Carbon nanotubes reinforced chitosan films: mechanical properties and cell response of a novel biomaterial for cardiovascular tissue engineering

Carbon nanotubes have been proposed as fillers to reinforce polymeric biomaterials for the strengthening of their structural integrity to achieve better biomechanical properties. In this study, a new polymeric composite material was introduced by incorporating various low concentrations of multiwalled carbon nanotubes (MWCNTs) into chitosan (CS), aiming at achieving a novel composite biomaterial with superior mechanical and biological properties compared to neat CS, in order to be used in cardiovascular tissue engineering applications. Both mechanical and biological characteristics in contact with the two relevant cell types (endothelial cells and vascular myofibroblasts) were studied. Regarding the mechanical behavior of MWCNT reinforced CS (MWCNT/CS), 5 and 10 % concentrations of MWCNTs enhanced the mechanical behavior of CS, with that of 5 % exhibiting a superior mechanical strength compared to 10 % concentration and neat CS. Regarding biological properties, MWCNT/CS best supported proliferation of endothelial and myofibroblast cells, MWCNTs and MWCNT/CS caused no apoptosis and were not toxic of the examined cell types. Conclusively, the new material could be suitable for tissue engineering (TE) and particularly for cardiovascular TE applications.     

Hydrogel/bioactive glass composites for bone regeneration applications: Synthesis and characterisation

Due to the deficiencies of current commercially available biological bone grafts, alternative bone graft substitutes have come to the forefront of tissue engineering in recent times. The main challenge for scientists in manufacturing bone graft substitutes is to obtain a scaffold that has sufficient mechanical strength and bioactive properties to promote formation of new tissue. The ability to synthesise hydrogel based composite scaffolds using photopolymerisation has been demonstrated in this study. The prepared hydrogel based composites were characterised using techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectrometry (EDX), rheological studies and compression testing. In addition, gel fraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), porosity and swelling studies of the composites were carried out. It was found that these novel hydrogel bioglass composite formulations did not display the inherent brittleness that is typically associated with bioactive glass based bone graft materials and exhibited enhanced biomechanical properties compared to the polyethylene glycol hydrogel scaffolds along. Together, the combination of enhanced mechanical properties and the deposition of apatite on the surface of these hydrogel based composites make them an ideal candidate as bone graft substitutes in cancellous bone defects or low load bearing applications.     

碳纳米管表面活性化及其在生物医药中的应用

综合了国内外文献资料,介绍了碳纳米管的表面处理的方法,对不同处理方法对碳纳米管带来的物理化学变化进行了综述;重点介绍了处理后的碳纳米管在生物医药领域的应用;最后对碳纳米管表面活化方法选择进行了总结.     

基于碳纳米管的三维编织复合材料健康监测技术

分析了三维编织复合材料试件结构健康监测技术现状,结合三维编织复合材料编织工艺,提出了碳纳米管在三维编织复合材料试件健康监测方面的应用方法。结果说明碳纳米管应用于三维编织复合材料整体结构监测是可行的。碳纳米管传感器在三维编织复合材料试件结构健康监测中具有优异的应变传感特性,且嵌入的碳纳米管传感器对复合材料的力学性能影响不大。这为内置碳纳米管传感器应用于复合材料制件的健康检测提供了一种新的综合和分布式技术,为先进智能复合材料的研发与应用提供了依据。     

Carbon Nanotubes and Nanofluidic Transport

Recent strides have been made in both the modeling and measurement of fluid flow on the nanoscale. Carbon nanotubes, with their atomic dimensions and atomic smoothness, are ideal materials for studying such flows. This Progress Report describes recent modeling and experimental advances concerning fluid transport in carbon nanotubes. The varied flow characteristics predicted by molecular dynamics are described, as are the roles of defects and chirality on transport. Analytical models are increasingly being used to describe nanofluidic transport by relaxing many of the assumptions commonly used to describe bulk water. Recent experimental studies examine the size dependence of flow enhancements through carbon nanotubes and use varied spectroscopies to probe water structure and dynamics in these systems. Carbon nanotubes are finding increasing applications in biology, from protein filters to platforms for cell interrogation.     

