Biological evaluation of chitosan‐based in situ‐forming hydrogel with low phase transition temperature

The aims of current study were to choose a method for preparing sterile chitosan‐α,β‐glycerophosphate (CS‐α,β‐GP) in situ‐forming hydrogel which had potential applications in tissue engineering and evaluated its biocompatibility and degradation characteristics. The results of sterilization stability tests indicated that sterile formulations could be obtained by ultraviolet irradiation of CS powders, 0.22 µm filtration of α,β‐GP and lactic acid solutions, and sterile preparation of CS‐α,β‐GP formulations. The obtained sterile CS‐α,β‐GP formulations showed low hemolysis rates and low BSA adsorption at physiological conditions. When injected in vivo the CS‐α,β‐GP sol turned into gel implant in situ and could be degraded gradually. A minimal inflammatory reaction which could not be found by macroscopic evaluation was induced after injection and new capillary formation was found around the hydrogel humps, making the CS‐α,β‐GP hydrogel worthwhile to be considered for tissue engineering and biomedical applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41594.     

Evaluation of macrophage injury and activation by amphotericin B-loaded polymeric nanoparticles

The objectives of present work were to prepare water soluble nanoformulation of amphotericin B by radical polymerization using N-isopropylacrylamide–acrylic acid and vinyl pyrrolidone for targeted delivery and minimized toxicity in mild experimental conditions with relatively narrow size distribution. The prepared formulations were extensively characterized in terms of size, morphology, thermal stability, drug loading and toxicity. The results demonstrates that the prepared nanoformulation have the potential to deliver amphotericin B with increased bioavailability and cellular uptake.     

Babassu Biodiesel Doped with Antioxidants: Assessment of Thermo-Oxidative Stability by Borchardt and Daniels Method

In this study, three antioxidants namely N,N′-di-sec-butyl-p-phenylenediamine (PDA), 2,4,6-Tri-tert-butylphenol/2,6-Di-tert-butylphenol (IONOL), and unsaturated cardanol (U-CDN) were added to babassu biodiesel (BB) at a concentration of 100 mg kg⁻¹ to improve its oxidative stability. Differential Scanning Calorimetry (DSC) was used to evaluate the oxidative stability of the samples using synthetic air atmosphere and two temperatures (25 and 110 °C) instead of the conventional Rancimat method. The kinetic parameters were calculated according to Borchardt and Daniels method (ASTM E2041). All doped samples showed higher thermo-oxidative stability when compared to pure babassu biodiesel with increasing activation energies of 66.5% for PDA, 19.4% for IONOL, and 3.9% for U-CDN. At 25 °C, the babassu biodiesel showed a high oxidation reaction rate of 1.76 × 10⁻¹⁵ min⁻¹. For the doped samples at the same temperature, that rate was reduced by a factor of 2, 200, and 3 × 10⁸ times for U-CDN, IONOL, and PDA, respectively. At 110 °C, the BB and the BB + U-CDN samples showed high reaction rates, whereas the formulations with IONOL and PDA had rates reduced by 10 and 7.4 × 10³ times, respectively. The thermal data showed R² values higher than 0.99. All results confirmed the action of the antioxidants in retarding oxidation reactions in biodiesel. DSC is a promising alternative method for the determination of oxidative stability of biodiesel and its formulations with antioxidants.     

