Magnetic Particle Imaging of Magnetoendosymbionts for Cellular Control

Magnetic Particle Imaging (MPI) is a tracer-based modality that quantitatively maps magnetic nanoparticles with exceptional sensitivity and zero tissue background. Unlike MRI, MPI directly detects the nonlinear magnetization response of superparamagnetic tracers, providing quantitative information on particle concentration, localization, and dynamics. We are extending the reach of this physical imaging method into the domain of cellular engineering by developing magnetoendosymbionts—genetically engineered intracellular organisms that biomineralize magnetic nanoparticles and function as living magnetic transducers within mammalian cells. These magnetoendosymbionts generate biogenic magnetite cores that serve as intrinsic MPI tracers, enabling precise tracking of cellular populations in vivo. Beyond imaging, their magnetic properties allow controlled energy conversion under oscillating magnetic fields. By tuning field amplitude and frequency, we achieve nanoscale magnetothermal heating sufficient to actuate temperature-sensitive genetic switches, providing remote, reversible control over gene expression and cellular behavior. This integrated approach unites the physics of magnetic nanoparticle relaxation with the biological principles of symbiosis and genetic regulation, creating a platform for magnetically addressable living systems. MPI provides quantitative readouts of magnetoendosymbiont distribution and activity, while magnetothermal actuation enables on-demand modulation of cellular programs such as differentiation or therapeutic protein production. The convergence of magnetic imaging, energy transduction, and cellular engineering establishes a foundation for closed-loop control of biological function using purely physical inputs. This work illustrates how principles of magnetic particle physics and non-equilibrium energy transfer can be harnessed to interrogate and direct living matter, opening a new frontier in bio-integrated magnetism and the physical control of cell-based therapeutics.