FOURIER TRANSFORM INFRARED VIBRATIONAL SPECTROSCOPIC IMAGING: Integrating Microscopy and Molecular Recognition

Abstract

The recent development of Fourier transform infrared (FTIR) spectroscopic imaging has enhanced our capability to examine, on a microscopic scale, the spatial distribution of vibrational spectroscopic signatures of materials spanning the physical and biomedical disciplines. Recent activity in this emerging area has concentrated on instrumentation development, theoretical analyses to provide guidelines for imaging practice, novel data processing algorithms, and the introduction of the technique to new fields. To illustrate the impact and promise of this spectroscopic imaging methodology, we present fundamental principles of the technique in the context of FTIR spectroscopy and review new applications in various venues ranging from the physical chemistry of macromolecular systems to the detection of human disease.

Vibrational spectroscopic mapping and imaging of tissues and cells

“…This has been assisted by the availability of a raft of new techniques that are designed to obtain specific information. The differentiation of biological samples relies on subtle but multiple changes in the ratios and wavenumbers of bands that are objectively compared with chemometrics to remove sampling variability, rather than on absolute values that are subject to experimental conditions (Geladi 2003;Geladi et al 2004;Levin and Bhargava 2005). Thus, while functional group maps provide useful information, the more objective discrimination of organelles or tissue type (and changes within these with treatments or disease states) requires the use of chemometric analyses.…”

“…The mapping of biological samples with a benchtop globar source is slow because of the relatively weak IR intensity resulting from the use of apertures in the microscope to physically restrict the IR absorption to the sample area of interest (Levin and Bhargava 2005). The long time required for such measurements means that the spatial resolution is normally nowhere near the diffraction limit.…”

“…Because of the rapid expansion of biological applications of vibrational spectroscopic mapping and imaging techniques, it is not possible to provide an extensive review of recent research within the space limitations of this article, but an overview of the diversity of applications in medicine and biology, including medical diagnostics, studies of physiological and diseases processes and treatments of diseases and plant biology, can be found in a number of recent reviews (Bailo and Deckert 2008;Bhargava 2007;Boskey and Mendelsohn 2005;Chan et al 2008;Gierlinger and Schwanninger 2007;Levin and Bhargava 2005;Moreira et al 2008;Movasaghi et al 2007;Petibois and Guidi 2008;Petter et al 2009;Srinivasan and Bhargava 2007;Swain and Stevens 2007). As outlined in these reviews and the current review, the increase in the speed of acquisition, sensitivity, discrimination and spatial resolution of the emerging techniques of vibrational spectroscopic microscopies has greatly expanded the horizons of what is possible in terms of an explosion of new knowledge that is being generated.…”

Spectroscopic and chemometric approaches to radiobiological analyses

“…The higher signal levels achievable with FTIRM result in increased speed of measurement and consequently higher sample throughput over CRM [21]. The strengths of both are now well established in hyperspectral imaging for non-invasive and label-free histopathology [22][23][24][25][26][27][28][29][30], while the capabilities of CRM to detect tissue abnormalities in-vivo without the complication of contamination of spectral measurements by water and atmospheric features has resulted in a move to the development of clinical devices [31].…”

Paclitaxel distribution in poly(ethylene glycol)/poly(lactide-co-glycolic acid) blends and its release visualized by coherent anti-Stokes Raman scattering microscopy

“…FT-IR imaging of PEG dissolution in an aqueous environment has been implemented to investigate the drug release mechanism [12][13][14][15]. While this method provides chemical selectivity, the long excitation wavelength used in FT-IR microscopy offers the spatial resolution of several to tens micrometer, which does not allow the visualization of 3D distribution of drug molecules in thin polymer films or microparticles.…”