Preparation and properties of a novel high‐performance resin system with low injection temperature for resin transfer moulding

A novel high‐performance resin system with low injection temperature for resin transfer moulding, M4506, was developed, which was made of 4,4′‐bismaleimidodiphenylmethane, o,o′‐diallyl bisphenol A, o,o′‐diallyl bisphenol A ether, and 1,1′‐bis(4‐cyanatophenyl)ethane. The processing characteristics, thermal and mechanical properties of the system were studied, and the effect of differing stoichiometries of each component on the processing and performance parameters was discussed. Investigations show that the processing properties of the M4506 system are greatly dependent on the stoichiometries of each component in the formulations, while all the three formulations developed in this paper have good processing characteristics, their suitable injection temperature are between 40 and 50 °C, depending on their respective formulation. The three formulations exhibited outstanding heat resistance (T_g = 294–300 °C) and thermal stability, good toughness and high strength, evidence that the M4506 system is a potential candidate as a high‐performance RTM matrix for advance composites as well as high‐performance paints with no solvents. Copyright © 2004 Society of Chemical Industry     

Biopolymer-based microparticles for encapsulation of all-trans-retinoic acid

This work aims to investigate the potential of complex coacervation technique to encapsulate and protect all-trans retinoic acid (RA). Gelatin and κ-carrageenan were used as wall material and pequi oil was employed as a hydrophobic phase. Three formulations with different protein: polysaccharide ratio and pH were defined to produce the microparticles based on the zeta potential and turbidity analysis: (F1) ratio 3:1 and pH 3.5, (F2) ratio 8:1 and pH 3.5, and (F3) ratio 8:1 and pH 5.0. Microparticles were evaluated regarding their morphology, yield, encapsulation efficiency (EE), and stability. The properties of microparticles were mainly affected by the protein: polysaccharide ratio and the turbidity of the mixtures, which is directly related to the protein-polysaccharide interaction. Formulation 1 showed the optimal values of yield (75.6%), EE (100.2%), and stability (85% of the encapsulated RA remained in the particle). The results demonstrated the high potential of this innovative technique to encapsulate RA for a future application in topical formulations.     

Palm oil‐based organogels and microemulsions for delivery of antimicrobial drugs

This study has been designed to develop palm oil (PO) based organogels using span 80/tween 80 mixture (OG) as a gelator system by fluid‐filled structure mechanism. The results suggested formation of organogels, emulsions, and microemulsions as the proportions of PO, OG and water were varied. The emulsions were found to be thermodynamically unstable as compared to the organogels and the microemulsions. Accelerated thermal stability test suggested that all the microemulsions and the organogels of only eight compositions were stable. The organogels showed viscoelastic property while the microemulsions showed viscous flow behavior. Both the organogels and the microemulsions were found to be highly hemocompatible and nonirritant. The antimicrobial efficiency of the ciprofloxacin HCl‐loaded formulations showed equivalent efficiency as compared to marketed formulations. The rates of drug release from the organogels were found to be relatively slower as compared to the microemulsions. The preliminary studies suggested that the developed organogel and microemulsion‐based formulations may be tried for topical delivery of antimicrobials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39979.     

Development and application starch films: PBAT with additives for evaluating the shelf life of Tommy Atkins mango in the fresh-cut state

In this study, formulations of cassava starch and poly(butylene adipate-co-terephthalate) flexible films were developed, with glycerol, coconut nanocellulose, annatto, and citric acid in different concentrations, as well as the effectiveness of the selected materials in fresh-cut mangoes storage was evaluated. The tensile strength of the different formulations varied from 1.90 (E4) to 6.65 MPa (E3c), and the strain varied from 206.31 (E1c) to 278.41% (E8); this variation was dependent on the percentage of the polymer matrix incorporated. The a_w values of the formulations ranged from 0.396 (E2) to 0.569 (E3c). The Formulations E4 and E7 (with additives) presented good properties and were selected to condition mangoes. The micrographs of these films showed regions of micropores that can facilitate the diffusion of water from the packaged product to the surface, allowing decreases in moisture and a_w, which is associated with higher color maintenance during fruit storage. E7 presented better barrier properties than E4 (lower values of WVP and water solubility) which may have influenced in a positive way to maintain the stability of the package in the studied period. E7 can be considered as a viable alternative for minimally processed mango storage. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48150.     

