Optical Tweezers: Empowering Precision at the Nanoscale

Optical tweezers Revolutionize Cell-Cell Interaction Studies

The MMI optical tweezers enable the manipulation of cells to promote cell-cell interactions and directly measure their binding forces while maintaining complete control over the cell’s orientation and the time of the cell-cell contact. This is incredibly valuable for conducting dynamic studies on cell-cell interaction forces and measuring cell avidity with single-cell resolution.

A frequent application for optical tweezers is measuring the cell-cell interaction forces between immune cells.

• The MMI optical tweezers facilitates cell-cell interactions and enable the measurement of binding forces
• Complete control over cell orientation and contact time is maintained

One of the most important application for optical tweezers is to measure the detailed motions of motor proteins such as kinesin, dynein and myosin. Motor proteins support a wide variety of cellular functions including organelle transport, cell and chromosomal division and muscle contraction.

Study life under tension
Thanks to numerous technical improvements, optical trapping with the MMI CellManipulator allows synthesizing up to 10 multiple independent optical traps and to measure the forces of motor proteins in sub-pN resolution. To measure these forces, the molecule of interest needs to be attached at two points: One end to a small microparticle, and the other end to a fixed substrate or a second microparticle in a separate optical trap. The following visualization shows two typical applications to study motor proteins: 1. Measurement of the stall force of dynein motor proteins transporting vesicles along microtubules and 2. studying actomyosin interaction with a dual-beam trap.

Combining optical tweezers and microfluidic chip technologies
The isolation and manipulation of rare cells with high recovery and purity are crucial for downstream multi-omics profiling. The combination of the MMI optical tweezers with microfluidic chip technology enables the real-time sorting of small cell populations with high accuracy. The system is using a laminar flow to focus the targeted cells. The optical tweezers can then precisely move the cell in a non-invasive manner to the desired destination. In contrast to traditional cell sorting technologies, such as flow cytometry, cell sorting with optical tweezers has the unique advantage of its high recovery rate, flexibility and purity in small cell population sorting.

Arthur Ashkin has been awarded with the Nobel Prize for physics in 2018 for “optical tweezers and their application to biological systems”. The optical tweezers principle is based on the discovery that light has momentum. Once a laser beam is encountering an object such as a glass sphere or a cell, the light will be refracted. In the center of the beam, the light will be brighter and more light is refracted from here than from the outside of the beam. As momentum needs to be constant, the object will be trapped in the center of the beam where the forces generated by refracted light is cancelling out. For optical trapping, laser based optical tweezers are applied which have the optimal properties to generate the optical trap.

Yes, optical tweezers are ideally suited to study single cells. Using optical traps, the target cells can be manipulated in a precise and contact-free way thereby avoiding any risks of contamination. In addition, using infrared lasers, the cell’s viability is not compromised during the experiment. Thus, the laser tweezer technology is also suitable for work with living cells, such as for drug discovery projects. Some optical tweezer systems, such as the MMI CellManipulator, are equipped with a second tweezer level to independently hold two cells or particles at the very same time and to precisely measure their interaction forces by force spectroscopy.