The properties and degradation characteristics of several commonly used degradable polymer materials, including polyglycolide, polylactic acid, (glycolide-lactide) copolymer, polycaprolactone, polydioxanone, polyhydroxyl fat Acid esters, polytrimethylene carbonates and polyurethanes and polyether urethanes, etc., and their applications in medical devices, including implants, tissue engineering scaffolds, drug controlled release carriers, etc., are reviewed. Biomaterials play an important role in disease treatment and health care. According to the nature of materials, biomaterials can be divided into inert materials and degradable materials. At present, the development of biomaterials shows inertness to degradability (hydrolysis and Enzymatic degradation) The trend of transformation suggests that many bio-inert devices that now have a temporary therapeutic effect (helping the body repair or regenerate damaged tissue) will be replaced by degradable material devices. Compared with inert materials, degradable polymer materials are a more ideal medical device material. Inert devices generally have poor long-term compatibility and require secondary surgery, while degradable polymer materials do not have these defects. In the past 20 years, some new medical technologies have emerged in biomedicine, including tissue engineering, drug controlled release, regenerative medicine, gene therapy and bio-nanotechnology. These new medical technologies need to be supported by degradable polymer materials. Correspondingly, the development of degradable polymer materials has been promoted. Degradable polymer materials need to have good compatibility throughout the degradation process, including the following: Does not cause persistent inflammation or toxic effects after implantation in humans; a suitable degradation cycle; In the degradation process, having mechanical properties corresponding to the function of treatment or tissue regeneration; The degradation products are non-toxic and can be excreted by metabolism or infiltration; Processability. There are many factors affecting the biocompatibility of degradable polymer materials. Some properties of the material itself, such as the shape and structure of the implant, hydrophilic and lipophilicity, water absorption, surface energy, molecular weight and degradation mechanism, need to be considered. Polyurethane (PUR) and polyether urethane (PEU) Non-degradable PUR and PEU have good biocompatibility and mechanical properties and can be used to make long-term medical implants such as pacemakers and artificial blood vessels. Because of the synthetic pathways of non-degradable PUR with good biological properties and diversity, researchers began to try to develop degradable PUR. PUR is generally prepared by polycondensation of a diisocyanate with a diol/diamine, but common diisocyanates such as 4,4'-diphenylmethane diisocyanate (MDI), toluene-2,4-diisocyanate (TDI), etc. Too much toxicity, the researchers developed other aliphatic diisocyanates [such as 1,4-butane diisocyanate (BDI), hexamethylene diisocyanate (HDI), succinyl chloride (LDI), isophorone diisocyanate ( IPDI) and lysine triisocyanate, etc.] to synthesize degradable PUR. LDI reacts with DL–LA, CL and other monomers to produce degraded PEU, and its properties can be adjusted over a wide range. In these PEUs, the aliphatic polyester constitutes a soft segment and the polypeptide constitutes a hard segment. J.Podporska-Carroll et al. used a phase reversal technique to prepare a poly(ester-urethane) urea (PEUU) three-dimensional porous scaffold. The human osteosarcoma MG–63 cells were inoculated into the scaffold for 4 weeks, and the results showed that the scaffold had supporting cell adsorption. The role of growth and proliferation is a potential alternative to cancellous bone. JRMartin et al. prepared a selectively degraded polythioketal urethane (PTK-UR) tissue engineering scaffold that is selectively degraded by reactive oxygen species (ROS) produced by cells to achieve coordination between tissue growth and material degradation. ROS is a key mediator of cell function, especially in areas of inflammation and tissue healing. The body's natural response to implants is inflammation and ROS. In addition, the researchers also prepared PH-sensitive PUR, which can self-assemble to form micelles, and is expected to become a multi-functional active intracellular drug transport carrier. In tissue engineering, researchers are developing PEU (Degrapol®) as a scaffold material; in orthopedics, researchers have developed an injectable two-component PUR (PolyNova®) that is in the form of a liquid under arthroscopy. Used to provide suitable attachment and support after polymerization at body temperature in situ, exhibiting equivalent or superior performance to commonly used bone cement, and it also promotes cell adhesion and proliferation.
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