Synthesis, characterization, degradation of biodegradable castor oil based polyesters

A new family of castor oil based biodegradable polyesters was synthesized by catalyst free melt condensation reaction between two different diacids and castor oil with d-mannitol. The polymers synthesized were characterized by NMR spectroscopy, FT-IR and the thermal properties were analysed by DSC. The results of DSC show that the polymer is rubbery in physiological conditions. The contact angle measurement and hydration test results indicate that the surface of the polymer is hydrophilic. The mechanical properties, evaluated in the tensile mode, shows that the polymer has characteristics of a soft material. In vitro degradation of polymer in PBS solution carried out at physiological conditions indicates that the degradation goes to completion within 21 days and it was also found that the rate of degradation can be tuned by varying the curing conditions.     

Preparation and Characterization of Nanotitanium Dioxide Coating Film Doped with Fe^3＋ Ions on Porous Ceramic

The nanotitanium dioxide （TiO2） photocatalytic and porous ceramic filtering technique is one of the advanced methods to effectively treat organic wastewater. The TiO2 sol doped with Fe^3＋ ions was prepared by sol-gel processing. The influences of the process conditions of coating nanophotocatalytic material- Fe^3＋-TiO2 film on the surface of porous ceramic filter by dipping-lift method on the performance of porous ceramic filter were studied. The porous ceramic filters have two functions at the same time, filtration and photocatalytic degradation. The results of this study showed that the pH and viscosity of the sol, amount of Fe^3＋ ions doped as well as the coating times greatly affect the quality of coating film, the performance parameters and the photocatalytic activity of the porous ceramic filter. When the pH of the sol is 3-4, the viscosity is about 6 mPa.S, the amount of doped Fe^3＋ ions is about 2.0 g/L, the porous ceramic filter has been shown to have the best filtering performance and photocatalytic activity. In this condition, the porosity of porous ceramic is about 42.5%, the pore diameter is 8-10μm. The degradation of methyl-orange is 74.76% under lighting for 120 rain.     

末端带有磷酰胆碱基团的聚丁二酸丁二醇酯的合成、表征和性能研究

采用四步反应合成了一种新的具有良好生物相容性和生物降解性的末端带有磷酰胆碱(PC)基团的聚丁二酸丁二醇酯PBS-PC. 采用1H NMR、IR、凝胶色谱(GPC)和X射线光电子能谱(XPS)表征了聚合物的结构. 同时研究了聚合物的亲疏水性能、体外降解、溶胀率和对模型药物中性红的缓释性能. 结果显示: PC基团引入, 在一定程度上提高了PBS的亲水性、降解速率、溶胀率和对中性红的缓释性能.     

Study on biodegradability of poly(amide-imide)s containing N-trimellitylimido-L-amino acids and 3,5-diamino-N-(pyridin-3-yl)benzamide linkages

A series of novel biodegradable functional amino acid-based poly(amide-imide)s (PAI)s were designed and synthesized by the direct polycondensation reaction of chiral bioactive diacids composed of naturally occurring α-amino acids with 3,5-diamino-N-(pyridin-3-yl) benzamide in the presence of molten tetrabutylammonium bromide as a green solvent. These new biodegradable polymers were characterized with Fourier transfer infrared and ¹H NMR spectroscopy, field emission scanning electron microscopy. In addition, in vitro toxicity and biodegradability behavior of the starting diacids, diamine and obtained PAIs were investigated in culture media and the results showed that the synthesized monomers and their derived polymers are biologically active and their degradation products are probably nontoxic to microbial growth.     

