Preparation and Properties of Novel Maleated Poly (D,L-lactide-co-glycolide) Porous Scaffolds for Tissue Engineering

Three-dimensional biodegradable porous scaffolds play an important role in tissue engineering. A new polymer based on maleated poly(lactic-co-glycolic acid) (MPLGA) was synthesized using direct melt copolymerization from maleic anhydride (MAH), D, L-lactide, and glycolide monomers. MPLGA porous biodegradable scaffolds were prepared by a solution-casting/salt-leaching method. The effects of content and size of the NaHCO₃ porogen on the compressive strength of the MPLGA scaffolds were investigated, and the effect of content of the porogen on the porosity of the MPLGA scaffolds was also studied. The results indicated that MAH was grafted onto PLGA successfully and MPLGA scaffolds with interconnective and open pore structure were obtained. Increasing content of NaHCO₃ porogen resulted in an increase of porosity and decrease of the compressive strength of the MPLGA scaffolds with the compressive strength of the scaffolds also decreasing with increasing porogen size.     

Study on Direct Grafting Maleic Anhydride onto Poly(D,L-lactide-co-glycolide) Chains

Direct graft copolymerization of maleic anhydride (MAH) onto poly(D,L-lactide-co-glycolide) (PLGA) was performed by use of benzoyl peroxide (BPO) as initiator. Fourier transform infrared spectra, nuclear magnetic resonance, titration analysis of maleation extent and water contact angle were employed to characterize the obtained MPLGA. The effects of monomer concentration, initiator concentration and reaction temperature on the degree of maleation were investigated. The MPLGA scaffold was obtained by using NaCl as the porogen. The results showed that maleic anhydride was successfully grafted onto the PLGA chains. The monomer and initiator concentrations played an important role in the graft copolymerization; the extent of maleation first increased with increasing content of MAH and BPO and then declined. The extent of maleation continuously increased with increasing temperature to 100°C, and then the rate of increase decreased. The extent of maleation could be controlled in the range from 0.15 to 0.71% by adjusting the graft copolymerization conditions. The introduction of anhydride enhanced the water contact angle of PLGA. The MPLGA scaffold showed a network of interconnected pores ranging from 50 to 300 μm.     

Polypropylene/clay nanocomposites prepared with masterbatches of polypropylene ionomer and organoclay

Polypropylene (PP) ionomers were obtained by the neutralization of maleic anhydride groups in a maleated PP of which maleic anhydride content was 1 wt%; these were studied as vehicle resins for the masterbatches of an organoclay for PP nanocomposites. PP/clay nanocomposites were prepared by melt mixing of PP with the masterbatches employing a twin screw extruder. Intercalation and/or exfoliation of the organoclay in the PP nanocomposites were observed. It was found that the PP nanocomposite prepared with the masterbatch of an organoclay and the PP ionomer obtained by 75% neutralization of maleic anhydride groups in the maleated PP showed the largest improvement in dispersion of organoclay. Very large increase of Young's modulus was observed in the nanocomposites with the PP ionomer obtained by 75% neutralization of maleic anhydride groups in the maleated PP. The improvements in the dispersion and mechanical properties were attributed to strong interactions between ionic groups of the PP ionomer and ionic surfactants of the organoclay.     

