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Freeze Drying

3D Bioprinting


Ekran Alıntısı2.PNG

In our lab, three-dimensional scaffolds for tissue engineering applications are employed as an artificial extracellular matrix (ECM) for an accurate and quick regeneration of tissue. To mimic the natural tissue, 3D scaffolds should be physically, structurally, and chemically similar to ECM. The following are the methods used for the production of scaffolds in our laboratory;


The filamentous fiber structures produced with this technique, which includes the electrospinning technique, and engineering and medicine disciplines together, have entered many areas of our lives in a short time. When a liquid solution used in the electrospinning method is exposed to a strong electric field, the molecules of the liquid solution are charged with positive and negative charges, and the molecules begin to repel each other. This repulsive force causes the liquid solution to lengthen and thin after a certain level. The liquid solution then dries and accumulates into continuous filamentous fibers. These bulk filamentous structures used in tissue engineering and biomaterials can provide both the surface roughness and porous structure required for the interaction between the material and the biological environment and the desired mechanical strength. The electrospinning method has developed porous structures with the electrospinning method, by allowing the materials produced to resemble natural extracellular ECM and the fibers to provide a large surface area for cell interaction and to allow the transfer of liquids such as nutrients. The use of synthetic polymers offers advantages in terms of changing the mechanical properties of polymers and making the surface functional by modifying it with proteins and cells.


Micro and nanofibers are continuously rotated by a permanent rotating magnet. This method is a newer method than the other two methods. The purpose of magnetospinning; is to produce thin and magnetic nanofibers. For this, it uses magnetic forces and the hydrodynamic properties of the stretched yarns. Unlike electrospinning, which is a conventional method, the solution is independent of dielectric properties and does not require high voltages. In an experimental setup, the polymer solution is pushed through the needle to become spherical. At this point, the magnet continues to rotate circularly. As the magnet approaches the ferrofluid, the magnetic force begins to attract and the polymer droplet moves towards the magnet. Its polymer forms a liquid bridge between the magnet and the needle. Finally, the magnet moves away and the solvent evaporates; polymer fiber is drawn.

Freeze Drying;

The freeze-drying method has been introduced as an advanced technology for producing highly porous 3D scaffolds with complex pore morphology, using a wide range of materials, including natural polymer, and synthetic polymer, which presents a great opportunity, especially in hard and soft tissue engineering. The principle of freeze drying is a sublimation process in which the frozen water in the polymer nanocomposites is directly converted from solid to a gas without apparent liquefaction. In the first step, a polymer is completely dissolved in an appropriate solvent. Then this solution is added to water, in which it is immiscible. Thus, phase separation between solvent and water occurs. The contents are subjected to freezing temperature, to realize the solidification of solvent molecules. In the last step, the solvent and water are removed by lyophilization under a vacuum. The highly porous interconnected polymeric structure so obtained is used as a scaffold for tissue engineering. The resultant scaffold generally has high porosity, but it can be further adjusted as per desired requirements by varying the freezing regime, amount of water, the concentration of the polymer, size of the ice crystals, and pH of the solution. Freeze drying is widely used for the preparation of scaffolds, but some limitations associated with this procedure include longer time, high energy consumption, use of cytotoxic solvents, and formation of closed pores by gas foaming. In conclusion, by freeze-drying, a product unstable in water is transformed into a dry, stable product.


Fatma Yaren YEŞİL

Ayşe Deniz ŞENYURT

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