Atomic Force Microscopy in PeakForce Quantitative NanoMechanics mode (AFM PeakForce QNM) under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce (Picea abies) earlywood (EW) and latewood (LW) tracheid cell walls over three absorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM nanoInfraRed measurements (AFM NanoIR) indicate variations in lignin and cellulose with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC (cell corner). Earlywood and latewood cell walls display the same hygronanomechanical behavior during S/D cycle, i.e., the IM values decrease during absorption up to 85

The Tau protein is involved in several neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. Under physiological conditions, Tau binds to microtubules and participates in neuronal integrity. Under pathological conditions, Tau misfolds and aggregates into insoluble amyloid fibers, ultimately leading to neuronal death. Most studies have focused on Tau aggregation promoted by negatively charged cofactors such as anionic lipids or polyanions, while its interactions with neutral membrane components have received less attention. Notably, phosphatidylcholine (PC), the most abundant zwitterionic phospholipid in the plasma membrane, has been detected within Tau aggregates in vivo, and Tau can directly interact with membranes through their lipid or protein components. Here, we investigated the interaction between Tau and PC-containing model membranes using polarized infrared spectroscopy and atomic force microscopy. Supported bilayers composed of DOPC, mixed DOPC:DPPC, and DPPC containing cholesterol were used to modulate membrane fluidity. Our results show that Tau binds to and perturbs PC membranes only when sufficient fluidity is present, while retaining its native structural conformation. These findings highlight a previously underexplored aspect of Tau-membrane interactions and suggest that the physical state of the membrane may play a key role in modulating Tau pathogenicity.

AFM PeakForce QNM under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce ( Picea abies ) earlywood (EW) and latewood (LW) tracheid cell walls over three sorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM IR indicate a gradient of lignin and cellulose across the cell wall with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC. Earlywood and latewood cell walls display the same hygro–nanomechanical behavior during S/D cycle, i.e., the IM decrease with during sorption up to 85% and re–increase during desorption. Gaussian fits of the IM distribution were narrower for late wood than early wood and vary with the type of layer and with the relative humidity. The responses of the indentation moduli to RH of the cell wall layers in early- and latewood were fitted according to a three-parameter logistic function. Significant differences are observed for the S2 in both EW and LW indicating a higher slope in the response of indentation moduli to RH between 15 and 50% RH in desorption as compared to sorption. For both desorption and sorption, the comparison between EW vs LW reveals differences in CC and S1, with a higher slope in moduli response to RH in LW between 15 and 50% RH and the opposite between 50 to 85% RH.

Lignin, produced from papermaking and biorefinery industrial processes, is an interesting green substitute for petroleum-based derivative products with multiple functional properties, including bioplasticizing, bioadhesive, UV resistance and antioxidant properties. Although lignin is a major wood component (20-25 wt%) available in large quantities, it is seldom used industrially because of its difficult handling in the manufacture of high-value products. Controlling the lignin structural morphology in native and composite materials remains challenging because of the wide variety of chemical functional groups influencing its spatial organization and final network physicochemical properties. In thermoplastics applications, improving the interfacial interactions between the lignin charge and polymer matrix is essential. This work reports a combination of experimental approaches to investigate the chemical and adhesive properties of lignin at the molecular level, both in preparation of atomic force microscopy probes and in measurement at a nanometric scale through single-molecule force spectroscopy (SMFS), nano-infrared spectroscopy and imaging. The application of an original Langmuir-Blodgett (LB) deposition procedure produced homogeneous ultrathin coatings with controlled thicknesses in comparison with classical chemical deposition routes. Both procedures were verified for two synthetic lignins, guaiacyl and mixed guaiacyl-syringyl dehydrogenation polymers, before being applied to pine lignin as a proof-of-concept for the development of green lignin-based (nano)composites. Functionalizing the tip via the LB approach increased the adhesion force measurement resolution and provided new insights into the molecular affinity of lignin for other materials at the nanoscale, which prefers xylan polymers, such as those in native plant cell walls, and apolar/polar polymer matrices, such as those in composite materials, albeit to a lesser extent.