Effect of intercalating agents on clay dispersion and thermal properties in polyethylene/montmorillonite nanocomposites

Alkyl pyridinium, 1‐vinyl alkyl imidazolium, 1,3‐dialkyl imidazolium, and tetraalkyl phosphonium bromides were successfully used as intercalants for the preparation of highly thermally stable organophilic montmorillonites. Nanocomposites of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE/LLDPE‐g‐MAH) were prepared from those organoclays. The micro‐ and nano‐dispersions were analyzed through X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM): intercalation and/or partial exfoliation were found to occur only for formulations based on organoclays having an initial basal distance higher than 20 Å, suggesting the existence of a critical interfoliar distance for the delamination of silicate layers in a noninteracting polymer matrix. The properties of the nanocomposites were analyzed through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and oscillatory rheometry. The dynamic crystallization of LLDPE was not significantly affected by the presence of clay. TGA in oxidative atmosphere proved to be very sensitive to the dispersion state of the organoclay: the thermal stability was drastically enhanced for intercalated and partially exfoliated formulations. However, the inherent thermal stability of the organoclay did not appear to influence significantly the overall thermal stability of the composite in the range of temperatures investigated (160–230°C). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Burkholderia multivorans SB6 Lipase as a Detergent Ingredient: Characterization and Stabilization

In this study, 265 bacterial isolates were collected from kitchen wastewater samples using Rhodamine B agar medium. Of these, 115 isolates were found to respond positively to the addition of commercial detergents. Using 16S rRNA sequence analysis, the isolate demonstrating the high stability towards commercial detergents was identified as Burkholderia multivorans. An SB6 lipase with a molecular mass of 70 kDa was purified from B. multivorans. The purified enzyme showed optimal activity at pH 9.0 and 40 °C and remained stable in the presence of various metal ions, surfactants, and oxidizing agents. The addition of boron compounds improved the pH stability and thermostability of the enzyme, which displayed stability against some commercial detergents; moreover, this stability increased when boron compounds were added to the incubation medium as stabilizers. These properties make SB6 lipase an ideal choice as an additive in detergent formulations.     

Trichoderma harzianum‐based novel formulations: potential applications for management of Next‐Gen agricultural challenges

Fungi of the Trichoderma spp. genus, notably Trichoderma harzianum, are commonly used for biological management of deleterious seed‐ and soil‐borne pathogens. The global biopesticides market is booming with a major share of various commercial formulations of T. harzianum. However, there are some major drawbacks associated with these commercial formulations including short shelf life, low on‐field stability and irregular performance in different agro‐climatic regions. For effectively resolving these issues, new strategies are urgently required for efficient management of pathogens. The present review provides an overview of the use of Trichoderma spp., with special emphasis on T. harzianum, and discusses future trends for biological control. Technologies are described for the microencapsulation of fungi and for the biogenic synthesis of nanoparticles, with the aim of improving the biological control of pathogens and contributing to sustainable agricultural practices. © 2018 Society of Chemical Industry     

The interaction of hydrogen sulfide with lead- and barium–cadmium–zinc-stabilized poly(vinyl chloride)

Poly(vinyl chloride) polymers stabilized with tribasic lead sulfate discolor upon exposure to hydrogen sulfide gas as a result of lead sulfide formation. The discoloration occurs for samples in both cord and sheet forms and is shown to be a function of total H₂S exposure, reaching a limiting value that is determined by the amount of lead stabilizer used in the polymer formulation. The permeation and diffusion constants for H₂S through PVC stabilized with tribasic lead sulfate and with a liquid Ba–Cd–Zn formulation are found to be P_Pb = (6.0 ± 0.2) × 10^?9, P_BaCdZn = (5.2 ± 0.2) × 10^?9 (both in cm³ gas?cm film/cm² area?sec?cm Hg), D_Pb = (1.3 ± 0.2) × 10^?7 cm²/sec, and D_BaCdZn = (6.4 ± 0.6) × 10^?8 cm²/sec, all measured at 21°C. The stabilizing efficiencies of the formulations were assessed by HCl evolution measurements, which show that exposure to H₂S decreases the initial polymer stability for both Pb-stabilized and Ba–Ca–Zn-stabilized formulations. Protection of stabilized PVC formulations from diffusing hydrogen sulfide is thus advisable for long-term stability as well as for color integrity.     

