Bradley Brianna, Gomez-Cruz Juan, Escobedo Carlos
Department of Chemical Engineering, Queen's University, Kingston, ON K7L 3N6, Canada.
Bioengineering (Basel). 2023 Sep 1;10(9):1034. doi: 10.3390/bioengineering10091034.
Magnetotactic bacteria have great potential for use in biomedical and environmental applications due to the ability to direct their navigation with a magnetic field. Applying and accurately controlling a magnetic field within a microscopic region during bacterial magnetotaxis studies at the single-cell level is challenging due to bulky microscope components and the inherent curvilinear field lines produced by commonly used bar magnets. In this paper, a system that integrates microfluidics and electromagnetic coils is presented for generating a linear magnetic field within a microenvironment compatible with microfluidics, enabling magnetotaxis analysis of groups or single microorganisms on-chip. The platform, designed and optimised via finite element analysis, is integrated into an inverted fluorescent microscope, enabling visualisation of bacteria at the single-cell level in microfluidic devices. The electromagnetic coils produce a linear magnetic field throughout a central volume where the microfluidic device containing the magnetotactic bacteria is located. The magnetic field, at this central position, can be accurately controlled from 1 to 10 mT, which is suitable for directing the navigation of magnetotactic bacteria. Potential heating of the microfluidic device from the operating coils was evaluated up to 2.5 A, corresponding to a magnetic field of 7.8 mT, for 10 min. The maximum measured heating was 8.4 °C, which enables analysis without altering the magnetotaxis behaviour or the average swimming speed of the bacteria. Altogether, this work provides a design, characterisation and experimental test of an integrated platform that enables the study of individual bacteria confined in microfluidics, under linear and predictable magnetic fields that can be easily and accurately applied and controlled.
趋磁细菌因其能够在磁场中引导自身导航，在生物医学和环境应用方面具有巨大潜力。在单细胞水平的细菌趋磁研究中，由于显微镜组件体积庞大以及常用条形磁铁产生的固有曲线磁场线，在微观区域内施加并精确控制磁场具有挑战性。本文提出了一种集成微流体和电磁线圈的系统，用于在与微流体兼容的微环境中产生线性磁场，从而能够对芯片上的群体或单个微生物进行趋磁分析。该平台通过有限元分析进行设计和优化，集成到倒置荧光显微镜中，能够在微流体装置中实现单细胞水平的细菌可视化。电磁线圈在包含趋磁细菌的微流体装置所在的中心区域产生线性磁场。在这个中心位置，磁场可以精确控制在1至10毫特斯拉之间，这适合引导趋磁细菌的导航。对于工作线圈，评估了微流体装置在高达2.5安培（对应7.8毫特斯拉的磁场）下持续10分钟的潜在发热情况。测得的最大发热为8.4摄氏度，这使得在不改变细菌趋磁行为或平均游动速度的情况下进行分析成为可能。总之，这项工作提供了一个集成平台的设计、表征和实验测试，该平台能够在易于精确施加和控制的线性且可预测的磁场下，对微流体中受限的单个细菌进行研究。
