Loessberg-Zahl Joshua, Beumer Jelle, van den Berg Albert, Eijkel Jan C T, van der Meer Andries D
BIOS/Lab on a Chip, University of Twente, 7500-AE Enschede, The Netherlands.
Applied Stem Cell Technologies, University of Twente, 7500-AE Enschede, The Netherlands.
Micromachines (Basel). 2020 Dec 16;11(12):1112. doi: 10.3390/mi11121112.
Microfluidic devices are used extensively in the development of new in vitro cell culture models like organs-on-chips. A typical feature of such devices is the patterning of biological hydrogels to offer cultured cells and tissues a controlled three-dimensional microenvironment. A key challenge of hydrogel patterning is ensuring geometrical confinement of the gel, which is generally solved by inclusion of micropillars or phaseguides in the channels. Both of these methods often require costly cleanroom fabrication, which needs to be repeated even when only small changes need be made to the gel geometry, and inadvertently expose cultured cells to non-physiological and mechanically stiff structures. Here, we present a technique for facile patterning of hydrogel geometries in microfluidic chips, but without the need for any confining geometry built into the channel. Core to the technique is the use of laminar flow patterning to create a hydrophilic path through an otherwise hydrophobic microfluidic channel. When a liquid hydrogel is injected into the hydrophilic region, it is confined to this path by the surrounding hydrophobic regions. The various surface patterns that are enabled by laminar flow patterning can thereby be rendered into three-dimensional hydrogel structures. We demonstrate that the technique can be used in many different channel geometries while still giving the user control of key geometric parameters of the final hydrogel. Moreover, we show that human umbilical vein endothelial cells can be cultured for multiple days inside the devices with the patterned hydrogels and that they can be stimulated to migrate into the gel under the influence of trans-gel flows. Finally, we demonstrate that the patterned gels can withstand trans-gel flow velocities in excess of physiological interstitial flow velocities without rupturing or detaching. This novel hydrogel-patterning technique addresses fundamental challenges of existing methods for hydrogel patterning inside microfluidic chips, and can therefore be applied to improve design time and the physiological realism of microfluidic cell culture assays and organs-on-chips.
微流控装置在诸如芯片器官等新型体外细胞培养模型的开发中得到了广泛应用。此类装置的一个典型特征是对生物水凝胶进行图案化处理，以便为培养的细胞和组织提供可控的三维微环境。水凝胶图案化的一个关键挑战是确保凝胶的几何形状受限，这通常通过在通道中包含微柱或相位引导器来解决。这两种方法通常都需要昂贵的洁净室制造工艺，即使只需对凝胶几何形状进行微小更改也需要重复操作，而且会在不经意间使培养的细胞暴露于非生理且机械刚性的结构中。在此，我们提出了一种在微流控芯片中轻松实现水凝胶几何形状图案化的技术，但无需在通道中构建任何限制几何形状。该技术的核心是利用层流图案化来创建一条穿过原本疏水的微流控通道的亲水路径。当将液态水凝胶注入亲水区域时，它会被周围的疏水区域限制在这条路径内。由此，层流图案化实现的各种表面图案可以转化为三维水凝胶结构。我们证明该技术可用于许多不同的通道几何形状，同时仍能让用户控制最终水凝胶的关键几何参数。此外，我们表明人脐静脉内皮细胞可以在带有图案化水凝胶的装置内培养多天，并且在跨凝胶流的影响下可以被刺激迁移到凝胶中。最后，我们证明图案化的凝胶能够承受超过生理间质流速的跨凝胶流速而不会破裂或脱离。这种新颖的水凝胶图案化技术解决了微流控芯片内现有水凝胶图案化方法的基本挑战，因此可用于缩短设计时间并提高微流控细胞培养分析和芯片器官的生理真实性。
