Adhesion Dynamics Research Articles

Nanosecond laser interference ablation of fluorine-free aluminum alloy surfaces for dynamic adhesion and static wettability synergistically modulating water collection

Water collection from mist is a potential solution to water scarcity, which is a critical issue worldwide. In this paper, laser interference ablation assisted with stearic acid immersion has been used to achieve synergistic modulation of dynamic adhesion and static wettability for water collection on fluorine-free aluminum alloy surface. The research demonstrates that there is an optimal balance point between dynamic adhesion and static wettability for water collection. This optimal point shifts toward low dynamic adhesion at the high misting rate due to the flooding on metastable surfaces with high dynamic adhesion. In addition, wetting transition induced by tilting is observed on metastable surfaces. The good stability of the proposed fluorine-free surface has been demonstrated by the long-term water collection and long periods of immersion in water. This work can provide theoretical inspiration and a scalable preparation method for green and stable water collection strategies.

Synthesis, characterisation, and thermal degradation kinetics of lignin-based polyurethane wood adhesives

Synthesis, characterisation, and thermal degradation kinetics of lignin-based polyurethane wood adhesives

Effect of shear rate on early Shewanella oneidensis bacterial adhesion dynamics monitored by Deep Learning

Effect of shear rate on early Shewanella oneidensis bacterial adhesion dynamics monitored by Deep Learning

A Microfluidic Design for Quantitative Measurements of Shear Stress-Dependent Adhesion and Motion of Dictyostelium discoideum Cells

Shear stress plays a crucial role in modulating cell adhesion and signaling. We present a microfluidic shear stress generator used to investigate the adhesion dynamics of Dictyostelium discoideum, an amoeba cell model organism with well-characterized adhesion properties. We applied shear stress and tracked cell adhesion, motility, and detachment using time-lapse videomicroscopy. In the precise shear conditions generated on-chip, our results show cell migration patterns are influenced by shear stress, with cells displaying an adaptive response to shear forces as they alter their adhesion and motility behavior. Additionally, we observed that DH1-10 wild-type D. discoideum cells exhibit stronger adhesion and resistance to shear-induced detachment compared to phg2 adhesion-defective mutant cells. We also highlight the influence of cell density on detachment kinetics.

Spatiotemporal analysis of F-actin polymerization with micropillar arrays reveals synchronization between adhesion sites.

We repurposed micropillar-arrays to quantify spatiotemporal inter-adhesion communication. Following the observation that integrin adhesions formed around pillar tops we relied on the precise repetitive spatial control of the pillars to reliably monitor F-actin dynamics in mouse embryonic fibroblasts as a model for spatiotemporal adhesion-related intracellular signaling. Using correlation-based analyses we revealed localized information-flows propagating between adjacent pillars that were integrated over space and time to synchronize the adhesion dynamics within the entire cell. Probing the mechanical regulation, we discovered that stiffer pillars or partial actomyosin contractility inhibition enhances inter-adhesion F-actin synchronization, and that inhibition of Arp2/3, but not formin, reduces synchronization. Our results suggest that adhesions can communicate and highlight the potential of using micropillar arrays as a tool to measure spatiotemporal intracellular signaling. [Media: see text].

Engineering tunable catch bonds with DNA

Unlike most adhesive bonds, biological catch bonds strengthen with increased tension. This characteristic is essential to specific receptor-ligand interactions, underpinning biological adhesion dynamics, cell communication, and mechanosensing. While artificial catch bonds have been conceived, the tunability of their catch behaviour is limited. Here, we present the fish-hook, a rationally designed DNA catch bond that can be finely adjusted to a wide range of catch behaviours. We develop models to design these DNA structures and experimentally validate different catch behaviours by single-molecule force spectroscopy. The fish-hook architecture supports a vast sequence-dependent behaviour space, making it a valuable tool for reprogramming biological interactions and engineering force-strengthening materials.

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here, we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall.

