Natural fibre-reinforced composites for bioengineering and environmental engineering applications

Recently, the mankind has realized that unless environment is protected, he himself will be threatened by the over consumption of natural resource as well as substantial reduction of fresh air produced in the world. Conservation of forests and optimal utilization of agricultural and other renewable resources like solar and wind energies, and recently, tidal energy have become important topics worldwide. In such concern, the use of renewable resources such as plant and animal based fibre-reinforce polymeric composites, has been becoming an important design criterion for designing and manufacturing components for all industrial products. Research on biodegradable polymeric composites, can contribute for green and safe environment to some extent. In the biomedical and bioengineered field, the use of natural fibre mixed with biodegradable and bioresorbable polymers can produce joints and bone fixtures to alleviate pain for patients. In this paper, a comprehensive review on different kinds of natural fibre composites will be given. Their potential in future development of different kinds of engineering and domestic products will also be discussed in detail.     

Preparation and characterization of electrospun PCL/PLGA membranes and chitosan/gelatin hydrogels for skin bioengineering applications

In this study, two distinct systems of biomaterials were fabricated and their potential use as a bilayer scaffold (BS) for skin bioengineering applications was assessed. The initial biomaterial was a polycaprolactone/poly(lacto-co-glycolic acid) (PCL/PLGA) membrane fabricated using the electrospinning method. The PCL/PLGA membrane M-12 (12% PCL/10% PLGA, 80:20) displayed strong mechanical properties (stress/strain values of 3.01 ± 0.23 MPa/225.39 ± 7.63%) and good biocompatibility as demonstrated by adhesion of keratinocyte cells on the surface and ability to support cell proliferation. The second biomaterial was a hydrogel composed of 2% chitosan and 15% gelatin (50:50) crosslinked with 5% glutaraldehyde. The CG-3.5 hydrogel (with 3.5% glutaraldehyde (v/v)) displayed a high porosity, ≥97%, good compressive strength (2.23 ± 0.25 MPa), ability to swell more than 500% of its dry weight and was able to support fibroblast cell proliferation. A BS was fabricated by underlaying the membrane and hydrogel casting method to combine these two materials. The physical properties and biocompatibility were preliminarily investigated and the properties of the two biomaterials were shown to be complementary when combined. The upper layer membrane provided mechanical support in the scaffold and reduced the degradation rate of the hydrogel layer. Cell viability was similar to that in the hydrogel layer which suggests that addition of the membrane layer did not affect the biocompatibility.     

Multi-scale mechanical characterization of highly swollen photo-activated collagen hydrogels

Biological hydrogels have been increasingly sought after as wound dressings or scaffolds for regenerative medicine, owing to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate while remaining mechanically competent in situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from the nano- up to the macro-scale), uniquely high swelling ratios and retained (more than 70%) triple helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4-vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (F: 16 ± 12–91 ± 7 mol%) of introduced moieties governed the structure–property relationships in resulting collagen networks, so that the swelling ratio (SR: 707 ± 51–1996 ± 182 wt%), bulk compressive modulus (E_c: 30 ± 7–168 ± 40 kPa) and atomic force microscopy elastic modulus (E_AFM: 16 ± 2–387 ± 66 kPa) were readily adjusted. Because of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care.     

牛肌腱胶原纤维提取条件优化及其结构表征

以牛肌腱为原料,通过酸-酶结合法提取胶原纤维,比较不同时间、pH值、酶用量下的胶原纤维提取率以及可溶性胶原含量,从而得到提取胶原纤维最优工艺,并用SDS-PAGE电泳、DSC、IR、SEM、AFM对胶原纤维进行了结构表征.研究结果表明,在4℃下,酸-酶结合法水解的最佳条件为,时间40h、pH值为2.5、酶用量1.0％.该条件下所得胶原纤维提取率较高,红外特征峰明显,分子量大且分布窄,变性温度为66.7℃;SEM显示胶原纤维呈现孔隙均匀的三维网状结构,孔径约为100～300μm;AFM观察到胶原纤维以单根原纤维、纤维束等形式存在,明暗相间的横纹间距为60.35nm.综合认为制备得到了具有天然三股螺旋结构的胶原纤维.     