Multiscale analysis of carbon nanotube-reinforced nanofiber scaffolds

Biopolymers play a significant role in tissue engineering, as they simulate the physiological environment required for the development of tissue cultures. Use of carbon nanotube polymeric scaffolds for tissue engineering applications has gained attention recently due to the enhanced mechanical properties of carbon nanotubes. In this paper, a hierarchical approach by studying the atomistic properties of carbon nanotube based polymers using molecular dynamics and coupling the scales through complex multi-scale nonlinear hyperelastic material-based mathematical homogenization models are developed. These homogenization methods offer a systematic and rigorous treatment of up-scaling the properties from the micro or nanoscale to the macroscales. The material constitutive properties estimated using the developed methods for nanotube polymeric scaffold materials show excellent comparison with experimental studies.     

The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder

A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.     

Biomimetic Bonelike Composites and Novel Bioactive Glass Coatings

Metallic orthopaedic implants have been successfully used for decades but they have serious shortcomings related to their osseointegration and the fact that their mechanical properties do not match those of bone. This paper reviews recent advances in the fabrication of novel coatings to improve implant osseointegration and in the development of a new generation of hybrid organic‐inorganic implant materials specifically designed for orthopaedic applications.     

Bivalent cationic ions doped bioactive glasses: the influence of magnesium,zinc, strontium and copper on the physical and biological properties

Bioactive glass and glass ceramic materials are widely used as substitutes for bone augmentation and restoration, in orthopaedic, dental and maxillofacial surgery and in the tissue engineering field. Indeed, these materials are bioactive, biocompatible, mechanically stable, biodegradable and favour osteointegration, being able to promote bone tissue formation at their surface and to bond to surrounding living tissues when implanted in the human body. It has been demonstrated that bioglass (BG) ionic dissolution products (e.g. Si, Ca, P and Na) are able to induce and stimulate the expressions of genes related to the osteoblastic differentiation and bone formation, to stimulate angiogenesis in vitro and in vivo, as well as to play possible antibacterial and anti-inflammatory actions. Thus, it is possible to tailor BGs properties properly formulating their chemical composition and adding selected ions with specific functional and biological role. In this perspective, Hench proposed a new generation of genetically designed glasses, on the basis of their ability to activate specific genes involved in in situ tissue regeneration, by doping silicate and phosphate glasses with several active ions, particularly metallic ions with therapeutic effects. In this framework, the present review is aimed to provide an overview about the effect of selected cationic substitutions (i.e. magnesium, zinc, strontium and copper), incorporated within the bioglasses structure, on the physical and biological properties of these materials, since the comprehension of the influence of the most employed metallic ions has to be considered pivotal to address the formulation of more promising and performing glasses.     

Carbon microfibers sheathed with aligned carbon nanotubes: towards multidimensional, multicomponent, and multifunctional nanomaterials

Multicomponent and multifunctional hybrid structures based on microsized carbon fibers sheathed with aligned carbon nanotubes and their derivatives have been successfully prepared, and have been demonstrated to be an effective means for connecting nanoscale entities to the outside world and to possess interesting electrochemical properties attractive for a wide range of potential applications, including in methanol direct fuel cells and highly sensitive biological and chemical sensors. Judicious modification of the carbon-fiber-supported aligned carbon nanotubes with various functional moieties could lead to a class of novel multidimensional, multicomponent, and multifunctional materials of practical significance.     

