Reconfigurable Microfluidic Circuits for Isolating and Retrieving Cells of Interest

Microfluidic devices
are widely used in many fields of biology,
but a key limitation is that cells are typically surrounded by solid
walls, making it hard to access those that exhibit a specific phenotype
for further study. Here, we provide a general and flexible solution
to this problem that exploits the remarkable properties of microfluidic
circuits with fluid wallstransparent interfaces between culture
media and an immiscible fluorocarbon that are easily pierced with
pipets. We provide two proofs of concept in which specific cell subpopulations
are isolated and recovered: (i) murine macrophages chemotaxing toward
complement component 5a and (ii) bacteria (Pseudomonas
aeruginosa) in developing biofilms that migrate toward
antibiotics. We build circuits in minutes on standard Petri dishes,
add cells, pump in laminar streams so molecular diffusion creates
attractant gradients, acquire time-lapse images, and isolate desired
subpopulations in real time by building fluid walls around migrating
cells with an accuracy of tens of micrometers using 3D printed adaptors
that convert conventional microscopes into wall-building machines.
Our method allows live cells of interest to be easily extracted from
microfluidic devices for downstream analyses.

微流控设备（Microfluidic devices）已被广泛应用于生物学诸多领域，但存在一项关键局限：通常情况下细胞会被固体壁面包裹，导致难以获取具备特定表型的细胞以开展后续研究。对此，本文提出一种通用且灵活的解决方案，该方案利用了带有流体壁面的微流控回路的卓越特性——流体壁面是培养基与不混溶氟碳化合物（fluorocarbon）之间的透明界面，可通过移液管轻松刺穿。我们开展了两项概念验证实验，以分离并回收特定的细胞亚群：(i) 向补体成分5a（complement component 5a）产生趋化运动的小鼠巨噬细胞；(ii) 发育中生物被膜（biofilm）内可向抗生素迁移的细菌——铜绿假单胞菌（Pseudomonas aeruginosa）。我们可在标准培养皿（Petri dish）上于数分钟内搭建微流控回路，加入细胞后泵入层流（laminar stream），通过分子扩散形成趋化因子梯度，随后采集延时影像（time-lapse image）；并借助可将常规显微镜改造为壁面构建装置的3D打印适配器（3D printed adaptors），以数十微米的精度在迁移细胞周围构建流体壁面，实现目标细胞亚群的实时分离。本方法可便捷地从微流控设备中提取目标活细胞，用于下游分析。