title: Effects of Superparamagnetic Nanoparticles on Nucleation and Crystal Growth in the Vitrified VS55 During Warming.
abstract: BACKGROUND：Magnetic nanoparticles (mNPs), once excited by radiofrequency (RF) energy, could heat uniformly and rapidly the vitrified biospecimens. However, there are few studies about the impact of mNPs on crystallization kinetics of vitrified samples.
  
  
  OBJECTIVE
  The present work aims to investigate the nucleation and crystal growth in the vitrification solution VS55 with mNPs.
  
  
  METHODS
  Ferrotec EMG308 superparamagnetic nanoparticles (10 ± 2.5 nm in diameter) coated with an anionic surfactant was used in this study with Fe2+ concentration around 10 mg/ml. The thermal range and the kinetics of nucleation and crystal growth are conducted by DSC and cryomicroscope through different thermal treatments.
  
  
  RESULTS
  The fusion heat of VS55+ mNPs is lower than that of VS55 around the rubbery region (-110 to -82 degree C), which suggests the suppression of ice nuclei formation at this temperature range by mNPs. Upon slow cooling especially, much more nuclei in vitrified VS55 forms than that in vitrified VS55+mNPs. The activation energy Eaof VS55 is lower than that of VS55+mNPs (41.6 kJ/mol vs 46.2 kJ/mol) during devitrification. The presence of mNPs helps to form more stable glass. And these results are consistent with the observations by cryomicroscope.
  
  
  CONCLUSIONS
  The presence of mNPs suppresses ice nuclei formation, especially at slow cooling conditions, and stabilize the cryoprotective solution. The findings can assist the design of magnetic nanoparticles with functional surface coating.
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and Technology, Shanghai, China. xuyi@usst.edu.cn.
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and Technology, Shanghai, China.
authors.forename: H M
authors.initials: HM
authors.lastname: Yu
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and Technology, Shanghai, China.
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Niu
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and Technology, Shanghai, China.
authors.forename: S C
authors.initials: SC
authors.lastname: Luo
authors.affiliation: Institute of Biothermal Science and Technology, University of Shanghai for Science and Technology, Shanghai, China.
authors.forename: X
authors.initials: X
authors.lastname: Cheng
mesh_terms: D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D003460:Crystallization; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D005559:Formamides / Q000494:pharmacology*; D006531:HEPES / Q000494:pharmacology*; D007700:Kinetics; D058185:Magnetite Nanoparticles; D011409:Propylene Glycols / Q000494:pharmacology*; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents; D005559:Formamides; D058185:Magnetite Nanoparticles; D011409:Propylene Glycols; C481729:VS55 solution; D006531:HEPES; D004121:Dimethyl Sulfoxide