Screening biomaterials with a new in vitro method for potential calcification: Porcine aortic valves and bovine pericardium

Calcification is still a major cause of failure of implantable biomaterials. A fast and reliable in vitro model could contribute to the study of its mechanisms and to testing different anticalcification techniques. In this work, we attempted to investigate the potential calcification of biomaterials using an in vitro model. We purposed to test the ability of this model to screening possible anticalcification efficacy of different biomaterials. Porcine heart valve (PAV) and bovine pericardial (BP) tissues, fixed with glutaraldehyde were immersed into biological mimicking solution, where the pH and the initial concentrations of calcium and phosphoric ions were kept stable by the addition of precipitated ions during calcification. Kinetics of calcification was continuously monitored. The evaluation of biomaterials was carried out by comparing the kinetic rates of formation of calcific deposits. After 24 h, the calcific deposits on PAVs were found to be developed at significant higher rates (ranged from 0.81 x 10(-4)-2.18 x 10(-4)mol/min m2) than on BP (0.19 x 10(-4)-0.52 x 10(-4)mol/min m2) (one-way ANOVA, p < 0.05) depending on the experimental conditions (supersaturation of the solution). Parallel tests for similar biomaterials implanted subcutaneously in animal (rat) model showed after 49 days that significant higher amounts of total minerals deposited on PAV (236.73+/-139.12, 9 animals mg minerals/g dry net tissue) (mean+/-standard deviation) compared with that formed on BP (104.36+/-79.21, #9 mg minerals/g dry net tissue) (ANOVA, p < 0.05). There is evidence that in vitro calcification was correlated well with that of animal model and clinical data.     

Isolation and characterization of drug delivering potential of type-I collagen from eel fish Evenchelys macrura

Acid soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the outer skin waste of marine eel fish (Evenchelys macrura) were isolated and characterized. The prepared collagen was used to test its effective drug delivering potential in vitro condition. Present results were confirmed as collagen by different physico-chemical techniques like SDS-PAGE, HPLC, FTIR and SEM. Further amino acid analysis corroborates isolation of type I collagen. Both ASC and PSC comprising two different α-chains (α 1 and α 2) were characterized as type I and contained imino acid of 190-200 residues, respectively. The denaturation temperatures (T(d)) of ASC and PSC were 38.5 and 35.0?°C, respectively, which is promising as an advantage for biomedical application due to closeness in T(d) to mammalian collagen. Furthermore, the gel and film forming capability of collagen samples containing implant standard antibiotic was proved to be a suitable drug delivering system.     

Synthesis and characterization of nano-biomaterials with potential osteological applications

The manufacture of high-surface area, un-agglomerated nano-sized (1–100 nm) bioceramic particles are of interest for many applications including injectable/controlled setting bone cements, high strength porous/non-porous synthetic bone grafts, and the reinforcing phase in nano-composites that attempt to mimic the complex structure and superior mechanical properties of bone. In the present study, we report on the manufacture of nano-particle hydroxyapatite powders by several wet chemical methods, which incorporate a freeze-drying step. In particular, it was found that the emulsion-based syntheses yielded powders with high surface areas and small primary particle sizes. Freeze drying rather than oven drying of powders prepared by conventional wet chemical synthesis yielded a nano-sized powder with a comparatively higher surface area of 113 m²/g. All powders were calcined in air in a furnace at 900 °C to investigate the effects of synthesis method on phase purity and surface area. The materials were characterized by a range of analytical methods including Fourier-transform infrared spectroscopy employing the photo acoustic (PAS-FTIR) sampling technique, BET surface area analysis, X-ray powder diffraction (XRD), and the particles were examined using a transmission electron microscope (TEM).     

Coumarin-conjugated multiwalled carbon nanotubes for potential biological applications: development and characterization

This work presents a novel cascade of chemical functionalization of multiwalled carbon nanotubes which allows the conjugation with differently substituted coumarins. Aim of the present work is to synthesize new materials able to rescue cells from the adverse effect of CNT particles since pristine CNTs are practically insoluble and tend to accumulate inside cells, organs and tissues. Moreover, it was reported that single walled CNTs particles show an adverse effect on keratinocytes through an oxidative mechanism, leading to NF-kB activation. The conjugation with coumarins, known superoxide anion scavengers, could switch the cytotoxicity of the new materials. The cascade functionalization of MWCNTs by sequential steps of carboxylation, acylation, amine modification and finally, coumarin conjugation have been performed and the synthesis and the chemical properties of several f-MWCNTs-coumarins have been exploited.     

