Superhydrophobic cotton fabrics coated by chitosan and titanium dioxide nanoparticles with enhanced antibacterial and UV-protecting properties.

Superhydrophobic cotton fabrics were fabricated using chitosan/titanium dioxide (TiO2) nanocomposites. Morphology results revealed that the fabric's surface was utterly coated by the nanoparticles leading to the formation of a highly packed nano-scale structure in the case of superhydrophobic coating. X-ray photoelectron spectroscopy results also proved that TiO2 nanoparticles were highly adsorbed onto the fabric's top layer. Durability of the superhydrophobic coating was investigated by immersing the fabric into harsh solutions and also by subjecting the fabric to sonication. The results showed the high resistance of the superhydrophobic fabric against harsh conditions. The nanocomposite-coated fabrics were found to exhibit promising UV-protecting properties especially for the superhydrophobic fabric which showed around 80% enhancement in the UV protecting properties as compared with the uncoated fabric. The bacterial adhesion results revealed that the combination of chitosan and TiO2 results in high antibacterial properties against E. coli and S. aureus bacteria. The bacterial reduction percentages were further increased to 99.8 and 97.3% against E. coli and S. aureus, respectively, once the superhydrophobic character was also induced to the fabrics. The developed nanocomposite coated fabrics exhibited promising potential to be used as antibacterial and self-cleaning garments in hospital-related applications.

Preparation and characterization of polylactic-co-glycolic acid/insulin nanoparticles encapsulated in methacrylate coated gelatin with sustained release for specific medical applications.

This study aimed to examine the possibility of using insulin orally with gelatin encapsulation to enhance the usefulness of the drug and increase the lifespan of insulin in the body using polylactic-co-glycolic acid (PLGA) nanoparticles alongside gelatin encapsulation. In this regard, PLGA was synthesized via ring opening polymerization, and PLGA/insulin nanoparticles were prepared by a modified emulsification-diffusion process. The resulting nanoparticles with various amounts of insulin were fully characterized using FTIR, DSC, DLS, zeta potential, SEM, and glucose uptake methods, with results indicating the interaction between the insulin and PLGA. The process efficiency of encapsulation was higher than 92%, while the encapsulation efficiency of nanoparticles, based on an insulin content of 20 to 40%, was optimized at 93%. According to the thermal studies, the PLGA encapsulation increases the thermal stability of the insulin. The morphological studies showed the fine dispersion of insulin in the PLGA matrix, which we further confirmed by the Kjeldahl method. According to the release studies and kinetics, in-vitro degradation, and particle size analysis, the sample loaded with 30% insulin showed optimum overall properties, and thus it was encapsulated with gelatin followed by coating with aqueous methacrylate coating. Release studies at pH values of 3 and 7.4, alongside the Kjeldahl method and standard dissolution test at pH 5.5, and glucose uptake assay tests clearly showed the capsules featured 3-4 h biodegradation resistance at a lower pH along with the sustained release, making these gelatin-encapsulated nanoparticles promising alternatives for oral applications.[Figure: see text].

Enhanced compatibility of starch with poly(lactic acid) and poly(ɛ-caprolactone) by incorporation of POSS nanoparticles: Study on thermal properties.

In this work, we explore the ability of polyhedral oligomeric silsesquioxane (POSS) nanoparticles to increase the compatibility of hydrophilic starch with hydrophobic poly(lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL). Morphological analysis demonstrated that lower contents of POSS (0.5 and 1 wt%) enhances the compatibility of the system. However, higher inclusion of POSS results in the formation of aggregates and thus a lower level of compatibility. Transmission electron microscopy revealed that PCL acts as an intermediate between PLA and starch, and that POSS is primarily localized within the PLA and PCL phases. Based on differential scanning calorimetry, PLA's crystallinity increases from 22.9% to 31.6% upon adding a very low content of POSS (0.5 wt%). However, the PCL's crystallinity is slightly hampered due to formation of these PLA crystallites. In contrast with the crystallization behavior and based on the thermal degradation kinetics, we found the composite's thermal stability is greatly increased when moderate to high contents (3 and 5 wt%) of POSS are utilized. Dynamic mechanical analysis results also confirmed good POSS dispersion within the matrix, especially at lower contents. In conclusion, POSS serves as an efficient compatibilizer for PLA/starch/PCL systems with improved thermal properties.

Preparation and Characterization of Composite Blends Based on Polylactic Acid/Polycaprolactone and Silk.

Silk-reinforced polylactic acid/poly ε-caprolactone composites containing 1-7 wt % of silk fibers were fabricated through the melt-mixing method. The composites were then characterized by implementing Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and rheometry to investigate functional groups, thermal properties, rheological properties, and intrinsic viscosities of each composite. The crystallinity of the composites was found to decrease upon addition of silk, while, both storage modulus ( G') and loss modulus ( G″) were increased which is an indication of interface bonding between the polymer and silk. The composite containing 5% silk fiber (PLACLS5) showed the optimum results. The composites' morphological analysis was conducted by scanning electron micrograph coupled with energy dispersive X-ray (SEM-EDX) mapping to assess the fiber dispersion in the composite matrix. The contact angle measurements and in vitro degradation were performed to evaluate the hydrophilicity, free surface energy, and hydrolytic degradation of the composites. The results implied that addition of higher contents of silk fiber could reduce the degradation duration of the composites, which is due to the high hydrophilicity of the fiber, uniform fiber dispersion within the matrix, the porous structure, and consequently, the hydrophilic behavior of the composites. These composites can be great alternatives for both soft and hard tissue engineering applications.