水华蓝藻粉/低密度聚乙烯复合材料光谱特征与性能反馈研究

为了解决周期性爆发的巢湖水华蓝藻难以处置的问题,同时改善低密度聚乙烯材料降解周期长的现状,以低密度聚乙烯(LDPE)为基体,以巢湖新鲜水华蓝藻制得的蓝藻粉为生物材料,以马来酸酐接枝聚乙烯 (PE-g-MAH)为增容剂,以聚乙烯蜡和白油为润滑剂制备复合材料。设置蓝藻粉含量和增容剂含量2个因素作为实验因素,实验材料按一定比例充分混合后,双螺杆挤出制得了复合材料颗粒,再经过注塑方式获得待测样条。通过紫外-可见光谱扫描(UV-VIS)联合傅里叶变换红外光谱扫描(FTIR)的光谱学方法了解水华蓝藻粉、增容剂和复合材料的光谱学特征,分析复合材料制备过程中的结构变化,能够先决性判断该种实验方法对制备新型生物材料的可行性。并以力学性能测试和扫描电镜(SEM)等方法作为辅助手段,与光谱分析的结果相互反馈,充分分析水华蓝藻粉、增容剂含量对复合材料结构与性能的影响。结果显示：通过紫外可见光谱分析,蓝藻初提液在260和620 nm处出现藻蛋白质的特征吸收峰,表明了蓝藻细胞液中藻蛋白的存在,具备作为生物反应材料的基本条件。红外光谱分析可知,蓝藻粉在1 630,1 540和1 440 cm-1附近出现特征吸收峰,符合酰胺键的出峰规律,在3 300 cm-1附近出现O-H的特征吸收峰,进一步验证了蓝藻粉活性位点的存在;马来酸酐的红外光谱图中,酸酐在1 850和1 740 cm-1处出现C═O基的特征峰,环状酸酐中C-O-C的伸缩振动特征峰出现在1 200 cm-1附近;而经过反应所得的复合材料红外光谱中,除聚乙烯的特征吸收峰以外,蓝藻粉中的酰胺键和O-H,以及马来酸酐对应得特征吸收峰都已减弱或消失了,基本可以推测马来酸酐与-OH发生了开环酯化反应,马来酸酐在生物复合材料的制备过程中起到了连接两个不同反应体系的作用。而且,通过扫描电镜可直观的看出,蓝藻粉含量增加将会导致复合体系中成团现象加剧,增容剂的加入增强了复合体系界面的粘结性;力学性能测试的结果为蓝藻粉含量的增加导致复合材料力学性能下降,尤其冲击性能下降显著降幅达54.10%;当蓝藻粉的添加量为15.00%时,随着增容剂用量的增加,材料的拉伸强度、弯曲性能和冲击性能均呈现先增大后减小的趋势。扫描电镜和力学性能的结果也从侧面验证了光谱分析结果的前瞻性和正确性,避免了盲目实验带来的资源浪费等问题。综合考虑,该生物复合材料可选取蓝藻粉含量15.00%,增容剂含量3.00%,聚乙烯蜡和白油用量3.00%和1.00%的配方,此时的力学性能为：拉伸强度为11.70 MPa,冲击强度为20.00 kJ·m-2,弯曲强度为8.80 MPa,弯曲模量为220.00 MPa。     

纳米金刚石的分散、修饰及载药应用研究

纳米金刚石(nanodiamond,ND)作为一种重要的碳纳米材料,具有表面易修饰、比表面积大、生物毒性低以及物理化学稳定性好等特点,使其在生物医学领域具有独特的优势.本文通过对ND进行分散和化学修饰得到了分散性良好的羧基化纳米金刚石(ND-COOH),并通过透射电子显微镜、X-射线衍射、傅里叶变换红外谱仪等手段对其形貌和结构进行了表征分析.ND-COOH在水溶液中水解后呈现出较高的负电位,致使其可以通过静电相互作用吸附带正电的抗癌药物盐酸阿霉素(dox),且对阿霉素的负载量可达325μg/mg.由于ND-COOH与dox之间通过带负电的羧酸根与带正电的质子化氨基结合,因此在H~+浓度较高的酸性溶液中,药物复合体ND-dox呈现出显著的p H值依赖药物释放特性,在p H值为5.0的磷酸盐缓冲液中药物释放率达到85%,而在p H值为7.4的PBS中药物释放率低于40%.此外,ND-COOH和ND-dox的细胞毒性和体外细胞杀伤能力结果表明,ND-COOH在0—150μg/m L范围内对细胞活性没有明显抑制,而ND装载药物dox后的ND-dox对SGC-7901胃癌细胞活性则表现出显著的抑制作用,表明ND-COOH作为药物载体具有较低的生物毒性,而负载药物后则对肿瘤细胞具有较强的杀伤能力.通过对ND进行简单的分散和表面改性,使ND具备良好的药物装载和独特的p H值依赖药物释放特性,这对于促进纳米金刚石在药物载体方面的应用具有重要的借鉴意义.     

