Reactive TiO2 Nanoparticles Compatibilized PLLA/PBSU Blends:Fully Biodegradable Polymer Composites with Improved Physical,Antibacterial and Degradable Properties

The fully biodegradable polymer blends remain challenges for the application due to their undesirable comprehensive performance.Herein,remarkable combination of superior mechanical performance,bacterial resistance,and controllable degradability is realized in the biodegradable poly(L-lactide)/poly(butylene succinate) (PLLA/PBSU) blends by stabilizing the epoxide group modified titanium dioxide nanoparticles (m-TiO2) at the PLLA-PBSU interface through reactive blending.The m-TiO2 can not only act as interfacial compatibilizer but also play the role of photodegradation catalyst:on the one hand,binary grafted nanoparticles were in situ formed and stabilized at the interface to enhance the compatibility between polymer phases.As a consequence,the mechanical properties of the blend,such as the elongation at break,notched impact strength and tensile yield strength,were simultaneously improved.On the other hand,antibacterial and photocatalytic degradation performance of the composite films was synergistically improved,it was found that the m-TiO2 incorporated PLLA/PBSU films exhibit more effective antibacterial activity than the neat PLLA/PBSU films.Moreover,the analysis of photodegradable properties revealed that that m-TiO2 nanoparticles could act as a photocatalyst to accelerate the photodegradation rate of polymers.This study paves a new strategy to fabricate advanced PLLA/PBSU blend materials with excellent mechanical performance,antibacterial and photocatalytic degradation performance,which enables the potential utilization of fully degradable polymers.     

Poly(ethylene oxide) induced microstructure and hydrolytic degradation behavior changes of poly(butylene succinate)

Degradable polyesters exhibit wide application in many fields due to the fact that the waste of these polymers can be easily reclaimed, which greatly reduces the environmental risk. In this work, a small quantity of water-soluble poly(ethylene oxide) (PEO) was introduced into biodegradable poly(butylene succinate) (PBS). Crystallization behavior of the PBS matrix was comparatively investigated using polarized optical microscope (POM), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The results demonstrate that PEO affects the crystallization behavior of the PBS matrix, which is greatly dependent upon the PEO content. At relatively low PEO content, accelerated crystallization is achieved for the PBS matrix, while the role of PEO becomes inconspicuous at relatively high PEO content. The sample surface hydrophilicity was evaluated through contact angle measurement of distilled water. The results demonstrate that incorporating PEO into PBS greatly enhances the hydrophilicity of the sample surface. The hydrolytic degradation measurements were carried out under an alkaline condition. The results clearly show that the presence of PEO accelerates the hydrolytic degradation of the PBS matrix. Furthermore, the sample obeys the surface erosion mechanism. The mechanism for the largely enhanced hydrolytic degradation ability is then analyzed.     

The hydrolytic effect of moisture and hygrothermal aging on poly(butylene succinate)/organo-montmorillonite nanocomposites

The study of hydrolysis on biodegradable poly(butylene succinate) (PBS) is essential to predict the materials properties in a humid environment. In this study, PBS nanocomposites were exposed to different conditions of relative humidity (RH) and temperature. The moisture uptake increased with organo-montmorillonite (OMMT) loading and the RH of the testing environment. The exposure of PBS and the nanocomposites to a humid environment caused changes in the mechanical properties. The hydrolytic degradation becomes more pronounced upon hygrothermal aging at high temperature, whereby premature failure occurred. PBS nanocomposites were found to exhibit a better hydrolytic stability than neat PBS. The degradation was evaluated through Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). A drastic reduction in the molecular weight of PBS has revealed the occurrence of degradation after exposure to moisture and heat. This has led to an alteration of the thermal behavior as investigated using differential scanning calorimetry (DSC).     

脉冲电沉积制备HA/ZrO2纳米复合涂层的稳定性及生物相容性评价

采用脉冲电化学沉积法成功地在生物医用钛金属表面制备出均匀的纳米HA/ZrO₂复合涂层. 通过热处理提高涂层的致密性, 同时保留涂层的微纳结构. 考察了热处理后复合涂层的成分、形貌、生物相容性及生理稳定性. X射线衍射分析表明, 复合涂层成分为HA和ZrO₂. 扫描电镜观察发现, 热处理后复合涂层的致密性有所提高. 研究发现, ZrO₂的加入大大降低了HA/ZrO₂复合涂层中钙离子的释放速度, 提高了HA/ZrO₂复合涂层的生理稳定性. 纳米划痕实验结果表明, HA/ZrO₂复合涂层具有较好的结合强度. 通过培养成骨细胞考察了复合涂层的生物相容性. Alamar Blue检测表明, HA/ZrO₂复合涂层表面细胞黏附及增殖能力较好. ALP检测发现, 热处理后HA/ZrO₂复合涂层表面的细胞分化能力较强. 综合细胞培养结果显示, HA/ZrO₂复合涂层有较好的生物相容性.     

