Imaginary magnetic tweezers for massively parallel surface adhesion spectroscopy

Area of Science:

• Biophysics
• Materials Science
• Surface Science

Background:

• Understanding bead-surface interactions is crucial in various scientific fields.
• Existing methods often lack the throughput or sensitivity for low-force measurements.
• Characterizing adhesion at low loading rates is essential for revealing complex binding dynamics.

Purpose of the Study:

• To develop and validate a massively parallel magnetic tweezer system for high-throughput adhesion measurements.
• To investigate the unbinding kinetics of polystyrene beads on different surfaces at ultra-low force loading rates.
• To identify and differentiate between kinetic and quasi-equilibrium unbinding regimes.

Main Methods:

• Construction of a massively parallel magnetic tweezer system utilizing magnetic dipole image forces for bead self-repulsion.
• Simultaneous application of uniform magnetic force to thousands of colloidal beads (9.8 μm polystyrene).
• Measurement of unbinding histograms across a range of force loading rates (10⁻³–10⁰ pN/s) on fluorocarbon, PEG, and UV-irradiated PEG surfaces.

Main Results:

• The system successfully enabled measurements at the lowest force loading rates reported to date.
• Adhesion forces of polystyrene beads were quantified on diverse surfaces.
• Distinct kinetic and quasi-equilibrium unbinding regimes were observed, dependent on surface properties and force loading rates.

Conclusions:

• The developed magnetic tweezer system offers a powerful platform for high-throughput, low-force single-molecule biophysics studies.
• The findings highlight the importance of force loading rate in determining molecular unbinding mechanisms.
• This work provides new insights into the fundamental principles governing bead-surface adhesion.