Application of polymer materials in 3D printed scaffolds

3D printing technology is an additive manufacturing technology that mainly uses the principle of discrete accumulation in mathematics. It uses computer software to customize the parts to be printed and then slices them layer by layer. The 3D printer then prints layer by layer according to the program. This results in a three-dimensional part. Different from traditional mechanical processing, 3D printing uses additive manufacturing ideas and methods. Compared with subtractive manufacturing technology, 3D printing can achieve personalized customization, especially for the processing of some complex products, which has unparalleled advantages. At present, 3D printing technology is no longer limited to the field of machinery manufacturing. It has played an important role in many fields such as medical care, jewelry, and culture.

3D printing technology plays a huge role in the biomedical field because of its unique advantages. Scientific researchers use cells and biomedical materials as discrete materials, and use the personalized customization characteristics of 3D printing to prepare different organs and tissue structures, which will largely solve the problem of insufficient organ donors. Especially in the application of bones and bone scaffolds, the advent of 3D printing technology provides solutions for the treatment of patients with complex bone defects.

In addition to the limitations of its own technology during the application process of 3D printing, the selection of printing materials also plays a crucial role. The materials currently used in 3D printing biological bones and bone scaffolds include metal materials, inorganic non-metallic materials, polymer materials, etc. Metal materials have shortcomings such as high melting temperature, difficulty in printing, and high cost; inorganic non-metallic materials are limited in application due to their low toughness, hard and brittle, difficulty in processing and forming, and easy cracking of the green body; polymers There are many types of materials with excellent properties, which can meet the material performance requirements of different technologies, equipment and uses, becoming the most basic and most widely used material for 3D printing.

Synthetic polymer

1.1 Polyetheretherketone

Polyetheretherketone has the advantages of radiolucency and no artifacts in magnetic resonance scanning, which can better evaluate postoperative recovery. It has been used in artificial joints of the jaw, skull, spine, lumbar spine, and oral defect repair. Not only that, compared with traditional metal materials (stainless steel, titanium alloys) implanted in the human body, polyetheretherketone has good biocompatibility, and its elastic modulus is equivalent to human cortical bone, which can effectively reduce " Stress shielding effect". Due to its excellent properties, polyetheretherketone has become the most promising artificial bone matrix composite material at present, and can be independently used as an artificial bone replacement material. Medical polyetheretherketone is the "best long-term bone transplant" material certified by the U.S. Food and Drug Administration. However, polyetheretherketone also has some shortcomings, such as lack of biological activity and low surface osteogenesis efficiency.

1.2 Polyamide

Polyamide, commonly known as nylon, is a common medical polymer with high polarity and exhibits excellent properties in terms of biocompatibility. Composite materials prepared by combining polyamide and hydroxyapatite significantly improve the mechanical strength and biological activity of bone scaffolds. Compared with single materials, they have great advantages. As 3D printing materials, they have great potential in the treatment of bone defects in the future.

1.3 Polylactic acid

Polylactic acid is an aliphatic polyester that can be extracted from renewable plant resources (such as corn and potatoes). It uses starch in renewable resources as raw materials, obtains lactic acid through biological fermentation, and then polymerizes it. Polylactic acid can be converted into carbon dioxide and water in nature and organisms, and is a truly environmentally friendly new biodegradable material. The reason why polylactic acid can be used as a 3D printing material is mainly because it has good biocompatibility, gloss and transparency, mechanical properties, degradability, low melting point, low viscosity and other excellent properties. However, as a 3D printing material, it also has Defects: such as greater brittleness and poor impact resistance. Therefore, polylactic acid is often compounded with other materials to prepare artificial bone scaffolds so that the prepared scaffolds can meet the required standards.

1.4 Polycaprolactone

Polycaprolactone is a biodegradable polyester with good biocompatibility and non-toxicity. It is widely used in the medical field as a medical biodegradable material; it has controllable degradation, easy processability and sufficient mechanical properties. , high crystallinity and low melting point, excellent rheological properties and viscoelasticity give it good melt printing capabilities; not only that, polycaprolactone also has the ability to store and recover deformation, and can adapt to the rapid development of 3D printing technology.

It is suitable for making tissue engineering scaffolds and has become a commonly used material for bio-3D printing. Microstructural scaffolds designed with polycaprolactone as raw materials can provide structural support and material transport channels to induce tissue regeneration. They can also serve as a place for cell adhesion, proliferation and differentiation, providing a suitable physical environment for newly formed tissues.

