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Tiny Tweezers Aid Biomed Research

Schematic A shows the chip layout, with circular nickel pads (blue), which can be magnetized by an external magnet flanked by interdigitated gold electrodes (red). Schematic B shows paramagnetic beads introduced to the chip surface by microfluidics and loaded onto the magnetic pads by magnetic manipulation, facilitating the formation of bead surface tethers via antibody-antigen interactions. Schematic C shows interactions probed by application of sufficient nDEP force to displace non-specifically bound beads, but not specifically bound beads. Schematic D shows how the devices are fabricated. (Image courtesy of Lizhi Cao)

A new type of biomolecular tweezers could help researchers study how mechanical forces affect the biochemical activity of cells and proteins. The tweezers, too small to see without a microscope, use opposing magnetic and electrophoretic forces to precisely stretch the cells and molecules, holding them in position so the activity of receptors and other biochemical activity can be studied.

Arrays of tweezers could allow the study of multiple molecules and cells simultaneously, providing a high-throughput capability for assessing the effects of mechanical forces.

“Our lab has been very interested in mechanical-chemical switches in the extracellular matrix, but we currently have a difficult time interrogating these mechanisms and discovering how they work in vivo,” said Thomas Barker, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “This device could help biologists and biomedical engineers answer questions that cannot be answered right now.”

Researchers (l-r) Thomas Barker, Lizhi Cao and Wilbur Lam are shown in the Marcus Nanotechnology Building, where the molecular tweezers are fabricated in clean rooms. (Georgia Tech Photo: Rob Felt)

For example, a cell in the extracellular matrix may bind with one receptor while the matrix is being stretched, and with a different receptor while not under stress. Those binding differences could drive changes in cell phenotype and affect processes such as cell differentiation.

“Having a device like this will allow us to interrogate what the specific binding sites are and what the specific binding triggers are,” Barker explained. Details of the devices were published in the journal Technology.

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