Micron scale electromagnetic tweezers with light controlled magnetic nanoparticles for force manipulation inside live cells

There is a significant unmet need for new biophysical tools that can apply and measure physical forces generated by individual macromolecular ensembles inside living cells. Such methods are required to address fundamental outstanding questions about the mechanisms of the cell and genome rearrangements as well as for decoding molecular causes of diseases like cancer, chromosomal disorders, and neurological diseases.

Single-molecule methods that can measure forces like optical tweezers, magnetic tweezers, and atomic force microscopy revolutionised our understanding of biomolecular systems that generate and sense mechanical forces including molecular motors, DNA and RNA polymerases and many others. However, these techniques generally cannot be applied in live cells limiting further progress in the field.

This project seeks to address this challenge by introducing ground-breaking innovations in magnetic tweezers.

Magnetic tweezers is one of the most promising tools that has been used to apply force intracellularly by using calibrated magnets to exert force on small magnetic particles injected in live cells. However, a major constraint of current instruments is the need for large particles to exert sufficient force. Large particles are damaging to cells; their size prevents particle diffusion in cells making specific attachment to required targets as well as interpretation of results challenging.

Our solution lies in two complimentary approaches. First, instead of one large particle, we will use many smaller particles that move much more free and are less damaging to cells. To apply force, we will controllably aggregate these particles on required targets using chemical and optogenetic tools.

Second, we optimize and finely-engineer magnetic tips that can apply forces at the physical limit by generating extremely steep magnetic gradients at the scale of few microns. We have already shown that this allows for the use of particles that are approximately ten times smaller than those presently used. Additionally, very steep gradients allow us to independently control and manipulate two independent particles inside one cell, which was not possible previously. Together these innovations will allow for precise and specific force application in live cells.

In this proposal, our primary objective is to demonstrate the combined potential of our innovations by physically manipulating targeted components inside both interphase and dividing cells. In future, our tool will pave the way for transformative applications in cell division, cell motility, neuron growth as well as at tissue scales in regeneration and morphogenesis.