Magnetic tweezers shed light on the mechanical properties of cells

By introducing tiny magnetic particles into a living cell and activating them with a magnetic ' tweezers ', scientists at the University of Twente, the Netherlands, have a better understanding of the mechanics of the cell nucleus.

The way DNA is ' translated ' into specific cellular functions depends greatly on mechanics, so this information is of great value. Scientists Anthony de Vries, Hans Kanger and Vinod Subramaniam of the Ly Sinh Technology Group presented their findings in the journal Nano Letters .

Super-mechanical testing plan.Magnetic poles (6 microns wide, 30 microns apart) create a force on a paramagnetic particle inside the nucleus of the HeLa cell.The electric coils allow to control the amplitude and direction of the force.Magnetic Yoke coils and electric coils are not the same scale.Photo: University of Twente.

Spatial organization in a living cell gives a lot of information about cell activity and internal molecular processes. This proves that the mechanical properties of DNA and chromatin - components of DNA and protein - play a major role in the activity of thousands of genes. Gene expression, in which DNA expresses into functional proteins, seems to be highly dependent on these mechanical properties. Until now, only individual chromosomes have been studied. The new method allows scientists to monitor the mechanical function of chromatin within the cell and carefully examine the internal structure of the cell nucleus.

Three magnets

So scientists put a particle into the cell nucleus using a micro pipette tube (extremely small tip with a pointed tip). This bead has a diameter of about 1 micron. Cells are placed in the center of 3 small magnets (micron-sized). Each magnet can create a force on the particle. From nanometer distances, particles can move, elasticity and ductility of chromatin can be determined. Using an intuitive polymer model of chromatin predict the structure of chromatin in the cell: They establish themselves in parts that do not completely fill the cell nucleus.

Scientists say the technique is an important step for magnetic nanoscale devices that can be implanted inside a living cell, acting as 'biological sensors' to Track chemical and physical processes inside cells and tissues. In addition, interact with this process by using magnetic techniques.

The study was conducted by the Biophysical Technology Group, an organization of the BMTI Biomedical Technology Institute and MESA (Midlle East Studies Association) + Nano Technology Institute, both of the University of Twente.

Thanh Van