title: Comparative Study on Two Different Methods for Determination of Hydraulic Conductivity of HeLa Cells During Freezing.
abstract: BACKGROUND
  The measurement of hydraulic conductivity of the cell membrane is very important for optimizing the protocol of cryopreservation and cryosurgery. There are two different methods using differential scanning calorimetry (DSC) to measure the freezing response of cells and tissues. Devireddy et al. presented the slow-fast-slow (SFS) cooling method, in which the difference of the heat release during the freezing process between the osmotically active and inactive cells is used to obtain the cell membrane hydraulic conductivity and activation energy. Luo et al. simplified the procedure and introduced the single-slow (SS) cooling protocol, which requires only one cooling process although different cytocrits are required for the determination of the membrane transport properties. To the best of our knowledge, there is still a lack of comparison of experimental processes and requirements for experimental conditions between these two methods. This study made a systematic comparison between these two methods from the aforementioned aspects in detail.
  
  
  METHODS
  The SFS and SS cooling methods mentioned earlier were utilized to obtain the reference hydraulic conductivity (Lpg) and activation energy (ELp) of HeLa cells by fitting the model to DSC data.
  
  
  RESULTS
  With the SFS method, it was determined that Lpg= 0.10 μm/(min·atm) and ELp= 22.9 kcal/mol; whereas the results obtained by the SS cooling method showed that Lpg= 0.10 μm/(min·atm) and ELp= 23.6 kcal/mol.
  
  
  CONCLUSIONS
  The results indicated that the values of the water transport parameters measured by two methods were comparable. In other words, the two parameters can be obtained by comparing the heat releases between two slow cooling processes of the same sample according to the SFS method. However, the SS method required analyzing heat releases of samples with different cytocrits. Thus, more experimental time was required.
authors.affiliation: 1 School of Mechanical and Automotive Engineering, Hefei University of Technology , Hefei, Anhui, China .
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.affiliation: 1 School of Mechanical and Automotive Engineering, Hefei University of Technology , Hefei, Anhui, China .
authors.forename: Cai
authors.initials: C
authors.lastname: Gao
authors.affiliation: 2 Department of Electronic Science and Technology, Centre for Biomedical Engineering, University of Science and Technology of China , Hefei, Anhui, China .|3 Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei, Anhui, China .
authors.forename: Gang
authors.initials: G
authors.lastname: Zhao
authors.affiliation: 4 School of Mechanical and Materials Engineering, Washington State University , Everett, Washington.
authors.forename: Zhiquan
authors.initials: Z
authors.lastname: Shu
authors.affiliation: 3 Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei, Anhui, China .|5 Center for Reproductive Medicine, The Affiliated Hospital of Anhui Medical University , Hefei, China .
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Cao
authors.affiliation: 3 Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei, Anhui, China .|6 Department of Mechanical Engineering, University of Washington , Seattle, Washington.
authors.forename: Dayong
authors.initials: D
authors.lastname: Gao
mesh_terms: D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000502:physiology; D015925:Cryopreservation / Q000379:methods*; D006367:HeLa Cells / Q000166:cytology*; D006801:Humans; D008954:Models, Biological; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water
keywords: HeLa cells; cryopreservation; differential scanning calorimetry; hydraulic conductivity