Novel biodegradable polymers as gene carriers

This study investigated two new biodegradable polymers as gene controlled-released coatings for gene transfer. Poly(ethylene glycol)-co-poly(D,L-lactic acid) (PELA) and poly(ethylene glycol)-co-poly(lactic acid)-co-poly(glycolic acid) random copolymer (PELGA) were synthesized and used as microspheres matrices with encapsulated plasmid pCH110. The plasmid loading efficiency, cytotoxicity, transfection efficiency and in vitro degradation and release profiles of microsphere complexes were evaluated in details. The biodegradable polymers showed high DNA loading efficiency and low cytotoxicity as gene controlled-released coatings, and the poly(ethylene glycol) (PEG) contents of polymer matrices influenced the diameter, loading efficiency and transfection efficiency of plasmid DNA within the microspheres. The average diameters of PELA and PELGA microspheres were between 0.5 and 1.5 microm, and the plasmid loading efficiency was 62 and 73% for PELA and PELGA microspheres with 10% PEG content, respectively. In vitro testing showed a gradual release profile of DNA from polymeric matrices. The polymers/DNA microspheres had high transfection efficiency and early gene expression and maintenance of gene expression level for up to 96 h, although transfection efficiency were slightly lower than that of liposome in the initial 24 h. The biodegradable polymeric materials possess potential superiority as gene carriers.     

Morphology and characterization of 3D micro-porous structured chitosan scaffolds for tissue engineering

This research studies the morphology and characterization of three-dimensional (3D) micro-porous structures produced from biodegradable chitosan for use as scaffolds for cells culture. The chitosan 3D micro-porous structures were produced by a simple liquid hardening method, which includes the processes of foaming by mechanical stirring without any chemical foaming agent added, and hardening by NaOH cross linking. The pore size and porosity were controlled with mechanical stirring strength. This study includes the morphology of chitosan scaffolds, the characterization of mechanical properties, water absorption properties and in vitro enzymatic degradation of the 3D micro-porous structures. The results show that chitosan 3D micro-porous structures were successfully produced. Better formation samples were obtained when chitosan concentration is at 1–3%, and concentration of NaOH is at 5%. Faster stirring rate would produce samples of smaller pore diameter, but when rotation speed reaches 4000 rpm and higher the changes in pore size is minimal. Water absorption would reduce along with the decrease of chitosan scaffolds’ pore diameter. From stress–strain analysis, chitosan scaffolds’ mechanical properties are improved when it has smaller pore diameter. From in vitro enzymatic degradation results, it shows that the disintegration rate of chitosan scaffolds would increase along with the processing time increase, but approaching equilibrium when the disintegration rate reaches about 20%.     

Plasticization of poly(lactide) with blends of tributyl citrate and low molecular weight poly(d,l-lactide)-b-poly(ethylene glycol) copolymers

Polylactide (PLA) is a potential candidate for the partial replacement of petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by its high tensile strength, unfortunately the brittleness and rigidity limit its applicability. For a great number of applications such as packaging, fibers, films, etc., it is of high interest to formulate new PLA grades with improved flexibility and better impact properties.In order to develop PLA-based biodegradable packaging, the physico-mechanical properties of commercially available PLA should be modified using biodegradable plasticizers. To this end, PLA was melt-mixed with blends of tributyl citrate and more thermally stable low molecular weight block copolymers based on poly(d,l-lactide) and poly(ethylene glycol) of different molecular weights and topologies. The copolymers have been synthesized using a potassium based catalyst which is expected to be non toxic and were characterized by utilization of TGA, GPC and NMR techniques.The effect of the addition of up to 25 wt% plasticizer on the thermo-mechanical properties of PLA was investigated and the results were correlated with particular attention to the relationship between properties and applications.To confirm the safety of the catalyst used for the preparation of the copolymers, in vitro cytotoxicity tests have been carried out using MTS assay and the results show their biocompatibility in the presence of the fibroblast cells.Compost biodegradation experiments carried out using neat and plasticized PLA have shown that the presence of plasticizers accelerates the degradation of the PLA matrix.     

Capillary electrophoresis-mass spectrometry of a new cross-linker with acrylic functionality

Analytical characterization of dimethacrylate-tyrosine-lysine-tyrosine (DMTLT, a new biodegradable acrylic cross-linker synthesized at our laboratory) is carried out using CE-MS. DMTLT is a pseudopeptide composed by tyrosine-lysine-tyrosine amino acids linked through urea bonds with two methacrylic groups, one at each end of the molecule, making this compound an excellent cross-linker for polymerization reactions and for obtaining new biodegradable materials. A new CE-MS method is developed for the characterization of DMTLT and its products of degradation after basic hydrolysis. In order to carry out an exhaustive examination of such degradation products methods based on CE coupled to IT and TOF-MS are employed. Based on CE-IT-MS results and the elemental composition of the degradation products obtained by CE-TOF-MS, conclusions on the mechanism and kinetic of hydrolysis of DMTLT are obtained confirming both the usefulness of CE-MS to characterize new biomaterials and the applicability of DMTLT for preparing new biodegradable polymers. These results are corroborated through the CE-MS detection of the identified products of degradation in a dimethyl acrylamide polymer cross-linked with DMTLT.     

