Biologists have developed and successfully tested a system that transports the required substances into the cell nucleus. Scientists plan to use similar schemes for targeted drug delivery.
The achievement is described in a scientific article published in the journal PNAS.
The cell nucleus protects its DNA from violent chemical processes in the cytoplasm. Not every substance can get into this citadel of our hereditary information.
The membrane (wall) of the nucleus has a system of inlets and outlets called nuclear pores. This name should not be misleading: in this case, the pores are not literally holes.
The nuclear pore is a complex of protein molecules that transports the necessary substances to the nucleus and back. To enter the holy of holies, a molecule or particle must have a special chemical tag. Bodies that do not have this "seal pass" do not pass through the pores. The only exceptions are very small objects (less than five nanometers), which the "guards" simply cannot catch.
Some viruses have evolved to trick this control system by mimicking a chemical entry ticket. Scientists use the same trick to create nanoscale objects that penetrate the core.
Various scientific groups have experimented with nanoparticles of gold, silicon oxide and other substances. Such a nanoparticle is like a primitive cannonball: just a solid piece of metal or other material.
This time, the researchers set themselves a more difficult task: to create capsules that store the desired substance inside and release it upon arrival. Continuing the artillery analogy, we can compare them with modern shells: a charge is hidden under a thin shell, only not explosives, but medicines.
The capsule shell consisted of biocompatible polymers, which were chemically labeled to allow them to enter the core. In this regard, the authors call them polymersomes (from the Greek "soma" - body).
"These polymersomes, about 60 nanometers in size, are encased in a flexible polymer shell that mimics natural membranes," says co-author Cornelia Palivan of the University of Basel.
The scientist notes that the polymeric membranes are more stable and functional than the lipid ones, which surround small organelles in the cell - vesicles.
Various colorants were used as the chemical filling of the granules. In the future, drugs should take their place.
Biologists tested their brainchild on HeLa cell culture. Recall that this is a human cancer cell line that began in 1951 with a single cell taken from a patient. Cancer eukaryotic cells, unlike ordinary ones, have no limitation on the number of divisions: an arbitrarily distant "descendant" of such a cell can divide again. Therefore, HeLa has been serving as experimental material for a wide variety of studies that require human cells for seven decades.
Experiments showed that the dyes enclosed in capsules actually accumulated in the cell nucleus. Scientists have confirmed this using several microscopic methods.
Researchers have also launched a batch of capsules that do not have a chemical "pass". The substances charged in them did not enter the nucleus. This proves that the system works exactly as the developers intended.