Inimitable properties of carbon quantum dots as well as a cheap production contribute to their possible application in biomedicine especially as antibacterial and antibiofouling coatings. Fluorescent ...hydrophobic carbon quantum dots are synthesized by bottom-up condensation method and used for deposition of uniform and homogeneous Langmuir–Blodgett thin films on different substrates. It is found that this kind of quantum dots generates singlet oxygen under blue light irradiation. Antibacterial and antibiofouling testing on four different bacteria strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa) reveals enhanced antibacterial and antibiofouling activity of hydrophobic carbon dots thin films under blue light irradiation. Moreover, hydrophobic quantum dots show noncytotoxic effect on mouse fibroblast cell line. These properties enable potential usage of hydrophobic carbon quantum dots thin films as excellent antibacterial and antibiofouling coatings for different biomedical applications.
•Electrospinning is a scaffold fabrication method.•Integrating other materials such as metals nanoparticles with polymers is emerging as a route to new composites materials.•Electrospun ...polymer-nanoparticles composites are a new frontier in biomedicine.•We summarise advances in electrospun tissue engineering and wound dressing platforms.•Polymer-titanium dioxide nanocomposites is discussed here.
Electrospinning is widely used to fabricate nanoscale fibers from natural and synthetic polymers. Electrospun fibers have potential application in tissue engineering as well as in the design of catalysts, batteries, electronic sensors, packages, filtration membranes, medical implants, wound dressings, and medical fabrics, and drug delivery systems. Fibers offer a porous structure with a high surface area to volume ratio, which is a highly desired property in various applications. Integrating other materials such as metals nanoparticles or ceramics in electrospun fibers is emerging as a route to new nanoscale composites materials with enhanced functional properties. Incorporating nanoparticles on or within the nanofibrous scaffold impart functional properties with implication for catalysis, optoelectronics, and biomedicine. Indeed, these electrospun polymer-nanoparticles composites are a new frontier in biomedicine, where their relevance to tissue engineering, wound dressing, drug delivery is emerging. Here, we summarise advances in electrospun tissue engineering and wound dressing platforms developed from polymer-titanium dioxide nanocomposites.
Carbon nanotubes have long been recognized as the stiffest and strongest man-made material known to date. In addition, their high electrical conductivity has roused interest in the area of electrical ...appliances and communication related applications. However, due to their miniscule size, the excellent properties of these nanostructures can only be exploited if they are homogeneously embedded into light-weight matrices as those offered by a whole series of engineering polymers. We review the present state of polymer nanocomposites research in which the fillers are carbon nanotubes. In order to enhance their chemical affinity to engineering polymer matrices, chemical modification of the graphitic sidewalls and tips is necessary. In this review, an extended account of the various chemical strategies for grafting polymers onto carbon nanotubes and the manufacturing of carbon nanotube/polymer nanocomposites is given. The mechanical and electrical properties to date of a whole range of nanocomposites of various carbon nanotube contents are also reviewed in an attempt to facilitate progress in this emerging area.
The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the morphological, electrical, mechanical and thermal properties of high-density polyethylene (HDPE)-based ...nanocomposites are investigated. The HDPE nanocomposites with various amounts up to 18.74 wt% of MWCNTs that have two different aspect ratios (AR) (200-400 (M58) and 500-3000 (M12)) were prepared by a melt mixing method, followed by compression molding. The results demonstrate that the addition of MWCNTs enhances the electrical, mechanical and thermal properties of the HDPE/MWCNTs nanocomposites. The HDPE nanocomposites with higher aspect ratio MWCNTs demonstrated a slightly better enhancement in the morphological and electrical properties than the other ones with lower aspect ratio MWCNTs. Additionally, Young's modulus and the thermal stability increased with increasing aspect ratio of MWCNTs.
Eco-friendly materials like carbohydrate-based polymers are important for a sustainable future. Starch is particularly promising because of its biodegradability and abundance but its processing to ...thermoplastic starch requires optimization. Here we developed thermoplastic maize starch materials based on three manufacturing protocols, namely: (1) starch/glycerol manual mixing and extrusion, (2) starch/glycerol manual mixing, extrusion, and kneading, (3) starch/glycerol/water manual mixing and kneading. The physical properties were investigated by differential scanning calorimetry, thermogravimetric analysis, and broadband dielectric spectroscopy. As expected from a partially miscible blend, the dielectric spectra revealed two distinct α-relaxations for the glycerol-rich and the starch-rich phases, respectively. By employing kneading after extrusion, the miscibility between the two phases was found to improve based on thermal and dielectric methods. Moreover, the addition of water during the premixing stage was observed to facilitate phase separation between starch and glycerol, with the α-relaxation dynamics of the latter being comparable to pure glycerol.
