Robotic Micromanipulation and Mechanical Characterization of Intracellular Structures

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The past two decades have seen strides in single-cell manipulation and measurement. This research will go beyond the state of the art to develop a transformative platform technology for 3D manipulation and mechanical measurement inside a cell. The new platform and techniques will enable 3D navigation of a sub-micron magnetic bead (and later more sophisticated magnetic devices) inside a cell to perform mechanical measurements, which will open an exciting new era of intracellular physical measurement and manipulation.******The near-term objectives include: Aim 1: Establish a new robotic magnetic tweezers platform for 3D intracellular navigation and measurement; Aim 2: Develop new magnetic force models and force/position control methods for controlling a sub-micron magnetic bead with 3D confocal microscopy image feedback; Aim 3: Perform mechanical measurements at different locations on the cell nucleus in an intact cell to quantify stiffness heterogeneity along different directions of the cell nucleus. To achieve these goals, we will develop a new multi-pole magnetic tweezers platform and technologies to manipulate a sub-micron magnetic bead and tackle the challenges of low-bandwidth high-resolution visual feedback, sub-micron position control, and picoNewton force control. Specifically, we will pursue 3D magnetic tweezers platform design, construction, analytical modeling, numerical simulation, system testing/debugging, and optimization. We will establish nonlinear magnetic field models that relate driving currents to magnetic field generation and quantify force application. Magnetic field simulation will also be conducted to calculate magnetic forces exerted on the sub-micron magnetic bead. Calibration experiments will be performed and position-force errors will be quantified among experimental results and results from analytical modeling and finite element simulation for each point in the workspace. ******Generalized predictive controllers based on bead dynamics will be developed to position a sub-micron bead to different locations on the cell nucleus in an intact cell to indent the cell nucleus at varying speeds. Experimental data will be analyzed with mechanics models to generate a stiffness/modulus/viscosity map for each measured location on the cell nucleus at different stages of cancer cell development. Polarity of mechanical properties along the major and minor axes of the cell nucleus, force-induced stiffening of the softer axis, and alteration of the migratory behavior of cancer cells will be measured. The necessity of mechanical polarity of the cell nucleus for cancer cell migration will be unequivocally demonstrated. This research program will train HQP to pursue research careers in NSE or fulfill the great demand of Canadian instrumentation and biotech industries.