Fourier transform infrared spectroscopy as a non-destructive method for analysing herbarium specimens.

Dried plant specimens stored in herbaria are an untapped treasure chest of information on environmental conditions, plant evolution and change over many hundreds of years. Owing to their delicate nature and irreplaceability, there is limited access for analysis to these sensitive samples, particularly where chemical data are obtained using destructive techniques. Fourier transform infrared (FTIR) spectroscopy is a chemical analysis technique which can be applied non-destructively to understand chemical bonding information and, therefore, functional groups within the sample. This provides the potential for understanding geographical, spatial and species-specific variation in plant biochemistry. Here, we demonstrate the use of mid-FTIR microspectroscopy for the chemical analysis of Drosera rotundifolia herbarium specimens, which were collected 100 years apart from different locations. Principal component and hierarchical clustering analysis enabled differentiation between three main regions on the plant (lamina, tentacle stalk and tentacle head), and between the different specimens. Lipids and protein spectral regions were particularly sensitive differentiators of plant tissues. Differences between the different sets of specimens were smaller. This study demonstrates that relevant information can be extracted from herbarium specimens using FTIR, with little impact on the specimens. FTIR, therefore, has the potential to be a powerful tool to unlock historic information within herbaria

Fourier transform infrared spectra of cells on glass coverslips: a further step in spectral pathology

Over the last few years, great effort has been placed on developing Fourier Transform Infrared (FTIR) microspectroscopy as a tool to help in the histopathological diagnosis of cancer. The ever increasing workload in pathology departments is calling for a technique that could identify the presence of cancer cells in cytology and tissue samples in an objective, fast and automated way. However, pathologists use glass slides which absorb infrared (IR) radiation thus removing important mid-IR spectral data in the fingerprint region (proteins, DNA, RNA; 1800 cm-1 to 900 cm-1). To this purpose, we hypothesised whether using thinner glass slides, i.e., glass coverslips, would allow us to obtain spectral data not only from the lipid region (3100 cm-1 to 2700 cm-1) but also from the fingerprint region. To this purpose, we studied peripheral blood mononuclear cells (PBMC), a leukaemia cell line (K562) and a lung cancer cell line (CALU-1). Cells were placed on DAKO coverslips and their FTIR spectra obtained at MIRAS beamline, Alba synchrotron light source (Barcelona, Catalonia). The data presented here not only shows for the first time that it is possible to obtain spectral data from most of the amide I region (1800 cm-1 to 1570 cm-1) of cells placed on glass coverslips but more important, principal component analysis was able to separate between the three types of cells for both the lipid and the amide I regions. The methodology here described is a further step in the application of FTIR microspectroscopy in histopathology departments