An original synthesis route has been developed to optimize silicon's utility in replacing graphite as anode material in Li-ion batteries. This involves blending silicon with aluminum to enhance its conductivity. The silicon-aluminum is codeposited on a nanoporous titanium dioxide nanotube matrix, which serves as an active current collector, thereby eliminating the need for inactive binders and ensuring robust mechanical stability during cycling. The nanostructured negative electrode is fabricated through two electrochemical synthesis steps: first, the anodization of a titanium foil, followed by the coelectrodeposition of silicon and aluminum using a room temperature ionic liquid electrolyte. This coelectrodeposition enables the in situ integration of aluminum into the silicon deposit. The resulting Si-Al/TiO2 nanotube nanocomposite anode exhibits improved cyclic stability and enhanced rate capability. The observed enhancement in battery electrochemical performance underscores the significance of this electrochemical process in fabricating such nanostructured silicon negative composite electrodes.

The Tau protein is implicated in various diseases collectively known as tauopathies, including Alzheimer's disease and frontotemporal dementia. The precise mechanism underlying Tau pathogenicity remains elusive. Recently, the role of lipids has garnered interest due to their implications in Tau aggregation, secretion, uptake, and pathogenic dysregulation. Previous investigations have highlighted critical aspects: (i) Tau's tendency to aggregate into fibers when interacting with negatively charged lipids, (ii) its ability to form structured species upon contact with anionic membranes, and (iii) the potential disruption of the membrane upon Tau binding. In this study, we examine the disease-associated P301L mutation of the 2N4R isoform of Tau and its effects on membranes composed on phosphatidylserine (PS) lipids. Aggregation studies and liposome leakage assays demonstrate Tau's ability to bind to anionic lipid vesicles, leading to membrane disruption. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) reveals the accumulation of Tau on the membrane surface without protein insertion, structuration, or lipid removal. Plasmon waveguide resonance (PWR) demonstrates a strong binding of Tau on PS bilayers with an apparent Kd in the micromolar range, indicating the deposition of a thick protein layer. Atomic force microscopy (AFM) real-time imaging allows the observation of partial lipid solubilization and the deposition of polymorphic aggregates in the form of thick patches and fibrillary structures resembling amyloid fibers, which could grow from a combination of extracted anionic phospholipids from the membrane and Tau protein. This study deepens our understanding of full-length Tau's multifaceted interactions with lipids, shedding light on potential mechanisms leading to the formation of pathogenic Tau assemblies. The Tau protein strongly binds to phosphatidylserine membranes, with partial membrane disruption and formation of polymorphic aggregates.

Dendrigrafts are multivalent macromolecules with less ordered topology and higher branching than dendrimers. Exhibiting a high density of terminal amines, poly-L-lysine dendrigrafts of the fifth generation (DGL G5) allow hydrogel formation with tailorable crosslinking density and surface modification. This work presents DGL G5 as multifunctional crosslinkers in biomimetic PEG hydrogels to favour the osteogenic differentiation of human mesenchymal stem cells (hMSCs). DGL G5 reaction with dicarboxylic-acid PEG chains yielded amide networks of variable stiffness, measured at the macro and surface nanoscale. Oscillatory rheometry and compression afforded consistent values of Young's modulus, increasing from 8 to more than 30 kPa and correlating with DGL G5 concentration. At the surface level, AFM measurements showed the same tendency but higher E values, from approximately 15 to more than 100 kPa, respectively. To promote cell adhesion and differentiation, the hydrogels were functionalised with a GRGDSPC peptide and a biomimetic of the bone morphogenetic protein 2 (BMP-2), ensuring the same grafting concentrations (between 2.15 ± 0.54 and 2.28 ± 0.23 pmols mm-2) but different hydrogel stiffness. 6 h after seeding on functionalised hydrogels in serum-less media, hMSC showed nascent adhesions on the stiffer gels and greater spreading than on glass controls with serum. After two weeks in osteogenic media, hMSC seeded on the stiffer gels showed greater spreading, more polygonal morphologies and increased levels of osteopontin, an osteoblast marker, compared to controls, which peaked on 22 kPa-gels. Together, these results demonstrate that DGL G5-PEG hydrogel bioactivity can influence the adhesion, spreading and early commitment of hMSCs.

