Modulating motility of intracellular vesicles in cortical neurons with nanomagnetic forces on-chip

Vesicle transport is a major underlying mechanism of cell communication. Inhibiting vesicle transport in brain cells results in blockage of neuronal signals, even in intact neuronal networks. Modulating intracellular vesicle transport can have a huge impact on the development of new neurotherapeutic concepts, but only if we can specifically interfere with intracellular transport patterns. UCLA researchers propose to modulate motion of intracellular lipid vesicles in rat cortical neurons based on exogenously bioconjugated and cell internalized superparamagnetic iron oxide nanoparticles (SPIONs) within microengineered magnetic gradients on-chip. Upon application of 6-126 pN on intracellular vesicles in neuronal cells, the researchers explored how the magnetic force stimulus impacts the motion pattern of vesicles at various intracellular locations without modulating the entire cell morphology. Altering vesicle dynamics was quantified using, mean square displacement, a caging diameter and the total traveled distance. They observed a de-acceleration of intercellular vesicle motility, while applying nanomagnetic forces to cultured neurons with SPIONs, which can be explained by a decrease in motility due to opposing magnetic force direction. Ultimately, using nanomagnetic forces inside neurons may permit us to stop the mis-sorting of intracellular organelles, proteins and cell signals, which have been associated with cellular dysfunction. Furthermore, nanomagnetic force applications will allow us to wirelessly guide axons and dendrites by exogenously using permanent magnetic field gradients.

Chitosan-functionalized magnetic nanoparticles (fMNPs)
heap up in DiI labeled intracellular vesicles

(a1) A chip-based approach facilitates a highly parallelized single cellular study of vesicle interactions with fMNPs and magnetic forces. The chip has quadratic poly-l-lysine patterns (PLL) aligned on top of magnetic elements (MEs) or several micrometers spaced apart. (a2) Schematic shows potential routes for intracellular uptake of fMNPs and their location in different vesicle types dependent on their uptake mechanism. EE = early endosomes, B-LE = late endosomes, Lyso = lysosomes, Vesicles = lipid, membrane, synaptic, receptor vesicles. (a3) Single cell and magnetic element pattern assembly. (b) Changing hydrodynamic diameter over time of Chi-fMNP (green) and D-fMNP (red) clusters in neurobasal media (+B-27, +GlutaMAX). (c1 & c2) False-colored fluorescent images show co-labeling of different vesicles with Chi-fMNPs in primary cortical neurons (E18, 2 DIV) on-chip. Chi-fMNPs are green fluorescent. DiD (red) and DiI (blue) stained unspecified different types of lipid vesicles. B-LE (blue) stained late endosomes and Lyso (red) lysosomes. (d) Relative count of Chi-fMNPs located in specific vesicle types. NNP = 86 (Lyso/DiI images), NNP = 55 (DiD/BLE). (e) COMSOL/MATLAB based computed magnetic force field 1 μm above two 3-rowed magnetic element pattern (Bmax = 150 mT, nanoparticle cluster diameter d = 0.8 μm).