Substrate dependent differences in morphology and elasticity of living osteoblasts investigated by atomic force microscopy

We have used the atomic force microscope (AFM) as a tool for testing the biocompatibility of implant materials by investigating the adhesion behavior of osteoblast cells in vitro. This technique allowed the investigation of cytomorphology and cytomechanical properties of living cells on a submicrometer scale. Cell adhesion was investigated on Cobalt–Chromium (CoCr), Titanium (Ti) and Titanium–Vanadium (TiV) substrates, which are of great interest in the field of implant research. The elastic properties and the morphology of living osteoblasts on the metallic substrates were compared with those of osteoblasts cultured on glass and tissue culture polystyrene (PS). Furthermore, a characterization of the surface roughness of the substrates was performed and the surface coverage of proteins after incubation with cell culture medium on the substrates was observed with the AFM.     

基于乳酸和β-丙氨酸的聚酯酰胺共聚物合成及降解

采用直接熔融共缩聚方法成功地制备了L-乳酸/β-丙氨酸共聚物, 用红外光谱、核磁共振、凝胶色谱和DSC等方法对共聚物结构进行了表征; 考察了催化剂用量、投料比、聚合反应时间和反应温度等聚合条件对产物分子量及其结晶性能的影响. 实验结果表明, 采用质量分数为1.5%的亚锡复合催化剂在180 ℃下真空反应15 h为最佳聚合条件, 所得到的产物具有相对最大的分子量; 随着β-丙氨酸投料比增加, 相应共聚物的分子量明显下降. 所得到的L-乳酸/β-丙氨酸共聚物具有良好的降解性能, 聚合时间和β-丙氨酸含量对材料的结晶性能和降解性能均有较大的影响.     

体外电化学测试对镁合金体内降解行为的预测

可生物降解镁合金因同时具有优良的生物相容性和力学性能,在生物医学界显示出其作为新型骨科内植入物的巨大潜在优势和市场前景。目前,作为制约镁合金医用产业化的关键因素,即过快的降解速率已经成为研究重点。本文回顾了体外电化学测试技术对镁合金抗腐蚀性能的研究,并分析了模拟腐蚀体系对镁合金腐蚀行为的影响;同时评估了电化学测试方法作为快速有效预测镁合金体内降解性能前期分析手段的可行性与局限性。最后,对如何发展更合理的体外电化学测试技术来预测镁合金体内降解提出了可能的解决方法及构思。     

Hierarchical Functionalized Polymeric‐Ceramic Coatings on Mg‐Ca Alloys for Biodegradable Implant Applications

Magnesium‐based implants present several advantages for clinical applications, in particular due to their biocompatibility and degradability. However, degradation products can affect negatively the cell activity. In this work, a combined coating strategy to control the implant degradation and cell regulation processes is evaluated, including plasma electrolytic oxidation (PEO) that produces a 13 µm‐thick Ca, P, and Si containing ceramic coating with surface porosity, and breath figures (BF) approach that produces a porous polymeric poly(ε‐caprolactone) surface. The degradation of PCL‐PEO‐coated Mg hierarchical scaffold can be tailored to promote cell adhesion and proliferation into the porous structure. As a result, cell culture can colonize the inner PEO‐ceramic coating structure where higher amount of bioelements are present. The Mg/PEO/PCL/BF scaffolds exhibit equally good or better premyoblast cell adhesion and proliferation compared with Ti CP control. The biological behavior of this new hierarchical functionalized scaffold can improve the implantation success in bone and cardiovascular clinical applications.     

A new method for the evaluation of biodegradable plastic using coated cellulose paper

A highly sensitive analytical method for evaluation of poly(L-lactide) (PLA), poly(epsilon-caprolactone) (PCL), poly(beta-hydroxybutyrate) (PHB), and poly(butylene succinate) (PBS) degradability was developed using coated cellulose paper, prepared by penetration and adhesion of these plastics into/onto the cellulose paper. Enzymatic degradability of the obtained plastic coated papers was evaluated using various commercial proteases and lipases. PLA coated paper was highly susceptible to subtilisin and mammalian enzymes, alpha-chymotrypsin, elastase and trypsin. To our knowledge, this is the first report on the degradation of PLA coated paper using subtilisin and mammalian enzymes. Almost all lipase preparations degraded PCL and PHB coated papers but not PBS coated paper. The biodegradability of plastic coated paper was greater than that of plastic powder. The penetration of plastic into cellulose paper by coating improved the plastic degradability, and can be regulated easily.     

