title: Comparison of speed-vacuum method and heat-drying method to measure brain water content of small brain samples.
abstract: A 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.
  
  
  
  Centrifugal 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).
  
  
  
  Both 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.
  
  
  
  The 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).
  
  
  
  The 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.
authors.affiliation: Department of Anesthesiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Sebastiani
authors.affiliation: Department of Anesthesiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hirnet
authors.affiliation: Institute of Medical Biostatistics, Epidemiology and Informatics, Medical Center of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Jahn-Eimermacher
authors.affiliation: Department of Anesthesiology, Medical Center of the Johannes Gutenberg University, Mainz, Germany. Electronic address: serge@thal.de.
authors.forename: Serge C
authors.initials: SC
authors.lastname: Thal
mesh_terms: D000818:Animals; D019540:Area Under Curve; D001923:Brain Chemistry; D001929:Brain Edema / Q000188:drug therapy / Q000378:metabolism; D000070642:Brain Injuries, Traumatic / Q000188:drug therapy / Q000378:metabolism; D002498:Centrifugation; D003890:Desiccation / Q000295:instrumentation / Q000379:methods*; D004195:Disease Models, Animal; D005240:Feasibility Studies; D060005:Genotyping Techniques; D006358:Hot Temperature; D008297:Male; D008810:Mice, Inbred C57BL; D018696:Neuroprotective Agents / Q000494:pharmacology; D012372:ROC Curve; D017693:Sodium Bicarbonate / Q000494:pharmacology; D013997:Time Factors; D014618:Vacuum; D014867:Water / Q000032:analysis*
chemical_list: D018696:Neuroprotective Agents; D014867:Water; D017693:Sodium Bicarbonate
keywords: Brain edema; Brain water content; Centrifugal vacuum concentrators; Drying technique; Heat-drying; Oven; Speed-vacuum drying; SpeedVac; Vacuum; Vacuum-drying