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here, we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

Molecular dynamics-based targeted adsorption of hazardous substances from rubberized asphalt VOCs by UiO-67

The interplay among UiO-67 and rubberized-asphalt components has been examined according to its molecular scale. The adhesion kinetics of UiO-67 to VOCs molecules in asphalt was modeled. The binding energy, radial distribution function (RDF), solubility parameters (SP), mean square displacement (MSD) and other parameters among UiO-67 to rubberized-asphalt components were evaluated in depth. The Sorption module was simulated the adsorption behavior of UiO-67 on 12 malodorous gases and 5 primary carcinogens. In combination with GC-MS results, the conjugative bonds and target attachment mechanisms for UiO-67 with VOCs were clarified. It was indicated that the binding energy among UiO-67 to the components were all negative. The radial distribution of asphalt was characterized as proximally ordered and remotely disordered. The ΔSP was less than 1.6, which was indicated that UiO-67 could be compatible with asphalt. The overall inhibition effect of UiO-67 on a group of carcinogens was exceeded 70 %. The presence of conjugation effect was allowed the adsorption sites of vinyl chloride and 1,3 butadiene to occur at high densities within the benzenoid. The concentration reduction of UiO-67 for hydrogen sulfide, carbon disulfide, and dimethyl sulfide was more than 80 %. The higher polarity was predisposed substances such as hydrogen sulfide and isobutanol to interact with the non-benzene ring region of UiO-67.

LncRNA FAISL Inhibits Calpain 2-Mediated Proteolysis of FAK to Promote Progression and Metastasis of Triple Negative Breast Cancer.

Triple negative breast cancer (TNBC) is the most aggressive subtype in breast tumors. When re-analyzing TCGA breast cancer dataset, we found cell adhesion molecules are highly enriched in differentially expressed genes in TNBC samples, among which Focal Adhesion Kinase (FAK) is most significantly associated with poor survival of TNBC patients. FAK is precisely modulated in the focal adhesion dynamics. To investigate whether lncRNAs regulate FAK signaling, we performed RNA immunoprecipitation sequencing and found FAISL (FAK Interacting and Stabilizing LncRNA) abundantly enriched in FAK-interacting lncRNAs and frequently overexpressed in TCGA TNBC tissues. FAISL promotes TNBC cell adhesion, cytoskeleton spreading, proliferation, and anchor-independent survival. FAISL doesn't affect FAK mRNA but positively regulates FAK protein level by blocking Calpain 2-mediated proteolysis. FAISL interacts with the C-terminus domain of FAK, whereby masks the binding site of Calpain 2 and prevents FAK cleavage. High level of FAISL correlates with FAK expression in tumor tissues and poor prognosis of TNBC patients. A siRNA delivery system targeting FAISL using reduction-responsive nanoparticles effectively inhibits tumor growth and metastasis in TNBC mouse models. Together, these findings uncover a lncRNA-mediated mechanism of regulating FAK proteolysis in the TNBC progression, and highlight the potential of targeting lncRNA FAISL for TNBC treatment.

Bubble adhesion dynamics on solid surfaces: Interfacial behavior, force, and energy perspectives using a self-developed dynamic force testing system

Bubble-solid surface adhesion is crucial for industrial processes such as wastewater treatment, and the separation of minerals, plastics, and biomass. In this paper, a novel dynamic force testing system was developed to provide a detailed understanding of bubble-solid adhesion dynamics by simultaneously collecting “time-displacement-force” signals and capturing real-time images. The interfacial behavior and force mechanisms of bubble adhesion to solid surfaces with varying hydrophobicity were investigated. Higher hydrophobicity results in more pronounced “snap-in” adhesion and greater adhesion strength. Instead of fully detaching, bubble breaks at the capillary neck and leaves a microbubble on the solid surface, whose size increases with hydrophobicity, indicating different interfacial behaviors in subsequent reaction. The evolution of Laplace force and surface tension force was further analyzed and the toroidal approximation shows over 60 μN error in Laplace force calculation for large bubble deformations. Thus, for the first time, the “gorge” method was employed to calculate the bubble adhesion force in the presence of a capillary neck. Error analysis indicates that this method, while maintaining simplicity, achieved higher accuracy (lower error) by calculating the Laplace force based on the neck area and accounting for the surface tension force along the tangent at the neck. Energy analysis show that the detachment energies in the stretching and sliding phases correspond to the energy barrier to be overcome for detachment and the “effective work” of interfacial change, respectively. This provides new insights into detachment mechanisms and industrial process modelling, such as flotation.

