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Polyurethane (PU) is a kind of high polymer with unique properties and wide use, especially as a medical material. The purpose of this paper is to design and synthesize poly (polyurethane) scaffold suitable for bone tissue engineering. The polyurethane tissue engineering scaffolds with good biocompatibility, biodegradability, mechanical properties and biological activity are the key points of this study by optimizing the reaction conditions and adjusting the ratio of raw materials to make good biocompatibility, biodegradability, mechanical properties and biological activity.
This paper uses soluble starch (Soluble starch, ST), polyethylene glycol 400 (polyethylene glycol-400, PEG-400), isophorone diisocyanate (Isophorone diisocyanate, IPDI) as the raw material, with stannous octanate (Stannous octanate) as the catalyst, 1-4 butanediol as the chain extender, and water as a foaming agent.
A series of medical polyurethane tissue engineering scaffolds have been designed. The effects of different hard segment and soft segment, starch and polyethylene glycol 400 ratio on the properties of polyurethane were investigated. The results show that with the increasing proportion of hard segments, the mechanical properties of PU increase obviously, the degradation rate decreases, and porosity keeps fluctuating in a certain range.
When the ratio of the soft and hard segment is constant and the amount of starch is increased, the mechanical properties of PU are obviously improved, while the degradation rate and porosity also have a certain increase, but the fluctuation range is not large.
Keywords: polyurethane; starch; biodegradation; tissue engineering scaffold
Biomedical materials, also known as biomaterials, are used to diagnose, treat, repair and replace damaged tissues and organs of organisms and enhance their functions.
Damage to articular cartilage due to trauma, tumors and inflammation is particularly common in clinical practice.However, there are no nerves, blood vessels, or lymphoid tissue in human cartilage.In the articular cavity, nutrients can only be obtained by synovial fluid.Its main metabolic pathway is anaerobic digestion, which determines its limited self-repair ability .However, the existing repair and treatment technologies cannot be constructed from the biological environment and the mechanical environment of cartilage regeneration and repair, so it is difficult to make a breakthrough in articular cartilage repair.It is an important research direction to reconstruct cartilage regeneration and repair based on biological environment and mechanical environment.
Tissue engineering adds hope for cartilage repair.Scaffold material is a very important factor in tissue engineering.The commonly used support materials are synthetic materials and natural materials.Although natural materials have good biocompatibility, they are of limited source and difficult to be processed.It is difficult to ensure the properties of different batches of materials and has the disadvantages of antigenicity and difficult to control degradation rate.The synthetic material has good mechanical properties.They are easy to machine without being restricted by their sources, and can adjust the advantages of physics, chemistry, biomechanics and degradation as needed .However, the material has poor cellular affinity, hydrophilicity and cellular attachment.To build a tissue-engineering scaffold system, it is necessary to synthesize polymer materials with mechanical and biological properties similar to cartilage, which can be applied to repair cartilage damage and have good performance in the treatment of articular cartilage damage.
Since the 1950s and 1960s, polyurethane has been used in repairing bone defects for more than 50 years.Products include artificial windpipe and blood vessels, artificial heart valves, artificial lungs, bone adhesives, pacemaker insulation lines, sutures, artificial skin, burn dressings, and various splints.Generally speaking, the requirements for medical macromolecular materials are: good stability, not easy biological aging, no inflammation, cancer or other diseases, non-toxic;Good biocompatibility;With a certain heat resistance, easy to sterilize at high temperature, easy to shape at high temperature;For some non-permanent materials in the body, they should be able to degrade within the proper time.Polyurethane materials can meet these requirements .On this basis, modified polyurethane has better properties.Early PU materials were mainly used to treat cardiovascular diseases and orthopaedic diseases, and then gradually extended to other fields.With the development of tissue engineering research, PU has been made into scaffolds constructed by various tissues due to its various kinds of molecular structures and the changeable properties of functional groups.
Polyurethane (PU) is polyurethane throughout the whole process, which is the general name of the macromolecular compound containing carbamate (-NHCO-) on the main chain.Usually, polyether or polyester diols are used to form soft segments of the polymer, with lower vitrification temperatures and lower polarities.Hard segment has high vitrification temperature and strong polarity.The -CO-NH- functional group in the hard segment produces a large number of hydrogen bonds between the molecular chains.The existence of hydrogen bond has strong interaction force and crystalline state, which controls the heat resistance and strength of PU .
Due to the good elasticity of PU, PU was initially studied as a blood contact material.Since then, PU materials have been used in more and more medical applications, including cardiac assist devices, neural catheters, blood vessels, artificial hearts and ureters.From the classification of hard segments of PU, PU can be divided into circular diisocyanate PU, aromatic diisocyanate PU and linear aliphatic PU.From the synthesis of PU soft segment classification, PU can be polyester PU, polyether PU and polycarbonate PU.According to the degradability of materials, PU can be classified into biodegradable PU and non-biodegradable PU.
In the late 1990s, PU was introduced as a potential biomaterial for bone and cartilage repair.Since then, PU has been used in cement, injectable interstitial fillers, detergents, drug delivery systems, shape memory materials, etc.Due to its unique properties and the possibility of chemical or physical modification, PU has attracted people’s attention.Proper PU design is non-toxic and biocompatible, which can promote calcification in vivo.PU has excellent mechanical, physiological and chemical adaptability.The ideal performance of PU can be adjusted by changing the chemical composition, raw material proportion, synthesis or technical parameters.As a result, they can be stable or biodegradable, hydrophobic or hydrophilic, thermoplastic or thermosetting, and hence a wide range of products, such as foam, coatings, fibers or films.
Soluble starch, polyethylene glycol 400, isophorone diisocyanate, 1, 4-butylene glycol, acylate are purchased from Shanghai Aladdin biochemical technology co., LTD. According to literature review, the design proportion of soft and hard sections is 1:1, 1:1, 1:1.2 and 1:1.3 respectively.The content of starch in soft segment was 5%, 10%, 20% and 30% respectively.
Figure. 1-1 macro view of polyurethane samples
As shown in FIG. 2-1, where FIG. a and b show the elevation of the sample without finishing, FIG. C and d show the cross-section of the sample, FIG.It is concluded that the macroscopic appearance of polyurethane obtained by polymerization of starch as soft material is in line with the biological requirements of bone and cartilage.
Tissue engineering porous scaffolds are considered as a substitute for ECM.The growth of cultured cells in vitro is similar to that in vivo.Significant progress has been made in the study of tissue and organ repair of skin, bone, cartilage, blood vessels and bladder.Different cells or tissues have special requirements for the structure and surface properties of the scaffold, and various techniques and methods have been developed for the preparation of the scaffold.However, various preparation methods have advantages and disadvantages in adjusting micropore structure and physical and chemical properties.It is necessary to select suitable methods or several methods to complement each other in order to prepare porous scaffolds with different characteristics to simulate the structure of different parts.The combination of porous scaffold and various methods will be one of the future research directions .
In addition, due to the hydrophobicity of PU surface, which is not conducive to the growth of cells, the choice of suitable surface modification technology will be one of the factors that must be considered.From what has been discussed above, we can think better PU porous scaffolds should be considered, such as good overall performance, and suitable mechanical properties, excellent surface biocompatibility and suitable mechanical stimulation and other factors, it is also the PU long-short stents in the field of regenerative medicine and tissue engineering in the scope of the necessary condition to get a better application and development and research direction.
This work was supported by my tutor Dr.Du.I also thank Dr. Karen for her guidance and support.I would like to express my sincere thanks to all those who have helped me.
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