A better in vivo understanding of lignin formation within plant cell walls will contribute to improving the valorization of plant-derived biomass. Although bioorthogonal chemistry provides a promising platform to study the lignification process, methodologies that simultaneously detect multiple chemical reporters in living organisms are still scarce. Here, we have developed an original bioorthogonal labeling imaging sequential strategy (BLISS) to visualize and analyze the incorporation of both p-hydroxyphenyl (H) and guaiacyl (G) units into lignin in vivo with a combination of strain-promoted and copper-catalyzed azide-alkyne cycloadditions. On our path to BLISS, we designed a new azide-tagged monolignol reporter for H units in metabolic lignin engineering and used it in conjunction with an alkyne-tagged G unit surrogate to study lignification dynamics in flax. Here, we show that BLISS provides precise spatial information on the zones of active lignification and reveals polarization in single-cell lignification dynamics.

Fabrication of silver nanowires (AgNWs) with fine and independent control of both the diameter (from 30 to 120 nm) and length (from 5 to 120 μm) by concomitant addition of co-nucleants and temperature control is demonstrated, and used for the preparation of size standards. Percolating random networks were fabricated using these standards and their optoelectronic properties were measured and compared with regard to the nanowire dimensions. The transparent electrodes appear suitable for various applications and exhibit excellent performances (e.g. 16 ohm sq −1 at 93% transparency), with haze values varying from 1.6 to 26.2%. Besides, in vitro toxicological studies carried out on murine macrophages with the same size standards revealed that AgNWs are weakly toxic (no toxicity observed below 50 μg mL −1 Ag), in particular compared to other silver nanoparticles. Short AgNWs (4 μm) appeared to be slightly more toxic than longer AgNWs (10 and 20 μm). Conversely, long AgNWs (20 μm) induced a more prolonged pro-inflammatory response in murine macrophages. These results contribute, in a safer by design approach, to promoting the use of short AgNWs. The global knowledge dealing with the combination of nanowire dimensions associated with optoelectronic performances and related toxicity should encourage the rational use of AgNWs, and guide the choice of the most adequate AgNW dimensions in an integrated approach. 684 | Environ. Sci.: Nano, 2019, 6, 684-694 This journal isThe use of silver nanowires is a promising alternative for the fabrication of transparent electrodes. They will be increasingly introduced in consumer devices. The relationship between the nanowires' dimensions and their toxicity is still insufficiently studied. We demonstrate a straightforward method to prepare silver nanowires with controlled dimensions. We propose a global approach, starting from tailor-made nanowires, based on a study of both their physical properties when used as random percolating networks, which is of interest from the technological point of view, and their toxicological behaviour toward murine macrophages, which is of interest from the health, safety & environment point of view. These results contribute, in a "safer by design approach", to promoting the use of short AgNWs.