Long-term in vivo experimental investigations on magnesium doped hydroxyapatite bone substitutes

Despite several efforts to find suitable alternatives to autologous bone, no bone substitute currently available provides the same characteristics and properties. Nevertheless, among the wide range of materials proposed as bone substitutes, calcium phosphate materials represent the most promising category and the present study is aimed at improving the knowledge on non-stoichiometric magnesium-doped hydroxyapatite substitutes (Mg-HA), tested in two different formulations: Mg-HA Putty and Mg-HA Granules. These bone substitutes were implanted bilaterally into iliac crest bone defects in healthy sheep and comparative histological, histomorphometric, microhardness and ultrastructural assessments were performed 9, 12, 18 and 24 months after surgery to elucidate bone tissue apposition, mineralization and material degradation in vivo. The results confirmed that the biomimetic bone substitutes provide a histocompatible and osteoconductive structural support, during the bone formation process, and give essential information about the in vivo resorption process and biological behavior of biomimetic bone substitutes.     

Bioinspired peptide nanotubes as supercapacitor electrodes

Bioinspired materials offer new routes in nanotechnology. These materials are composed from chemically synthesized biomolecules and inspired by natural biological structures. They are self assembled into highly ordered nanostructures (nanotubes, nanospheres, etc.) from elementary building blocks of biological origin such as peptide and proteins. We developed a new technique of physical vapor deposition of peptide nanotubes (PNT) and applied it to electrochemical energy storage devices—supercapacitors (SC). In this work, aligned and homogenously distributed diphenylalanine PNT have been used to modify carbon electrodes for SC devices. Electrochemical properties of PNT coatings of different density and height, modifying carbon electrodes have been studied. We have found that aligned PNT arrays significantly increase the double layer capacitance of the carbon electrodes. The found enlargement of the PNT-modified electrode capacitance has been ascribed to increasing of usable electrode surface area of the carbon electrodes coated by PNT. We show that the critical factor of the accumulation process of the electrolyte ions at the PNT-modified electrode surface is a wetting process of the PNT nanoscale hydrophilic channels by aqueous electrolyte.     

碳纳米管气敏传感器响应机理研究进展

碳纳米管以其优异的表面化学性能和良好的电学性能成为制作化学传感器的理想材料.论述了碳纳米管的结构特点及其气敏响应机理的最新进展,包括气敏吸附和电学传感机理和复合型碳纳米管气敏材料响应机理研究的进展.     

聚合物/碳纳米管复合材料研究进展

聚合物／碳纳米管复合材料近年来引起人们广泛的关注。本文综述了聚合物／碳纳米管复合材料的研究进展，重点介绍了聚合物／碳纳米管复合材料的类型、制备方法及力学、电学和光学性能等。     

Protein immobilization on carbon nanotubes through a molecular adapter

A new approach to the modification of carbon nanotubes with biomolecules for the development of nanoscale biosensors is presented. Alkaline phosphatase was immobilized on the surface of multi-wall carbon nanotubes utilizing a layer-by-layer methodology. Carbon nanotubes were incubated with streptavidin, resulting in the formation of a protein layer on the surface of the nanotubes. Biotinylated alkaline phosphatase was then allowed to bind to streptavidin, anchoring the sensing protein onto the surface. Electrochemical biosensors were constructed by using carbon nanotubes compacted into pellets. 1-Naphthyl phosphate, which is hydrolyzed by alkaline phosphatase to the electroactive 1-naphthol, was used as a substrate. Electrodes constructed in this manner were observed to generate an electrochemical signal that was a function of substrate concentration.     

Natural‐Based Nanocomposites for Bone Tissue Engineering and Regenerative Medicine: A Review

Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional substitutes aimed to repair and regenerate damaged tissues and organs. Inspired by the hierarchical nature of bone, nanostructured biomaterials are gaining a singular attention for tissue engineering, owing their ability to promote cell adhesion and proliferation, and hence new bone growth, compared with conventional microsized materials. Of particular interest are nanocomposites involving biopolymeric matrices and bioactive nanosized fillers. Biodegradability, high mechanical strength, and osteointegration and formation of ligamentous tissue are properties required for such materials. Biopolymers are advantageous due to their similarities with extracellular matrices, specific degradation rates, and good biological performance. By its turn, calcium phosphates possess favorable osteoconductivity, resorbability, and biocompatibility. Herein, an overview on the available natural polymer/calcium phosphate nanocomposite materials, their design, and properties is presented. Scaffolds, hydrogels, and fibers as biomimetic strategies for tissue engineering, and processing methodologies are described. The specific biological properties of the nanocomposites, as well as their interaction with cells, including the use of bioactive molecules, are highlighted. Nanocomposites in vivo studies using animal models are also reviewed and discussed.     

