Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada.
Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, Ontario M5S 3E1, Canada.
ACS Appl Mater Interfaces. 2023 Feb 8;15(5):6326-6337. doi: 10.1021/acsami.2c17317. Epub 2023 Jan 25.
Fouling at liquid-solid interfaces is a pernicious problem for a wide range of applications, including those that are implemented by digital microfluidics (DMF). There are several strategies that have been used to combat surface fouling in DMF, the most common being inclusion of amphiphilic surfactant additives in the droplets to be manipulated. Initial studies relied on Pluronic additives, and more recently, Tetronic additives have been used, which has allowed manipulation of complex samples like serum and whole blood. Here, we report our evaluation of 19 different Pluronic and Tetronic additives, with attempts to determine (1) the difference in antifouling performance between the two families, (2) the structural similarities that predict exceptional antifouling performance, and (3) the mechanism of the antifouling behavior. Our analysis shows that both Pluronic and Tetronic additives with modest molar mass, poly(propylene oxide) (PPO) ≥50 units, poly(ethylene oxide) (PEO) mass percentage ≤50%, and hydrophilic-lipophilic balance (HLB) ca. 13-15 allow for exceptional antifouling performance in DMF. The most promising candidates, P104, P105, and T904, were able to support continuous movement of droplets of serum for more than 2 h, a result (for devices operating in air) previously thought to be out of reach for this technique. Additional results generated using device longevity assays, intrinsic fluorescence measurements, dynamic light scattering, asymmetric flow field flow fractionation, supercritical angle fluorescence microscopy, atomic force microscopy, and quartz crystal microbalance measurements suggest that the best-performing surfactants are more likely to operate by forming a protective layer at the liquid-solid interface than by complexation with proteins. We propose that these results and their implications are an important step forward for the growing community of users of this technique, which may provide guidance in selecting surfactants for manipulating biological matrices for a wide range of applications.
固液界面结垢是广泛应用中的一个有害问题，包括那些通过数字微流控（DMF）实现的应用。已经有几种策略被用于对抗 DMF 中的表面结垢，最常见的方法是在要操作的液滴中加入两亲性表面活性剂添加剂。最初的研究依赖于 Pluronic 添加剂，最近，Tetronic 添加剂也被使用，这使得像血清和全血这样的复杂样本的操作成为可能。在这里，我们报告了对 19 种不同的 Pluronic 和 Tetronic 添加剂的评估，试图确定（1）这两种添加剂家族之间在抗污性能上的差异，（2）预测出异常抗污性能的结构相似性，以及（3）抗污行为的机制。我们的分析表明，具有中等摩尔质量、聚（丙烯氧化物）（PPO）≥50 个单元、聚（氧化乙烯）（PEO）质量百分比≤50%和亲水-亲脂平衡（HLB）约 13-15 的 Pluronic 和 Tetronic 添加剂都能在 DMF 中表现出异常的抗污性能。最有前途的候选物 P104、P105 和 T904 能够支持血清液滴的连续运动超过 2 小时，这一结果（对于在空气中运行的设备）以前被认为是该技术无法达到的。使用设备耐久性测定、本征荧光测量、动态光散射、非对称流场流分级、超临界角荧光显微镜、原子力显微镜和石英晶体微天平测量生成的其他结果表明，表现最好的表面活性剂更有可能通过在液-固界面形成保护层而不是与蛋白质络合来起作用。我们提出，这些结果及其意义是对使用这种技术的不断增长的用户群体的重要一步，这可能为选择用于操作各种生物基质的表面活性剂提供指导。
