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3D bioprinting brings us closer and closer to artificial organs

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Author : Joe Wong
Update time : 2020-07-31 16:46:53
3D bioprinting brings us closer and closer to artificial organs

  3D printing, also known as additive manufacturing, is a technology that forms data based on computer-aided (CAD/CAM), tomography (CT) or nuclear magnetic (MRI) technology, and then builds a three-dimensional architecture through layered processing and layer-by-layer overlay methods. 3D printing has the characteristics of personalization and high precision, and has significant advantages in constructing complex microstructures. In recent years, it has been widely used in the medical field.

Achieve organ regeneration

 3D printing technology is currently mostly used in the printing of human hard tissues, such as tissue models, implantable medical devices, etc., and the technology is relatively mature. In terms of tissue model, some studies have successfully produced a left atrial appendage model based on ultrasound data to assist in the pre-operative evaluation of the left atrial appendage occlusion. It can visually show how the left atrial appendage structure and diameter affect the release of the occluder and optimize the operation. ; There is also research using 3D printing technology to print a patient's personalized mitral valve annulus model, which can better evaluate the patient's mitral valve annulus geometry, size and shape before surgery. The 3D printing research of implantable medical devices is also constantly developing. For example, the biodegradable coronary drug-eluting stent product manufactured by Beijing Amat Medical Device Technology Co., Ltd. using 3D printing technology has been approved in China for domestic clinical trials. Experimental Research.

  In addition to its application in the field of hard tissues, 3D printing of human soft tissues is also a current research hotspot, such as printing functional vascular networks, artificial hearts, and artificial skins. In 2016, Sichuan Languang Yingnuo Company used 3D printing technology to print biological artificial blood vessels and successfully implanted them in rhesus monkeys, which greatly promoted the application of 3D printed organs in organ transplantation in my country. In 2019, the cover article of Science magazine reported on 3D printing of the intricately tangled blood vessel network in human organs. 3D printing has been able to build pipelines with simulated alveoli that can transport air, lymph and other substances. It is expected to help scholars in the field of tissue engineering to improve Have a good understanding of 3D printed organs and promote the development of artificial organ research. In April 2019, researchers from Tel Aviv University in Israel announced that they had successfully designed and printed a complete heart full of cells, blood vessels, ventricles and atria using the patient's own cells and biological materials, the first in the world.

  Different from the ordinary 3D printing technology mainly used to print hard tissues, soft tissue 3D printing needs to rely on more complex 3D bioprinting technology.

3D bioprinting technology and materials

  3D bioprinting is developed based on 3D printing technology, which has important research significance and broad application prospects. Generally speaking, 3D bioprinting is to print biocompatible materials containing living cells into three-dimensional functional living tissues through 3D printing technology. In the field of regenerative medicine, 3D bioprinting has unique advantages.

  The key factors of 3D bioprinting include printing methods, biocompatible materials and cells.

The three types of printing methods have their own characteristics

  The technical conditions of 3D bioprinting are relatively harsh and there are many influencing factors. The main printing technologies are divided into three categories: inkjet bioprinting, microextrusion bioprinting and laser-assisted bioprinting.

  Inkjet bioprinting uses electric heating to generate air pulses, or generates pulses through piezoelectric, ultrasonic, and other methods, and then forms droplets at the nozzle. The method has the advantages of fast speed, low cost, wide application range, adjustable cell and material concentration, but it has disadvantages such as the necessity to use liquid materials and the nozzles are easy to block. Inkjet printing technology has great potential in the regeneration of human functional structure, and is currently mainly used for in-situ regeneration of skin and cartilage.

  Micro-extrusion bioprinting is a simple and universal method. Through the extrusion of mechanical force, the material in the sample cell can be continuously extruded, and then the three-dimensional structure can be obtained by controlling the X, Y, and Z axis directions. This method is applicable to a wide range of materials with a wide range of viscosities. High-viscosity materials are usually used for supporting structures, and low-viscosity materials are often used to provide an extracellular environment to maintain cell viability. In terms of material properties, representative materials include temperature-sensitive materials and shear thinning materials. Temperature-sensitive materials are in a fluid state at room temperature, can be co-extruded with other materials, and cross-link and solidify when the temperature is close to body temperature; The viscosity of the thinned material decreases with the increase of the shear rate, and this characteristic just satisfies the extrusion process. The main advantage of micro-extrusion bioprinting technology is that it can deposit high cell density, which is beneficial to meet the needs of tissue engineering. The disadvantage is that the cell survival rate is low. Although this technology takes a long time to print high-resolution complex structures, it can print more types of products. At present, this technology has been used to create a variety of tissues and models, including aortic valves, branch vascular trees, in vitro drug metabolism and tumor models.

  The principle of laser-assisted bioprinting can be simply summarized as: laser pulses act on the energy absorbing layer to generate high-pressure bubbles, and the high-pressure bubbles push the printing material containing cells onto the receiving substrate to build a three-dimensional structure. The advantages of this technology are high resolution and high cell deposition density, but it has high requirements for cross-linking speed and high cost, so it is currently less used.