Expanded polytetrafluoroethylene (ePTFE) is made of 100% polytetrafluoroethylene resin (PTFE) using special processing methods such as paste extrusion and stretching. It is a new type of medical polymer material. It has a network structure formed by the connection of fine fibers. These fine fibers form many holes, so expanded polytetrafluoroethylene (ePTFE) can be bent more than 360 degrees, has good toughness, high longitudinal strength, easy to deform in the transverse direction, and improved material flexibility and blood compatibility. Expanded polytetrafluoroethylene (ePTFE) is an ideal medical polymer material widely used in artificial blood vessels.
Polytetrafluoroethylene (PTFE) products have high temperature resistance, acid and alkali resistance, solvent resistance, excellent electrical insulation and biocompatibility. They have long been used in traditional industries such as chemistry, machinery and electronics. The expanded polytetrafluoroethylene (ePTFE) microporous membrane developed since the 1970s has developed the application range of microporous membranes in the fields of sealing, electronics, textile, medical, environmental protection and other fields.
In the medical field, the incidence of vascular occlusive diseases such as arteriosclerosis is increasing. Artificial blood vessels have important clinical application value as a substitute for many severe stenosis or occlusion blood vessels. With the rapid development of bioengineering and biomaterials, in the current surgery, artificial blood vessels are mainly used to temporarily or permanently replace the defects of patients' arteries or veins, or as shunt channels and renal diseases when arteries are blocked. The patient was replaced with an arteriovenous graft required for hemodialysis. It can be seen that artificial synthetic blood vessels are used as substitutes, especially large-diameter artificial blood vessels have been widely used in tissue repair and vascular reconstruction surgery.
The ideal synthetic vascular material should meet the following requirements: good biocompatibility, with special emphasis on excellent blood compatibility, non-immunogenicity, strong plasticity, certain strength, vascular biomechanical requirements, and easy cell planting. Therefore, the materials used to manufacture artificial blood vessels can be divided into natural biological materials and synthetic materials. Natural biological materials include macromolecular materials such as acellular matrix, collagen, polyamino acids, peptides, hyaluronic acid and their complexes; synthetic materials are non-degradable materials such as polytetrafluoroethylene (PTFE) and nylon-6. However, due to the immature technical conditions of degradable materials, expanded polytetrafluoroethylene (ePTFE) has become a substitute for synthetic artificial blood vessels due to its porosity and good surface properties and flexibility.
1. Preparation of expanded polytetrafluoroethylene
Expanded polytetrafluoroethylene (ePTFE) is made of polytetrafluoroethylene dispersion resin as raw material, and liquid propellant is added. After mixing, it is pre-pressed into a blank, placed on special equipment, and extruded into a tube as required. The rod-shaped product is dried to remove the extrusion aid. At this time, the tubular product can be pulled out, and the rod-shaped product can be calendered before drying and stretching. The stretched product should be heat set in a specific temperature range. After cooling, the expanded polytetrafluoroethylene (ePTFE) medical product can be obtained.
2. Structure and performance of expanded polytetrafluoroethylene
As we all know, PTFE is called "the king of plastics". It is very inert, has excellent chemical stability, electrical properties, surface properties and good physical and mechanical properties.
As a medical material, expanded polytetrafluoroethylene (ePTFE) has excellent medical properties. For example, it is non-toxic, has good tissue compatibility, and does not cause cancer. Anti-biological aging, long-term implantation of the human body is not affected, tissue irritation is slight, and tissue response to it is very small. The surface of the material is negatively charged, the surface tension is small, it is not easy to coagulate, it does not leak, no pre-coagulation treatment is needed, it is easy to disinfect, white, soft and elastic.
Expanded polytetrafluoroethylene (ePTFE) medical products manufactured by the drawing method have a unique microstructure. Structural features can be observed by scanning the surface structure of an expanded polytetrafluoroethylene (ePTFE) container with an electron microscope. It consists of multiple fine fibers connected to the network structure through nodes, and many fine through holes (micropores with a diameter of about 30 μm) are formed between the fine fibers. The continuous porous network structure makes the expanded polytetrafluoroethylene (ePTFE) medical products soft, elastic, and high-strength, easy to sew during surgery, and does not produce burrs and scattered when cut with scissors, which is more beneficial of. Cells and tissues grow in the body, and finally form a new inner membrane on the inner wall, which is integrated with the surrounding tissue to form a whole. ePTFE can be fixed without forming a fibrous capsule. Moreover, since the length (ie pore diameter) of the fiber can be controlled within the desired range by selecting process conditions, the material does not leak blood and does not require pre-coagulation treatment.
3. Application of expanded polytetrafluoroethylene
(1) Expanded polytetrafluoroethylene (ePTFE) blood vessel
Expanded polytetrafluoroethylene (ePTFE) blood vessels overcome easy thrombosis, and burrs are prone to burrs when cutting blood vessels, and the operation of pre-coagulation treatment before implantation in the human body is troublesome. At present, the product is mainly used for vascular transplantation of femoral artery pseudoaneurysms; aortic constriction resection or repair of artificial blood vessel transplantation; bridging material for portal hypertension shunt; upper and lower vena cava and right atrium bypass; intestinal vein and right atrium Road; hemodialysis. Obtain good clinical results.
(2) Expanded polytetrafluoroethylene (ePTFE) heart patch
The expanded polytetrafluoroethylene (ePTFE) patch has the same uniformity as the base wood, with no difference between the front and back. When the patch is repaired, the patch and the recipient tissue are evenly applied, and can be arbitrarily cut into a desired shape without burrs, and are not required during surgery. Pre-condensation. The patch is used to repair atrial septal defect and ventricular septal defect in children with congenital heart disease; enlargement of the right ventricular outflow tract; and repair of four diseases. It can also repair abdominal walls and blood vessels, as well as gaskets used in cardiac surgery. At present, there are more than 700 clinical applications, and the longest period of use has been nearly ten years. Due to material reasons, no case had complications or sudden death.
(3) Expanded polytetrafluoroethylene (ePTFE) artificial trachea
The tube is used for tracheal collapse caused by large area tracheal cartilage defects such as bullets, trauma, laryngeal cancer surgery and normal breathing that cannot form a lumen, so that it can restore normal breathing. In the early clinical medicine of our country, metal artificial trachea was used to treat tracheal defects, and then the silicone rubber tube indwelling method was used. 80% of patients can remove the hose and restore normal breathing by this method, but this method is more However, the extubation of various defects has not been successful, and patients can only wear the tube for life and become disabled. Inflatable polytetrafluoroethylene (ePTFE) artificial trachea has rescued this type of patient. It has been used clinically in 10 cases and has been followed up for 7 years with satisfactory results.
(4) Expanded polytetrafluoroethylene (ePTFE) endoscopic catheter catheter
Expanded polytetrafluoroethylene (ePTFE) endoscopic forceps catheter is an important part of endoscope in medical equipment. It is used for biopsy sampling in the human body to remove foreign bodies and pick up hoof polyps. It can be operated freely, protecting patients from unnecessary pain. Therefore, it has positive significance for the diagnosis and treatment of stomach, intestine and duodenum.