Polluted air is a major global health risk factor, yet the chemical composition and toxicity of airborne gases and particles remain underexplored due to their complexity and difficulties in sampling. We recently introduced how polydimethylsiloxane (PDMS) foam─or silicone foam─can be synthesized for passive air sampling, enabling simple and cost-effective nontarget chemical profiling of indoor air. Here, we demonstrate expanded applications, indoors and outdoors, with commercial PDMS-foam, including for: (i) wide-scope target analysis of >220 priority substances by quantitative liquid- and gas chromatography-high-resolution mass spectrometry, (ii) microscopic characterization and nontarget profiling of accumulated fine particles, and (iii) effect-guided discovery of harmful substances, combining toxicological data with nontarget analysis in silico. Median method quantification limits were 0.12 ng/mL, 90% of target analytes had absolute recoveries between 70 and 130%, and hazardous substances were discovered, including ethylene glycols, insecticides, and UV filters. Microscopy revealed the accumulation of abundant fine particles, and the automated characterization of the fluorescent fraction revealed that most were <4 μm. Extracts from outdoor samples reduced human lung cell viability, and multivariate modeling flagged families of potentially toxic substances in a virtual effect-directed analysis. PDMS-foam disks require field calibration to determine their linear sampling rate(s), but current results and applications establish PDMS-foam as a multimodal passive sampler, enabling integrated chemical quantitation, toxicological analysis, and molecular discovery in air.

Lignins constitute the second most abundant carbon-storing biopolymers in the biosphere. These phenolic polymers accumulate in different concentrations, compositions, and localisations within and between cell wall layers and cell types. Lignins were acquired during plant terrestrialisation 450 million years ago, and the diversification of their chemistries and structures during plant evolution and speciation allowed plant cells to adjust and/or gain new functions for facing developmental and environmental challenges. The main property conferred by any lignin polymer is to modify the hygroscopic capacities of plant cell walls to set their responsiveness to changes in water content. To do so, lignin accumulation increases the impermeable, antioxidant, recalcitrant and/or mechanical properties of cell walls to modify their water responsiveness. Adjusting these diverse properties depends on the chemistry, structure and distribution pattern of the lignin polymers, collectively named topochemistry. Lignin topochemistries are differently regulated spatially and temporally for each cell type. In this review, we provide a unifying description of lignins as regulators of cell wall hygroscopy and biomechanics for plant physiology as well as describe the molecular and cellular processes, enabling each cell wall layer to specifically adjust lignin properties.

Lignin is a group of cell wall localised heterophenolic polymers varying in the chemistry of the aromatic and aliphatic parts of its units. The lignin residues common to all vascular plants have an aromatic ring with one para hydroxy group and one meta methoxy group, also called guaiacyl (G). The terminal function of the aliphatic part of these G units, however, varies from alcohols, which are generally abundant, to aldehydes, which represent a smaller proportion of lignin monomers. The proportions of aldehyde to alcohol G units in lignin are, nevertheless, precisely controlled to respond to environmental and development cues. These G aldehyde to alcohol unit proportions differ between each cell wall layer of each cell type to fine-tune the cell wall biomechanical and physico-chemical properties. To precisely determine changes in lignin composition, we, herein, describe the various methods to detect and quantify the levels and positions of G aldehyde units, also called coniferaldehyde residues, of lignin polymers in ground plant samples as well as in situ in histological cross-sections.

Lignins are a key adaptation that enables vascular plants to thrive in terrestrial habitats. Lignin is heterogeneous, containing upward of 30 different monomers, and its function is multifarious: It provides structural support, predetermined breaking points, ultraviolet protection, diffusion barriers, pathogen resistance, and drought resilience. Recent studies, carefully characterizing lignin in situ, have started to identify specific lignin compositions and ultrastructures with distinct cellular functions, but our understanding remains fractional. We summarize recent works and highlight where further in situ lignin analysis could provide valuable insights into plant growth and adaptation. We also summarize strengths and weaknesses of lignin in situ analysis methods.

Inducing the differentiation of specific cell type(s) synchronously and on-demand is a great experimental system to understand the sequential progression of the cellular processes, their timing and their resulting properties for distinct isolated plant cells independently of their tissue context. The inducible differentiation in cell suspension cultures, moreover, enables to obtain large quantities of distinct cell types at specific development stage, which is not possible when using whole plants. The differentiation of tracheary elements (TEs) – the cell type responsible for the hydro-mineral sap conduction and skeletal support of plants in xylem tissues – has been the most studied using inducible cell suspension cultures. We herein describe how to establish and use inducible pluripotent suspension cell cultures (iPSCs) in Arabidopsis thaliana to trigger on-demand different cell types, such as TEs or mesophyll cells. We, moreover, describe the methods to establish, monitor, and modify the sequence, duration, and properties of differentiated cells using iPSCs.