Toughened Poly(Trimethylene Terephthalate) by Blending with a Functionalized Metallocenic Poly(Ethylene-Octene) Copolymer

New toughened poly(trimethylene terephthalate) (PTT) materials were obtained by melt blending with maleic anhydride grafted poly(ethylene-octene) (POEg). Rheological properties, mechanical properties, and morphological characteristics of PTT/POEg blends at four different compositions—95/5, 90/10, 80/20, and 70/30—were studied. The melt viscosity of the blends shows a linear decrease on increasing the POEg content. The addition of rubbery POEg to the PTT matrix increases the impact strength, while tensile properties decrease. Scanning electron microscopy (SEM) displayed a very good dispersion of POEg particles in the PTT matrix. Differential scanning colorimetry (DSC) experiments showed that for all samples the melting point was almost constant and the crystallinity did not show obvious differences. SEM results showed shear yielding of the PTT matrix was the major toughening mechanism.     

Microstructures and Mechanical Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly(Ethylene-octene)/Polypropylene Blends

A range of blends based on 70 wt% of poly(trimethylene terephthalate) PTT with 30 wt% dispersed phase were produced via melt blending. The dispersed phase composition was varied from pure maleic anhydride grafted poly(ethylene-octene) (POE-g-MA) over a range of POE-g-MA:polypropylene (PP) ratios. The micromorphology and mechanical properties of the ternary blends were investigated. The results indicated that the domains of the POE-g-MA are dispersed in the PTT matrix, and at the same time the POE-g-MA encapsulate the PP domains. The interfacial reaction between the hydroxyl-end group of PTT and maleic anhydride (MA) during melt blending changes the formation from “isolated formation” to “capsule formation,” where the PP domains are encapsulated by POE-g-MA. Compared to the PTT/POE-g-MA blends, mechanical properties of ternary blends, such as tensile strength and Young's modulus, were improved significantly.     

Influence of Compatibilizer-Type and Processing Approach on the Dispersion of OMMT in High-Density Polyethylene Matrix

High-density polyethylene/organoclay nanocomposites were prepared via melt intercalation in an internal mixer using both a direct mixing and master batching method. Two types of maleic anhydride grafted polyethylene, high-density polyethylene grafted maleic anhydride, and linear low-density polyethylene grafted maleic anhydride, (HDPE-g-MA, LLDPE-g-MA) were used as compatibilizers to enhance the dispersibility of nanoclay in HDPE. Dispersion of organoclay in the nanocomposites was characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and rheological mechanical spectroscopy (RMS). Effects of clay content and degree of clay dispersion on the rheological and tensile properties were also investigated. Furthermore, the effect of order of mixing on the dispersion and distribution of the clay layers was studied. The obtained results showed that organoclay in the nanocomposites were dispersed homogeneously and exfoliated better when HDPE-g-MA and the direct mixing route were used. Although in the master batching method clay intercalated better, clay layers chiefly remain in compatibilizer rich areas. On the other hand, direct mixing was observed to lead to clay particles being dispersed in the HDPE matrix or at the interface of the matrix and compatibilizer and, consequently, better improvement in the tensile modulus was achieved. It was determined that the compatibilizer with the higher miscibility with the matrix was the key factor for achieving better exfoliation of clay sheets.     

