Since their first allusion, carbon nanotubes have attracted significant research interest, especially with respect to composite manufacturing as a filler material for enhancing their mechanical and electrical properties. Several methods have been developed for modifying the electrical properties of carbon nanotubes such as CNTs wall's carbon atoms substitution with other appropriate atoms including engineering of their outer surfaces by covalent and noncovalent molecules, such as CNTs channel filling and nano-chemical reactions therein. CNTs with tailored electrical conduction open large perspectives for their applicabilities in advanced technologies. Taking into consideration the innovative advantages of pure and hybrid CNTs, in this article we have comprehensively reviewed the latest state-of-art research developments in the direction of different synthesis strategies, structure-property relationships, and advanced applications towards energy storage, supercapacitors, electrodes, catalytic supports, as well as biosensing.
Hydroxyapatite is a calcium phosphate intensively proposed as a bone substitution material because of its resemblance to the constituents of minerals present in natural bone. Since hydroxyapatite's properties are mainly adequate for non-load bearing applications, different solutions are being tested for improving these properties and upgrading them near the target-values of natural bone. On the other hand, starch (a natural and biodegradable polymer) and its blends with other polymers have been proposed as constituents in hydroxyapatite mixtures due to the adhesive, gelling and swelling abilities of starch particles, useful in preparing well dispersed suspensions and consolidated ceramic bodies. This article presents the perspectives of
Ever since the discovery of graphene, its potential has been predicted for a number of applications in various fields such as electronics, sensors, environmental decontamination techniques, separations and biomedicine to name a few. Among various such fields, the research in graphene-based nanocomposites membranes is still in its infancy as there is not a significant research published in this field so far. However, interestingly this field is registering an exponentially upward trend recently. This review article provides a brief description of polymer nanocomposite membranes with graphene as one of the most indispensable components in the membranes. In this article, we describe in a systematic and comprehensive manner the most recent research published so far in the nanocomposite membranes with graphene and the most commonly used polymers namely the polysulfone and the cellulose derivatives. This article also describes the main applications of these polymeric membranes in the fuel cells and in water purification processes containing the current literature data as well as the authors' own research.
This article presents a facile synthesis method used to obtain new composite films based on polylactic acid and micro-structured hydroxyapatite particles. The composite films were synthesized starting from a polymeric solution in chloroform (12 wt.%) in which various concentrations of hydroxyapatite (1, 2, and 4 wt.% related to polymer) were homogenously dispersed using ultrasonication followed by solvent evaporation. The synthesized composite films were morphologically (through SEM and atomic force microscopy (AFM)) and structurally (through FT-IR and Raman spectroscopy) characterized. The thermal behavior of the composite films was also determined. The SEM and AFM analyses showed the presence of micro-structured hydroxyapatite particles in the film’s structure, as well as changes in the surface morphology. There was a significant decrease in the crystallinity of the composite films compared to the pure polymer, this being explained by a decrease in the arrangement of the polymer chains and a concurrent increase in the degree of their clutter. The presence of hydroxyapatite crystals did not have a significant influence on the degradation temperature of the composite film.
Green bio-based polymeric membranes are rapidly emerging as materials of choice for a number of biomedical applications such as in the osseointegration processes. In this work, we report our preliminary studies on the covalent immobilization of sericin on to green cellulose membranes for potential applications in the osseointegration field. Initially, the surface of the cellulose acetate membrane was immobilized with the amino-propyl-triethoxysilane (APTS) functional group, while the protein was immobilized through glutaraldehyde that was used as a linker between amino-propyl-triethoxysilane and sericin. The functionalized membranes were thoroughly characterized by different characterization techniques such as infrared spectroscopy (FT-IR); Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTG). All these techniques confirmed the successful functionalization and uniform immobilization of the protein onto the membrane surface. Subsequently, the performance of the membranes was characterized both in terms of flows and retention of bovine serum albumin and haemoglobin in the case of immobilized protein membranes. The retention was found to be more than 90% after 90 minutes of process. Since in these membranes cases, their speed of degradation is essential in the physiological pH conditions, so the degradation was also studied over a period of three months and the degradation mechanism is also explained. Furthermore, the membrane functionalized with sericin has proven to hold great promise for application in bone regeneration.
The main objective of this research is to prove the viability of obtaining magnesium (Mg) filled polylactic acid (PLA) biocomposites as filament feedstock for material extrusion-based additive manufacturing (AM). These materials can be used for medical applications, thus benefiting of all the advantages offered by AM technology in terms of design freedom and product customization. Filaments were produced from two PLA + magnesium + vitamin E (α-tocopherol) compositions and then used for manufacturing test samples and ACL (anterior cruciate ligament) screws on a low-cost 3D printer. Filaments and implant screws were characterized using SEM (scanning electron microscopy), FTIR (fourier transform infrared spectrometry), and DSC (differential scanning calorimetry) analysis. Although the filament manufacturing process could not ensure a uniform distribution of Mg particles within the PLA matrix, a good integration was noticed, probably due to the use of vitamin E as a precursor. The results also show that the composite biomaterials can ensure and maintain implant screws structural integrity during the additive manufacturing process.
Despite their good biocompatibility and adequate mechanical behavior, the main limitation of Mg alloys might be their high degradation rates in a physiological environment. In this study, a novel Mg-based alloy exhibiting an elastic modulus E = 42 GPa, Mg-1Ca-0.2Mn-0.6Zr, was synthesized and thermo-mechanically processed. In order to improve its performance as a temporary bone implant, a coating based on cellulose acetate (CA) was realized by using the dipping method. The formation of the polymer coating was demonstrated by FT-IR, XPS, SEM and corrosion behavior comparative analyses of both uncoated and CA-coated alloys. The potentiodynamic polarization test revealed that the CA coating significantly improved the corrosion resistance of the Mg alloy. Using a series of in vitro and in vivo experiments, the biocompatibility of both groups of biomaterials was assessed. In vitro experiments demonstrated that the media containing their extracts showed good cytocompatibility on MC3T3-E1 pre-osteoblasts in terms of cell adhesion and spreading, viability, proliferation and osteogenic differentiation. In vivo studies conducted in rats revealed that the intramedullary coated implant for fixation of femur fracture was more efficient in inducing bone regeneration than the uncoated one. In this manner, the present study suggests that the CA-coated Mg-based alloy holds promise for orthopedic aplications.
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