As a versatile nanomaterial derived from renewable sources, nanocellulose has attracted considerable attention for its potential applications in various sectors, especially those focused on water treatment and remediation. Here, we have combined atomic force microscopy (AFM) and reactive molecular dynamics (RMD) simulations to characterize the interactions between cellulose nanofibers modified with carboxylate or phosphate groups and the protein foulant model bovine serum albumin (BSA) at pH 3.92, which is close to the isoelectric point of BSA. Colloidal probes were prepared by modification of the AFM probes with the nanofibers, and the nanofiber coating on the AFM tip was for the first time confirmed through fluorescence labeling and confocal optical sectioning. We have found that the wet-state normalized adhesion force is approximately 17.87 +/- 8.58 pN/nm for the carboxylated cellulose nanofibers (TOCNF) and about 11.70 +/- 2.97 pN/nm for the phosphorylated ones (PCNF) at the studied pH. Moreover, the adsorbed protein partially unfolded at the cellulose interface due to the secondary structure's loss of intramolecular hydrogen bonds. We demonstrate that nanocellulose colloidal probes can be used as a sensitive tool to reveal interactions with BSA at nano and molecular scales and under in situ conditions. RMD simulations helped to gain a molecular- and atomistic-level understanding of the differences between these findings. In the case of PCNF, partially solvated metal ions, preferentially bound to the phosphates, reduced the direct protein-cellulose connections. This understanding can lead to significant advancements in the development of cellulose-based antifouling surfaces and provide crucial insights for expanding the pH range of use and suggesting appropriate recalibrations.

Nanocellulose with specific surface chemistry exhibits divergent effects on bacterial growth. Here, we report the interaction between different nanocelluloses and Escherichia coli (E. coli). When E. coli is exposed to lignin-containing cellulose nanocrystals (L-CNCs) and TEMPO-oxidized cellulose nanofibers (T-CNFs), the growth rate is reduced, but not the viability of bacterial cells in liquid media, with L-CNCs having the most prominent effect. In situ, PeakForce quantitative nanomechanical mapping (PFQNM) revealed that the surface roughness and stiffness of E. coli were affected when in direct contact with the nanocellulose during incubation, except for the cells attached to CNCs, which promote strong adhesion and even the embedding of E. coli. Thus, nanocelluloses with certain surface chemistries, such as T-CNFs and L-CNCs, could be used as complements or alternatives to antimicrobial drugs for controlling and limiting bacterial growth in liquid media and further biofilm formation on surfaces.

Properly patterned deposition of cell wall polymers is prerequisite for the morphogenesis of plant cells. A cortical microtubule array guides the two-dimensional pattern of cell wall deposition. Yet, the mechanism underlying the three-dimensional patterning of cell wall deposition is poorly understood. In metaxylem vessels, cell wall arches are formed over numerous pit membranes, forming highly organized three-dimensional cell wall structures. Here, we show that the microtubule-associated proteins, MAP70-5 and MAP70-1, regulate arch development. The map70-1 map70-5 plants formed oblique arches in an abnormal orientation in pits. Microtubules fit the aperture of developing arches in wild-type cells, whereas microtubules in map70-1 map70-5 cells extended over the boundaries of pit arches. MAP70 caused the bending and bundling of microtubules. These results suggest that MAP70 confines microtubules within the pit apertures by altering the physical properties of microtubules, thereby directing the growth of pit arches in the proper orientation. This study provides clues to understanding how plants develop three-dimensional structure of cell walls. In plant metaxylem, three-dimensional cell wall arches are formed over pit membranes. Here, the authors show that the microtubule-associated proteins, MAP70-5 and MAP70-1, confine microtubules within the pit aperture and direct growth of pit arches in the proper orientation.

Vascular plants reinforce the cell walls of the different xylem cell types with lignin phenolic polymers. Distinct lignin chemistries differ between each cell wall layer and each cell type to support their specific functions. Yet the mechanisms controlling the tight spatial localization of specific lignin chemistries remain unclear. Current hypotheses focus on control by monomer biosynthesis and/or export, while cell wall polymerization is viewed as random and nonlimiting. Here, we show that combinations of multiple individual laccases (LACs) are nonredundantly and specifically required to set the lignin chemistry in different cell types and their distinct cell wall layers. We dissected the roles of Arabidopsis thaliana LAC4, 5, 10, 12, and 17 by generating quadruple and quintuple loss-of-function mutants. Loss of these LACs in different combinations led to specific changes in lignin chemistry affecting both residue ring structures and/or aliphatic tails in specific cell types and cell wall layers. Moreover, we showed that LAC-mediated lignification has distinct functions in specific cell types, waterproofing fibers, and strengthening vessels. Altogether, we propose that the spatial control of lignin chemistry depends on different combinations of LACs with nonredundant activities immobilized in specific cell types and cell wall layers.

The airborne chemical exposome is a dynamic complex mixture of gases and particles, and despite clear links to chronic disease and premature death, its molecular composition and variability remains largely uncharacterized. To overcome this, we aimed to pair nontarget analysis by high-resolution mass spectrometry (HRMS) with an inexpensive and stable passive sampling media for airborne gases and particles. To this end, we synthesized silicone (polydimethylsiloxane; PDMS) foam disks resulting in a low cost (0.02$/disk) and ultraclean material suitable for analysis by gas or liquid chromatography (GC/LC)HRMS. When tested for indoor passive sampling over 1-3 months, alongside a PDMS sheet, PDMS foam accumulated many nonpolar gas phase environmental contaminants (e.g., polychlorinated biphenyls), and a surprisingly complex mixture of larger polar substances (e.g., oxygen, nitrogen and sulfur-containing) that were absent from the PDMS sheet, suggesting sampling of the particulate phase. The airborne molecular discovery potential was further demonstrated using an open-science LC-HRMS workflow integrating molecular networks and in silico structural predictions tailored on PubChemLite for Exposomics, which revealed series of known and unknown substances, including aromatic nitrophenols and sulfonyls. Future studies may benefit from implementing PDMS foam as wearable or stationary passive samplers to support advances in understanding exposure and contaminant sources in the indoor, outdoor, and personal airborne exposomes.