Combining FEM and optical tweezers to better understand mechanical properties of erythrocytes

Red blood cell (erythrocyte) membrane elasticity is a critical factor in the condition of stored blood, which is known to deteriorate over time. While most previous research assumed a constant erythrocyte thickness, a research team at Jiangsu Key Laboratory of Advanced Laser Materials and Devices at Jiangsu National University in China combined simulation and experiment to better characterize the mechanical properties of erythrocytes. They report their findings in AIP Advances.

The team, led by biophysicist Ying Liu, conducted measurements of the membrane shear moduli and the size of the erythrocytes using a commercial optical tweezers system. In addition to this experimental approach, the team developed a linear stretching model of the erythrocyte simulated by FEM using commercial simulation software COMSOL Multiphysics. The model is divided into 5508 triangle meshes, in order to achieve higher accuracy. This allowed the team to optimize the resulting erythrocyte model, comparing simulations with experimental results.

The experimental results of the linear stretching demonstrated that the longer the storage time of the blood, the less elasticity the erythrocyte cell membrane retained and the smaller their size became over time. Using a parameter-optimized model, the researchers then simulated the tensile state of stored erythrocytes. The simulation showed that on days 2-6 the cell membrane thickness undergoes slow change, then on days 6-14 the erythrocyte thickness changes very fast, before becoming slow again between 14-18 days.

The research team’s approach helps to generate an understanding of the mechanical properties of erythrocyte. It also demonstrates the potential of using FEM to investigate internal mechanical property changes of erythrocytes in different environments that can provide a baseline for studying different diseases.

Source: “Experiment study and FEM simulation on erythrocytes under linear stretching of optical micromanipulation,” by Ying Liu, Huadong Song, Panpan Zhu, Hao Lu, and Qi Tang, AIP Advances (2017). The article can be accessed at https://doi.org/10.1063/1.4989980 .