Assessment of alternatives to environmental toxic formalin for DNA conservation in biological specimens

Abstract

One essential step of museum and clinical specimen preservation is immersion in a fixative fluid to prevent degradation. Formalin is the most largely used fixative, but its benefit is balanced with its toxic and carcinogenic status. Moreover, because formalin-fixation impairs nucleic acids recovery and quality, current museum wet collections and formalin-fixed, paraffin-embedded clinical samples do not represent optimal tanks of molecular information. Our study has been developed to compare formalin to two alternative fixatives (RCL2® and ethanol) in a context of molecular exploitation. Based on a unique protocol, we created mammalian fixed collections, simulated the impact of time on preservation using an artificial ageing treatment and followed the evolution of specimens' DNA quality. DNA extraction yield, purity, visual integrity and qualitative and quantitative ability to amplify the Cox1 gene were assessed. Our results show that both RCL2 and ethanol exhibit better performances than formalin. They do not impair DNA extraction yield, and more importantly, DNA alteration is delayed over the preservation step. The use of RCL2 or ethanol as fixative in biological collections may insure a better exploitation of the genetic resources they propose.

Reducing DNA damage by formaldehyde in liquid‐based cytology preservation solutions to enable the molecular testing of lung cancer specimens

“…With regard to DNA quality, fixation in 95% ethanol has been reported in previous studies to result in better stability than fixation in CytoRich Red or 10% formalin . Ethanol fixatives have powerful effects on the stability of nucleic acids, and thus improved results may be observed by using ethanol.…”

“…With regard to DNA quality, fixation in 95% ethanol has been reported in previous studies to result in better stability than fixation in CytoRich Red or 10% formalin. 26,27 Ethanol fixatives have powerful effects on the stability of nucleic acids, and thus improved results may be observed by using ethanol. For example, when preparing a specimen, a sample for DNA extraction could be placed in 95% ethanol after a 30-minute incubation in CytoRich Red.…”

Phylogenetic Relationships Within Chrysogorgia (Alcyonacea: Octocorallia), a Morphologically Diverse Genus of Octocoral, Revealed Using a Target Enrichment Approach

“…In the past, collection and preservation protocols for octocorals have sometimes employed an initial fixation step using formalin, after which samples are transferred to ethanol for long-term storage (Alderslade and Fabricius, 2001;Etnoyer et al, 2006;Williams and Van Syoc, 2007). Fixation with formalin is well documented to negatively affect both the quality and quantity of DNA which can be obtained from biological specimens (Sarot et al, 2017). Factors such as the duration of exposure to the fixative and environmental conditions such as temperature as well as the duration of the sampling event and time spent on deck will contribute to the degradation of samples and the challenges around extracting PCR-amplifiable DNA from octocorals.…”