Bioengineers have created a hybrid microparticles with properties identical to the real red blood cells: they are identical in size, shape, ability to deform and to carry oxygen. To generate particles from live red blood cells scientists have made a silicon form that is covered by a layer of polymer and the cell membrane, and then dissolved. The microparticles remained in the bloodstream of mice and chicken embryos and was not toxic. In artificial red blood cells have managed to place a number of cargoes: hemoglobin contrast agents for MRI, anticancer drug, iron oxide to control the particle using a magnetic field and fluorescent sensor for ATP sensitivity to toxins. Article published in the journal ACS Nano.
Erythrocytes, or red blood cells, is a relatively simple system (they have no nucleus and many other organelles), while they have a number of gadgets to perform various functions. Erythrocytes have biconcave discoid shape that provides the maximum ratio of surface area to volume and enables red blood cells to bend and flattened to squeeze through narrow capillaries. The main function of red blood cells — transport of oxygen and carbon dioxide, for this purpose they are formed quickly and become each other of various complexes of hemoglobin with gases. Finally, on the membrane of red blood cells are biomarkers by which macrophages recognize in them their “own” and do not phagocytose.
Scientists have made a number of attempts to mimic the individual properties of red blood cells to synthetic particles: formed polymer vesicles with hemoglobin, are flexible biconcave disks of hydrogel coated membranes of these erythrocytes for the particledriven by a magnetic field in the micromotor. These works inspired a group of researchers from China and the United States under the leadership of Jeffrey Brinker (Jeffrey Brinker) from the University of new Mexico to create artificial red blood cells that have repeated all the properties of red blood cells, could carry the load and perform a number of additional functions.
The artificial particles created in four stages. To precisely copy the shape of red blood cells, live cells were covered with 10-nm layer of amorphous silicon oxide: in formaldehyde fixed red blood cells were placed in a solution of silicic acid for 24 hours and then the precipitated acid using enzymes. The resulting particles were used as a form for self-assembling layer-by-layer deposition of biocompatible polymers: positively charged chitosan molecule and the negatively — alginate alternately sat on the surface of the silicon oxide. Then, particles of the etched silicon oxide with hydrofluoric acid, and the polymer skeleton (its thickness was about 90 nm) were covered with a membrane, which is separated from the red blood cells.