Nanostructured silicon surfaces and silicon nanoparticles were shown to inhibit division of stem cells and cancer cells, and nanoparticles, enforced with ultrasonic sound, kill these cells, Russian physicists and medics say.

Silicon nanoparticles are known to have several valuable properties: they are biocompatible, biodegradable, and have fantastic penetrating power. They enhance permeability of cell membranes, thus helping reduce dosage of treating agents, bound with these particles. Moreover, silicon nanoparticles can be used together with toothpaste, because they softly remove bacteria from our teeth without damaging enamel. Silicon nanoparticles are also a brilliant preservative – they prevent pathogenic microflora from growing in food products. Well, there are many reasons for you to find these particles inside your organism. That is the reason why many researchers throughout the world, including Russian scientists, actively study properties and interaction of these particles with cells.

Researchers worked with nanostructured silicon surfaces and silicon nanoparticles. Nanostructured surfaces were generated by means of electrochemical etching of crystal silicon plates. After treating, plates became covered with a 15-micron-thick layer, consisting of knobs and holes sized between 10 and 100 nanometers. The plates were then transferred to Petri dishes with growth medium, where stem cells of human bone marrow were growing. The cells were viable for 10 days, but almost failed to divide, while on the same growth medium, but without silicon plates, these cells divided actively. Such an effect could have been caused by two processes, researchers say. First one is local electric fields, appearing on the surface of structured silicon surface, and the second – chemical activity of orthosilicic acid, which forms after silicon plates get partly dissolved with water. Since silicon films inhibit growth of stem cell, they can possibly be used for cell conservation.

 

 

Second part of the experiment of Russian researchers was dedicated to properties pf nanoparticles of polycrystalline or porous silicon. These nanoparticles were added to growth medium, where cells of human throat cancer or mouse fibroblasts were grown. Cancer cells didn’t get into the experiment by accident – foreign researchers intentionally introduce silicon nanoparticles, bound with treating agents, into cancer cells. Study of the Russian scientists revealed that silicon nanoparticles in concentrations exceeding 3 milligrams per milliliter inhibited growth of both types of cells.

Ultrasonic sound is known to enhance destruction ability of nanoparticles. High-power radiation itself destroys up to 30% of cells, and combination of nanoparticles and ultrasonic sound leaves less than 20% of living cells. Nanoparticles of porous silicon are more effective killers than polycrystalline silicon particles – they destroy almost all cells. Low intensity of ultrasonic sound didn’t kill cells with nanoparticles, however, they fully stopped division within 80 hours after treatment.

Nanoparticles are possibly centres of formation for cavitation bubbles, which lead to cell destruction. They can also mechanically damage cells, when fluctuating in an ultrasonic wave.