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Deep eutectic solvents (DESs) have been intensively investigated in recent years for their antibacterial properties, with DESs that comprise organic acids (OA-DESs) showing promising antibacterial action. However a majority of the reports focused only on a limited number strains and techniques, which is not enough to determine the antibacterial potential of a substance. To bridge this gap, the antibacterial activity of classical DESs and OA-DESs is assessed on twelve Gram-negative and Gram-positive bacteria strains, with some of them exhibiting specific resistance toward antibiotics. The investigated formulations of OA-DESs comprise glycolic, malic, malonic, and oxalic acids as representatives of this group. Using a range of microbiological assays as well as physicochemical characterization methods, a major difference of the effectiveness between the two groups is demonstrated, with OA-DESs exhibiting, as expected, greater antibacterial effectiveness than classical DESs. Most interestingly, slight differences in the minimum inhibitory and bactericidal concentration values as well as time-kill kinetics profiles are observed between Gram-positive and Gram-negative strains. Transmission electron microscopy analysis reveals the effect of the treatment of the bacteria with the representatives of both groups of DESs, which allows us to better understand the possible mechanism-of-action of these novel materials., (© 2024 Wiley‐VCH GmbH.)

Shapeable and flexible pressure sensors with superior mechanical and electrical properties are of major interest as they can be employed in a wide range of applications. In this regard, elastomer-based composites incorporating carbon nanomaterials in the insulating matrix embody an appealing solution for designing flexible pressure sensors with specific properties. In this study, PDMS chains of different molecular weight were successfully functionalized with benzoxazine moieties in order to thermally cure them without adding a second component, nor a catalyst or an initiator. These precursors were then blended with 1 weight percent of multi-walled carbon nanotubes (CNTs) using an ultrasound probe, which induced a transition from a liquid-like to a gel-like behavior as CNTs generate an interconnected network within the matrix. After curing, the resulting nanocomposites exhibit mechanical and electrical properties making them highly promising materials for pressure-sensing applications., (© 2023 Wiley-VCH GmbH.)

Negative capacitance (NC), already observed in conducting polymer-based nanocomposites, was recently reported and evidenced at low frequencies (<10 kHz) in non-conducting polymer-based nanocomposites containing conductive particles. In this contribution, we demonstrate that it is possible to produce economic high-density polyethylene (HDPE) nanocomposites exhibiting an NC effect at low frequencies via a convenient and environmentally friendly extrusion-like process by only adjusting the duration of melt-mixing. Nanocomposite materials are produced by confining a limited quantity, i.e., 4.6 wt.%, of multiwalled carbon nanotubes (CNTs) within semi-crystalline HDPE to reach the percolation threshold. With increasing melt processing time, crystallites of HDPE developing at the surface of CNTs become bigger and perturbate the connections between CNTs leading to a dramatic change in the electrical behavior of the systems. More specifically, the link between NC and current oscillations is stressed while the dependence of NC with the size of polymer crystallites is evidenced. NC tends to appear when space charge effects take place in HDPE/MWCNT interfaces, in structures with convenient crystallite sizes corresponding to 10 min of melt-mixing.

Medical implants have improved the quality of life of many patients. However, surgical intervention may eventually lead to implant microbial contamination. The aims of this research were to develop an easy, robust, quantitative assay to assess surface antimicrobial activities, especially the anti-nascent biofilm activity, and to identify control surfaces, allowing for international comparisons. Using new antimicrobial assays to assess the inhibition of nascent biofilm during persistent contact or after transient contact with bacteria, we show that the 5 cent Euro coin or other metal-based antibacterial coins can be used as positive controls, as more than 4 log reduction on bacterial survival was observed when using either S. aureus or P. aeruginosa as targets. The methods and controls described here could be useful to develop an easy, flexible and standardizable assay to assess relevant antimicrobial activities of new implant materials developed by industries and academics.