Reduction of Breakdown Pressure by Filter Cake Removal Using Thermochemical Fluids and Solvents: Experimental and Numerical Studies

The process of well cleanup involves the removal of an impermeable layer of filter cake from the face of the formation. The inefficient removal of the filter cake imposes difficulty on fracturing operations. Filter cake’s impermeable features increase the required pressure to fracture the formation. In this study, a novel method is introduced to reduce the required breakdown pressure to fracture the formation containing the water-based drilling fluid filter cake. The breakdown pressure was tested for five samples of similar properties using different solutions. A simulated borehole was drilled in the core samples. An impermeable filter cake using barite-weighted drilling fluid was built on the face of the drilled hole of each sample. The breakdown pressure for the virgin sample without damage (filter cake) was 6.9 MPa. The breakdown pressure increased to 26.7 MPa after the formation of an impermeable filter cake. Partial removal of filter cake by chelating agent reduced the breakdown pressure to 17.9 MPa. Complete dissolution of the filter cake with chelating agents resulted in the breakdown pressure approximately equivalent to the virgin rock breakdown pressure, i.e., 6.8 MPa. The combined thermochemical and chelating agent solution removed the filter cake and reduced the breakdown pressure to 3.8 MPa. Post-treatment analysis was carried out using nuclear magnetic resonance (NMR) and scratch test. NMR showed the pore size redistributions with good communication between different pores after the thermochemical removal of filter cake. At the same time, there was no communication between the different pores due to permeability impairment after filter cake formation. The diffusion coupling through NMR scans confirmed the higher interconnectivity between different pores systems after the combined thermochemical and chelating agent treatment. Compressive strength was measured from the scratch test, confirming that filter cake formation caused added strength to the rock that impacts the rock breakdown pressure. The average compressive strength of the original specimen was 44.5 MPa that increased to 73.5 MPa after the formation of filter cake. When the filter cake was partially removed, the strength was reduced to 61.7 MPa. Complete removal with chelating agents removed the extra strength that was added due to the filter cake presence. Thermochemical and chelating agents resulted in a significantly lower compressive strength of 25.3 MPa. A numerical model was created to observe the reduction in breakdown pressure due to the thermochemical treatment of the filter cake. The result presented in this study showed the engineering applications of thermochemical treatment for filter cake removal.     

Thermomechanical degradation of PLA‐based nanobiocomposite

Nanobiocomposites are a new class of biodegradable polymer materials with nanometric dispersion of inert particles in a biodegradable polymer matrix that show very interesting properties often very different from those of conventional‐ filled polymers and also biodegradability. An important issue in the applications of the biodegradable polymers is their easy degradability during processing due to the thermomechanical stress or to the presence of humidity. In this work, the thermomechanical degradation behavior of a nanobiocomposite made by a PLA‐based blend and an organomodified montmorillonite has been investigated. The degradation kinetics has been followed by means of rheological, mechanical and morphological characterization. In particular, the influence of temperature and of the presence of humidity have been considered. The presence of the nanoparticles slightly increases the thermomechanical degradation of the pure matrix and in particular with increasing time and temperature processing. In the more severe conditions, indeed, the organomodifier undergoes some slight decomposition of the organomodifier of the clay because of the Hoffmann elimination. The radicals formed through this decomposition enhance the degradation of the matrix. However, this decomposition is at the first stage, and the evolved CO₂ remains entrapped in the clay increasing the level of intercalation and causing also some exfoliation. Then the morphology of the nanobiocomposite changes because of the processing conditions. Moreover, the thermomechanical degradation remarkably increased if the materials are not pre‐dried because of the hydrolytic degradation of the biodegradable polyesters of the matrix. Copyright © 2015 John Wiley & Sons, Ltd.     

