In vitro investigations of a novel wound dressing concept based on biodegradable polyurethane

Non-healing and partially healing wounds are an important problem not only for the patient but also for the public health care system. Current treatment solutions are far from optimal regarding the chosen material properties as well as price and source. Biodegradable polyurethane (PUR) scaffolds have shown great promise for in vivo tissue engineering approaches, but accomplishment of the goal of scaffold degradation and new tissue formation developing in parallel has not been observed so far in skin wound repair. In this study, the mechanical properties and degradation behavior as well as the biocompatibility of a low-cost synthetic, pathogen-free, biocompatible and biodegradable extracellular matrix mimicking a PUR scaffold was evaluated in vitro. The novel PUR scaffolds were found to meet all the requirements for optimal scaffolds and wound dressings. These three-dimensional scaffolds are soft, highly porous, and form-stable and can be easily cut into any shape desired. All the material formulations investigated were found to be nontoxic. One formulation was able to be defined that supported both good fibroblast cell attachment and cell proliferation to colonize the scaffold. Tunable biodegradation velocity of the materials could be observed, and the results additionally indicated that calcium plays a crucial role in PUR degradation. Our results suggest that the PUR materials evaluated in this study are promising candidates for next-generation wound treatment systems and support the concept of using foam scaffolds for improved in vivo tissue engineering and regeneration.     

In vitro biocompatibility evaluation of silk-fibroin/polyurethane membrane with cultivation of HUVECs

In order to investigate the in vitro biocompatibility of a novel polyurethane （PU） membrane modified by incorporation of superfine silk-fibroin powder （SFP）, which was prepared for small-diameter vascular grafts, with the cultivation of human umbilical vein endothelial cells （HUVECs）, PU and SFP were mixed with the ratios of 9：1, 7：3, 5：5, 3：7 （PU：SFP） to make four composite materials. Unmodified PU and polytetrafluoroethylene （PTFE） were added as control groups. CCK-8 assay was used to evaluate the cytotoxicity of these biomaterials. Data were processed using SPSS, and P〈 0.05 was considered to be statistically significant. Adherence and spreading of HUVECs on the surface of specimens was observed using direct contact cultivation. The toxicity ratings of the novel composites were grade 0-1, which is in the acceptable range. In all the experimental groups except control, SFP/PU with ratio of 1：9 had the least cytotoxicity property, and more content of SFP in the composite showed no improvement of the biocompatibility. HUVECs strongly attached to and grew on the surface of the biomaterials, and proliferated rapidly. The proliferation ability increased with increased proportion of SFP; however the cell quantity on the surface of the materials decreased when the proportion of SFP was equal to or larger than that of PU in the composite. It is concluded that this novel material has excellent cellular affinity with no cytotoxicity to HUVECs. Adding SFP gives PU better biocompatibility, while further research on optimum blend ratios is still needed.     

柔性海藻酸钙海绵伤口敷料的制备及性能

采用甘油为增塑剂对海藻酸钙海绵进行改性处理,制备了可用作伤口敷料的柔性海绵。结果表明,改性后海藻酸钙海绵的柔韧性增强,可任意弯折,表面光滑平整,不易碎,摩擦不掉渣,能同时满足医用伤口敷料的功能性和舒适性的要求。随着甘油含量的增加,海绵的柔韧性增强,断裂延伸率和对蒸馏水的保液量增加,但是海绵的断裂强度、初始模量、孔隙率、透气率和吸液量下降。海藻酸钙海绵的最佳增塑工艺为甘油浓度6%,处理时间12h,处理温度30℃,此时其柔软度指标为326.8°,断裂强度为0.376MPa,孔隙率为82.3%,透气率为59.8%,对蒸馏水的吸液量和保液量为13.1和6.73g/g。     

Injectable hydrogel wound dressing based on strontium ion cross-linked starch

Severe skin wounds cause great problems and sufferings to patients. In this study, an injectable wound dressing based on strontium ion cross-linked starch hydrogel (SSH) was developed and evaluated. The good inject-ability of SSH made it easy to be delivered onto the wound surface. The good tissue adhesiveness of SSH ensured a firm protection of the wound. Besides, SSH supported the proliferation of NIH/3T3 fibroblasts and facilitated the migration of human umbilical vein endothelial cells (HUVECs). Importantly, SSH exhibited strong antibacterial effects on Staphylococcus aureus (S. aureus), which could prevent wound infection. These results demonstrate that SSH is a promising wound dressing material for promoting wound healing.     

