Gel electrophoresis is a ubiquitous bioanalytical technique used to characterize the components of cell lysates. However, analyses of bulk lysates sacrifice detection sensitivity because intracellular biomolecules become diluted, and the liberation of proteases and nucleases can degrade target analytes. This report describes a method to enrich cells directly within a microfluidic gel as a first step toward online measurement of trace intracellular biomolecules with minimal dilution and degradation. Thermal gels were employed as the gel matrix because they can be reversibly converted between liquid and solid phases as a function of temperature. Rather than fabricate costly heating elements into devices to control temperature—and thus the phase of the gel—Joule heating was used instead. Adjoining regions of liquid-phase and solid-phase gel were formed within microfluidic channels by selectively inducing localized Joule heat. Cells migrated through the liquid gel but could not enter the solid gel—accumulating at the liquid–solid gel boundary—whereas small molecule contaminants passed through to waste. Barriers were then liquified on-demand by removing Joule heat to collect the purified, non-lysed cells for downstream analyses. Using voltage-controlled Joule heating to regulate the phase of thermal gels is an innovative approach to facilitate in-gel cell enrichment in low-cost microfluidic devices.

中文翻译：

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利用微流热凝胶电泳中的焦耳热为细胞富集创建可逆屏障


凝胶电泳是一种普遍存在的生物分析技术，用于表征细胞裂解物的成分。然而，大量裂解物的分析会牺牲检测灵敏度，因为细胞内生物分子被稀释，并且蛋白酶和核酸酶的释放会降解目标分析物。该报告描述了一种直接在微流体凝胶内富集细胞的方法，作为以最小的稀释和降解在线测量痕量细胞内生物分子的第一步。热凝胶被用作凝胶基质，因为它们可以作为温度的函数在液相和固相之间可逆地转换。我们没有将昂贵的加热元件制造到设备中来控制温度，从而控制凝胶的相，而是使用焦耳加热。通过选择性诱导局部焦耳热，在微流体通道内形成相邻的液相和固相凝胶区域。细胞迁移穿过液体凝胶，但无法进入固体凝胶，在液-固凝胶边界处积聚，而小分子污染物则会进入废物。然后通过消除焦耳热按需液化屏障，以收集纯化的、未裂解的细胞用于下游分析。使用电压控制焦耳加热来调节热凝胶的相是一种促进低成本微流体装置中凝胶内细胞富集的创新方法。