Department of Mechanical & Industrial Engineering, Montana State University, Bozeman MT, USA.
Department of Mechanical & Industrial Engineering, Montana State University, Bozeman MT, USA; Department of Microbiology & Cell Biology, Montana State University, Bozeman MT, USA.
J Biomech. 2024 Nov;176:112307. doi: 10.1016/j.jbiomech.2024.112307. Epub 2024 Sep 7.
Agarose is commonly used for 3D cell culture and to mimic the stiffness of the pericellular matrix of articular chondrocytes. Although it is known that both temperature and mechanical stimulation affect the metabolism of chondrocytes, little is known about the thermal properties of agarose hydrogels. Thermal properties of agarose are needed to analyze potential heat production by chondrocytes induced by various experimental stimuli (carbon source, cyclical compression, etc). Utilizing ASTM C177, a custom-built thermal conductivity measuring device was constructed and used to calculate the thermal conductivity of 4.5 % low gelling temperature agarose hydrogels. Additionally, Differential Scanning Calorimetry was used to calculate the specific heat capacity of the agarose hydrogels. Testing of chondrocyte-embedded agarose hydrogels commonly occurs in Phosphate-Buffered Saline (PBS), and thermal analysis requires the free convection coefficient of PBS. This was calculated using a 2D heat conduction simulation within MATLAB in tandem with experimental data collected for known boundary and initial conditions. The specific heat capacity and thermal conductivity of 4.5 % agarose hydrogels was calculated to be 2.85 J/g°C and 0.121 W/mK, respectively. The free convection coefficient of PBS was calculated to be 1000.1 W/mK. The values of specific heat capacity and thermal conductivity for agarose are similar to the reported values for articular cartilage, which are 3.20 J/g°C and 0.21 W/mK (Moghadam, et al. 2014). These data show that cyclical loading of hydrogel samples with these thermal properties will result in negligible temperature increases. This suggests that in addition to 4.5 % agarose hydrogels mimicking the physiological stiffness of the cartilage PCM, they can also mimic the thermal properties of articular cartilage for in vitro studies.
琼脂糖常用于 3D 细胞培养和模拟关节软骨细胞细胞外基质的刚度。虽然已知温度和机械刺激都会影响软骨细胞的代谢，但对琼脂糖水凝胶的热性质知之甚少。需要分析琼脂糖水凝胶的热性质，以研究各种实验刺激（碳源、周期性压缩等）引起的软骨细胞潜在产热量。利用 ASTM C177，构建了一种定制的导热率测量装置，并用于计算 4.5%低凝胶温度琼脂糖水凝胶的导热率。此外，还使用差示扫描量热法计算了琼脂糖水凝胶的比热容。通常在磷酸盐缓冲盐水 (PBS) 中测试嵌入软骨细胞的琼脂糖水凝胶，而热分析需要 PBS 的自由对流系数。这是通过在 MATLAB 中使用二维热传导模拟与为已知边界和初始条件收集的实验数据相结合来计算的。计算出 4.5%琼脂糖水凝胶的比热容和导热率分别为 2.85 J/g°C 和 0.121 W/mK。PBS 的自由对流系数计算为 1000.1 W/mK。琼脂糖的比热容和导热率值与关节软骨的报告值相似，分别为 3.20 J/g°C 和 0.21 W/mK（Moghadam 等人，2014 年）。这些数据表明，具有这些热性质的水凝胶样品周期性加载将导致可忽略的温度升高。这表明，除了 4.5%琼脂糖水凝胶模拟软骨 PCM 的生理刚度外，它们还可以模拟关节软骨的热性质，用于体外研究。