In vivo tests of a novel wound dressing based on biomaterials with tissue adhesion controlled through external stimuli

The high incidence of wounds by second intention and the high costs associated with their treatment give rise to the need for the development of wound dressings that protect not only the wounds themselves but that are also able to promote cell proliferation and skin regeneration. Moreover, it is also very important that no damage to the new regenerated tissue is generated while removing the dressing. In this work, a novel wound dressing, which would be able to favor tissue repair and be removed at an appropriate scheduled moment by means of an external stimulus without promoting extensive damage to the new tissue, was produced and tested. Polyurethane membranes were modified by grafting polymers based on poly(n-isopropylacrylamide) (P-N-IPAAm). P-N-IPAAm undergoes a phase transition at approximately 32°C, which changes its behavior from hydrophilic (below 32°C) to hydrophobic. It was hypothesized that, by reducing the temperature near the wound dressing to values lower than 32°C, the detachment of the dressing would become more effective. The wound dressings containing P-N-IPAAm grafts were tested in vivo by covering excisional wounds produced in mice. The produced dressings were placed in direct contact with the lesions for 3 days. Results showed that the hypothermia due to anesthesia required to remove the dressings from mice lowered the local temperature to 28°C and favored the detachment of the wound dressings containing P-N-IPAAm grafts. Histological analyses showed that lesions covered by dressings presented less intense inflammatory events and denser connective tissue than did the wounds without dressings. The wounds covered by polyurethane membranes with P-N-IPAAm grafts showed signs of more intense re-epithelization and angiogenesis than did the lesions covered by polyurethane without grafts.     

Synthesis and characterization of gelatin based polyester urethane scaffold

For tissue engineering purpose two gelatin based polyester urethane scaffolds of different compositions were prepared from lactic acid, polyethylene glycol 400 (PEG 400) and characterized by FTIR, XRD for their mechanical and morphological properties using SEM and optical microscopic analyses. Degradation and swelling studies of gelatin based polyester urethane scaffolds in phosphate buffer saline (PBS) were performed. Human keratinocyte cells were cultured within these scaffolds, which showed good cell adherence and proliferation.     

聚氨酯软骨-骨双层复合材料的构建及性能研究

关节软骨损伤是临床上的常见病,由于其组织再生能力差,可能导致骨性关节炎的发生,因此,研究开发骨-软骨移植替代材料非常重要。目的就是设计一体化软骨-骨双层复合材料,以解决软骨与骨的整合问题。该双层复合体上层软骨材料为聚氨酯,软骨下骨为羟基磷灰石/聚氨酯复合支架材料,两层结构中引用了同一种材料——聚氨酯,将双层结构有机黏合在一起,使黏合更牢固。下层多孔HA/PU复合支架材料的孔与孔之间相互贯通,孔隙率约为83%,孔径范围分布在200～600μm。体外细胞相容性实验表明,该一体化双层复合材料为细胞的黏附、增殖以及生存活力的维持提供了有利环境。上述结果表明该双层复合材料有望用于软骨组织工程修复。     

新型聚氨酯微球的合成及其形态研究

通过自乳化的方法合成了具有聚己内酯-聚乙二醇-聚己内酯嵌段结构的聚氨酯水溶液,再采用凝聚相分离法合成了一种新型的聚氨酯微球.研究了聚乙二醇分子量、异氰酸基与羟基的摩尔比、聚己内酯与聚乙二醇的摩尔比、预聚温度、聚氨酯水溶液浓度、CaCl2浓度和搅拌速度等条件对聚氨酯微球的影响,以及傅立叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)表征了微球的化学结构和表面形态结构.通过对合成条件的优化,找出了合成稳定、均匀和形态好的聚氨酯微球的最佳条件.实验结果表明,制备的聚氨酯微球平均粒径2mm左右,分布相对均匀,球形较好.     