Water-resistant adhesive tackified by dynamic adhesion factor of nucleotide

Underwater adhesives have gained much attention across diverse fields including tissue adhesives, wearable electronics, and underwater electronics. However, it remains challenging to design a tough and stable underwater adhesion interface only relying on physical adhesion mechanisms, because the adhesion factors of the physical adhesives are limited and bound by molecular networks. Inspired by the toughening theory of “sacrificial bonds”, we present a strategy of dynamic adhesion factor to fabricate a tough and stable underwater adhesion interface. The adhesives tackified by nucleotide of dynamic adhesion factor are successfully developed and demonstrate excellent adhesion behavior in aquatic environments. The adhesion factor of nucleotide featuring reversible dynamic structural characteristics not only facilitates easier interaction with the substrate but also effectively dissipates failure stress and mitigates stress concentration when exposed to destructive stress. Moreover, the adhesives exhibit excellent recyclability, on-demand detachability, and long-term stability. Importantly, this strategy demonstrated a universality for variable monomers to construct tough underwater adhesion. It is anticipated that the dynamic adhesion factor strategy will inspire a new paradigm in the advancement of next-generation water-resistant adhesives.

A flow cytometry method for quantitative measurement and molecular investigation of the adhesion of bacteria to yeast cells

The study of microorganism interactions is important for understanding the organization and functioning of microbial consortia. Additionally, the interaction between yeast and bacteria is of interest in the field of health and nutrition area for the development of probiotics. To investigate these microbial interactions at the cellular and molecular levels, a simple, reliable, and quantitative method is proposed. We demonstrated that flow cytometry enables the measurement of interactions at a single-cell level by detecting and counting yeast cells with bound fluorescent bacteria. Imaging flow cytometry revealed that the number of bacteria attached to yeast followed a Gaussian distribution whose maximum reached 14 bacterial cells using a clinical Escherichia coli strain E22 and the laboratory yeast strain BY4741. We found that the dynamics of adhesion resemble a Langmuir adsorption model, albeit it is a rapid and almost irreversible process. This adhesion is dependent on the mannose-specific type 1 fimbriae, as E. coli mutants lacking these appendages no longer adhere to yeast. However, this type 1 fimbriae-dependent adhesion could involve additional yeast cell wall factors, since the interaction between bacteria and yeast mutants with altered mannan content remained comparable to that of wild-type yeast. In summary, flow cytometry is an appropriate method for studying bacteria-yeast adhesion, as well as for the high-throughput screening of candidate molecules likely to promote or counteract this interaction.

Comprehensive profiling of migratory primordial germ cells reveals niche-specific differences in non-canonical Wnt and Nodal-Lefty signaling in anterior vs posterior migrants.