Surface treatments and roughness properties of Ti-based biomaterials

Nowadays, the use of implanted devices is a well-acknowledged practice in the field of orthopaedic and dental surgery. Scientific research and clinical experience suggest that the successful exploitation of these devices mainly depends on osseointegration, considered as both anatomical congruency and load-bearing capacity. Indeed, the osseointegration process is influenced by a wide range of factors: anatomical location, implant size and design, surgical procedure, loading effects, biological fluids, age and sex, and, in particular, surface characteristics. For this reason, several attempts have been aimed at modifying implant surface composition and morphology to optimise implant-to-bone contact and improve integration. Preliminary interactions between implanted materials and biological environment are deemed to be governed by the surface properties; they control the amount and quality of cell adhesion on the surface and, consequently, cell/tissue growth. Thus, surface properties govern new bone tissue formation and implant osseointegration. This paper reviews the state of art in the field of physical, chemical and biochemical treatments commonly used on Ti-based biomaterials for the production of biomedical devices. In particular, roughness characteristics due to physical and chemical techniques are investigated; the development of biologically active surfaces by means of biochemical functionalisation is also considered.     

失效AB5型贮氢合金电极材料在制备纳米碳管中的应用

纳米碳管是一种性能优异的新型功能材料.利用循环失效后的AB5型贮氢合金电极材料作为反应催化剂、乙炔气体作为原料气体通过CVD法制备出多壁纳米碳管,研究了经过破碎、清洗、氧化处理后的失效AB5型贮氢合金电极材料在合成纳米碳管中的催化性能,讨论了不同氧化温度处理催化剂对纳米碳管产率、形貌和结构稳定性的影响.结果表明,氧化处理温度对催化剂的催化效能有明显的影响,600℃为最佳氧化处理温度.以氧化处理后的失效AB5型贮氢合金电极材料作为催化剂制备碳纳米管,方法简单易行,为废旧镍氢电池负极材料的回收再利用提供了一种新的思路.     

Osteoblast, fibroblast and in vivo biological response to poly(vinylidene fluoride) based composite materials

Electroactive materials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidene fluoride), PVDF, have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.     

In vitro evaluation of bioactive strontium-based ceramic with rabbit adipose-derived stem cells for bone tissue regeneration

The development of bone replacement materials is an important objective in the field of orthopaedic surgery. Due to the drawbacks of treating bone defects with autografts, synthetic bone graft materials have become optional. So in this work, a bone tissue engineering approach with radiopaque bioactive strontium incorporated calcium phosphate was proposed for the preliminary cytocompatibility studies for bone substitutes. Accumulating evidence indicates that strontium containing biomaterials promote enhanced bone repair and radiopacity for easy imaging. Hence, strontium calcium phosphate (SrCaPO₄) and hydroxyapatite scaffolds have been investigated for its ability to support and sustain the growth of rabbit adipose-derived mesenchymal stem cells (RADMSCs) in vitro. They were characterized via Micro-CT for pore size distribution. Cells used were isolated from New Zealand White rabbit adipose tissue, characterized by FACS and via differentiation into the osteogenic lineage by alkaline phosphatase, Masson’s trichome, Alizarin Red and von Kossa staining on day 28. Material-cell interaction was observed by SEM imaging of cell morphology on contact with material. Live–Dead analysis was done by confocal laser scanning microscopy and cell cluster analysis via μCT. The in vitro biodegradation, elution and nucleation of apatite formation of the material was evaluated using simulated body fluid and phosphate buffered saline in static regime up to 28 days at 37 °C. These results demonstrated that SrCaPO₄ is a good candidate for bone tissue engineering applications and with osteogenically-induced RADMSCs, they may serve as potential implants for the repair of critical-sized bone defects.