Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois.
Biotechnol Bioeng. 2014 Mar;111(3):597-607. doi: 10.1002/bit.25107. Epub 2013 Sep 30.
We present two novel microfluidic flow cells developed to provide reliable control of flow distributions and chemical gradients in biofilm studies. We developed a single-inlet microfluidic flow cell to support biofilm growth under a uniform velocity field, and a double-inlet flow cell to provide a very smooth transverse concentration gradient. Both flow cells consist of a layer of polydimethylsiloxane (PDMS) bonded to glass cover slips and were fabricated using the replica molding technique. We demonstrate the capabilities of the flow cells by quantifying flow patterns before and after growth of Pseudomonas aeruginosa biofilms through particle imaging velocimetry, and by evaluating concentration gradients within the double-inlet microfluidic flow cell. Biofilm growth substantially increased flow complexity by diverting flow around biomass, creating high- and low-velocity regions and surface friction. Under a glucose gradient in the double-inlet flow cell, P. aeruginosa biofilms grew in proportion to the local glucose concentration, producing distinct spatial patterns in biofilm biomass relative to the imposed glucose gradient. When biofilms were subjected to a ciprofloxacin gradient, spatial patterns of fractions of dead cells were also in proportion to the local antibiotic concentration. These results demonstrate that the microfluidic flow cells are suitable for quantifying flow complexities resulting from flow-biofilm interactions and investigating spatial patterns of biofilm growth under chemical gradients. These novel microfluidic flow cells will facilitate biofilm research that requires flow control and in situ imaging, particularly investigations of biofilm-environment interactions.
我们提出了两种新颖的微流控流池，旨在可靠地控制生物膜研究中的流动分布和化学梯度。我们开发了一种单入口微流控流池，以在均匀速度场下支持生物膜生长，以及一种双入口流池，以提供非常平滑的横向浓度梯度。这两种流池都由一层聚二甲基硅氧烷（PDMS）与玻璃盖玻片键合而成，并使用复制成型技术制造。我们通过粒子成像测速法在铜绿假单胞菌生物膜生长前后量化流动模式，以及通过评估双入口微流控流池内的浓度梯度，展示了流池的功能。生物膜生长通过将流动绕过生物量来极大地增加流动复杂性，从而产生高速和低速区域以及表面摩擦力。在双入口流池中的葡萄糖梯度下，铜绿假单胞菌生物膜的生长与局部葡萄糖浓度成正比，相对于施加的葡萄糖梯度，生物膜生物量产生了明显的空间模式。当生物膜受到环丙沙星梯度时，死亡细胞分数的空间模式也与局部抗生素浓度成正比。这些结果表明，微流控流池适合量化由于流动-生物膜相互作用而产生的流动复杂性，并研究化学梯度下生物膜生长的空间模式。这些新型微流控流池将促进需要流动控制和原位成像的生物膜研究，特别是生物膜-环境相互作用的研究。