Mammalian primordial germ cells (PGCs) migrate asynchronously through the embryonic hindgut and dorsal mesentery to reach the gonads. We previously found that interaction with different somatic niches regulates PGC proliferation along the migration route. To characterize transcriptional heterogeneity of migrating PGCs and their niches, we performed single-cell RNA sequencing of 13,262 mouse PGCs and 7,868 surrounding somatic cells during migration (E9.5, E10.5, E11.5) and in anterior versus posterior locations to enrich for leading and lagging migrants. Analysis of PGCs by position revealed dynamic gene expression changes between faster or earlier migrants in the anterior and slower or later migrants in the posterior at E9.5; these differences include migration-associated actin polymerization machinery and epigenetic reprogramming-associated genes. We furthermore identified changes in signaling with various somatic niches, notably strengthened interactions with hindgut epithelium via non-canonical WNT (ncWNT) in posterior PGCs compared to anterior. Reanalysis of a previously published dataset suggests that ncWNT signaling from the hindgut epithelium to early migratory PGCs is conserved in humans. Trajectory inference methods identified putative differentiation trajectories linking cell states across timepoints and from posterior to anterior in our mouse dataset. At E9.5, we mainly observed differences in cell adhesion and actin cytoskeletal dynamics between E9.5 posterior and anterior migrants. At E10.5, we observed divergent gene expression patterns between putative differentiation trajectories from posterior to anterior including Nodal signaling response genes Lefty1, Lefty2, and Pycr2 and reprogramming factors Dnmt1, Prc1, and Tet1. At E10.5, we experimentally validated anterior migrant-specific Lefty1/2 upregulation via whole-mount immunofluorescence staining for LEFTY1/2 proteins, suggesting that elevated autocrine Nodal signaling accompanies the late stages of PGC migration. Together, this positional and temporal atlas of mouse PGCs supports the idea that niche interactions along the migratory route elicit changes in proliferation, actin dynamics, pluripotency, and epigenetic reprogramming.

DEM analysis of cohesive granular shear flow using dynamic adhesion force model – Model validation for contact-dominated regime

When the DEM simulations are performed, the particle stiffness of the Discrete Element Method (DEM) is often reduced to reduce the computational cost. The Dynamic Adhesion/Cohesion Force Model (DAFM/DCFM) was proposed for adhesive/cohesive particles to make the effect of adhesion/cohesion force on the collisional motion of a particle with a reduced particle stiffness equivalent to that of the original system.This study validates the applicability of DCFM to the contact-dominated regime by means of a series of DEM simulations of two-dimensional simple shear flow of cohesive spherical particles. The results demonstrate that DCFM accurately represents the cohesive nature of the original system with respect to the fluid-to-solid phase transition of granular medium due to a reduction in shear rate, as well as the shear stress of the granular medium. It is demonstrated that the bond-breaking model proposed in the present study describes well the validity of DCFM in the contact-dominated regime.

Exploring buried interface in all-vapor-deposited perovskite photovoltaics

All-vapor-deposited perovskite solar cells (PSCs) offer promising potential for maintaining high efficiency across large-area solar modules. However, a comprehensive understanding of device stability, particularly the crucial photodegradation mechanism under sunlight exposure, remains scarce in the existing literature. In this study, we investigate thermally co-evaporated perovskite polycrystals grown on two typical organic hole-transporting layers (HTLs), macrocyclic copper (Ⅱ) phthalocyanine (CuPc) and the arylamine derivative of N4,N4,N4′,N4′-tetra([1,1′-biphenyl]-4-yl)-[1,1′:4′,1′-terphenyl]-4,4′-diamine (TaTm). Surprisingly, the robust CuPc limits the device performance with substantial non-radiative recombination loss and accelerates device degradation under light exposure. When built upon TaTm, the PSCs demonstrate a 47 times prolonged T80 lifetime (the efficiency drops to 80 % of the initial efficiency) of 1128 h by regulating the surface crystallography. By reducing the perovskite thickness to approach the buried heterojunction interface, we unravel the loss mechanism by directly observing crystallization dynamics. Our investigation reveals that surface polarity significantly influences the precursor adhesion, grain growth, and recombination dynamics at the HTL-perovskite interface. These findings underscore the critical role of the underlying surface in vapor-deposited PSCs, highlighting the potential for improved photostability through the regulation of interface imperfections.