Ultrasonic compatibilization of polyelectrolyte complex based on polysaccharides for biomedical applications

In recent years, there has been an increasing interest in the design of biomaterials for cartilage tissue engineering. This type of materials must meet several requirements. In this study, we apply ultrasound to prepare a compatibilized blend of polyelectrolyte complexes (PEC) based on carboxymethyl cellulose (CMC) and chitosan (CHI), in order to improve stability and mechanical properties through the inter-polymer macroradicals coupling produced by sonochemical reaction. We study the kinetic of the sonochemical degradation of each component in order to optimize the experimental conditions for PEC compatibilization. Scaffolds obtained applying this methodology and scaffolds without ultrasound processing were prepared and their morphology (by scanning electron microscopy), polyelectrolyte interactions (by FTIR), stability and mechanical properties were analyzed. The swelling kinetics was studied and interpreted based on the structural differences between the two kinds of scaffolds. In addition we evaluate the possible in vitro cytotoxicity of the scaffolds using macrophage cells in culture. Our results demonstrate that the ultrasound is a very efficient methodology to compatibilize PEC, exhibiting improved properties compared with the simple mixture of the two polysaccharides. The test with murine macrophage RAW 264.7 cells showed no evince of cytotoxicity, suggesting that PEC biomaterials obtained under ultrasound conditions could be useful in the cartilage tissue engineering field.     

Thermal and Thermo-Oxidative Degradation of Biodegradable Poly(Ester Urethane) Containing Poly(L-Lactic Acid) and Poly(Butylene Succinate) Blocks

A novel biodegradable poly(ester urethane; PEU) was synthesized by chain extension reaction of dihydroxylated poly(L-lactic acid; PLLA) and poly(butylene succinate; PBS) using diisocyanate as a chain extender. The kinetics of thermal and thermo-oxidative degradation of PEU containing PLLA and PBS blocks were studied by thermogravimetric analysis (TGA). TGA results indicated that PEU was more stable in air than in nitrogen and went through a two-stage degradation process irrespective of the experimental atmosphere. Activation energy of each stage was calculated by means of Kissinger, Kim-Park, Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose methods. For the first stage, the activation energy value obtained in air was slightly higher than the corresponding value obtained in nitrogen; and for the second stage, the activation energy showed a much higher value in air than in nitrogen. The Coats-Redfern method was employed to study the degradation mechanism of each stage. The results indicated that the degradation of the first stage follows the P3/4 mechanism irrespective of the experimental atmosphere; the degradation of the second stage of PEU obeys the P1 mechanism in nitrogen while P3/2 in air.     

Hydrolysis and stability of thin pulsed plasma polymerised maleic anhydride coatings

The stability of plasma polymerised layers has become important because of their widespread use. This study explored the hydrolysis and degradation stability of coatings of plasma polymerised maleic anhydride. Coatings made with different plasma parameters were exposed to aqueous media of different pH as a function of time. ATR-FTIR was used for structure analysis and a toluidine blue staining method allowed quantitative analysis of the hydrolysis of anhydride groups to acid groups. Coatings with constant thickness were obtained at different plasma powers and layers with varying thickness were obtained at constant plasma power by adjusting the polymerisation time. The results show that the hydrolysis resistance of the modified layer is determined by the power used in the plasma polymerisation, while changes in the chemistry of the modified layer are insignificant.     

A comparative study of the spectral and kinetic properties of photochromic dihetarylethenes based on maleic anhydride and maleimide

A comparative spectral-kinetic study of the photochromism of a number of new thermally irreversible 1,2-diarylethenes, considered as possible candidates for 3D optical data storage, is performed. The diarylethenes studied contain as bridges either maleic anhydride or maleimide derivatives. A relation between the structure of the bridges and substituents of these compounds and their photochromic properties is established.     

Mechanical Properties and Morphology of Polypropylene/Polypropylene-g-Maleic Anhydride/Long Glass Fiber Composites

Long glass fiber (LGF)-reinforced polypropylene (PP) was prepared using a self-designed impregnation device. The effect of dicumyl peroxide (DCP) and maleic anhydride (MA) content on the compatibilizer, PP grafted with maleic anhydride (PP-g-MA), was investigated by means of scanning electron microscopy (SEM) and mechanical properties. The experimental results demonstrated that the increase of DCP and MA could effectively improve the interfacial interaction between PP and GF. Good interfacial adhesion between PP and GF in PP/ PP-g-MA /LGF composites was observed from SEM studies for the higher contents of MA. The best mechanical properties of PP/ PP-g-MA /LGF(30%) composites were obtained when the content of DCP and MA were 0.4 and 0.8 wt%, respectively. The storage modulus of the PP/PP-g-MA/LGF composites increased and then decreased with the content of MA. When the content of MA was 0.8 wt%, tan δ had the lowest value, indicating that the corresponding composites had the best compatibility.     

