High-Barrier and Antioxidant Poly(lactic acid)/Nanocellulose Multilayered Materials for Packaging.

In the current context, the development of bio-based and high-performance materials is one of the main research priorities. This study aims to combine the outstanding properties of cellulose nanofibrils (CNFs) or nanocrystals (CNCs) with those of bio-based poly(lactic acid) (PLA). Three-phase multilayered materials (TMLs) were built up by complexing a dry CNF- or CNC-based film with two PLA sheets, using a heat-pressing process. Before the preparation of the nanocellulosic films, CNFs and CNCs were modified by the adsorption of a rosin-based nanoemulsion. The rosin mixture as a natural compound is of interest because of its low cost, renewability, hydrophobicity, and its antimicrobial and antioxidant properties. After demonstrating the efficiency of the complexing procedure, we investigated the barrier properties of the multilayered materials against both oxygen and water vapor, with highly encouraging results. In fact, the presence of nanocellulose as an inner layer between the two PLA films significantly enhanced the oxygen barrier, with a decrease in oxygen permeability comprised between 84 and 96% and between 44 and 50% for neat nanocelluloses and nanocelluloses with rosins as the inner layer, respectively. On the other hand, the antioxidant properties of the final multilayered materials including rosins were highlighted, with a highly encouraging radical scavenging activity close to 20%. Because of the simplicity and the efficiency of the proposed method, this study paves the way toward the development of hybrid multimaterials that could be highly attractive for food packaging applications.

Screen-Printed Polyaniline-Based Electrodes for the Real-Time Monitoring of Loop-Mediated Isothermal Amplification Reactions.

Nucleic acid amplification testing is a very powerful method to perform efficient and early diagnostics. However, the integration of a DNA amplification reaction with its associated detection in a low-cost, portable, and autonomous device remains challenging. Addressing this challenge, the use of screen-printed electrochemical sensor is reported. To achieve the detection of the DNA amplification reaction, a real-time monitoring of the hydronium ions concentration, a byproduct of this reaction, is performed. Such measurements are done by potentiometry using polyaniline (PAni)-based working electrodes and silver/silver chloride reference electrodes. The developed potentiometric sensor is shown to enable the real-time monitoring of a loop-mediated isothermal amplification (LAMP) reaction with an initial number of DNA strands as low as 10 copies. In addition, the performance of this PAni-based sensor is compared to fluorescence measurements, and it is shown that similar results are obtained for both methods.

Studies of interactions between silane coupling agents and cellulose fibers with liquid and solid-state NMR.

The hydrolysis of three alkoxy-silane coupling agents, gamma-methacryloxypropyl trimethoxy silane (MPS), gamma-aminopropyl triethoxy silane (APS), and gamma-diethylenetriaminopropyl trimethoxy silane (TAS), was carried out in ethanol/water solutions (80/20 w/w) at different pH values and followed by 1H, 13C and 29Si NMR spectroscopy. Acidic media were found to stabilize the hydrolyzed forms. As expected, the formation of silanol groups was followed by their self-condensation to generate oligomeric structures, yielding, ultimately, solid homopolycondensated structures, as analyzed by 29Si and 13C high-resolution solid-state NMR. Hydrolyzed MPS in acidic media was then successfully adsorbed onto a cellulose surface and the ensuing substrates submitted to thermal treatment at 110-120 degrees C under reduced pressure, in order to create covalent bonds between cellulose and the coupling agent.