High-Throughput Generation, Manipulation, and Degradation of Magnetic Nanoparticle-Laden Alginate Core-Shell Beads for Single Bacteria Culturing Analysis

Microbes could be found almost everywhere around us and have significant impacts on our human society. The treatment of microorganisms has long been seen as a complex problem. Till now, most of the genetic and phenotypic information regarding rare species is buried in the bulk microbial colony due to a lack of efficient tools to screen live bacteria. Droplet microfluidics offers a powerful approach to address this problem. However, the interactions among bacteria and their living environment are entirely restricted by the water/oil interfaces in conventional water/oil single emulsion-based microfluidic systems. Here, we demonstrate an oil-mediated all-aqueous microfluidic workflow that can overcome this drawback. In contrast to the previous works, our all-aqueous culturing environment allows cell-cell and cell-environment interactions, thus facilitating the growth of bacteria. Fe3O4 magnetic nanoparticles added into the alginate beads enables on-chip manipulation of the microcapsules. The core-shell structure separately encapsulates bacteria and magnetic particles in the core and shell to avoid contamination. We demonstrate the feasibility of this approach by single bacterium culturing in droplet-templated alginate beads. Finally, a new approach is proposed to degrade the alginate beads for post-treatment. This novel microfluidic workflow can create new opportunities for microbial applications, such as bacteria culturing and screening.