Sustainable Bioactive Packaging Based on Thermoplastic Starch and Microalgae

This study combines the use of corn starch and Tetradesmus obliquus microalgae for the production of antioxidant starch films as flexible packaging material. Starch was plasticized with glycerol and blended with 1 w% polyallylamine chosen as an agent to modify the film physical properties. The addition of polyallylamine improved film water stability and water vapor transmission rate as well as mechanical stiffness and tenacity. The dried Tetradesmus obliquus microalgae, which showed an EC₅₀ value of 2.8 mg/mg DPPH (2.2-Diphenyl-1-picrylhydrazyl radical), was then used as antioxidant filler. The addition of microalgae provided the films with good antioxidant activity, which increased with microalgae content increasing. To our knowledge, this is the first study reporting the development of sustainable bioactive packaging films composed of almost 100% starch, and follows the European union’s goals on plastics strategy concerning the promotion of bio-based, compostable plastics and the setting up of approaches to prevent food waste with a simple plastic packaging.     

Isolation and molecular characterization of antibiotic-resistant lactic acid bacteria from poultry and swine meat products

The transfer via the food chain from animals to humans of microbes that are resistant to antimicrobial agents is of increasing concern. To determine the contributions of nonpathogenic microflora to the occurrence and spread of antibiotic resistance (AR) genes in the food chain, 123 lactic acid bacteria were isolated from 29 samples of raw and processed pork and chicken meat products that had previously tested positive for one or more AR genes that encode clinically relevant ARs: tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), aac (6')-Ie aph (2")-Ia, mecA, and blaZ. All of the isolates were initially tested for their AR gene profiles by PCR. The 59 isolates carrying a tet, erm, or blaZ gene were taken through molecular identification, analyzed by determination of the MIC, and subjected to genetic fingerprinting. Lactococcus garvieae was the predominant species (28 isolates), followed by Lactobacillus plantarum (11 isolates) and L. salivarius (6 isolates), whereas Lactococcus lactis subsp. lactis, Lactobacillus johnsonii, L. reuteri, L. crispatus, and L. brevis were identified at lower frequencies. The tet(M) and erm(B) genes were the most frequently detected. Assessment of multiple resistances in 18 tet positive (tet+) isolates revealed that tet(M) plus erm(B) and tet(K) plus erm(B) were the most frequent AR gene patterns. Partial sequencing of the tet(M) open reading frame of three selected strains showed high sequence similarities (> 99%) with tet(M) genes previously found in human pathogens (Listeria monocytogenes and Neisseria meningitidis). Southern hybridization with plasmid profiles revealed these strains contained tet(M)-carrying plasmids.     

Exploring the impact of formulation and temperature shock on metered dose inhaler priming

The interplay between canister, valve design, formulation, and environmental temperature is crucial to dose retention in metered dose inhalers (MDIs). Previous studies that have utilized MDIs with polymeric capillary retention valves, have shown that exposure to environmental changes can create a temporary temperature gradient between the formulation retained in the metering chamber and the formulation reservoir in the metal canister, which can cause inconsistencies in the dose delivered to the patient. The purpose of this study was to more fully quantify these effects. This was achieved by deliberately varying the temperature difference between inhalers and environment within ranges representative of routine usage, and assessing the resulting loss of prime effect via shot weight and delivered dose testing.

The shot weights delivered by three fixed-dose commercial MDIs—Foster®, flutiform® and Seretide®, were investigated under different experimental conditions. Exposure to temperature changes of up to 15°C did not appear to affect unprimed shot weights (USW) or subsequent doses from the Foster product. In contrast, flutiform maintained prime at a temperature differential of 8.6°C, but delivered a low USW following exposure to a ΔT of 15°C under both realistic and controlled conditions. Seretide exhibited loss of prime at lower temperature differentials (ΔT 8.6°C) and a reduction in USW. The results suggest that the inclusion of ethanol in a solution-based formulation may inhibit loss of prime, leading to more robust performance in the face of temperature variations.

