Infrared spectroscopy enables visualization of gross differences between individual cells based on their absorption spectra. A cell can be arrested at a particular point by formalin fixation, after which the IR spectra can be obtained within just a few minutes.
“Infrared cytology is an objective analysis of the cells and brings a unique angle to cytological examination,” comments Peter Gardner, Ph.D., director of assessment at the School of Chemical Engineering and Analytical Science, The University of Manchester. Dr. Gardner anticipates that IR spectroscopy will become an integral part of diagnostics, helping to identify and grade diseased cells in pathology specimens.
Another opportunity lies in personalized medicine. Instead of searching for specific molecular markers to predict a patient’s response to drug therapy, the same prediction can be made by using IR analysis of the person’s own cells.
Using ovarian cancer cell lines, Dr. Gardner’s group demonstrated clear spectroscopic separation between cell lines responding and not responding to treatment with the cytotoxic drug cisplatin. Moreover, when treated with a new experimental compound, KF101, the cells presented yet another unique spectral signature. This observation indicated that KF101 acts by a mechanism different from that of cisplatin.
“I see another opportunity for IR spectroscopy in studies of stem cells,” continues Dr. Gardner. “Stem cell differentiation induces changes in the spectrum. If stem cell implantation has to happen at a certain differentiation stage, the IR spectral data would provide a robust measure of whether the cells have reached that stage.”
Dr. Gardner says that he and his colleagues have resolved a long-standing issue of spectral distortion. Mid-infrared radiation scatters strongly from the organelles distorting the absorption spectrum. The scientists modified the existing Mie scattering theory, which describes scattering of light from the objects of a size comparable to the illuminating wavelength.
A new mathematical algorithm was able to correct the spectral distortion. This methodology was recently applied to identification of stem cells among a side population of tumor cells. This population is thought to be enriched with stem cells, but their low counts prevent further fractionation and characterization. FTIR spectroscopy was able to record the fingerprints of individual cells, confirming their biochemical differences.