Scientists have found that regular food coloring, which is derived from bilberry, may help to play a key role in three-dimensional printing geometrically complex biological tissues such as blood vessels and pulmonary alveoli. The authors of an article published in the journal Science, printed from hydrogel complex structure and verified in experiments with transplantation is that living cells can live in them.
Developers working on 3D printing of artificial tissues and organs, it is necessary to solve the problem of production of analogues of the blood vessels and respiratory tract. Extremely complex three-dimensional network of blood vessels twist around, for example, the alveoli in the lungs a large surface is needed to increase the speed and efficiency of gas exchange, the blood oxygen saturation. Intricate valves and membranes are present in the vessels, e.g. in veins, where they prevent the backflow of blood. The intricate three-dimensional structures are nearly impossible to print using traditional layer-by-layer 3D printing.
To solve this problem was developed a method of stereolithography. In this case, in a special container filled with photosensitive raw materials. A narrow beam of ultraviolet radiation passes over the surface of the liquid and causes it to harden in the desired locations, after which the printed product is slightly immersed in a liquid and the process repeats. This technology allows you to print (that is, to transfer to the solid phase) larger and to print millions of voxels (three-dimensional analogue of a pixel) in one step.
Usually UV print head “draws” the object in the horizontal plane along the x and y coordinates, and the z axis meets the light-absorbing coatings, which do not allow the material to harden, where it is not necessary. The problem, however is that used for this absorbing additives, such as Sudan I, have mutagenic and carcinogenic, and cannot be used for the production of artificial biological tissues.
Bagrat Grigoryan (Bagrat Grigoryan) from rice University in Houston and his colleagues decided to pick up this absorbing substance that could be used stereolithography print complicated biological structures and thus would not be toxic.
Researchers analyzed the optical properties of some compounds used in industry as a food coloring, and found that three of them are quite suitable for the role of photoperiodically: this is a synthetic yellow dye tartrazine (E102 index), a yellow natural dye curcumin (E100) and the red-purple dye anthocyanin (E163), which is derived from blueberries. In addition, as the absorber approached the biocompatible gold nanoparticles.
Scientists have conducted a series of experiments in which printed from hydrogel artificial blood vessel with valves with a diameter of 1 millimeter. All three types of dyes and gold nanoparticles provided acceptable print quality. However, curcumin worse tartrazine washed from the vessel after completion of printing, and gold nanoparticles might interfere with studying the structure using fluorescent microscopy, therefore in further experiments the authors used only tartrazine.
At the following stage scientists have made from hydrogel complex geometric structure: a vessel that spiral covered the ring, and then installed the artificial pulmonary alveolus — “bag”, braided mesh of blood vessels.