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Acc Chem Res. 2018 Apr 17;51(4):839-849. doi: 10.1021/acs.accounts.8b00004. Epub 2018 Mar 28.

Magnetic Nanotweezers for Interrogating Biological Processes in Space and Time.

Kim JW1,2,3, Jeong HK1,2,3, Southard KM4,5,6, Jun YW1,2,4,5,6, Cheon J1,2,3.

Author information

Center for NanoMedicine , Institute for Basic Science (IBS) , Seoul 03722 , Republic of Korea.
Yonsei-IBS Institute , Yonsei University , Seoul 03722 , Republic of Korea.
Department of Chemistry , Yonsei University , Seoul 03722 , Republic of Korea.
Department of Otolaryngology , University of California, San Francisco , San Francisco , California 94115 , United States.
Department of Pharmaceutical Chemistry , University of California, San Francisco , San Francisco , California 94115 , United States.
Programs in Chemistry and Chemical Biology , University of California, San Francisco , San Francisco , California 94115 , United States.


The ability to sense and manipulate the state of biological systems has been extensively advanced during the past decade with the help of recent developments in physical tools. Unlike standard genetic and pharmacological perturbation techniques-knockdown, overexpression, small molecule inhibition-that provide a basic on/off switching capability, these physical tools provide the capacity to control the spatial, temporal, and mechanical properties of the biological targets. Among the various physical cues, magnetism offers distinct advantages over light or electricity. Magnetic fields freely penetrate biological tissues and are already used for clinical applications. As one of the unique features, magnetic fields can be transformed into mechanical stimuli which can serve as a cue in regulating biological processes. However, their biological applications have been limited due to a lack of high-performance magnetism-to-mechanical force transducers with advanced spatiotemporal capabilities. In this Account, we present recent developments in magnetic nanotweezers (MNTs) as a useful tool for interrogating the spatiotemporal control of cells in living tissue. MNTs are composed of force-generating magnetic nanoparticles and field generators. Through proper design and the integration of individual components, MNTs deliver controlled mechanical stimulation to targeted biomolecules at any desired space and time. We first discuss about MNT configuration with different force-stimulation modes. By modulating geometry of the magnetic field generator, MNTs exert pulling, dipole-dipole attraction, and rotational forces to the target specifically and quantitatively. We discuss the key physical parameters determining force magnitude, which include magnetic field strength, magnetic field gradient, magnetic moment of the magnetic particle, as well as distance between the field generator and the particle. MNTs also can be used over a wide range of biological time scales. By simply adjusting the amplitude and phase of the applied current, MNTs based on electromagnets allow for dynamic control of the magnetic field from microseconds to hours. Chemical design and the nanoscale effects of magnetic particles are also essential for optimizing MNT performance. We discuss key strategies to develop magnetic nanoparticles with improved force-generation capabilities with a particular focus on the effects of size, shape, and composition of the nanoparticles. We then introduce various strategies and design considerations for target-specific biomechanical stimulations with MNTs. One-to-one particle-receptor engagement for delivering a defined force to the targeted receptor and the small size of the nanoparticles are important. Finally, we demonstrate the utility of MNTs for manipulating biological functions and activities with various spatial (single molecule/cell to organisms) and temporal resolution (microseconds to days). MNTs have the potential to be utilized in many exciting applications across diverse biological systems spanning from fundamental biology investigations of spatial and mechanical signaling dynamics at the single-cell and systems levels to in vivo therapeutic applications.

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