Effect of carbon-rich biochar on mechanical properties of PLA-biochar composites

Agricultural biomass residues are emerged from harvesting and processing of agricultural crops. When the crop production increases, a large amount of biomass residues is produced and remained after cutting of peel, bunch, straw and stalk of crops. In this work, agricultural biomass residues (cassava rhizome, durian peel, pineapple peel and corncob) were selected as feedstock for carbon-rich biochar (CRB) production using a facile pyrolysis method. Proximate analysis and thermogravimetric analysis (TGA) were used to characterize biomass feedstock. The results showed that the percentage of fixed carbon in biomass feedstock ranged between 11.91% and 17.51%. Characteristic differences of the CRB were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The carbon content in the CRB was found to significantly depend on biomass origin. Interestingly, cassava rhizome, which has a higher percentage of fixed carbon, is a superior precursor for CRB production. The study of different pyrolysis temperature indicated that the carbon content of cassava rhizome derived CRB is increased with pyrolysis temperature. The tensile properties of composite between poly(lactic acid) PLA and different types of biomass-derived CRB were investigated. PLA composite incorporated with a higher carbon content-CRB tended to exhibit improved mechanical properties. Specifically, the elastic modulus and impact energy of PLA/CRB composite specimens increased remarkably with the incorporation of CRB powder. The current research indicates that CRB prepared from agricultural biomass residues could be a sustainable material for utilization in PLA biocomposites.     

Identification of a Major Epitope Recognized by PLA2R Autoantibodies in Primary Membranous Nephropathy

Phospholipase A₂ receptor 1 (PLA2R) is a target autoantigen in 70% of patients with idiopathic membranous nephropathy. We describe the location of a major epitope in the N-terminal cysteine-rich ricin domain of PLA2R that is recognized by 90% of human anti-PLA2R autoantibodies. The epitope was sensitive to reduction and SDS denaturation in the isolated ricin domain and the larger fragment containing the ricin, fibronectin type II, first and second C-type lectin domains (CTLD). However, in nondenaturing conditions the epitope was protected against reduction in larger fragments, including the full-length extracellular region of PLA2R. To determine the composition of the epitope, we isolated immunoreactive tryptic fragments by Western blotting and analyzed them by mass spectrometry. The identified peptides were tested as inhibitors of autoantibody binding to PLA2R by surface plasmon resonance. Two peptides from the ricin domain showed strong inhibition, with a longer sequence covering both peptides (31-mer) producing 85% inhibition of autoantibody binding to PLA2R. Anti-PLA2R antibody directly bound this 31-mer peptide under nondenaturing conditions and binding was sensitive to reduction. Analysis of PLA2R and the PLA2R-anti-PLA2R complex using electron microscopy and homology-based representations allowed us to generate a structural model of this major epitope and its antibody binding site, which is independent of pH-induced conformational change in PLA2R. Identification of this major PLA2R epitope will enable further therapeutic advances for patients with idiopathic membranous nephropathy, including antibody inhibition therapy and immunoadsorption of circulating autoantibodies.     

GTR treatment of intrabony defects with PLA/PGA copolymer or collagen bioresorbable membranes in combination with deproteinized bovine bone (Bio-Oss)

The objectives of this study were to evaluate the results of guided tissue regeneration (GTR) treatment of intrabony defects with two kinds of bioresorbable membranes, with deproteinized bovine bone (Bio-Oss) used as an adjunct. Twenty-eight patients with at least one intrabony defect with a probing pocket depth (PPD) 7 mm and radiographic evidence of an intrabony component (IC) 4 mm were randomly treated with either a polylactic/polyglycolic (PLA/PGA) acid copolymer or a collagen bioresorbable membrane combined with Bio-Oss implantation. Immediately prior to surgery (baseline) and after 1 year, the following parameters were recorded: (1) PPD, (2) gingival recession (REC), (3) probing attachment level (PAL), (4) presence/absence of plaque (PI), and (5) presence/absence of bleeding on probing (BOP). Occurrence of membrane exposure during healing and the smoking habits of the patients were also recorded. Statistical analysis was carried out using x²-tests and t-tests. There were no significant differences between the two membrane groups regarding the clinical parameters at baseline. Statistically significant clinical improvements (PAL gains, reduced PPDs) were observed 1 year after treatment in both groups. There were no significant differences, however, between the PLA/PGA and the collagen membrane groups regarding any of the evaluated parameters (mean PAL gain: 2.9 mm vs 3.9 mm; mean residual PPD: 4.8 mm vs 4.1 mm, respectively). The membrane material per se does not seem to be a critical factor for the outcome of GTR treatment of intrabony defects with bioresorbable membranes.     