Studies addressing electroconductive composites based on rubber have attracted great interest for many engineering applications. To contribute to obtaining useful materials with reproducible ...behavior, this study focused on understanding the mechanism of conductivity changes during mechanical deformation for rubber composites based on styrene-butadiene rubber (SBR) or ethylene-propylene-diene terpolymer (EPDM) vulcanized for various times. The composites were characterized by static electrical conductivity, tensile testing, dynamic mechanical thermal analysis (DMTA), and crosslink density measurements. The tensile strength and Young’s modulus were found to increase significantly with rising vulcanization time. Higher static conductivity values of the composites were observed with the increase in vulcanization time. The most important aspect of this investigation consisted in the electrical current measurement online with recording the stress-strain curves, revealing the details of the uniaxial cyclic deformation effect on changes in the structure of conductive pathways indirectly. The electrical conductivity during five runs of repeated cyclic mechanical deformations for SBR composites increased permanently, although not linearly, whereas EPDM composites showed a slight increase or at least a nearly constant current, indicating healing of minor defects in the conductive pathways or the formation of new conductive pathways.
Carbon quantum dots and their incorporation in various polymer matrices are reviewed. In general, the importance of such polymer nanocomposites in biomedical applications is highlighted. In ...particular, the physical and antimicrobial properties of carbon quantum dots and their ability to produce reactive oxygen species under certain conditions using the principle of photodynamic therapy are explored. The characterization, preparation, mechanism of action, and use of carbon quantum dots are discussed. The known combinations of polymers and carbon quantum dots and their use in various industries are also described.
Carbon quantum dots and their incorporation in various polymers, especially in biomedical applications, are evaluated. The characterization, preparation, mechanism of action, and use of carbon quantum dots are discussed. Additionally, the known combinations of polymers and carbon quantum dots and their use in various industries are described.
Due to its slow degradation rate, polycaprolactone (PCL) is frequently used in biomedical applications. This study deals with the development of antibacterial nanofibers based on PCL and halloysite ...nanotubes (HNTs). Thanks to a combination with HNTs, the prepared nanofibers can be used as low-cost nanocontainers for the encapsulation of a wide variety of substances, including drugs, enzymes, and DNA. In our work, HNTs were used as a nanocarrier for erythromycin (ERY) as a model antibacterial active compound with a wide range of antibacterial activity. Nanofibers based on PCL and HNT/ERY were prepared by electrospinning. The antibacterial activity was evaluated as a sterile zone of inhibition around the PCL nanofibers containing 7.0 wt.% HNT/ERY. The morphology was observed with SEM and TEM. The efficiency of HNT/ERY loading was evaluated with thermogravimetric analysis. It was found that the nanofibers exhibited outstanding antibacterial properties and inhibited both Gram- (
) and Gram+ (
) bacteria. Moreover, a significant enhancement of mechanical properties was achieved. The potential uses of antibacterial, environmentally friendly, nontoxic, biodegradable PCL/HNT/ERY nanofiber materials are mainly in tissue engineering, wound healing, the prevention of bacterial infections, and other biomedical applications.
Breast cancer has become the most diagnosed cancer type, endangering the health of women. Patients with breast resection are likely to suffer serious physical and mental trauma. Therefore, breast ...reconstruction becomes an important means of postoperative patient rehabilitation. Polyvinyl alcohol hydrogel has great potential in adipose tissue engineering for breast reconstruction. However, its application is limited because of the lack of bioactive factors and poor structural stability. In this study, we prepared biodegradable polylactic acid-glycolic acid copolymer/polycaprolactone/gelatin (PPG) nanofibers. We then combined them with polyvinyl alcohol/collagen to create tissue engineering scaffolds to overcome limitations. We found that PPG fibers formed amide bonds with polyvinyl alcohol/collagen scaffolds. After chemical crosslinking, the number of amide bonds increased, leading to a significant improvement in their mechanical properties and thermal stability. The results showed that compared with pure PVA scaffolds, the maximum compressive stress of the scaffold doped with 0.9 g nanofibers increased by 500 %, and the stress loss rate decreased by 40.6 % after 10 cycles of compression. The presence of natural macromolecular gelatin and the changes in the pore structure caused by nanofibers provide cells with richer and more three-dimensional adsorption sites, allowing them to grow in three dimensions on the scaffold. So, the hydrogel scaffold by reinforcing polyvinyl alcohol hydrogel with PPG fibers is a promising breast reconstruction method.
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Carbohydrate polymers are promising materials for an eco-friendly future due to their biodegradability and abundance in nature. However, due to their molecular characteristics and hydrophilicity, are ...often complicated to be investigated via spectroscopic methods. Thermoplastic starch plasticized by glycerol was prepared through melt processing conditions using twin screw extruder. Here we show how the presence of water molecules affects the dielectric response and charge transport dynamics over broad frequency (10
−1
to 10
7
Hz) and temperature (− 140 to 150
o
C) ranges. Overall, 7 dielectric processes were observed and differentiation between electronic and ionic conductivities was achieved. Two segmental relaxation processes were observed for each sample, ascribed to the starch-rich and glycerol-rich phases. Although the timescales of the two segmental relaxations were found different, both arise from the same temperature, giving thus an alternative explanation on what is reported in the literature. The origin of the σ-relaxation was attributed to hydrogen ions and was found to be proportional to the ionic conductivity according to the Barton, Nakajima and Namikawa relation. The presence of water molecules was found to enhance the ionic conductivity, indicating that water contributes charge carriers when compared to the dried sample.
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