(159h) Maneuverability of micromotors in the low Reynolds fluid cytoplasm inside living cells

Intracellular manipulation and measurement reveal the properties and functions of structures and organelles inside a cell. The mechanical properties of the subcellular level are closely related to major diseases. For example, the mechanical properties of the nucleus are linked to heart disease and cancer, and the properties of endoplasmic reticulum (ER) control intracellular calcium storage and regulation. From the single cell era to the subcellular era, movement in subcellular cytoplasmic fluid environment and manipulation of organelles remain underexplored.

Micromotors has received more and more attentions in the field of active drug delivery. Researchers have done motion control in different fluid environments. There is excellent work at different levels of the human body, from organs, tissues, to single cells. However, control on subcellular level is still less studied. Spatiotemporally controlled active movement and manipulation of micromotors in living cells on subcellular level can be used in biomedical technologies such as new drug delivery carriers, nanoprobes for complex intracellular biophysical phenomena, and real-time mechanical mapping of intracellular environment.

Researchers attempted subcellular movement through acoustic propulsion, magnetic controlled helical nanomotors, etc., and initially achieved movement in a highly viscous fluid environment within the cytoplasm. However, in cytoplasm, the special low Reynolds number environment, the efficiency of the controlled motion is rather low, while the controllability, motility, stability of the movement is facing great challenges.

This work used the 3D magnetic close-loop control method, combined with biohybrid microalgae and surface modification, to solve the problems at this low Reynolds number of control degree of freedom (DOF), feedback of position, force generation, biocompatibility. Deeper understanding of the movement of micromotors in the special fluid environment was gained to help improve the controllability, motility and stability. Furthermore, this work improves the performance of micromotors in this low Reynolds number environment and provides the infrastructure for further subcellular-level manipulation and surgery.