Ethylene-vinyl acetate (EVA) encapsulants for photovoltaic modules: Degradation and discoloration mechanisms and formulation modifications for improved photostability

Long-term photothermal stability is needed for the polymeric encapsulants made of ethylenevinyl acetate (EVA) copolymer used in crystalline-silicon (c-Si) based photovoltaic (PV) modules. Severe browning of EVA was observed in late 1980s on Carrisa Plains PV arrays installed with reflecting mirrors and resulted in large losses of the power output. The EVA browning crisis prompted NREL scientists in 1990 to investigate the problems and search for solutions. The key degradation mechanisms and discoloration factors were investigated by using a variety of film samples, including field-degraded EVA samples and two commercial EVA formulations, regular-cure A9918 and fast-cure 15295, that were laminated, cured, and subjected to accelerated environmental exposures. Chemical, thermogravimetric, absorption/transmission, colorimetric, and fluorescence analyses were employed to characterize the EVA samples. Current-voltage (I-V) measurements were used to determine the electrical performance characteristics of solar cells. The results show that photothermal degradation is greater than thermal degradation and that the EVA A9918 discolors earlier and faster than EVA 15295. The UV absorber, Cyasorb UV 531,^TM in commercial formulations decomposes photochemically and its decomposition rate is directly related to the temporal evolution of discoloring polyenic chromophores. In general, the loss rate of the UV absorber and the progress of EVA discoloration from light yellow to brown follow a sigmoidal pattern. Physically, UV-filtering glass superstrates that remove UV ≤ 350 nm effectively reduce the discoloration rate of both commercial EVA formulations. Chemically, the EVA discoloration rate is affected by a number of factors, but more strongly by the formulation additives and curing conditions, in which additives and curinggenerated chromophores and their concentrations show a synergistic discoloring effect. Photobleaching reactions are responsible for the non-discolored but degraded EVA because of oxidative destruction of the curing-generated chromophores in the presence of oxygen. By using specifically selected stabilizers and curing agents in the new formulations, a large reduction in the chromophore generation by curing has been achieved and resulted in significant improvement of the photostability against discoloration.     

Synthesis of two PET waste derived bisacrylic and bisallylic monomers and their potential use as crosslinking agents and dental resin composites

Two novel bifunctional monomers obtained from PET waste glycolisis are reported. Bis(2‐(acryloyloxy)ethyl) terephthalate and bis(2‐(((allyloxy)carbonyl)oxy)ethyl) terephthalate (BACET) monomers were obtained from bis(hydroxyethyl) terephthalate derived from PET waste and acryloyl chloride and allyl chloroformate, respectively. The monomers were characterized by FTIR and ¹H‐NMR spectroscopies. They were evaluated as crossslinking agents for acrylic acid (AA) and methacrylic (MA) acids using thermally initiated polymerization. The obtained copolymers showed higher thermal stability than the acrylic homopolymers. They were also tested for dental formulations as Bis‐GMA substitutes in heat curing resin composites. In spite of its lower reactivity, only BACET was able to substitute Bis‐GMA, due to its high solubility in the TEGDMA comonomer. Resin formulations containing nanosized silica and the mixture Bis‐GMA/TEGDMA or BACET/TEGDMA were prepared in order to compare physical and chemical properties. Water sorption, solubility, and flexural strength were found statistically similar for both formulations. However, flexural modulus was lower and double bond conversion was higher for the BACET resin, which could make it appropriate for its potential use in dental resin composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41487.     