角膜内皮细胞载体壳聚糖基共混膜的制备及性质研究

为探讨壳聚糖基共混膜作为组织工程化角膜内皮细胞载体的可行性,制备了羟乙基壳聚糖/明胶/硫酸软骨素共混膜,并评价其性质。结果表明该膜片具有良好的透明度,适宜的含水量;细胞毒性0～1级;体外培养的角膜内皮细胞能够很好地贴附和生长于共混膜上;植入大鼠肌肉内,能够稳定地降解,诱发的炎症反应明显低于不可降解手术缝合线,说明该膜片具有良好的组织相容性,有望作为角膜细胞载体构建组织工程化角膜。     

Investigations on hygrothermal aging of thermoplastic polyurethane material

In this investigation, the absorption and diffusion of water in thermoplastic polyurethane (TPU) was studied. Water-sorption experiments, physical and mechanical property tests were performed after immersion in water at a set temperature of 70 °C for up to 6 months. Emphasis was given to the effect of immersion aging on thermal, mechanical and tribological properties. Fickian diffusion behaviour was found during the initial immersion time followed by saturation stage as time progressed. The use of differential scanning calorimetry (DSC) analysis showed that the glass transition temperature (Tg) was sensitive to the effect of hygrothermal aging and it decreased with increasing water uptake.More significantly, the mechanical properties in bulk material, obtained from tensile test, were affected by aging. Elastic modulus and stress at 200% of strain of the studied TPU were decreased after sufficient exposure to moisture. On the other hand, the mechanical properties of the material surface were equally investigated with the help of an abrasive wear test. A decrease in wear resistance of the aged TPU was discerned. The reversibility of mechanical and physical properties after moisture exposure was also assessed in this study. The polymer degradation was found as irreversible phenomenon.Finally, the evolution of the mechanical properties seems to be well correlated to structural modifications obtained from Fourier transform infrared spectroscopy (FTIR) characterization.     

可降解自乳化聚氨酯微球的合成及性能研究

将预聚-扩链-中和-乳化法联合运用,一步合成出自乳化聚氨酯微球。研究了自乳化聚氨酯微球的合成条件。包括二异氰酸酯单体种类对微球形态的影响;异佛尔酮二异氰酸酯（IPDI）和聚丙二醇（PPG）单体配比对乳化效果的影响;乳化时间对微球形态的影响;反应温度、聚合时间和搅拌速度等对微球合成的影响。并以可降解的聚乳酸（PLA）取代部分PPG合成出可降解的自乳化聚氨酯微球,对其在磷酸缓冲液中的降解性进行了研究。通过IR及SEM对自乳化聚氨酯微球进行了表征,找出了合成稳定、均匀和形态好的自乳化聚氨酯微球的最佳条件。     

基于聚氨酯的PEDOT核壳分散体的制备及应用

通过在聚氨酯分散体中原位聚合成功制备了以聚氨酯(PU)乳胶粒子为核,聚3,4-乙撑二氧噻吩(PEDOT)为壳的核壳分散体。改变单体EDOT与PU乳胶粒子的质量比,制备了一系列PEDOT-PU复合分散体,并通过红外光谱、透射电镜、动态光散射和四探针测试等手段进行了表征,探讨了核壳粒子形成过程。结果表明,EDOT与PU乳胶粒子质量比为1/10时,复合分散体的综合性能最佳,利用自制的复合分散体配制得到了抗静电涂料,并成功应用于PET、PVC、PP塑料基材。     

