Adeyiga Oladunni B, Murray Coleman, Muñoz Hector E, Escobar Alberto, Di Carlo Dino
Division of Infectious Diseases, David Geffen School of Medicine, Department of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America.
Ferrologix, Inc., Redondo Beach, California, United States of America.
PLoS One. 2021 Feb 18;16(2):e0246124. doi: 10.1371/journal.pone.0246124. eCollection 2021.
Magnetic ratcheting cytometry is a promising approach to separate magnetically-labeled cells and magnetic particles based on the quantity of magnetic material. We have previously reported on the ability of this technique to separate magnetically-labeled cells. Here, with a new chip design, containing high aspect ratio permalloy micropillar arrays, we demonstrate the ability of this technique to rapidly concentrate and collect superparamagnetic iron oxide particles. The platform consists of a mechatronic wheel used to generate and control a cycling external magnetic field that impinges on a "ratcheting chip." The ratcheting chip is created by electroplating a 2D array of high aspect ratio permalloy micropillars onto a glass slide, which is embedded in a thin polymer layer to create a planar surface above the micropillars. By varying magnetic field frequency and direction through wheel rotation rate and angle, we direct particle movement on chip. We explore the operating conditions for this system, identifying the effects of varying ratcheting frequency, along with time, on the dynamics and resulting concentration of these magnetic particles. We also demonstrate the ability of the system to rapidly direct the movement of superparamagnetic iron oxide particles of varying sizes. Using this technique, 2.8 μm, 500 nm, and 100 nm diameter superparamagnetic iron oxide particles, suspended within an aqueous fluid, were concentrated. We further define the ability of the system to concentrate 2.8 μm superparamagnetic iron oxide particles, present in a liquid suspension, into a small chip surface area footprint, achieving a 100-fold surface area concentration, and achieving a concentration factor greater than 200%. The achieved concentration factor of greater than 200% could be greatly increased by reducing the amount of liquid extracted at the chip outlet, which would increase the ability of achieving highly sensitive downstream analytical techniques. Magnetic ratcheting-based enrichment may be useful in isolating and concentrating subsets of magnetically-labeled cells for diagnostic automation.
磁棘轮细胞术是一种很有前景的方法，可基于磁性材料的量来分离磁性标记的细胞和磁性颗粒。我们之前曾报道过该技术分离磁性标记细胞的能力。在此，通过一种包含高纵横比坡莫合金微柱阵列的新型芯片设计，我们展示了该技术快速浓缩和收集超顺磁性氧化铁颗粒的能力。该平台由一个机电轮组成，用于产生和控制作用于“棘轮芯片”的循环外部磁场。棘轮芯片是通过将高纵横比坡莫合金微柱的二维阵列电镀到载玻片上制成的，载玻片嵌入薄聚合物层中，以在微柱上方形成一个平面表面。通过改变磁场频率和方向（通过轮的旋转速率和角度），我们引导颗粒在芯片上移动。我们探索了该系统的操作条件，确定了不同棘轮频率以及时间对这些磁性颗粒的动力学和最终浓度的影响。我们还展示了该系统快速引导不同尺寸超顺磁性氧化铁颗粒移动的能力。使用该技术，悬浮在水性流体中的直径为2.8μm、500nm和100nm的超顺磁性氧化铁颗粒被浓缩。我们进一步确定了该系统将存在于液体悬浮液中的2.8μm超顺磁性氧化铁颗粒浓缩到小芯片表面积范围内的能力，实现了100倍的表面积浓缩，并实现了大于200%的浓缩系数。通过减少芯片出口处提取的液体量，可以大大提高大于200%的浓缩系数，这将增强实现高灵敏度下游分析技术的能力。基于磁棘轮的富集在分离和浓缩磁性标记细胞亚群以实现诊断自动化方面可能是有用的。