Motion blur microscopy: in vitro imaging of cell adhesion dynamics in whole blood flow

Imaging and characterizing the dynamics of cellular adhesion in blood samples is of fundamental importance in understanding biological function. In vitro microscopy methods are widely used for this task but typically require diluting the blood with a buffer to allow for transmission of light. However, whole blood provides crucial signaling cues that influence adhesion dynamics, which means that conventional approaches lack the full physiological complexity of living microvasculature. We can reliably image cell interactions in microfluidic channels during whole blood flow by motion blur microscopy (MBM) in vitro and automate image analysis using machine learning. MBM provides a low cost, easy to implement alternative to intravital microscopy, for rapid data generation where understanding cell interactions, adhesion, and motility is crucial. MBM is generalizable to studies of various diseases, including cancer, blood disorders, thrombosis, inflammatory and autoimmune diseases, as well as providing rich datasets for theoretical modeling of adhesion dynamics.

Superposition of Substrate Deformation Fields Induced by Molecular Clutches Explains Cell Spatial Sensing of Ligands.

Cells can sense the physical properties of the extracellular matrices (ECMs), such as stiffness and ligand density, through cell adhesions to actively regulate their behaviors. Recent studies have shown that varying ligand spacing of ECMs can influence adhesion size, cell spreading, and even stem cell differentiation, indicating that cells have the spatial sensing ability of ECM ligands. However, the mechanism of the cells' spatial sensing remains unclear. In this study, we have developed a lattice-spring motor-clutch model by integrating cell membrane deformation, the talin unfolding mechanism, and the lattice spring for substrate ligand distribution to explore how the spatial distribution of integrin ligands and substrate stiffness influence cell spreading and adhesion dynamics. By applying the Gillespie algorithm, we found that large ligand spacing reduces the superposition effect of the substrate's displacement fields generated by pulling force from motor-clutch units, increasing the effective stiffness probed by the force-sensitive receptors; this finding explains a series of previous experiments. Furthermore, using the mean-field theory, we obtain the effective stiffness sensed by bound clutches analytically; our analysis shows that the bound clutch number and ligand spacing are the two key factors that affect the superposition effects of deformation fields and, hence, the effective stiffness. Overall, our study reveals the mechanism of cells' spatial sensing, i.e., ligand spacing changes the effective stiffness sensed by cells due to the superposition effect of deformation fields, which provides a physical clue for designing and developing biological materials that effectively control cell behavior and function.

A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall.

The Gram-negative bacterium Myxococcus xanthus glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here we show that AgmT, a highly abundant lytic PG transglycosylase homologous to Escherichia coli MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of E. coli MltG restores the connection between PG and bFACs and thus rescues gliding motility in the M. xanthus cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.

Label-Free Single-Cell Cancer Classification from the Spatial Distribution of Adhesion Contact Kinetics.

There is an increasing need for simple-to-use, noninvasive, and rapid tools to identify and separate various cell types or subtypes at the single-cell level with sufficient throughput. Often, the selection of cells based on their direct biological activity would be advantageous. These steps are critical in immune therapy, regenerative medicine, cancer diagnostics, and effective treatment. Today, live cell selection procedures incorporate some kind of biomolecular labeling or other invasive measures, which may impact cellular functionality or cause damage to the cells. In this study, we first introduce a highly accurate single-cell segmentation methodology by combining the high spatial resolution of a phase-contrast microscope with the adhesion kinetic recording capability of a resonant waveguide grating (RWG) biosensor. We present a classification workflow that incorporates the semiautomatic separation and classification of single cells from the measurement data captured by an RWG-based biosensor for adhesion kinetics data and a phase-contrast microscope for highly accurate spatial resolution. The methodology was tested with one healthy and six cancer cell types recorded with two functionalized coatings. The data set contains over 5000 single-cell samples for each surface and over 12,000 samples in total. We compare and evaluate the classification using these two types of surfaces (fibronectin and noncoated) with different segmentation strategies and measurement timespans applied to our classifiers. The overall classification performance reached nearly 95% with the best models showing that our proof-of-concept methodology could be adapted for real-life automatic diagnostics use cases. The label-free measurement technique has no impact on cellular functionality, directly measures cellular activity, and can be easily tuned to a specific application by varying the sensor coating. These features make it suitable for applications requiring further processing of selected cells.