421
15 FtIR Imaging of tissues: techniques and methods of Analysis
the stage is now set for the transplantation of the FtIR imaging spectrometer
from the laboratory to the clinic. this chapter provides an overview and update on
the progress in the field of FtIR imaging applied to cells and tissues. the chapter
starts with a summary on band interpretation in cell and tissue spectra before discussing instrumentation, image data processing, and finally moving onto some case
studies of different diseased tissues including cervical, brain, liver, and heart.
15.2 Spectral Features of Macromolecules in FTIR
Spectra of Cells and Tissues
Fourier transform infrared spectrum (FtIR) of any biological system such as a cell
or a tissue is a fingerprint of the phenotypic expression in response to environmental stimuli. It expresses the overall chemical information that highlights first of all
the presence of the major biocomponents such as proteins, lipids, carbohydrates,
and nucleic acids. here, it should be stressed that FtIR spectroscopy is not a technique that enables the detection of an individual chemical species that appears as a
metabolic product or a stress marker but it is rather a method to monitor the entire
biochemical status of the biological processes. the change of spectral biomarkers
specific for the given group of biomolecules can indicate the presence of a particular disease, environmental stress or genetic modifications. Such a “fingerprint”
of biochemical status can provide the first hint about the observed biological or
pathological processes; however, the comprehensive understanding of FtIR spectra
requires the use of advanced analytical methods such as a multivariate analysis.
this is discussed in detail in Sect. 4.
Figure 15.1 shows FtIR spectra of individual macromolecules present in a
sample of a biological origin and a spectrum typical for a cell or a tissue. the
comparison of band position and shape in all the spectra clearly shows that bands
originating from the most abundant biocomponents are observed in the spectrum
of a cell or a tissue. the second derivative IR spectrum presented in Fig. 15.2
emphasizes small differences in spectral band shapes and illustrates the dominant absorption features for proteins, lipids, carbohydrates, and nucleic acids. We
discuss these in detail below, while table 15.1 summarizes the assignment of IR
bands observed in FtIR spectra of cells and tissues to particular vibrations and
macromolecules.
15.2.1 Proteins
Proteins are the dominating constituents in all cells and tissues, and thus their vibrational fingerprint is easily observed in infrared microspectroscopy. the protein
IR spectrum has two primary features, the amide I and amide II bands, which are
15 FtIR Imaging of tissues: techniques and methods of Analysis
the stage is now set for the transplantation of the FtIR imaging spectrometer
from the laboratory to the clinic. this chapter provides an overview and update on
the progress in the field of FtIR imaging applied to cells and tissues. the chapter
starts with a summary on band interpretation in cell and tissue spectra before discussing instrumentation, image data processing, and finally moving onto some case
studies of different diseased tissues including cervical, brain, liver, and heart.
15.2 Spectral Features of Macromolecules in FTIR
Spectra of Cells and Tissues
Fourier transform infrared spectrum (FtIR) of any biological system such as a cell
or a tissue is a fingerprint of the phenotypic expression in response to environmental stimuli. It expresses the overall chemical information that highlights first of all
the presence of the major biocomponents such as proteins, lipids, carbohydrates,
and nucleic acids. here, it should be stressed that FtIR spectroscopy is not a technique that enables the detection of an individual chemical species that appears as a
metabolic product or a stress marker but it is rather a method to monitor the entire
biochemical status of the biological processes. the change of spectral biomarkers
specific for the given group of biomolecules can indicate the presence of a particular disease, environmental stress or genetic modifications. Such a “fingerprint”
of biochemical status can provide the first hint about the observed biological or
pathological processes; however, the comprehensive understanding of FtIR spectra
requires the use of advanced analytical methods such as a multivariate analysis.
this is discussed in detail in Sect. 4.
Figure 15.1 shows FtIR spectra of individual macromolecules present in a
sample of a biological origin and a spectrum typical for a cell or a tissue. the
comparison of band position and shape in all the spectra clearly shows that bands
originating from the most abundant biocomponents are observed in the spectrum
of a cell or a tissue. the second derivative IR spectrum presented in Fig. 15.2
emphasizes small differences in spectral band shapes and illustrates the dominant absorption features for proteins, lipids, carbohydrates, and nucleic acids. We
discuss these in detail below, while table 15.1 summarizes the assignment of IR
bands observed in FtIR spectra of cells and tissues to particular vibrations and
macromolecules.
15.2.1 Proteins
Proteins are the dominating constituents in all cells and tissues, and thus their vibrational fingerprint is easily observed in infrared microspectroscopy. the protein
IR spectrum has two primary features, the amide I and amide II bands, which are