3D printing is a relatively new method of the fabrication objects with controlled architecture. There are many various 3D printing techniques, including stereolithography, bioprinting, inkjet printing, fused deposition modelling (FDM), precision extruding deposition (PED), laser beam melting, polyjet, electron beam melting, digital laser printing (DLP), and selective laser sintering (SLS). The common feature of all mentioned methods is the general principle of material deposition layer-by-layer until the final product is created 3D scaffold is fabricated by the successive addition of consecutive 2D layers of a material. Additive manufacturing has numerous advantages, such as the ability to create complex structures and the possibility of the application of the Computer-Aided Design (CAD) methods. It enables the use of various types of biomaterials.
3D printing is used also to create scaffods for tissue engineering (TE). Using living cells and biodegradable polymers allows for the development of methods and novel strategies to create complex tissues and, possibly in the future, whole organs. A 3D-printed TE scaffold can be designed using patient-specific data. The CAD method allows for the precise designing of the 3D organ or its missing part. Selected features of living organs, such as porosity or vasculature, may be taken into account in the CAD 3D model.
This method allows for the fabrication of soft 3D tissue scaffolds combining biomaterials, living cells, as well as growth factors. It enables the fabrication of biomedical parts that maximally imitate natural tissue characteristics. Generally, 3D bioprinting utilizes the layer by layer deposition of materials known as bioinks to create tissue-like structures.
The extrusion bioprinting technique is based on liquid extrusion (paste, solution) from a pressurized syringe through a needle to a solution with controlled density. The materials are extruded in a form of long strands or dots to create complex structures The printing process can be conducted at room temperature and used to print natural biomaterials, especially hydrogels
Stereolithography (SLA) is the first developed method of rapid prototyping expanded in the late 1980s. Stereolithography uses a laser beam to control the polymerization process of bioinks in a 2D layer. After the deposition of each layer of a material, curing follows. During the curing process, a photosensitive hydrogel is subjected to UV or visible light. When a given layer is polymerized, the process is repeated, overlapping the previous layer, up to the moment when the whole scaffold is completed. This method allows the use of the following hydrogel (e.g gelatin methacryloyl (GelMA). SLA process is relatively time consuming, which makes the process feasible for small-detailed objects.
Fused Deposition Modeling (FDM)
In the fused deposition modelling technique, a coiled polimer filament is heated up and extruded through a nozzle on the platform. When the polimer contacts with the platform, it solidifies. The main limitations of using FDM printers in TE include spatial resolution and possible thermal degradation of the polymeric material. FDM enables the use of thermoresponsive polymers such as polycaprolactone (PCL), polylactide (PLA), or polyglycolide (PGA).
Melt electrospinning (MES)
Melt electrospinning (MES) is a relatively new 3D TE scaffold fabrication technique, being the alternative to conventional solution electrospinning (SES) known for disadvantages related to toxic solvents used in this methods. SES limitations are overcome by the use of the molten polymer instead of the polymer solution. To be jetted in an electric field, the molten polymer should be characterized by a suitable viscosity. The molten polymer would be collected by a rotating drum; however, implementation of the numerical control (NC) enables the precise deposition of fiber in X, Y axes. This technique allows for depositing continuous fibers characterized by a diameter less than 1 micrometer, which is comparable to the classic solution of electrospinning .
Our laboratory is equipped with a RegenHU 3D printer which enables the production of three-dimensional objects using the bioprinting, extrusion bioprinting, fused deposition modeling as well melt electrospinning techniques.