Influence of TiO2 Nanoparticles Incorporated into Elastomeric Polyesters on their Biocompatibility In Vitro and In Vivo

Fibroblasts proliferation and apoptosis as well as tissue response after implantation of elastomers containing nanocrystalline TiO₂ were investigated in the present in vitro and in vivo study. Materials investigated were soft poly(aliphatic/aromatic‐ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized linoleic acid (DLA) soft segments, respectively, containing 0.2 wt% TiO₂ nanoparticles. An investigation of the influence of TiO₂ nanoparticles incorporated into polymeric material on in vitro biocompatibility revealed enhanced cell proliferation and diminished number of necrotic and apoptotic cells as compared to nanoparticles‐free polymer. Implantation tests indicated that the observed tissue changes were similar to those observed with medical‐grade silicone elastomer, no evidence of contact necrosis being observed. The unchanged morphology of rat liver hepatocytes and the lack of parenchymal necrosis also indicated that exposure to the material containing TiO₂ nanoparticles, did not cause any cytotoxic reactions. The present study, thus, showed that elastomeric polyester containing TiO₂ nanoparticles are interesting biomimetic constructs for improved tissue regeneration.     

Fabrication of novel nanofiber scaffolds from gum tragacanth/poly(vinyl alcohol) for wound dressing application: In vitro evaluation and antibacterial properties

Gum tragacanth (GT) is one of the most widely used natural gums which has found applications in many areas because of its attractive features such as biodegradability, nontoxic nature, natural availability, higher resistance to microbial attacks and long shelf-life properties. GT and poly(vinyl alcohol) (PVA) were dissolved in deionized water in different ratios i.e., 0/100, 30/70, 60/40, 50/50, 40/60, 70/30, 0/100 mass ratio of GT/PVA. Nanofibers were produced from these solutions using electrospinning technique. The effect of different electrospinning parameters such as extrusion rate of polymer solutions, solution concentration, electrode spacing distance and applied voltage on the morphology of nanofibers was examined. The antibacterial activity of nanofibers and GT solution against Staphylococcus aureus and Pseudomonas aeruginosa was examined and these nanofibers showed good antibacterial property against Gram-negative bacteria. FTIR data showed that these two polymers may be having hydrogen bonding interactions. DSC data revealed that the exothermic peak at about 194 °C for PVA shifted to a lower temperature in GT/PVA blend. Human fibroblast cells adhered and proliferated well on the GT/PVA nanofiber scaffolds. MTT assay was carried out on the GT/PVA nanofiber to investigate the proliferation rate of fibroblast cells on the scaffolds.     

基于植物油改性的单组分水性聚氨酯的合成

介绍一种新的单组分水性聚氨酯合成工艺。采用气干性植物油为原料 ,经过甘油醇解改性 ,代替了传统工艺中的聚酯聚醚多元醇与甲苯二异氰酸酯(TDI)和扩链剂二羟甲基丙酸 (DMPA)反应得到自乳化改性水性聚氨酯。经检测 ,该乳液室温下静置 6个月不破乳 ;漆膜硬度 0 54;冲击强度(cm) :50 ;柔韧性 (mm) :1级 ;附着力 :1级 ;耐水性 :常温下水中浸泡 72h不起泡。讨论了中和反应温度及中和度等因素对乳液性能的影响 ,确定了最佳反应条件 :中和度≥ 1 0 0 % ,反应温度应控制在 40～50℃。     

N100基聚氨酯弹性体粘合剂的合成及表征

采用傅立叶变换红外光谱技术和力学性能测试技术对P(E-CO-T)-N100体系的预固化反应动力学及其在交联改性双基推进剂粘合剂体系中的应用进行了研究.结果显示,P(E-CO-T)-N100体系的预聚反应时间是180min,同时获得了预聚率与预聚时间的关系,预聚180min后,-NCO的转化率为80%.根据"相似相溶"原理,预聚物与推进剂的主要组分NG、DEGDN和NC的溶度参数差△δ均＜2,说明P(E-CO-T)-N100预聚物具有良好的相溶性.P(E-CO-T)-N100预聚物的加入使粘合剂体系的交联密度从1.03×10-5提高到了2.17×10-5.常温下的力学性能数据显示,P(E-CO-T)-N100预聚物上的活性-NCO与NC上的-OH进行了交联,使粘合剂体系的延伸率达到191.7%,提高了74%.     

