in some form for over 2000 years (Barnes, 2011). The comparison of a mark left by an individual at a crime scene with sets of reference prints taken under controlled conditions is a cornerstone of forensic investigation, first being proposed in 1880 (Faulds, 1880). Following the generation of classification systems for fingermark patterns (Galton, 1892) and filing systems enabling databases to be searched (Henry, 1901), fingerprint comparison and identification has been successfully employed for over 120 years. The fact that fingerprint patterns are ‘unique’ (to the best of scientific knowledge) and persistent throughout life makes them a powerful identification tool. Indeed, the term ‘fingerprint’ is widely used across many other branches of science to describe something that is characteristic and easily distinguished from (e.g.) spectra of other nominally similar substances. In criminal investigations the focus is on locating marks that may have been left by the suspect at the crime scene. These can be of three principal types; a positive mark where material is transferred from the fingertip to the surface, a negative mark where the fingertip removes material (e.g. dust) from the surface, or a ‘plastic’ mark where the fingertip leaves a permanent impression in a soft substance such as putty. The classification of a positive mark can be further divided into a ‘patent’ mark where the material transferred is readily visible to the eye (e.g. mud, ink), or a ‘latent’ mark where the material transferred cannot typically be readily seen by eye and needs further enhancement to be seen. The chemistry of the material transferred from the finger to the surface is important to the visualisation of the contact trace. This is because chemical substances present can be utilised by a range of processes that either convert a latent mark into one that is visible or assist in further enhancing the pre-existing detail in a patent mark. The chemical development of fingermarks was observed as early as the 1860s (Quinche & Margot, 2010) and was already being explored in a more focused way in the 1920s (Mitchell, 1920), with a range of chemical processes targeting different constituents being proposed for use. This review will focus on the material that is ultimately transferred from the fingertip to the surface to form a fingermark. It will consider how this highly complex chemistry can be utilised by a wide range of chemical reagents, and by advanced analytical techniques in combination with imaging capabilities, to reveal the fingermark ridge detail and additional information contained within it

A proteomic approach for the rapid, multi-informative and reliable identification of blood

Blood evidence is frequently encountered at the scene of violent crimes and can provide valuable intelligence in the forensic investigation of serious offences. Because many of the current enhancement methods used by crime scene investigators are presumptive, the visualisation of blood is not always reliable nor does it bear additional information. In the work presented here, two methods employing a shotgun bottom up proteomic approach for the detection of blood are reported; the developed protocols employ both an in solution digestion method and a recently proposed procedure involving immobilization of trypsin on hydrophobin Vmh2 coated MALDI sample plate. The methods are complementary as whilst one yields more identifiable proteins (as biomolecular signatures), the other is extremely rapid (5 minutes). Additionally, data demonstrate the opportunity to discriminate blood provenance even when two different blood sources are present in a mixture. This approach is also suitable for old bloodstains which had been previously chemically enhanced, as experiments conducted on a 9-year-old bloodstain deposited on a ceramic tile demonstrate

The analysis of latent fingermarks on polymer banknotes using MALDI-MS

In September 2016, the UK adopted a new Bank of England (BoE) £5 polymer banknote, followed by the £10 polymer banknote in September 2017. They are designed to be cleaner, stronger and have increased counterfeit resilience; however, fingermark development can be problematic from the polymer material as various security features and coloured/textured areas have been found to alter the effectiveness of conventional fingermark enhancement techniques (FETs). As fingermarks are one of the most widely used forms of identification in forensic cases, it is important that maximum ridge detail be obtained in order to allow for comparison. This research explores the use of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) profiling and imaging for the analysis of fingermarks deposited on polymer banknotes. The proposed methodology was able to obtain both physical and chemical information from fingermarks deposited in a range of scenarios including; different note areas, depletion series, aged samples and following conventional FETs. The analysis of forensically important molecular targets within these fingermarks was also explored, focussing specifically on cocaine. The ability of MALDI-MS to provide ridge detail and chemical information highlights the forensic applicability of this technique and potential for the analysis of fingermarks deposited onto this problematic surface