聚羟基烷酸酯酶降解动力学研究

研究了羟基丁酸 羟基戊酸共聚物 (PHBV)在脂肪酶中的降解行为 ,用滴定法测定降解速度并进行酶促反应动力学研究 .探讨了降解速度与酶浓度和底物浓度的数学关系和Michaelis Menten常数 ,从实验上和理论上证实了PHBV的物理形态和几何尺寸对酶降解过程的影响 ,以及实验数据与非均相动力学模型的拟合     

Persistent Polarization in Polymers and Blood Compatibility

The use of persistent electrical polarization in polymers has been explored as a means of reducing surface thrombogenicity. Parallel efforts have been carried out on the characterization of surface properties related to the electret state in polymers, on the stability of the electret state in desirable prosthetic materials under simulated blood pumping conditions, and on in vitro and in vivo blood compatibility experiments. Preliminary correlations among critical surface tension, electrical polarization, and blood compatibility have been obtained. In vitro blood compatibility has been explored using both a modified Lee-White clotting test and a platelet adsorption experiment. No significant difference in clotting time was found for polarized samples; however, those with a negative charge did adsorb fewer platelets. A series of in vivo studies has been carried out using electrified right atrial flags (36) of poly-vinylidene chloride and vena cava rings (22) of FEP Teflon, Hypalon rubber, and Hypalon/2% polysulfonate. Negatively polarized samples showed improved blood compatibility in all cases. About 2/3 of the negatively charged atrial flags showed little or no thrombus and the remainder moderate thrombus whereas 2/3 of the positively charged flags showed severe thrombus. About 3/4 of the negative ring implants showed little or no thrombus. A correlation with anomalous contact angle or low charge was found in 4 of 6 cases of the rings with moderate to heavy thrombus.     

具生物活性的快速光交联生物可降解水凝胶的设计合成

采用开环聚合方法合成了一系列水溶性生物可降解的低聚(丙交酯-co-丙烯酸酯碳酸酯)-b-聚乙二醇-b-低聚(丙交酯-co-丙烯酸酯碳酸酯)(OLAC-PEG-OLAC)三嵌段共聚物,并通过光交联方法方便制备得到具生物活性的新型生物可降解水凝胶.流变测试表明水凝胶储存模量(170～10000 Pa)和凝胶时间(0.8～8min)均可通过调节丙烯酸酯碳酸酯(AC)单元数、聚合物浓度及光引发剂浓度等得到控制.降解实验表明水凝胶的降解速率可通过改变AC和丙交酯(LA)单元数进行调控.含巯基的生物活性分子如RGDC短肽可通过迈克尔加成反应直接链接到OLAC-PEG-OLAC上,由此可方便制备可注射性的具生物活性的生物可降解水凝胶.MG63成骨细胞实验表明RGDC短肽功能化的OLAC-PEG-OLAC水凝胶可很好地促进细胞黏附和生长.该快速光交联生物可降解水凝胶以其优异的凝胶、降解和生物功能化等性能可望为生物组织工程提供理想的三维活性多孔支架.     

Thermal expansivity and degradation properties of PLA/HA and PLA/βTCP in vitro conditioned composites

Journal of Thermal Analysis and Calorimetry - The objective of this study was to investigate the thermal expansivities and degradation properties for several in vitro conditioned biodegradable...     

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。     

Novel Biodegradable Polymer with Redox‐Triggered Backbone Cleavage Through Sequential 1,6‐Elimination and 1,5‐Cyclization Reactions

In the past decade, the self‐immolative biodegradable polymer arose as a novel paradigm for its efficient degradation mechanism and vast potential for advanced biomedical applications. This study reports successful synthesis of a novel biodegradable polymer capable of self‐immolative backbone cleavage. The monomer is designed by covalent conjugations of both pendant redox‐trigger (p‐nitrobenzyl alcohol) and self‐immolative linker (p‐hydroxybenzyl alcohol) to the cyclization spacer (n‐2‐(hydroxyethyl)ethylene diamine), which serves as the structural backbone. The polymerization of the monomer with hexamethylene diisocyanate yields a linear redox‐sensitive polymer that can systemically degrade via sequential 1,6‐elimination and 1,5‐cyclization reactions within an effective timeframe. Ultimately, the polymer's potential for biomedical application is simulated through in vitro redox‐triggered release of paclitaxel from polymeric nanoparticles.     