Adhesion in polyamide/compatibilizer/polypropylene systems

The effect of compatibilization on the adhesion, fracture toughness, morphology, and mechanical properties of isotactic polypropylene (PP)/polyamide 6 (PA) blends was investigated. Maleic anhydride (MAH) functionalized poly-(ethylene-co-vinyl acetate) (EVA-g-MAH) and nonreactive EVA copolymer were used as compatibilizers in binary blends. An attempt of in situ compatibilization via addition of pure maleic anhydride to PA/EVA/PP melt was also made. The blends containing maleated EVA copolymer showed more regular and finer dispersion of phases, better adhesion at the interface, and improved mechanical properties.     

Ultrasound assisted copolymerization of acrylonitrile with N-amino phenyl maleimides and N-amino phenyl 2,3 dimethyl maleimides

The N-amino phenyl maleimide (N-APhM) and N-amino phenyl 2,3 dimethyl maleimide (N-APhDiMeM) derivatives were prepared by the condensation of phenyl hydrazine with maleic anhydride and 2,3 dimethyl maleic anhydride respectively. (13)C NMR spectroscopy proved the formation of the symmetric amino maleimide structure and not the pyridazinone or aminoisomaleimides. The copolymerization of acrylonitrile with the (N-APhM) and (N-APhDiMeM) were prepared using ultrasound. The thermal behavior of the prepared copolymers, under nitrogen atmosphere, was investigated using thermogravimetry (TG) techniques. The dyeing of the copolymers formed has been studied using both conventional and ultrasonic techniques. The effect of dye bath pH, ultrasonic power, dyeing time and temperature were studied. Color strength values obtained were found to be higher using ultrasound than with conventional heating. The results of fastness properties of the dyed copolymers were also studied.     

Preparation and Characterization of Gelatin–Poly(L-lactic) Acid/Poly(hydroxybutyrate-co-hydroxyvalerate) Composite Nanofibrous Scaffolds

Poly(L-lactic) acid (PLLA) scaffolds, prepared by electrospinning technology, have been suggested for use in tissue engineering. They remain a challenge for application in biological fields due to PLLA's slow degradation and hydrophobic nature. We describe PLLA, PLLA/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), and PLLA/PHBV/gelatin (Gt) composite nanofiberous scaffolds (Gt–PLLA/PHBV) electrospun by changing the electrospinning technology. The morphologies and hydrophilicity of these fibers were characterized by scanning electron microscopy (SEM) and water contact angle measurement. The results showed that the addition of PHBV and Gt resulted in a decrease in the diameters and their distribution and greatly improved the hydrophilicity. The in-vitro degradation test indicated that GT–PLLA/PHBV composite scaffolds exhibited a faster degradation rate than PLLA and PLLA/PHBV scaffolds. Dermal fibroblasts viabilities on nanofibrous scaffolds were characterized by [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] (MTT) assay and cell morphologies after 7 days culture. Results indicated that the GT–PLLA/PHBV composite nanofibers showed the highest bioactivity among the three scaffolds and increased with increasing time. The SEM images of cells/scaffolds composite materials showed the GT–PLLA/PHBV composite nanofibers enhanced the dermal fibroblasts's adhesion, proliferation, and spreading. It is suggested that the nanofibrous composite scaffolds of GT–PLLA/PHBV composites would be a promising candidate for tissue engineering scaffolds.     