复合人工骨双重机制修复骨质缺损的实验研究

目的　研究生物珊瑚 /聚乳酸和rhBMP 2合成人工骨 (复合骨 )修复兔颅骨缺损的骨修复能力。方法　选择 2 4只新西兰兔 ,随机分成 2组 ,每组 1 2只 ,建立兔颅骨缺损标准模型。植入复合骨 ,用珊瑚 /聚乳酸作为对照。术后 4、8、1 2周每组各处死 4只动物。进行X线片、组织学观察。结果　复合骨在植入缺损后 ,不仅在其周边部有骨组织长入 ,而且在整个植入物内均有新骨形成 ,即出现多中心成骨。复合骨在同一时间点的成骨量明显多于对照组 ,随时间推移 ,成骨量递增。结论　生物珊瑚 /聚乳酸和rhBMP 2合成人工骨在体内以传导成骨和诱导成骨双重机制完成骨修复 ,作为植骨材料具有良好的应用前景     

基因重组人骨形成蛋白-2和牛骨形成蛋白异位诱导成骨的比较

目的：观察基因重组人骨形成蛋白-2（rhBMP-2)和牛骨形成蛋白（bBMP)分别与珊瑚/聚乳酸形成复合人工骨的异位诱导成骨活性，同时比较两种骨形成蛋白的成骨效率，方法：把rhBMP-2和bBMP分别与珊瑚/聚乳酸形成复合人工骨，进行小鼠肌内种植1、3、6周后，组织学观察和组织形态测量，比较其异位诱导成骨活性。结果：rhBMP-2和bBMP存在骨诱导差异，rhBMP-2诱导成骨量相对较少但血管，骨髓含量丰富，bBMP则相反，结论：两种BMP都具有良好的诱骨活性，但在居骨量和血管，骨髓样组织的形成量上有明显不同。     

Biodegradable nanocomposite microparticles as drug delivering injectable cell scaffolds

Injectable cell scaffolds play a dual role in tissue engineering by supporting cellular functions and delivering bioactive molecules. The present study aimed at developing biodegradable nanocomposite microparticles with sustained drug delivery properties thus potentially being suitable for autologous stem cell therapy. Semi-crystalline poly(l-lactide/dl-lactide) (PLDL70) and poly(l-lactide-co-glycolide) (PLGA85) were used to prepare nanoparticles by the double emulsion method. Uniform and spherical nanoparticles were obtained at an average size of 270-300 nm. The thrombin receptor activator peptide-6 (TRAP-6) was successfully loaded in PLDL70 and PLGA85 nanoparticles. During the 30 days' release, PLDL70 nanoparticles showed sustainable release with only 30% TRAP-6 released within the first 15 days, while almost 80% TRAP-6 was released from PLGA85 nanoparticles during the same time interval. The release mechanism was found to depend on the crystallinity and composition of the nanoparticles. Subsequently, mPEG-PLGA nanocomposite microparticles containing PLDL70 nanoparticles were produced by the ultrasonic atomization method and evaluated to successfully preserve the intrinsic particulate properties and the sustainable release profile, which was identical to that of the nanoparticles. Good cell adhesion of the human fibroblasts onto the nanocomposite microparticles was observed, indicating the desired cell biocompatibility. The presented results thus demonstrate the development of nanocomposite microparticles tailored for sustainable drug release for application as injectable cell scaffolds.     

The clinicopathologic spectrum of segmental membranous glomerulopathy

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