Mechanical and Electrical Engineering Department, Facultad de Ingeniería, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México.
CONACYT-Universidad Autónoma de San Luis Potosí, San Luis Potosí, México.
Lasers Surg Med. 2022 Sep;54(7):1027-1037. doi: 10.1002/lsm.23554. Epub 2022 Apr 21.
One of the reported pathways of cancer spread is the transcoelomic pathway, which is understood as the spread of cancer cells in the abdominal and thoracic cavities through interstitial fluid. It has been proven that the shear stresses caused by microfluidic currents on cancer tumors in the abdominal and thoracic cavities cause the detachment of cancer cells triggering transcoelomic metastasis; however, the magnitude of shear stresses has not yet been measured experimentally.
The objective of this study is to develop an experimental methodology using optical tweezers to approximate the shear stresses suffered by a nonporous, rigid artificial cancerous nodule model.
Artificial cancerous nodule model was made by the agglomeration of 2 μm diameter polystyrene particles in a microfluidic platform. Optical tweezers were used as a velocimetry tool and shear stresses on the surface of the nodule model were approximated with the viscous shear stress equation. The results were verified with a numerical simulation performed in Ansys Fluent.
Shear stress originated by microflow over artificial cancerous nodule model were quantified both experimentally and numerically, showing good agreement between both methods. Such stress on the nodules' surface was much greater than that suffered by the wall on which the nodule model was located and dependent of the nodule model geometry. Although the experiment and simulation of this study were performed using a rigid and nonporous nodule model, the conclusion obtained about the increase of shear stresses applies to permeable, porous, and soft nodules as well, because the shear stresses are associated to the acceleration of the fluid originated by the reduction of the cross-sectional area.
Shear stress over artificial nodule model were successfully quantified using optical tweezer-based velocimetry technique and verified through numerical calculation. Advantages of experimental technique are: (1) it allows to control the position in a three-dimensional plane, allowing measurements in the vicinity of the analyzed surfaces, and (2) it is applicable for very low Reynolds number (R « 1). On the other hand, as disadvantages: (1) it tends to be complicated to perform velocity measurements over obstacles and (2) it is limited in trapping distance.
癌症转移的一种报道途径是透壁转移途径，该途径被理解为癌细胞通过间质液在腹腔和胸腔中的扩散。已经证明，腹腔和胸腔中肿瘤上的微流体电流产生的剪切应力会导致癌细胞脱落，从而引发透壁转移；然而，剪切应力的大小尚未通过实验测量。
本研究的目的是开发一种使用光镊的实验方法来近似模拟非多孔刚性人工癌性结节模型所承受的剪切应力。
人工癌性结节模型是通过在微流控平台中聚集 2 μm 直径的聚苯乙烯颗粒制成的。光镊被用作速度测量工具，通过粘性剪切应力方程来近似结节模型表面的剪切应力。结果通过在 Ansys Fluent 中进行数值模拟进行了验证。
通过实验和数值模拟两种方法都定量了微流对人工癌性结节模型产生的剪切应力，两种方法之间的结果吻合良好。结节表面的这种应力远大于结节所在壁面所承受的应力，并且与结节模型的几何形状有关。尽管本研究的实验和模拟都是使用刚性非多孔结节模型进行的，但关于剪切应力增加的结论也适用于可渗透的多孔和柔软的结节，因为剪切应力与由于横截面面积减小而产生的流体加速度有关。
成功地使用基于光镊的速度测量技术对人工结节模型的剪切应力进行了定量，并通过数值计算进行了验证。实验技术的优点是：（1）它允许在三维平面上控制位置，允许在分析表面附近进行测量；（2）它适用于非常低的雷诺数（R « 1）。另一方面，其缺点是：（1）在障碍物上进行速度测量往往比较复杂；（2）捕获距离有限。
