Comparison of speed-vacuum method and heat-drying method to measure brain water content of small brain samples

Publication date: Available online 25 November 2016
Source:Journal of Neuroscience Methods
Author(s): Anne Sebastiani, Tobias Hirnet, Antje Jahn-Eimermacher, Serge C. Thal
BackgroundA reliable measurement of brain water content (wet-to-dry ratio) is an important prerequisite for conducting research on mechanisms of brain edema formation. The conventionally used oven-drying method suffers from several limitations, especially in small samples. A technically demanding and time-consuming alternative is freeze-drying.New MethodCentrifugal vacuum concentrators (e.g. SpeedVac/speed-vacuum drying) are a combination of vacuum-drying and centrifugation, used to reduce the boiling temperature. These concentrators have the key advantages of improving the freeze-drying speed and maintaining the integrity of dried samples, thus, allowing e.g. DNA analyses. In the present study, we compared the heat-oven with speed-vacuum technique with regard to efficacy to remove moisture from water and brain samples and their effectiveness to distinguish treatment paradigms after experimental traumatic brain injury (TBI) caused by controlled cortical impact (CCI).ResultsBoth techniques effectively removed water, the oven technique taking 24h and vacuum-drying taking 48h. Vacuum-drying showed lower variations in small samples (30–45mg) and was suitable for genomic analysis as exemplified by sex genotyping. The effect of sodium bicarbonate (NaBic8.4%) on brain edema formation after CCI was investigated in small samples (2×1mm). Only vacuum-drying showed low variation and significant improvement under NaBic8.4% treatment.Comparison with an existing methodThe receiver operating curves (ROC) analysis demonstrated that vacuum-drying (area under the curve (AUC):0.867-0.967) was superior to the conventional heat-drying method (AUC:0.367-0.567).ConclusionsThe vacuum method is superior in terms of quantifying water content in small samples. In addition, vacuum-dried samples can also be used for subsequent analyses, e.g., PCR analysis.



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