Scalable and Spatially Selective Actuation of Living Microrobots

Abstract

In drug delivery, one key challenge is to minimize off- target accumulation in healthy regions, which can lead to toxicity or other associated complications. To address this challenge, drug delivery platforms can be designed either to localize the accumulation of active compounds to the target site or to selectively activate the portion that arrives in the targeted tissue. In the case of living bacterial therapeutics or bacteria-based biohybrid microrobots, bacteria can be equipped with onboard sensing, aiding their preferred accumulation in target regions such as tumors [1]. Nevertheless, robust tumor colonization by bacteria is still limited by low administrable doses and biological barriers that permit only a small portion to reach a target site after intravenous administration. Therefore, strategies that provide a means to target external energy to bacteria in a spatially selective manner can offer a much-needed element for enhanced targeting of living therapeutics [2]. Magnetotactic bacteria (MTB) are a group of bacteria noted for their intrinsic responsiveness to magnetic fields, and have been investigated as a drug carriers and potential living therapeutics. We previously demonstrated the possibility for enhancing tumor colonization using a scalable magnetic torque-based control approach employing a homogenous rotational magnetic field [3]. Here, we increase the spatial selectivity of this technique by employing a magnetostatic selection field that suppresses off target torque-based actuation.