Chemical Fixation of Tissue

Formalin fixation was also found to preserve lipid signals in Raman spectra of lipid rich tissue such as adipose tissue and white matter of the brain. Both 

Huang et al and Shim and Wilson reported that a direct spectral contaminant from formalin in the Raman spectrum is a weak peak appearing at 1040 cm However, this artefact can be successfully removed through copious washes with PBS.  

Pleshko et al have shown that 70% ethanol fixation of 35-day-old embryonic rat femur gave rise to FTIR spectra that exhibited Amide I and II peaks that were shifted to lower frequencies (1647cm and 1546cm respectively) compared with unfixed rat femur, which exhibited Amide I and II peaks at 1651 cm and 1550cm It was concluded that evaluation of protein structure in this tissue should be limited to snap-frozen samples, or formalin-fixed tissues where there were no observable shifts in the Amide I and II peaks. Although this does not conform to the observations made by Faolain et al., this difference may be due to the different types of tissue used in each study, calcified tissue in Pleshko et al and non-calcified tissue in Faolain et al  

Further studies of the effects of sample preparation on bone tissue were undertaken by Aparicio et al and Yeni et al In the study by Aparicio 

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