Optimization simulated injection molding process for ultrahigh molecular weight polyethylene nanocomposite hip liner using response surface methodology and simulation of mechanical behavior.

In this study, injection molding process of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with nano-hydroxyapatite (nHA) was simulated and optimized through minimizing the shrinkage and warpage of the hip liners as an essential part of a hip prosthesis. Fractional factorial design (FFD) was applied to the design of the experiment, modeling, and optimizing the shrinkage and warpage of UHMWPE/nHA composite liners. The Analysis of variance (ANOVA) was applied to find the importance of operative parameters and their effects. In this experiment, seven input parameters were surveyed, including mold temperature (A), melt temperature (B), injection time (C), packing time (D), packing pressure (E), coolant temperature (F), and type of liner (G). Two models were capable of predicting warpage and volumetric shrinkage (%) in different conditions with R2 of 0.9949 and 0.9989, respectively. According to the models, the optimized values of warpage and volumetric shrinkage are 0.287222 mm and 13.6613%, respectively. Meanwhile, a finite element analysis (FE analysis) was also carried out to examine the stress distribution in liners under the force values of demanding and daily activities. The Von-Mises stress distribution showed that both of the liners can be applied to all activities with no failure. However, UHMWPE/nHA liner is more resistant to the highest loads than UHMWPE liner due to the effect of nHA in the nanocomposite. Finally, according to the results of injection molding simulations, optimization, structural analysis as well as the tensile strength and wear resistance, UHMWPE/nHA liner is recommended for the production of a hip prosthesis.

Simulation of mechanical behavior and optimization of simulated injection molding process for PLA based antibacterial composite and nanocomposite bone screws using central composite design.

In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws.

Interface modified polylactic acid/starch/poly ε-caprolactone antibacterial nanocomposite blends for medical applications.

In this study, an optimized interface-modified ternary blend with antibacterial activity based on polylactic acid/starch/poly ε-caprolactone (PLASCL20), mixed with nano hydroxyapatite (nHA) via melt blending. This method results in a homogeneous nanocomposite blend in which the addition of 3% nHA improves the overall properties such as hydrolytic degradation, hydrophilicity, antibacterial activity and the drug release comparing to PLASCL20. Moreover, the simultaneous use of nHA and encapsulated triclosan (LATC30) compensated the negative effect of triclosan through increasing the possible cell attachment. According to the contact angle results, nHA was thermodynamically driven into the interface of PLA and PCL/Starch phases. The addition of 3% nHA showed a good adjustment between the hydrolytic degradation and the release profile, therefore, their electrospun microfibers demonstrated an improved fibroblast (L929) cell attachment. The aforementioned nanocomposite blend is a suitable antibacterial candidate for many medical applications with minimum side effects due to the controlled release of triclosan.

Enhanced hydrophobicity of polyurethane via non-solvent induced surface aggregation of silica nanoparticles.

Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface's top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique "triple-sized" structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method.

Tuning cell adhesion on polymeric and nanocomposite surfaces: Role of topography versus superhydrophobicity.

Development of surface modification procedures which allow tuning the cell adhesion on the surface of biomaterials and devices is of great importance. In this study, the effects of different topographies and wettabilities on cell adhesion behavior of polymeric surfaces are investigated. To this end, an improved phase separation method was proposed to impart various wettabilities (hydrophobic and superhydrophobic) on polypropylene surfaces. Surface morphologies and compositions were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Cell culture was conducted to evaluate the adhesion of 4T1 mouse mammary tumor cells. It was found that processing conditions such as drying temperature is highly influential in cell adhesion behavior due to the formation of an utterly different surface topography. It was concluded that surface topography plays a more significant role in cell adhesion behavior rather than superhydrophobicity since the nano-scale topography highly inhibited the cell adhesion as compared to the micro-scale topography. Such cell repellent behavior could be very useful in many biomedical devices such as those in drug delivery and blood contacting applications as well as biosensors.

Investigating the role of surface micro/nano structure in cell adhesion behavior of superhydrophobic polypropylene/nanosilica surfaces.

The main aim of the current study was to investigate the effects of different topographical features on the biological performance of polypropylene (PP)/silica coatings. To this end, a novel method including combined use of nanoparticles and non-solvent was used for preparation of superhydrophobic PP coatings. The proposed method led to a much more homogeneous appearance with a better adhesion to the glass substrate. Moreover, a notable reduction was observed in the required contents of nanoparticles (100-20 wt% with respect to the polymer) and non-solvent (35.5-9 vol%) for achieving superhydrophobicity. Surface composition and morphology of the coatings were also investigated via X-ray photoelectron spectroscopy and scanning electron microscopy. Based on both qualitative and quantitative evaluations, it was found that the superhydrophobic coatings with only nano-scale roughness strongly prevented adhesion and proliferation of 4T1 mouse mammary tumor cells as compared to the superhydrophobic surfaces with micro-scale structure. Such results demonstrate that the cell behavior could be controlled onto the polymer and nanocomposite-based surfaces via tuning the surface micro/nano structure.