Characterisation of a collagen membrane for its potential use in cardiovascular tissue engineering applications

In this study, Biomend, a collagen membrane conventionally used in the regeneration of periodontal tissue, is investigated for its possible use in the field of cardiovascular tissue engineering. A key requirement of most potential tissue engineering scaffolds is that degradation occurs in tandem with tissue regeneration and extra cellular matrix remodelling. To this end, it is crucial to understand the degradation mechanics and mechanisms of the material and to investigate the practicability of using Biomend as a possible scaffold material. With this in mind, methodologies for the initial characterisation of the scaffold material were determined. The mechanical properties of Biomend samples, subjected to various degrees of hydration and enzymatic degradation, were examined primarily through tensile testing experiments. The effects of enzymatic degradation were monitored quantitatively, by observing weight loss, and visually, by studying micrographs. Cell adhesion and viability were of primary concern. Confocal laser scanning microscopy was employed to illustrate endothelialisation on the surface of this collagen membrane. Fluorescence microscopy was used to visualise cell viability on the membrane surface. These images, coupled with assays to measure cell activity, suggest that Biomend is not a suitable substrate to allow endothelialisation. In summary, this collagen membrane has suitable mechanical properties with the potential to control its degradation rate. However, since poor endothelial cell viability was observed on the membrane, it may not be suitable for use in cardiovascular tissue engineering applications.     

Biotemplated silica and titania nanowires: synthesis, characterization and potential applications

A simple biotemplating method for the synthesis of silica (SiO2) and titania (TiO2) nanowires was designed on a fibrillar protein (alpha-synuclein) template. The diameter of SiO2 and TiO2 nanowires could be varied, between 20-100 nm, by varying the processing conditions. The nanowires were characterized by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Due to their high surface area and porosity, the nanowires were tested for potential applications in enzymatic biosensor design.     

ζ-potential characterization of collagen and bovine serum albumin modified silica nanoparticles: a comparative study

In this study, bovine serum albumin (BSA) and collagen (COLL) were adsorbed independent of one another, onto the surface of silica nanoparticles (SNPs) at pH’s where the ζ-potential of the proteins were equal in magnitude, but opposite to the SNP surface to ascertain the differences in surface coverage and conformation in the adsorbed layer. In both systems, increasing the concentration of free protein resulted in an increase in protein surface coverage and ζ values, with ζ values approaching that of native protein at high surface coverage. However, a lower critical charge reversal concentration range was measured for COLL relative to BSA (COLL: 0–25 μg/mL, BSA: 25–90 μg/mL). Additionally, a considerable difference in ζ for adsorbed protein versus free protein was observed. These results when interpreted in terms of the theory of Ottewill and Watanabe indicate a higher Gibbs energy of association for COLL versus BSA on SNP surfaces, accompanied by perturbation in protein structure.     

Extraction of cellulose to progress in cellulosic nanocomposites for their potential applications in supercapacitors and energy storage devices

Journal of Materials Science - Nanocellulose products derived from different forms of biomass have significant importance in the modern era. This is due to its extraordinary physical...     

Calcification and identification of metalloproteinases in bovine pericardium after subcutaneous implantation in rats

The purpose of this study was to evaluate the influence of two anticalcification pre-treatments (chloroform/methanol and ethanol) and serum conditioning of glutaraldehyde-crosslinked bovine pericardium on the calcification degree and the presence of gelatinase activities in a subcutaneous implantation model in rats. Regarding calcification of the implants, glutaraldehyde control treatments showed a significatively higher calcification degree than pericardium treated with anticalcification reagents. Serum conditioning of glutaraldehyde treated tissues did not influence the calcification degree; moreover, no differences were found in these samples with the time of implantation (30 and 90 days). On the other hand, anticalcification treatments resulted in a very significant decrease in the calcium content in the implanted membranes. Gelatinase activities were detected by gelatin zymography in almost all the implanted samples. However, control tissues with and without serum conditioning showed less gelatinase activities than those samples pre-treated with anticalcification treatments. Metalloproteinase (MMP-2) activity was detected in all the samples analyzed but a higher expression of MMP-9 was detected in those implants treated with chloroform/methanol and ethanol. Additional gelatinase activities showing lower molecular weight than MMP-2 were also detected in both anticalcification treated samples. The presence of these gelatinase activities is probably due to host cellular infiltrates and could contribute to the biomaterial degradation.     

Creating ultrathin nanoscopic collagen matrices for biological and biotechnological applications

The biofunctionalization of materials creates interfaces on which proteins, cells, or tissues can fulfill native or desired tasks. Here we report how to control the assembly of type I collagen into well-defined nanoscopic matrices of different patterns. Collagen fibrils in these ultrathin (approximately 3 nm) matrices maintained their native structure as observed in vivo. This opens up the possibility to create programmable biofunctionalized matrices using collagen-binding proteins or proteins fused with collagen-binding domains. Applied to eukaryotic cells, these nanostructured matrices can direct cellular processes such as adhesion, orientation and migration.     