可降解自固化类骨磷灰石支架的研究

0引言一直以来,钙磷生物材料如羟基磷灰石(hy-droxyapatite,HA)由于其成份与骨的无机成份相似,具有良好的生物相容性,作为骨修复材料引起了人们广泛的兴趣。磷酸钙骨水泥是一类可在生理条件下自固化的非陶瓷型类HA人工骨材料,这种由磷酸钙骨水泥(calcium phosphate cement,CPC)转变而成的HA,与天然骨磷灰石有类似的组成结构,植入人体后可参与新陈代谢,促进骨组织生长[1,2]。一些研究显示,CPC具有成骨活性和生物降解性,在体内被吸收的同时可引导新骨的生成,从而可克服自体骨、磷酸三钙陶瓷因吸收降解过快造成的局部缺陷以及陶瓷型HA长…     

Inter-spherulitic/inner-spherulitic localization of PBSU during crystallization of PVDF in PVDF/PBSU blend

In this work, the miscibility effect on the localization of poly(butylene succinate) (PBSU) during the crystallization of PVDF in their blend has been investigated. After annealed at 200 °C and 240 °C, homogeneous and phase-separated structures can be obtained respectively, which was followed by isothermal crystallization at 141 °C. In the case of 200°C, PBSU tends to enrich in inner-spherulitic regions because of the excellent miscibility of the blend and the higher growth rate of PVDF crystals. When the specimen was annealed at 240 °C, phase separation produces PVDF and PBSU domains. Upon cooling to 141 °C, one part of PBSU is miscible with , while the other part of it remains as phase-separated domains due to the high viscosity and slow relaxation of them. The former accounts for the distribution of PBSU in inner-spherulitic regions. In the latter, however, phase-separated structures depress the diffusion of PVDF during its crystallization, leading to the lower magnitude of growth rate of spherulites. Both of them contribute to the localization of PBSU in inter-spherulitic regions. The distribution of PBSU among PVDF spherulites has been validated by long periods, pore size, and mechanical performance of the porous PVDF membranes.     

Preparation and controlled degradation of oxidized sodium alginate hydrogel

Degradation is often a critical property of materials utilized in tissue engineering. Although alginate, a naturally derived polysaccharide, is an attractive material due to its biocompatibility and ability to form hydrogels, its slow and uncontrollable degradation can be an undesirable feature. In this study, the degradation behavior of hydrogel based on oxidized sodium alginate (OSA) crosslinked with Ca²⁺ was studied in phosphate buffer solution (PBS, pH = 7.4) and Tris-(hydroxymethyl) aminomethane–HCl (Tris–HCl, pH = 7.4) at 37 °C. The degradation behavior of OSA hydrogels with different degrees of oxidation was evaluated as a function of degradation time by monitoring the changes of molecular weight and weight loss. It was found that the degradation behavior relied heavily on the degree of oxidation and the surrounding medium. This result indicates that the degradation rates of OSA hydrogels can be controlled by changing the degree of oxidation.     

高分子量聚对二氧环己酮体外降解研究

对高分子量(Mν=2.8×105)的聚对二氧环己酮条状样品在37℃磷酸缓冲溶液(PBS)中的降解行为进行了研究,通过定期观察其吸水率与质量损失,pH,特性黏数,降解过程中样品形态与晶体结构,热力学性能与机械性能的改化,发现此高分子量的聚对二氧环己酮在体外降解过程中质量损失与吸水率变化不大,但分子量下降明显,同时样品表面缺陷逐渐增加;结晶度与玻璃化温度随之改变,但其晶体结构基本保持不变;到第6周时,其力学强度基本消失.证明高分子量PPDO具有较慢的降解速度,显示出很好的稳定性.     

Synthesis and characterization of biodegradable poly(?-caprolactone-co-β-butyrolactone)-based polyurethane

Poly(?-caprolactone-co-β-butyrolactone) (PCLBL)-based polyurethane (PCLBL-PU) was synthesized and its tensile properties and hydrolytic degradability were investigated in an attempt to improve the degradability of poly(?-caprolactone)-based polyurethane (PCL-PU). PCLBL was synthesized by the ring-opening polymerization of ?-caprolactone (CL) and β-butyrolactone (BL) with stannous octoate as a catalyst. The introduction of a small amount of BL units significantly decreased the crystallinity of PCLBL. The crystallinity of the soft segment of PCLBL-PU also decreased with increasing BL content, and thus its hydrolytic degradation rate was dramatically increased. PCLBL-PU polymerized with PCLBL containing 5.7 mol% of BL units showed very similar tensile properties to PCL-PU, but its hydrolytic degradation rate increased by 100% at 45 °C.     

Effect of Molecular Weight on the Properties of Poly（butylene succinate）

Poly（butylene succinate） （PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties （crystallinity as well as crystal morphology）. Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.     