Reaction and thermal behavior of vitrimer-like polyhydroxy esters based on polyethylene glycol diglycidyl ether

Vitrimers-like polyhydroxy esters networks were thermally synthesized from mixtures of the diepoxide monomer diglycidyl ether polyethyleneglycol (DGEPEG), citric (CA), and sebacic acids (SA), using zinc acetate in proportions of 1 to –5 mol%. as catalyst for bond exchange reactions. Reaction of DGEPEG with the acids is exothermic with enthalpy up to 326 J/g and takes place even without any catalyst. The progress of the reaction is reduced as the content of SA is increased in the formulations, but reaction enthalpy in mixtures containing 1% of Zn catalyst is higher than those with 5%mol Zn. These polyhydroxy esters networks are rubber-like materials with T_g varying from −24 to −43°C, with formulations containing SA showing the lowest T_g values. The presence of ester and hydroxyl groups and Zn catalyst in the polymers give rise to exchange reactions similar to those shown by vitrimers. However, the increase in Zn concentration from 1% to 5%, arouses a loss of thermal stability of these materials.     

Diffusion of amine stabilizers in vulcanized natural rubber compositions used in tires

The diffusion of amine stabilizers in vulcanized natural rubber formulations used in tires was investigated. Experiments were undertaken using a “sandwich” system composed of a sample disk containing the additive (source disk) between two external disks of nonadditivated rubber (reception disks). Diffusion coefficients (D) were calculated from the experimental migration curves following the Boltzman–Matano model. Theoretical diffusion curves for the additives were obtained according to the limited extension source in an infinite medium. Experimental data showed reasonable fitting with the theoretical curves, suggesting that D does not depend on the additive concentration. Thermooxidative stability data for the vulcanized rubber containing the additives showed no correlation to the diffusion process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 670–676, 2000     

Modeling the constant amplitude fatigue behavior of adhesively bonded pultruded GFRP joints

The constant amplitude fatigue behavior of adhesively bonded pultruded glass fiber reinforced polymer double-lap joints were modeled by a number of conceptually different phenomenological S–N (cyclic stress vs. number of cycle) formulations. An extended database containing constant amplitude fatigue data under tension (R?=?0.1), compression (R?=?10), and reversed loading (R?=??1) were analyzed in order to investigate whether or not there exists an appropriate fatigue formulation for accurate modeling of the behavior of the examined joints throughout their lifetime, from the very low-cycle fatigue to the high-cycle fatigue regions. Based on an extensive review, appropriate fatigue formulations that take into account the probabilistic nature of lifetime measurements were selected and their fundamental assumptions were examined. The validity of the statistical assumptions of these models was found to be influenced by the applied loading conditions. The modeling results were similar for all selected fatigue formulations with the derived S–N curves exhibiting differences mainly in the low- and high-cycle fatigue regimes. The formulations insensitive to the scatter in the experimental data were found to be the most appropriate models.     

A Comparison of the Deposition Patterns of Different Nasal Spray Formulations Using a Nasal Cast

For nasally delivered medications, it is quite a challenge in the formulation development to characterize the deposition pattern in vivo. An in vitro nose model has been developed recently and adopted in our study to compare the deposition pattern of different nasal solution formulations. One low-viscosity nasal solution and five other solutions containing either Avicel or hydroxypropyl methylcellulose (HPMC) as the viscosity enhancers were examined in this study. The viscosity, spray pattern, plume geometry, and droplet size were characterized. The in vitro deposition patterns were assessed using an anatomically correct silicone nasal cast combined with a color-based image-analysis method. The correlations between the formulation variables, the spray characteristics, and the deposition pattern were investigated. The addition of each viscosity enhancer resulted in increasing viscosity, larger droplet size, narrower plume angle, and lesser anterior deposition. However, it appears that the changes in spray characteristics and deposition pattern are influenced heavily by the identity of the viscosity enhancer, rather than merely by the formulation viscosity itself. Although the Avicel additions led to larger increases in the formulation viscosity, the HPMC additions had far greater impact on the spray characteristics and deposition pattern. The formulations with suboptimal deposition patterns, i.e., the formulations with ‘forward’ or ‘backward’ dripping, were successfully identified in this study. This in vitro method was able to discriminate between formulations, revealing differences in regional deposition and the tendency of formulations to drip. As such, the nasal cast method is recommended as a valuable tool for the development of nasal spray formulations.     