Resin–Sisal and Wood Flour Composites Made from Unsaturated Polyester Thermosets

Short fibers and wood flour were selected as fillers in the production of two types of unsaturated polyester composites (bisphenolic and isophthalic-based thermosets). Sisal fibers were subjected to washing in order to remove the organic coating on the fibers (which were originally prepared for cord manufacture) and to maleic anhydride (MAN) esterification. The effect of these treatments on the thermomechanical properties of the composites, as well as on the mechanical properties (flexural and compression) and water absorption was investigated. All the results are coincident in showing the improved interfacial adhesion obtained by washing and mainly by esterification of the fibers. Additionally, hybrid wood flour sisal composites were prepared and their mechanical properties compared to those of the one-filler composites. The hybrid composites showed improved modulus and maximum stress.     

Structure and Properties of Polypropylene/Polyolefin Elastomer/Organic Montmorillonite Nanocomposites

The crystallinity, mechanical properties, and thermal stability of polypropylene (PP)/organic montmorillonite (OMMT) and PP/polyolefin elastomer (POE)/OMMT composites, with polypropylene-g-maleic anhydride/styrene (PPMS) as a compatibilizer for both, were compared. The results showed that the strong interaction between the clay platelets and compatibilizer, which were generated by the maleic anhydride (MAH), improved the compatibility of the polymer matrices with the OMMT. A unique lamellar, flocculated structure of OMMT was formed after introduction of the POE. The highly dispersed clay layers could act as nucleating agents, resulting in smaller spherulites and higher crystallization temperatures. Compared with pure PP, the PP/OMMT nanocomposite showed enhanced mechanical properties and thermal stability; however, the PP/POE/OMMT had the best impact toughness.     

Size-dependent cytotoxicity of yttrium oxide nanoparticles on primary osteoblasts in vitro

Yttrium oxide nanoparticles are an excellent host material for the rare earth metals and have high luminescence efficiency providing a potential application in photodynamic therapy and biological imaging. In this study, the effects of yttrium oxide nanoparticles with four different sizes were investigated using primary osteoblasts in vitro. The results demonstrated that the cytotoxicity generated by yttrium oxide nanoparticles depended on the particle size, and smaller particles possessed higher toxicological effects. For the purpose to elucidate the relationship between reactive oxygen species generation and cell damage, cytomembrane integrity, intracellular reactive oxygen species level, mitochondrial membrane potential, cell apoptosis rate, and activity of caspase-3 in cells were then measured. Increased reactive oxygen species level was also observed in a size-dependent way. Thus, our data demonstrated that exposure to yttrium oxide nanoparticles resulted in a size-dependent cytotoxicity in cultured primary osteoblasts, and reactive oxygen species generation should be one possible damage pathway for the toxicological effects produced by yttrium oxide particles. The results may provide useful information for more rational applications of yttrium oxide nanoparticles in the future.     

Evaluation of DNA damage and cytotoxicity of polyurethane-based nano- and microparticles as promising biomaterials for drug delivery systems

The in vitro cytotoxicity and DNA damage evaluation of biodegradable polyurethane-based micro- and nanoparticles were carried out on animal fibroblasts. For cytotoxicity measurement and primary DNA damage evaluation, MTT and Comet assays were used, respectively. Different formulations were tested to evaluate the influence of chemical composition and physicochemical characteristics of particles on cell toxicity. No inhibition of cells growth surrounding the polyurethane particles was observed. On the other hand, a decrease of cell viability was verified when the anionic surfactant sodium dodecyl sulfate (SDS) was used as droplets stabilizer of monomeric phase. Polyurethane nanoparticles stabilized with Tween 80 and Pluronic F68 caused minor cytotoxic effects. These results indicated that the surface charge plays an important role on cytotoxicity. Particles synthesized from MDI displayed a higher cytotoxicity than those synthesized from IPDI. Size and physicochemical properties of the particles may explain the higher degree of DNA damage produced by two tested formulations. In this way, a rational choice of particles’ constituents based on their cytotoxicity and genotoxicity could be very useful for conceiving biomaterials to be used as drug delivering systems.