The enzymatic degradation of commercial biodegradable polymers by some lipases and chemical degradation of them

Biodegradable polyesters, poly(butylene succinate adipate) (PBSA), poly(butylene succinate) (PBS), poly(ethylene succinate) (PES), poly(butylene succinate)/poly(caprolactone) blend (HB02B) and poly(butylene adipate terephthalate) (PBAT), were evaluated about degradability for enzymatic degradation by lipases and chemical degradation in sodium hydroxide solution. In enzymatic degradation, PBSA was the most degradable by lipase PS, on the other hand, PBAT containing aromatic ring was little degraded by eleven kinds of lipases. In 1N NaOH solution, degradation rate of PES with ethylene unit was extremely fast, in comparison with other polyesters. Interestingly the degradation rate of PBSA in enzymatic degradation by lipase PS was faster than in chemical degradation.     

Incorporation of carboxylation multiwalled carbon nanotubes into biodegradable poly(lactic-co-glycolic acid) for bone tissue engineering

Biodegradable poly(lactic-co-glycolic acid) (PLGA)/carboxyl-functionalized multi-walled carbon nanotube (c-MWCNT) nanocomposites were successfully prepared via solvent casting technique. Rat bone marrow-derived mesenchymal stem cells (MSCs) were employed to assess the biocompatibility of the nanocomposites in vitro. Scanning electron microscopy (SEM) observations revealed that c-MWCNTs gave a better dispersion than unmodified MWCNTs in the PLGA matrix. Surface properties were determined by means of static contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis. The presence of c-MWCNTs increased the mechanical properties of the nanocomposites. Seven-week period in vitro degradation test showed the addition of c-MWCNTs accelerated the hydrolytic degradation of PLGA. In addition, SEM proved that the cells could adhere to and spread on films via cytoplasmic processes. Compared with control groups, MSCs cultured onto PLGA/c-MWCNT nanocomposites exhibited better adhesion and viability and also displayed significantly higher production levels of alkaline phosphatase (ALP) over 21 days culture. These results demonstrated that c-MWCNTs modified PLGA films were beneficial for promoting cell growth and inducing MSCs to differentiate into osteoblasts. This work presented here had potential applications in the development of 3-D scaffolds for bone tissue engineering.     

聚丁二酸丁二酯的无卤阻燃性能的研究

本文研究了聚苯基膦酸二苯砜酯(PSPPP)对聚丁二酸丁二酯(PBS)的阻燃作用。研究发现,在PBS中仅添加4wt%的PSPPP,其垂直燃烧就可以达到UL-94 V-0级,极限氧指数达到34,PSPPP对PBS表现出高效阻燃作用。然而,PSPPP对PBS有促进降解的作用,破坏了PBS的力学性能。通过在PBS/PSPPP体系中添加0.5wt%氧化锌后,有效抑制了PBS的降解,力学性能得到改善。     

Natural Biopolymers for Flexible Sensing and Energy Devices

Natural biopolymers feature natural abundance, diverse chemical compositions, tunable properties, easy processability, excellent biocompatibility and biodegradability, as well as nontoxicity, providing new opportunities for the development of flexible sensing and energy devices. Generally, biopolymers are utilized as the passive and active building blocks to endow the flexible devices with mechanical robustness and good biocompatibility. This review aims to provide a comprehensive review on natural biopolymer-based sensing and energy devices. The diverse structures and fabrication processes of three typical biopolymers, including silk, cellulose, and chitin/chitosan, are presented. We review their utilities as the supporting substrates/matrix, active middle layers, separators, electrolytes, and active components of flexible sensing devices(sensors, actuators, transistors) and energy devices(batteries, supercapacitors, triboelectric nanogenerators). Finally, the remaining challenges and future research opportunities are discussed.     

Accelerated degradation behaviour of poly(?-caprolactone) via melt blending with poly(aspartic acid-co-lactide) (PAL)

Poly(?-caprolactone) (PCL) has many favourable attributes for tissue engineering scaffold applications. A major drawback, however, is its slow degradation rate, typically greater than 3 years. In this study PCL was melt blended with a small percentage of poly(aspartic acid-co-lactide) (PAL) and the degradation behaviour was evaluated in phosphate buffer solution (PBS) at 37 °C. The addition of PAL was found to significantly enhance the degradation profile of PCL. Subsequent degradation behaviour was investigated in terms of the polymer's mechanical properties, molecular weight (M_w), mass changes and thermal characteristics. The results indicate that the addition of PAL accelerates the degradation of PCL, with 20% mass loss recorded after just 7 months in vitro for samples containing 8 wt% PAL. The corresponding pure PCL samples exhibited no mass loss over the same time period. In vitro assessment of PCL and PCL/PAL composites in tissue culture medium in the absence of cells revealed stable pH readings with time. SEM studies of cell/biomaterial interactions demonstrated biocompatibility of C₃H₁₀T_1/2 cells with PCL and PCL/PAL composites at all concentrations of PAL additive.