Thermal stability evaluation of polypropylene protected with grafted amine

Summary Polypropylene containing a grafted amine as oxidation protector was subjected to γ-irradiation for the evaluation of thermal stability. Several formulations were prepared containing hindered amine, Sanduvor PR 31 (0.1, 0.2 and 0.3% w/w) and CaCO₃ (0.6% w/w). The stability assessment was carried out in air by oxygen uptake procedure under isothermal and isobaric conditions (165 °C and normal pressure, respectively). The exposure doses were placed in the range from 0 to 70 kGy. The changes appeared in the main kinetic parameters (oxidation induction time and oxidation rate) evaluated for thermal degradation of irradiated PP specimens are presented and the stability analysis is explained starting from the behaviour differences of various formulations of radiation processed polypropylene. On the low dose range, the drop in thermal stability of modified polypropylene films occurs more abrupt than it was observed for the samples irradiated at higher doses.     

An Enhanced Water Solubility and Stability of Anthocyanins in Mulberry Processed with Hot Melt Extrusion

Mulberry fruits are rich sources of anthocyanins that exhibit beneficial biological activity. These anthocyanins become instable in an aqueous media, leading to their low bioavailability. In this study, a colloidal dispersion was produced by processing mulberry samples with hot-melt extrusion. In this process, hydrophilic polymer matrices were used to disperse the compound in an aqueous media. Mulberry samples were processed with hot-melt extrusion and in the presence of an ionization agent and sodium alginate to form mulberry-extrudate solid formulations. The particle size of mulberry-extrudate solid formulations decreased, while the total phenol content, the total anthocyanin content, and solubility increased. Fourier transform infrared spectroscopy (FT-IR) revealed that mulberry-extrudate solid formulations now contained new functional groups, such as –COOH group. We investigated whether mulberry-extrudate solid formulations had a positive impact on the stability of anthocyanins. The non-extrudate mulberry sample and mulberry-extrudate solid formulations were incubated with a simulated gastric fluid system and an intestinal fluid system. The number of released anthocyanins was determined with HPLC. We found that anthocyanins were released rapidly from non-extrudate mulberry extract. Mulberry-extrudate solid formulations contained a large number of available anthocyanins even after being incubated for 180 min in the intestinal fluid system. Thus, hot-melt extrusion enhanced water solubility and stability of anthocyanins with the prolonged release.     

Garlic oil–loaded PLGA nanoparticles with controllable size and shape and enhanced antibacterial activities

The present work focuses on producing polymer composite nanoparticles (NPs) composed of garlic oil (GO) and poly(lactic‐co‐glycolic) acid (PLGA) by the single emulsion/solvent evaporation (SE/SE) method and high‐speed homogenizing. Different preparation parameters were found to greatly affect the stability and size uniformity of the prepared PLGA/GO NP formulations, which were carefully controlled. Scanning electron microscopy, Fourier transform infrared spectroscopy, and UV–vis spectroscopy and dynamic light scattering and zeta potential were used to characterize the NPs. Antibacterial assessment of the prepared PLGA/GO NPs against E. coli and S. aureus was carried out. Interestingly, the NP size ranged between 201 and 319 nm, which is 10 times less than the size of the regular GO particles in bulk solution. The antibacterial activities show enhancement by 70–78% of bacterial inhibition compared with a GO bulk solution. This work sheds light on the potential use of GO NP formulations as nanobiotics and the critical NP preparation parameters that need to be considered. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46133.