Biochar applications and modern techniques for characterization

Biochar simply is the material produced when biomass undergoes any chemical processes under the conditions of pyrolysis. The variety of biomasses, including wood waste, agricultural crop leftover, organic waste, animal manure, and forestry residues, have been considered as raw material to produce biochar. Biochar is widely used for generation of heat and power and an addition to soils, in which it serves as a fertilizer and carbon sequestration agent. Also in the form of being activated, it finds significant role for various adsorption applications. The most beneficial use of a given char depends on its physical and chemical characteristics, even though the relationship of char properties to these applications is not well defined. Various widely used modern analytical techniques, which are applicable and crucial for biochar characterization, have been reviewed in the present work, such as solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-rays photoelectron spectroscopy, X-rays diffraction, thermogravimetric analysis, near edge X-rays absorption fine structure spectroscopy, and gas chromatography-mass spectroscopy. Utilization of these modern techniques provides the quantitative as well as qualitative information, i.e., determining the sizes, shapes, and physicochemical characteristics of biochar, which is reliable to track changes in the carbon arrangement over reaction time and temperature, and will be useful for efficient production of biochar and application. It provides the useful information for the researchers in this area and is beneficial not only for the effective biochar production, but also for potential utilization/application, and not only for environment but also for agriculture.     

新型催化材料——介孔氧化铝分子筛的合成、表征以及应用前景

与传统的γ-Al2O3相比,介孔氧化铝分子筛具有较大的比表面积和较窄的孔径分布,作为工业催化剂或催化剂载体,具有更为广阔的应用前景.本文重点介绍了介孔氧化铝分子筛的不同合成方法、结构表征方法和催化性能,分析了模板剂类型、凝胶pH值、洗涤方法、焙烧方式等制备条件对其结构的影响.并对其催化应用进行了评述和展望.     

Extraction and characterization of cellulose whiskers from commercial cotton fibers

During the past few years, there has been a growing interest in incorporating cellulose whiskers from different sources as nanoreinforcement in polymer matrixes. The purpose of this study is to evaluate the performance of the cellulose whiskers obtained from Brazilian commercial cotton. In this sense, cellulose whiskers were prepared by acid hydrolysis which was carried out with a sulfuric acid solution 6.5 M at 45 and 60 °C for 75 and 20 min, respectively, and dried using different methods—an oven, a freeze dryer, and an air circulation oven. Cellulose whiskers were investigated in respect of crystallinity, thermal stability, and morphologically by scanning transmission electron microscopy. Cellulose cotton whiskers, independently of extraction conditions, provided an average length and a diameter of 150 ± 50 nm and of 14 ± 5 nm, respectively, and showed a rod-like shape. Whiskers extracted at 45 °C for 75 min have shown similar crystallinity and better thermal stability in oxidizing atmosphere. The use of the freezing dry process resulted in whiskers with better thermal stability and similar crystallinity than those obtained when dried in the air circulation oven process.     

Stability and mechanical evaluation of bovine pericardium cross-linked with polyurethane prepolymer in aqueous medium

The present study investigates the potential use of non-catalyzed water-soluble blocked polyurethane prepolymer (PUP) as a bifunctional cross-linker for collagenous scaffolds. The effect of concentration (5, 10, 15 and 20%), time (4, 6, 12 and 24 h), medium volume (50, 100, 200 and 300%) and pH (7.4, 8.2, 9 and 10) over stability, microstructure and tensile mechanical behavior of acellular pericardial matrix was studied. The cross-linking index increased up to 81% while the denaturation temperature increased up to 12 °C after PUP crosslinking. PUP-treated scaffold resisted the collagenase degradation (0.167 ± 0.14 mmol/g of liberated amine groups vs. 598 ± 60 mmol/g for non-cross-linked matrix). The collagen fiber network was coated with PUP while viscoelastic properties were altered after cross-linking. The treatment of the pericardial scaffold with PUP allows (i) different densities of cross-linking depending of the process parameters and (ii) tensile properties similar to glutaraldehyde method.     

利用狭鳕加工废料制备胶原的表征及其生物学功能

以狭鳕加工废料为来源提取酸溶胶原并加以表征.该胶原在230nm处有最大紫外吸收,红外吸收光谱指示存在螺旋结构.电泳图谱分离出多个亚基,鉴定为Ⅰ型胶原.该胶原有独特的氨基酸组成,甘氨酸达19.8%,羟脯氨酸占6.9%.酸水解制备的胶原多肽平均分子量区间为3.2～53kDa.胶原多肽具有不同的生物学功能:较高分子量的胶原多...