Formalin fixed tissues stored as fixed slides are an invaluable resource in medical research and one of the most commonly biobanked sample types. Due to the broad prevalence of biobanking for ‘unspecified research’ both formalin fixed, paraffin embedded (FFPE) blocks and cut slides can be stored by biobanks for indefinite time periods spanning years to decades.
Consensus is absent within the literature as to the best way to store FFPE slides and a handful of studies comparing storage modalities over various timeframes suggests that greater consideration is required to ensure the longevity of these samples. Factors such as temperature [1, 2] as well as exposure to light [1, 2], oxidation [1] and moisture [1] have been cited as potential threats to sample integrity and to ensure the impact of these variables does not confound research results further characterisation is imperative.
To determine the optimal storage conditions for preservation of FFPE slides we are conducting a pilot study of frequently cited solutions documented in the literature. Our pilot will focus on the variable of temperature, and we hope that further studies at a later date will allow us to characterise additional variables. Tonsil tissue will be sectioned at baseline, and a subset of samples analysed for DNA and RNA quantity and integrity as well as suitability for immunohistochemistry. The remainder of the sectioned samples will be stored at 4 degrees, -20 degrees and -80 degrees and submitted to the same assessments at intervals of three, twelve and 24 months. Analysis will be conducted in triplicate to reduce the impact of compounding variables and increase the robustness of the findings.
These results will facilitate a review of current practices for long-term storage and pending practicality, will influence the ongoing storage and management of priority and high value collections stored at NSW Regional Biospecimen Services.