Centre for Biomedical Engineering, Department of Electronic Science & Technology, University of Science and Technology of China, Hefei 230027, China.
Centre for Biomedical Engineering, Department of Electronic Science & Technology, University of Science and Technology of China, Hefei 230027, China.
Cryobiology. 2014 Apr;68(2):234-43. doi: 10.1016/j.cryobiol.2014.02.002. Epub 2014 Feb 13.
In this study, the microwave rewarming process of cryopreserved samples with embedded superparamagnetic (SPM) nanoparticles was numerically simulated. The Finite Element Method (FEM) was used to calculate the coupling of the electromagnetic field and the temperature field in a microwave rewarming system composed of a cylindrical resonant cavity, an antenna source, and a frozen sample phantom with temperature-dependent properties. The heat generated by the sample and the nanoparticles inside the electromagnetic field of the microwave cavity was calculated. The dielectric properties of the biological tissues were approximated using the Debye model, which is applicable at different temperatures. The numerical results showed that, during the rewarming process of the sample phantom without nanoparticles, the rewarming rate was 29.45°C/min and the maximum temperature gradient in the sample was 3.58°C/mm. If nanoparticles were embedded in the sample, and the cavity power was unchanged, the rewarming rate was 47.76°C/min and the maximum temperature gradient in the sample was 1.64°C/mm. In the presence of SPM nanoparticles, the rewarming rate and the maximum temperature gradient were able to reach 20.73°C/min and 0.68°C/mm at the end of the rewarming under the optimized cavity power setting, respectively. The ability to change these temperature behaviors may prevent devitrification and would greatly diminish thermal stress during the rewarming process. The results indicate that the rewarming rate and the uniformity of temperature distribution are increased by nanoparticles. This could be because nanoparticles generated heat in the sample homogeneously and the time-dependent parameters of the sample improved after nanoparticles were homogeneously embedded within it. We were thus able to estimate the positive effect of SPM nanoparticles on microwave rewarming of cryopreserved samples.
本研究对嵌入超顺磁（SPM）纳米粒子的冷冻样本的微波复温过程进行了数值模拟。使用有限元方法（FEM）计算了由圆柱形谐振腔、天线源和具有温度相关特性的冷冻样本模型组成的微波复温系统中的电磁场和温度场的耦合。计算了样品和微波腔电磁场内部的纳米粒子产生的热量。使用 Debye 模型近似生物组织的介电特性，该模型适用于不同的温度。数值结果表明，在没有纳米粒子的样本复温过程中，复温速率为 29.45°C/min，样本中最大温度梯度为 3.58°C/mm。如果在样本中嵌入纳米粒子且腔功率不变，则复温速率为 47.76°C/min，样本中最大温度梯度为 1.64°C/mm。在 SPM 纳米粒子存在的情况下，在优化的腔功率设置下，复温结束时，复温速率和样本中的最大温度梯度分别可达到 20.73°C/min 和 0.68°C/mm。改变这些温度行为的能力可以防止玻璃化转变，并在复温过程中大大减少热应力。结果表明，纳米粒子提高了复温速率和温度分布的均匀性。这可能是因为纳米粒子在样品中均匀地产生热量，并且在纳米粒子均匀嵌入后，样品的时变参数得到改善。因此，我们可以估计 SPM 纳米粒子对冷冻样本的微波复温的积极影响。