Synthesis and characterization of a novel biodegradable elastomer based on citric-acid-crosslinked polyesters

In this study, poly(monoethylene diglycol sebacate) with a low molecular weight was synthesized from the reaction of ethylene diglycol and sebacic acid. The melt condensation reaction of the prepared polyester diol with citric acid produced a bioelastomer material comprising a network of transparent and flexible polyether esters. This material was amorphous, with a glass transition temperature of lower than 0°C. Its mechanical properties (tensile strength, 1.92–4.61 MPa; elongation at break, 201.9–348.9%) and degradation performance could be tuned by changing the molar ratio of the reacting monomers and controlling the crosslink curing time of the pre-polymer. As a biological material, the as-synthesized elastomer showed good hydrophilicity, water-absorption capability, and dimensional stability.     

水性聚氨酯-聚二甲基硅氧烷共混体系聚合物电解质的研究

通过共混法,将不同质量分数的聚二甲基硅氧烷(PDMS)添加到水性聚氨酯(WPU)中,并加入适量锂盐(LiClO4)得到一系列聚合物电解质膜.测试结果表明,与WPU聚合物电解质相比,PDMS改性后的WPU聚合物电解质体系具有良好的热稳定性.将聚合物膜浸泡在1 mol/L LiClO4(PC)溶液中12h,可得到吸液率为119%凝胶聚合物电解质,其电导率在30℃时可达到1.01×10-3S/cm,80℃为5.17×10-3/cm.     

蓖麻油-聚醚基聚氨酯弹性体的制备和表征

以可再生资源-蓖麻油作为起始荆,环氧丙烷开环聚合制备了不同分子量的蓖麻油-聚醚多元醇,并通过1HNMR 和 FTIR 等手段来分析蓖麻油-聚醚多元醇的结构.以不同分子量的蓖麻油-聚醚多元醇作为原料制备了一系列聚氨酯弹性体,并对其进行物理机械性能和热性能分析.研究结果表明:随着蓖麻油聚醚多元醇分子量的增加,其聚氨酯弹性体的扯断伸长率逐渐增加,拉伸强度、撕裂强度和硬度逐渐降低;同时,热稳定性提高,硬段的结晶熔融温度和结晶度降低.     

A preliminary study of cushion properties of a 3D printed thermoplastic polyurethane Kelvin foam

The cells in conventional packaging foams have random size and orientation, and the energy‐absorbing behaviour of these foams is determined by the collective contribution of different sizes of cells. In contrast to the random nature of stochastic foams, 3D printing technologies allow engineers to design and produce foams having engineered cellular structures. In this study, engineered cellular structures based on the classic Kelvin 1887 model were 3D printed in 30 × 30 × 30 mm thermoplastic polyurethane cubes with a repeating size of 216 unit cells. One hundred consecutive cyclic compression tests were performed to assess the 3D printed foam's resilience and energy absorption characteristics. The stress‐strain curve of the 3D printed thermoplastic polyurethane foam indicated viscoelastic behaviour and a Mullins effect indicative of resilient rubber. A long wave buckling mode was observed during cyclic compression cycles due to the Kelvin structure. The cushion factor computed from the stress‐strain curve was close to that of a metal spring with linear elasticity. The combination of the 3D printed foam's resilience, its much lower density than rubber, and the complete geometric freedom of the engineered cellular structures offer designers the potential to create high‐performance cushion materials tailored for packaging applications.