Microinjection Molded Biopolymeric Airway Stent with Antibacterial and Anti-Hyperplastic Properties

Central airway stenosis is a condition that the diameter of the trachea or main bronchus shrinkage is caused by external compression or internal tissue hyperplasia, which can cause difficulty breathing, asphyxia, and even death. Airway stenting is an easy way to restore the patency of the central airway, but airway stents commonly used in clinical practice can lead to complications such as mucus plugging, bacterial infection, and granulation tissue hyperplasia. Moreover, the non-degradable characteristic makes it requires a second operation to remove, which has the potential to cause tissue damage. In this study, a biodegradable airway stent is fabricated by microinjection molding using the bioelastomer of poly (L-lactide-co-ε-caprolactone) as the matrix material. The airway stent has excellent mechanical properties and an appropriate degradation rate. The hydrophilic surface of the airway stent can inhibit mucus plugging. The loading of silver nanoparticles and cisplatin endows the stent with antibacterial and anti-hyperplastic functions. In vitro and in vivo experiments demonstrate that this study provides an antibacterial and anti-hyperplastic biodegradable airway stent with elastic properties to avoid secondary removal operation and reduce complications associated with mucus plugging, bacterial infection, and granulation tissue hyperplasia.     

新极谱法实验数据的卡尔曼滤波

本文提出的"1:n+2"新卡尔曼滤波器,具有算法简单、占用计算机内存少、运行速度快等优点;同时又能有效地消除信号中的随机噪音和电容电流,讨论了"1:3"滤波器的结构性能,采用Cd⁺离子的阶梯扫描伏安法的实测数据来分析滤波结果的最优性,用于处理TI⁺、pb²⁺、In³⁺等离子的实测数据,均获得理想的滤波效果。     

Mechanical properties decay and morphological behaviour of biodegradable films for agricultural mulching in real scale experiment

The use of plastic materials in agriculture causes the serious drawback of huge quantities of waste. The introduction of biodegradable materials, which can be disposed directly into the soil, can be one possible solution to this problem. Biodegradable materials are actually innovative materials; therefore, their physical properties must be evaluated in relation to their functionality during the use in field. In the present research results of experimental tests carried out on biodegradable films used in strawberries protected cultivation are presented. The decay of some relevant physical parameters of biodegradable films during the cultivation period was monitored by laboratory tests (SEM analysis, mechanical tensile tests and infrared reflectance spectroscopy). Infrared spectroscopy clearly indicated that the mechanical degradation starts from the starch component of the material. Tensile tests showed that the value of elongation at break of biodegradable materials decreased in some cases by 300% after 10 days of field application.     

Preparation and characterization of aliphatic/aromatic copolyesters based on 1,4-cyclohexanedicarboxylic acid

A series of biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate)-co-poly(butylene cyclohexanedicarboxylate)-b-poly(ethylene glycol) (PTCG), were prepared by a two-step melt polycondensation method and characterized by means of GPC, FTIR, NMR, DSC, TGA, etc. The effects of aliphatic ester content on the physical, mechanical and thermal properties, as well as in vitro and in vivo degradation behaviors were investigated. The decrease in mechanical strength was observed with an increase in poly(butylene cyclohexanedicarboxylate) (PBC) molar fraction. DSC results showed one melting point and two glass transition temperatures in all samples, and the melting temperature was found to go down gradually as more cyclohexanedicarboxylic acid (CHDA) was added. During the in vitro and in vivo degradation processes, erosion of the surface was dominant as evidenced by scanning electron microscopic observations. The copolyesters containing many CHDA units were featured by the higher water uptake and faster degradation due to much richer amorphous phase within them.