1.5 Photosensitive resin

Photosensitive resin is also called light-curing solid material. It is mainly composed of photoinitiator, oligomer, reactive diluent (active monomer), etc. Its essence is a colloidal substance composed of polymers. These polymers are like fences. Scatteredly cross-linked with each other. When the photosensitive resin is irradiated by ultraviolet light, the photoinitiator in it absorbs energy, forms excited molecules, and decomposes active groups, causing the polymer to cross-link to form a polymer, which appears macroscopically. Transform the gum resin into a solid object. The light source in the 3D printer continuously cross-links the photosensitive resin through layer-by-layer scanning, thereby accumulating it into a three-dimensional physical product. As an excellent 3D printing consumable, photosensitive resin has the advantages of high molding accuracy and short curing time, and is suitable for manufacturing precision devices.

Natural polymer

1.1 Sodium alginate

Alginate is a natural polysaccharide compound extracted from seaweed. It has excellent bioadhesion, good biocompatibility and biodegradability unmatched by other materials. Therefore, alginate has been widely used in the biomedical field.

1.2 Collagen

Collagen is the most important structural protein in human tissues, an important component of the extracellular matrix, and the main component of the cartilage matrix. Collagen molecules are widely used in biomedical applications due to their weak antigenicity, degradability, excellent biocompatibility and bionic functions. Scaffolds prepared from collagen are beneficial to cell adhesion and support and protect cells. However, collagen also has some shortcomings, such as: no melting point, low denaturation temperature, insolubility in water, high viscosity, and low mechanical stability. , fast degradation rate and insufficient mechanical strength. Currently, these shortcomings are mainly solved by compounding collagen with other materials.

1.3 Silk fibroin

Silk fibroin is a natural polymer fiber protein with excellent physical and chemical properties. Silk fibroin has the following advantages: good biocompatibility, non-toxic, biodegradable, degradation products without toxic side effects, slow degradation rate in the body, and its degradation rate can be adjusted by changing its structural form. Silk fibroin has shown great application prospects in the biomedical field due to its unique and excellent properties. However, pure silk fibroin has insufficient mechanical properties. Modifying silk fibroin by compounding it with other materials can improve silk fibroin performance.

1.4 Chitosan

Chitosan is a biological material with rich resources and excellent performance. It is non-toxic, has excellent biocompatibility and biodegradability. It is an ideal extracellular matrix material and can promote the adhesion and proliferation of various tissue cells. Chitosan itself has biological activity, which can promote the growth of vascular endothelium and the proliferation of keratinocytes and osteoblasts. It also has anti-inflammatory, antibacterial, and immune function regulating properties. Chitosan has been used as a growth factor carrier and scaffold material in skin, nerve, bone and cartilage, and liver tissue engineering. It can also be used as wound dressings, drug sustained-release agents, defect fillers, etc. However, scaffolds prepared from pure chitosan also have many shortcomings, such as poor mechanical properties and lack of material surface specificity. Therefore, when chitosan is used in bone tissue engineering, it is usually compounded with other materials to achieve the required performance requirements. The researchers prepared a high-porosity hydroxyapatite/carboxymethylchitosan porous composite scaffold, and the mechanical properties of the composite scaffold could be significantly improved by adjusting the ratio of the two composite materials. The mechanical properties of composite materials are better than any of the single-component materials and are sufficient to meet the performance requirements of load-bearing bones. Although chitosan is abundant in nature, has excellent properties and is environmentally friendly, its mechanical properties are poor, which greatly limits the application of chitosan. Chitosan has relatively active free radicals and has relatively active properties. Chemical reagents are used to modify it to prepare corresponding composite materials, which further expands the application fields of chitosan.

Combining the content of natural polymers and synthetic polymers, it is not difficult to find that polymer materials used for biological tissue engineering need to meet the following requirements:

1) Good biocompatibility: Good biocompatibility is a biological The premise of tissue engineering scaffold materials is that the material itself and subsequent degradation products after implantation in the human body must have good biocompatibility in the organism;

2) Controllable degradability: Degradability is one of the basic requirements of current tissue scaffolds. With the growth and differentiation of cells, the scaffold must be able to degrade by itself, which can reduce the risk of secondary surgery and relieve pain for patients;

3) Mechanical properties: After being implanted into a living body, the scaffold serves as a metabolic site for cells and should have a certain ability to maintain its shape. Not only that, the density of the bone scaffold prepared by 3D printing should be similar to that of the replaced part, and it should have good "affinity";

4) Self-growth performance: The self-growth performance is mainly for some infant patients, and the implant should have the ability to grow with ease. The ability to grow according to the growth of pediatric patients;

5) Good sterilization: The ultimate goal of the tissue engineering scaffold after preparation is to be implanted into the human body for clinical operations, so it needs to have good sterilization.

Matexcel can provide you with natural polymer and synthetic polymer materials related to 3D printing research to assist your research work. If you have any needs, please feel free to contact us.

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