Sun Xuanhao, Weinlandt William D, Patel Harsh, Wu Mingming, Hernandez Christopher J
Sibley School of Mechanical and Aerospace Engineering, Biomedical Engineering, Cornell University, 219 Upson Hall, Ithaca, NY 14853, USA.
Lab Chip. 2014 Jul 21;14(14):2491-8. doi: 10.1039/c3lc51428e.
The ability to resist mechanical forces is necessary for the survival and division of bacteria and has traditionally been probed using specialized, low-throughput techniques such as atomic force microscopy and optical tweezers. Here we demonstrate a microfluidic technique to profile the stiffness of individual bacteria and populations of bacteria. The approach is similar to micropipette aspiration used to characterize the biomechanical performance of eukaryotic cells. However, the small size and greater stiffness of bacteria relative to eukaryotic cells prevents the use of micropipettes. Here we present devices with sub-micron features capable of applying loads to bacteria in a controlled fashion. Inside the device, individual bacteria are flowed and trapped in tapered channels. Less stiff bacteria undergo greater deformation and therefore travel further into the tapered channel. Hence, the distance traversed by bacteria into a tapered channel is inversely related to cell stiffness. We demonstrate the ability of the device to characterize hundreds of bacteria at a time, measuring stiffness at 12 different applied loads at a time. The device is shown to differentiate between two bacterial species, E. coli (less stiff) and B. subtilis (more stiff), and detect differences between E. coli submitted to antibiotic treatment from untreated cells of the same species/strain. The microfluidic device is advantageous in that it requires only minimal sample preparation, no permanent cell immobilization, no staining/labeling and maintains cell viability. Our device adds detection of biomechanical phenotypes of bacteria to the list of other bacterial phenotypes currently detectable using microchip-based methods and suggests the feasibility of separating/selecting bacteria based on differences in cell stiffness.
抵抗机械力的能力对于细菌的存活和分裂至关重要，传统上一直使用原子力显微镜和光镊等专门的低通量技术进行探究。在此，我们展示了一种微流控技术，用于分析单个细菌和细菌群体的硬度。该方法类似于用于表征真核细胞生物力学性能的微量移液器抽吸法。然而，相对于真核细胞，细菌的尺寸小且硬度大，这使得无法使用微量移液器。在此，我们展示了具有亚微米特征的装置，能够以可控方式对细菌施加负载。在装置内部，单个细菌流入并被困在锥形通道中。硬度较小的细菌会发生更大的变形，因此会进一步进入锥形通道。因此，细菌进入锥形通道的距离与细胞硬度成反比。我们展示了该装置一次能够表征数百个细菌的能力，同时在12种不同的施加负载下测量硬度。该装置能够区分两种细菌，即大肠杆菌（硬度较小）和枯草芽孢杆菌（硬度较大），并检测经抗生素处理的大肠杆菌与同一物种/菌株未处理细胞之间的差异。这种微流控装置的优势在于它只需要极少的样品制备，无需永久性细胞固定，无需染色/标记，并且能维持细胞活力。我们的装置将细菌生物力学表型的检测添加到目前可使用基于微芯片的方法检测的其他细菌表型列表中，并表明基于细胞硬度差异分离/选择细菌的可行性。
