Three-dimensional remote aggregation and steering of magnetotactic bacteria microrobots for drug delivery applications

Abstract

Magnetotactic bacteria (MTB) can be viewed as self-propelled natural microrobots. These bacterial microrobots can be remotely controlled using magnetic fields due to their internal chain of iron-oxide nanoparticles acting like a compass needle. This internal chain enables them to adopt a magnetotactic behavior that can be exploited to perform a variety of microscale tasks from microassembly and micro-manufacturing to the delivery through microvascular networks of therapeutic agents to tumors. To effectively support these applications, three-dimensional (3D) aggregations of MTB become essential in order to manipulate and guide the bacteria effectively in the human microvasculature to deliver a predefined dose of therapeutics. To achieve such aggregations in a 3D volume, time-varying magnetic field sequences were developed enabling us to simulate in time the existence of a magnetic monopole. This article presents and compares three different time-varying magnetic field sequences generated by three orthogonal pairs of electromagnets able to generate such 3D aggregations of MTB.