Emerging applications in mass spectrometry imaging; enablers and roadblocks

Mass spectrometry imaging (MSI) is a powerful and versatile technique able to investigate the spatial distribution of multiple non-labelled endogenous and exogenous analytes simultaneously, within a wide range of samples. Over the last two decades, MSI has found widespread application for an extensive range of disciplines including pre-clinical drug discovery, clinical applications and human identification for forensic purposes. Technical advances in both instrumentation and software capabilities have led to a continual increase in the interest in MSI; however, there are still some limitations. In this review, we discuss the emerging applications in MSI that significantly impact three key areas of mass spectrometry (MS) research—clinical, pre-clinical and forensics—and roadblocks to the expansion of use of MSI in these areas

Non-invasive screening of breast cancer from fingertip smears—a proof of concept study

Breast cancer is a global health issue affecting 2.3 million women per year, causing death in over 600,000. Mammography (and biopsy) is the gold standard for screening and diagnosis. Whilst effective, this test exposes individuals to radiation, has limitations to its sensitivity and specificity and may cause moderate to severe discomfort. Some women may also find this test culturally unacceptable. This proof-of-concept study, combining bottom-up proteomics with Matrix Assisted Laser Desorption Ionisation Mass Spectrometry (MALDI MS) detection, explores the potential for a non-invasive technique for the early detection of breast cancer from fingertip smears. A cohort of 15 women with either benign breast disease (n = 5), early breast cancer (n = 5) or metastatic breast cancer (n = 5) were recruited from a single UK breast unit. Fingertips smears were taken from each patient and from each of the ten digits, either at the time of diagnosis or, for metastatic patients, during active treatment. A number of statistical analyses and machine learning approaches were investigated and applied to the resulting mass spectral dataset. The highest performing predictive method, a 3-class Multilayer Perceptron neural network, yielded an accuracy score of 97.8% when categorising unseen MALDI MS spectra as either the benign, early or metastatic cancer classes. These findings support the need for further research into the use of sweat deposits (in the form of fingertip smears or fingerprints) for non-invasive screening of breast cancer

Changes in high-intensity precipitation on the northern Apennines (Italy) as revealed by multidisciplinary data over the last 9000 years

Several record-breaking precipitation events have struck the mountainous area of the Emilia-Romagna region (northern Apennines, Italy) over the last 10 years. As a consequence, severe geomorphological processes such as debris avalanches and debris flows, shallow landslides, and overbank flooding have affected the territory, causing severe damage to human-made structures. The unusual intensity of these phenomena prompted an investigation into their frequency in the past, beyond instrumental time. In the quest for an understanding of whether these phenomena are unprecedented in the region, peat bog and lake deposits were analyzed to infer the frequency of extreme precipitation events that may have occurred in the past. We present the results of a dedicated field campaign performed in summer 2017 at Lake Moo in the northern Apennines, a 0.15 km2peat bog located at an altitude of 1130ma.s.l. During the extreme precipitation event of 13-14 September 2015, several debris flows generated by small streams affected the Lake Moo plain. In such a small drainage basin (<2 km2), high-density floods can be triggered only by high-intensity precipitation events. The sedimentary succession (ca. 13m thick) was studied through the drilling of two cores and one trench. The sequence, characterized by clusters of coarse-grained alluvial deposits interbedded with organic-rich silty clays and peat layers, was analyzed by combining sedimentological, pollen, microanthracological and pedological data with radiocarbon dating (AMS 14C) in an innovative multidisciplinary approach for this area. Original data acquired during the field campaign were also correlated with other specific paleoclimatic proxies available in the literature for the northern Apennines area. We discover that the increase in extreme paleoflooding, associated with coarse-grained deposits similar to the ones observed recently, correlates well with the warm phases of the Holocene Thermal Maximum and with the ongoing warming trend observed that started at the beginning of the last century