The virulence of Staphylococcus aureus, a multi-drug resistant pathogen, notably depends on the expression of the phenol soluble modulins α3 (PSMα3) peptides, able to self-assemble into amyloid-like cross-α fibrils. Despite remarkable advances evidencing the crucial, yet insufficient, role of fibrils in PSMα3 cytotoxic activities towards host cells, the relationship between its molecular structures, assembly propensities, and modes of action remains an open intriguing problem. In this study, combining Atomic Force Microscopy (AFM) imaging and infrared spectroscopy, we first demonstrated in vitro that the charge provided by the N-terminal capping of PSMα3 alters its interactions with model membranes of controlled lipid composition, without compromising its fibrillation kinetics or morphology. N-formylation eventually dictates PSMα3 - membrane binding via electrostatic interactions with the lipid head groups. Furthermore, PSMα3 insertion within the lipid bilayer is favoured by hydrophobic interactions with the lipid acyl chains, only in the fluid-phase of membranes, and not in the gel-like ordered domains. Strikingly, our real-time AFM imaging emphasizes how intermediate protofibrillar entities, formed along PSMα3 self-assembly and promoted at the membrane interface, likely disrupt membrane integrity via peptide accumulation, and subsequent membrane thinning in a peptide concentration and lipid-dependent manner. Overall, our multiscale and multimodal approach sheds new light on the key roles of N-formylation and intermediate self-assembling entities, rather than mature fibrils, in dictating deleterious interactions of PSMα3 with specific membrane lipids, likely underscoring its ultimate cellular toxicity in vivo, and in turn S. aureus pathogenesis.

Deciphering breast cancer treatment resistance remains hindered by the lack of models that can successfully capture the four-dimensional dynamics of the tumor microenvironment. Here, we show that microextrusion bioprinting can reproducibly generate distinct cancer and stromal compartments integrating cells relevant to human pathology. Our findings unveil the functional maturation of this millimeter-sized model, showcasing the development of a hypoxic cancer core and an increased surface proliferation. Maturation was also driven by the presence of cancer-associated fibroblasts (CAF) that induced elevated microvascular-like structures complexity. Such modulation was concomitant to extracellular matrix remodeling, with high levels of collagen and matricellular proteins deposition by CAF, simultaneously increasing tumor stiffness and recapitulating breast cancer fibrotic development. Importantly, our bioprinted model faithfully reproduced response to treatment, further modulated by CAF. Notably, CAF played a protective role for cancer cells against radiotherapy, facilitating increased paracrine communications. This model holds promise as a platform to decipher interactions within the microenvironment and evaluate stroma-targeted drugs in a context relevant to human pathology.

The production of bio-based composites with enhanced characteristics constitutes a strategic action to minimize the use of fossil fuel resources. The mechanical performances of these materials are related to the specific properties of their components, as well as to the quality of the interface between the matrix and the fibers. In a previous research study, it was shown that the polarity of the matrix played a key role in the mechanisms of fiber breakage during processing, as well as on the final properties of the composite. However, some key questions remained unanswered, and new investigations were necessary to improve the knowledge of the interactions between a lignocellulosic material and a polar matrix. In this work, for the first time, atomic force microscopy based on force spectroscopy measurements was carried out using functionalized tips to characterize the intermolecular interactions at the single molecule level, taking place between poly(butylene succinate) and four different plant fibers. The efficiency of the tip functionalization was checked out by scanning electron microscopy and energy-dispersive X-ray spectroscopy, whereas the fibers chemistry was characterized by Fourier-transform infrared spectroscopy. Larger interactions at the nanoscale level were found between the matrix and hypolignified fibers compared to lignified ones, as in control experiments on single lignocellulosic polymer films. These results could significantly aid in the design of the most appropriate composite composition depending on its final use.

The challenge of imaging is to combine resolution and sensitivity in order to gain accuracy in diagnosis. No single modality can provide comprehensive information. Then, the solution is to design probes that are able to gather on a single platform the best features of the different imaging modalities. To achieve this objective, we have combined two types of probes, one associated with photoacoustic imaging (PAI) and the other with magnetic resonance imaging (MRI), within polysaccharide-based nanohydrogels. For that, chitosan (CS) which is a cationic polysaccharide was grafted with the photoacoustic probe ZW800-1. The synthesis of the corresponding CS-ZW800 and the purification conditions that allow to overcome ZW800 aggregation on the course of the protocol were carefully analyzed. Nanohydrogels that encapsulated gadolinium chelates as MRI probes were further obtained by ionic gelation between CS-ZW800 and the anionic hyaluronic acid (HA) in the presence of tripolyphosphate (TPP) as an ionogenic cross-linker. The bimodal nanohydrogels were then subjected to MSOT and MRI experiments. Upon excitation at 770 nm the nanoparticles were then able to produce a significant MSOT signal while in MRI at 3T, a significant positive contrast was obtained with low Gd doses. A new 'all in one' bimodal imaging system combining within nanohydrogels the photoacoustic probe ZW800-1 with magnetic resonance imaging contrast agents is presented.