Delivered dose testing was carried out to assess the effect of loss of prime on the device ability to deliver a dose to within 80–120% of the label claim. The results suggest that the drainage of propellant from the metering chamber of suspension MDIs leaves active pharmaceutical ingredient (API) residue, causing an increase in subsequent doses once the prime has been restored. Taken together, the results provide valuable insight into the likely performance of MDIs subjected to routine daily use, highlighting design and formulation strategies that could be applied to make performance more robust.     

Macrocyclization of Organo‐Peptide Hybrids through a Dual Bio‐orthogonal Ligation: Insights from Structure–Reactivity Studies

Macrocycles constitute an attractive structural class of molecules for targeting biomolecular interfaces with high affinity and specificity. Here, we report systematic studies aimed at exploring the scope and mechanism of a novel chemo‐biosynthetic strategy for generating macrocyclic organo‐peptide hybrids (MOrPHs) through a dual oxime‐/intein‐mediated ligation reaction between a recombinant precursor protein and bifunctional, oxyamino/1,3‐amino‐thiol compounds. An efficient synthetic route was developed to access structurally different synthetic precursors incorporating a 2‐amino‐ mercaptomethyl‐aryl (AMA) moiety previously found to be important for macrocyclization. With these compounds, the impact of the synthetic precursor scaffold and of designed mutations within the genetically encoded precursor peptide sequence on macrocyclization efficiency was investigated. Importantly, the desired MOrPHs were obtained as the only product from all the different synthetic precursors probed in this study and across peptide sequences comprising four to 15 amino acids. Systematic mutagenesis of the “i?1” site at the junction between the target peptide sequence and the intein moiety revealed that the majority of the 20 amino acids are compatible with MOrPH formation; this enables the identification of the most and the least favorable residues for this critical position. Furthermore, interesting trends with respect to the positional effect of conformationally constrained (Pro) and flexible (Gly) residues on the reactivity of randomized hexamer peptide sequences were observed. Finally, mechanistic investigations enabled the relative contributions of the two distinct pathways (side‐chain→C‐end ligation versus C‐end→side‐chain ligation) to the macrocyclization process to be dissected. Altogether, these studies demonstrate the versatility and robustness of the methodology to enable the synthesis and diversification of a new class of organo‐peptide macrocycles and provide valuable structure–reactivity insights to inform the construction of macrocycle libraries through this chemo‐biosynthetic strategy.     

In situ growth of well-dispersed CdS nanocrystals in semiconducting polymers

A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2''-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)₂]₂·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications.     

Laser irradiation of ZnO:Al/Ag/ZnO:Al multilayers for electrical isolation in thin film photovoltaics

Laser irradiation of ZnO:Al/Ag/ZnO:Al transparent contacts is investigated for segmentation purposes. The quality of the irradiated areas has been experimentally evaluated by separation resistance measurements, and the results are complemented with a thermal model used for numerical simulations of the laser process. The presence of the Ag interlayer plays two key effects on the laser scribing process by increasing the maximum temperature reached in the structure and accelerating the cool down process. These evidences can promote the use of ultra-thin ZnO:Al/Ag/ZnO:Al electrode in large-area products, such as for solar modules.     

Photoactive sol–gel hybrid coatings from modified fluorocarbon polymers and amorphous titania

