Fixation Studies of Exfoliated Cells

Since these second derivative spectra are nearly superimposable, one concludes that the average biochemical composition of dried cell samples is invariant over a period of 1 month, if the cells are stored in a dry and clean environment. In order to ascertain whether or not individual cells exhibit systematic spectral changes 

However, as previously observed for the unfixed cells, PCA was able to distinguish very small spectral changes and revealed individual clusters for each fixation methods [17]. The loading vectors (not shown) indicate that there is a slight shift of the amide I band for the formalin-fixed samples when compared to that of the unfixed and SurePath-fixed samples. These changes are discussed in more detail in the original literature [17]. When the spectral measurements were repeated after 1 week or 1 month, no further spectral differences could be detected. Thus, even prolonged exposure of samples to the fixatives did not produce any effects on the cellular spectra. 

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