In this study, we designed aptamer-based self-assemblies for the delivery of quinine. Two different architectures were designed by hybridizing quinine binding aptamers and aptamers targeting Plasmodium falciparum lactate dehydrogenase (PfLDH): nanotrains and nanoflowers. Nanotrains consisted in controlled assembly of quinine binding aptamers through base-pairing linkers. Nanoflowers were larger assemblies obtained by Rolling Cycle Amplification of a quinine binding aptamer template. Self-assembly was confirmed by PAGE, AFM and cryoSEM. The nanotrains preserved their affinity for quinine and exhibited a higher drug selectivity than nanoflowers. Both demonstrated serum stability, hemocompatibility, low cytotoxicity or caspase activity but nanotrains were better tolerated than nanoflowers in the presence of quinine. Flanked with locomotive aptamers, the nanotrains maintained their targeting ability to the protein PfLDH as analyzed by EMSA and SPR experiments. To sum-marize, nanoflowers were large assemblies with high drug loading ability, but their gelating and aggregating properties prevent from precise characterization and impaired the cell viability in the presence of quinine. On the other hand, nanotrains were assembled in a selective way. They retain their affinity and specificity for the drug quinine, and their safety profile as well as their targeting ability hold promise for their use as drug delivery systems.

The lipid composition of cellular membranes and the balance between the different lipid components can be impacted by aging, certain pathologies, specific diets and other factors. This is the case in a subgroup of individuals with psychiatric disorders, such as schizophrenia, where cell membranes of patients have been shown to be deprived in polyunsaturated fatty acids (PUFAs), not only in brain areas where the target receptors are expressed but also in peripheral tissues. This PUFA deprivation thus represents a biomarker of such disorders that might impact not only the interaction of antipsychotic medications with these membranes but also the activation and signaling of the targeted receptors embedded in the lipid membrane. Therefore, it is crucial to understand how PUFAs levels alterations modulate the different physical properties of membranes. In this paper, several biophysical approaches were combined (Laurdan fluorescence spectroscopy, atomic force microscopy, differential scanning calorimetry, molecular modeling) to characterize membrane properties such as fluidity, elasticity and thickness in PUFA-enriched cell membranes and lipid model systems reflecting the PUFA imbalance observed in some diseases. The impact of both the number of unsaturations and their position along the chain on the above properties was investigated. Briefly, data revealed that PUFA presence in membranes increases membrane fluidity, elasticity and flexibility and decreases its thickness and order parameter. Both the level of unsaturation and their position affect these membrane properties.

Defect engineering in two-dimensional materials expands the realm of their applications in catalysis, nanoelectronics, sensing, and beyond. As limited tools are available to explore nanoscale functional properties in non-vacuum environments, theoretical modeling provides some invaluable insight into the effect of local deformations to deepen the understanding of experimental signals acquired by nanoscale chemical imaging. We demonstrate the controlled creation of nanoscale strained defects in hexagonal boron nitride (h-BN) using atomic force microscopy and infrared (IR) light under an inert environment. Nanoscale IR spectroscopy reveals the broadening of the in-plane phonon (E1u) mode of h-BN during defect formation while density functional theory-based calculations and molecular dynamics provide quantification of the tensile and compressive strain in the deformation.

Cutaneous melanoma is a cancer with a very poor prognosis mainly because of metastatic dissemination and therefore a deregulation of cell migration. Current therapies can benefit from complementary medicines as supportive care in oncology. In our study, we show that a dynamized ultra-low dilution of Ruta Graveolens leads to an in vitro inhibition of migration on fibronectin of B16F10 melanoma cells, as well as a decrease in metastatic dissemination in vivo. These effects appear to be due to a disruption of plasma membrane organization, with a change in cell and membrane stiffness, associated with a disorganization of the actin cytoskeleton and a modification of the lipid composition of the plasma membrane. Together, these results demonstrate, in in vitro and in vivo models of cutaneous melanoma, an anti-cancer and anti-metastatic activity of ultra-low dynamized dilution of Ruta graveolens and reinforce its interest as complementary medicine in oncology.