title: Effects of freezing rates and cryoprotectant on thermal expansion of articular cartilage during freezing process.
abstract: The intact articular cartilage has not yet been successfully preserved at low temperature most likely due to the volume expansion from water to ice during freezing. The objective of this current study focuses on examining thermal expansion behavior of articular cartilage (AC) during freezing from 0 degree C to -100 degree C. Thermo Mechanical Analysis (TMA) was used to investigate the effects of different concentrations of dimethyl sulphoxide (DMSO) (0%, 10%, 30% and 60% v/v) and different freezing rates (1 C/min, 3 C/min and 5 C/min). The results showed that: (1) the inhomogeneous thermal expansion (or contraction) presents due to inhomogeneous water distributions in articular cartilage during freezing, which also may be the most likely reason that the matrix has been damaged in cryopreserved intact articular cartilage; (2) at the phase transition temperature range, the maximum thermal strain change value for 5C/min is approximately 1.45 times than that for 1 C/min, but the maximum thermal expansion coefficient of the later is about six times than that of the former; (3) the thermal expansion coefficient decreases with increasing cooling rate at the unfrozen temperature region, but some opposite results are obtained at the frozen temperature region; (4) the higher the DMSO concentration is, at the phase change temperature region, the smaller the thermal strain change as well as the maximum thermal expansion coefficient are, but DMSO concentration exhibits little effect on the thermal expansion coefficient at both unfrozen and frozen region. Once the DMSO concentration increasing enough, e.g. 60% v/v, the thermal strain decreases linearly and smoothly without any abrupt change due to little or no ice crystal forms (i.e. vitrification) in frozen articular cartilage. This study may improve our understanding of the thermal expansion (or contraction) behavior of cryopreserved articular cartilage and it may be useful for the future study on cryopreservation of intact articular cartilage.
authors.affiliation: Institute of Cryomedicine, University of Shanghai for Science and Technology, Shanghai, China. xu_hongyi@263.net
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: H J
authors.initials: HJ
authors.lastname: Sun
authors.forename: Y
authors.initials: Y
authors.lastname: Lv
authors.forename: J C
authors.initials: JC
authors.lastname: Zou
authors.forename: B L
authors.initials: BL
authors.lastname: Lin
authors.forename: T C
authors.initials: TC
authors.lastname: Hua
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000378:metabolism*; D005615:Freezing; D044367:Phase Transition; D013314:Stress, Mechanical; D013552:Swine; D013696:Temperature; D058989:Vitrification; D014867:Water / Q000378:metabolism*
chemical_list: D003451:Cryoprotective Agents; D014867:Water; D004121:Dimethyl Sulfoxide