A series of organic–inorganic hybrid coatings was prepared through sol–gel chemistry by combining silanized chlorotrifluoroethylene-vinylether (FEVE) binders with tetraalkoxy silicon and titania sols under acidic conditions. The best compositions to obtain highly transparent and homogeneous coatings after thermal curing were determined. All the hybrid coatings easily pass the MEK test and show high scratch hardness. The atomic force microscopy (AFM) shows the formation of very smooth surfaces (R_rms routinely <1 nm) without clear phase separation phenomena. The typical size of the “objects” which may be individuated is in the range of 40–80 nm. Wettability through contact angle measurements shows the formation of moderately hydrophobic surfaces with a low contact angle hysteresis (~20°) which is a further indication of very smooth, homogeneous and chemically stable surfaces. After irradiation with UV-B light only hybrid coatings containing titania phases show a significant switch to a superhydrophilic behavior with a contact angle against H₂O down to 6°, which is only partially recovered after storage of the material in the dark. Titania based hybrid coatings also showed a fast and efficient UV-induced discoloration of the resazurin ink. The formulation of the coatings with photostabilizers belonging to the class of radical scavengers and UV absorbers does not change the photoinduced surface properties while eliminating the yellowing of the coating after UV exposure. It is concluded that titania-fluoropolymer hybrid coating show photoactivity and UV-induced superhydrophylicity mostly through ionic mechanisms, which could be beneficial to develop high durability and self-cleaning protective coatings.     

Wollastonite/hydroxyapatite scaffolds with improved mechanical,bioactive and biodegradable properties for bone tissue engineering

Wollastonite/hydroxyapatite composite scaffolds are proposed as bone graft. An investigation on scaffold with varying reinforcing wollastonite content fabricated by polymeric sponge replica is reported. The composition, sintering behavior, morphology, porosity and mechanical strength were characterized. All the scaffolds had a highly porous well-interconnected structure. A significant increase in mechanical strength is achieved by adding a 50% wollastonite phase. The most mechanically resistant (50/50) wollastonite/hydroxyapatite scaffolds were soaked in both simulated body fluid (SBF) and Tris–HCl solution in order to assess bioactivity and biodegradability. A carbo-hydroxyapatite layer formed on their surfaces when immersed in SBF. The biodegradability tests reveals that the composite scaffold shows a higher degradation rate compared to pure hydroxyapatite used as comparison. These results demonstrate that the incorporation of a 50% of wollastonite phase in hydroxyapatite matrix is effective in improving the strength and the bioactive and biodegradable properties of the porous scaffolds.     

Electrochemical anticorrosion performance evaluation of Al2O3 coatings deposited by MOCVD on an industrial brass substrate

Alumina (Al₂O₃) coatings of different thickness were deposited on OT59 brass substrate (BS) using the metal organic chemical vapour deposition (MOCVD) technique to evaluate the corrosion performance by EIS measurements. The used precursor was dimethyl-aluminium-isopropoxide. Electrochemical characterizations of the deposited films were performed in a standard very aggressive acidic solution (aerated 1N H₂SO₄ at 25 °C up to 168 h of immersion time) by means of direct current method (Tafel curves) and electrochemical impedance spectroscopy (EIS). The Rutherford backscattering spectroscopy (RBS) indicated that the films are very pure with the correct Al₂O₃ stoichiometry, while the IR absorption spectra showed that the films did not contain any OH groups. The surface film morphology was investigated by atomic force microscopy (AFM) and displayed a globular texture. The films were very smooth, with a maximum root mean square roughness, for example, of 14 nm for a 0.96 μm thick coating. The EIS data confirmed, as expected, that a 2.40 μm Al₂O₃ layer ensures the best corrosion protection after 168 h of immersion in the very acidic environment used.     

Cycling stability of a hybrid activated carbon//poly(3-methylthiophene) supercapacitor with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid as electrolyte

A long cycle-life, high-voltage supercapacitor featuring an activated carbon//poly(3-methylthiophene) hybrid configuration with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid, a solvent-free green electrolyte, was developed. The cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60 °C over 16,000 galvanostatic charge-discharge cycles at 10 mA cm⁻² in the 1.5 and 3.6 V voltage range. The reported average and maximum specific energy and power, specific capacitance and capacity, equivalent series resistance and coulombic efficiency over cycling demonstrate the long-term viability of this ionic liquid as green electrolyte for high-voltage hybrid supercapacitors.