Microbial Cells with a Fe3 O4 Doped Hydrogel Extracellular Matrix: Manipulation of Living Cells by Magnetic Stimulus.

This study aims to develop an effective method to control motile microorganisms and enable their manipulation as functional 'live micro/nano robots'. A novel strategy based on Fe3 O4 nanoparticle-doped alginate hydrogel is developed to fashion an artificial extracellular matrix (ECM) for microbial cells (e.g., Saccharomyces cerevisiae and Flavobacterium heparinum). During this strategy, a single layer of alginate hydrogel is coated around the microbial cells doped with Fe3 O4 nanoparticles to form the alg-mag-cells. Transmission electron microscopy shows that Fe3 O4 nanoparticles are uniformly distributed in the hydrogel shell. Together with maintaining the cell activity and metabolism, the hydrogel coated microbial cells demonstrate high magnetic responsiveness in an external magnetic field and are able to form micro-scaled patterns using the magnetic template designed in this study. This strategy provides a building block to fabricate advanced biological models, medical therapeutic products, and non-medical biological systems using different microorganisms.