The impact of formalin fixation in the elemental content of tissues

Abstract

Formalin fixation is a crucial step in the preparation of tissue samples for anatomic pathology studies, however, research showed that prolonged formalin fixation, can alter the elemental composition of tissues with implications for pathology and biomedical research. In this study we aim to assess and parametrize the influence of short-term formalin fixation in tissues. Six sets of human colon tissue samples were exposed to different formalin fixation times, up until 48 h. The elemental content throughout time was compared to the elemental content of the snap-frozen sample of the same tissue that was not exposed to formalin using Energy Dispersive X-ray Fluorescence. Results showed a clear decrease of Cl and K concentration in the tissues solution reaching a plateau between 1 h and 3 h of fixation. Also, there is an uptake of P in the tissue, likely due to the buffered formalin solution, within the first 15 min of fixation. This behaviour was concomitant with an increase of Na determined using Particle Induced gamma-ray emission analysis (PIGE) and Elastic Backscattering Spectroscopy (EBS). The dynamic changes determined in the studied elements demonstrate that a better understanding of the fixation-related mechanisms is in demand as well as optimization of the fixation protocols implemented in anatomic pathology laboratories.