Single-molecular-level study of claudin-1-mediated adhesion

Claudins are proteins that are selectively expressed at tight junctions (TJs) of epithelial cells where they play a central role in regulating paracellular permeability of solutes across epithelia. However, the role of claudins in intercellular adhesion and the mechanism by which they regulate the diffusion of solutes are poorly understood. Here, using single molecule force spectroscopy, the kinetic properties and adhesion strength of homophilic claudin-1 interactions were probed at the single-molecule level. Within the range of tested loading rates (10(3)-10(5) pN/s), our results showed that homophilic claudin-1 interactions have a reactive compliance of 0.363 +/- 0.061 nm and an unstressed dissociation rate of 1.351 +/- 1.312 s-1. This is more than 100-fold greater than that of E-cadherin. The weak and short-lived interactions between claudin-1 molecules make them highly unstable and dynamic in nature. Such a dynamic interaction is consistent with a model where breaking and resealing of TJ strands regulate the paracellular diffusion of solutes.     

Molecular understanding of the adhesive interactions between silica surface and epoxy resin: Effects of interfacial water

The molecular mechanism of the adhesion between silica surface and epoxy resin under atmospheric conditions is investigated by periodic density-functional-theory (DFT) calculations. Slab models of the adhesion interface were built by integrating a fragment of epoxy resin and hydroxylated (0 0 1) surface of α-cristobalite in the presence of adsorbed water molecules. Effects of adsorbed water on the adhesion interaction are evaluated on the basis of geometry-optimized structures, adhesion energies, and forces. Calculated results demonstrate that adsorbed water molecules significantly reduce both the adhesion energies and forces of the silica surface–epoxy resin interface. The reduction of adhesion properties can be associated with structural deformation of water molecules confined in the tight space between the adhesive and adherend as well as structural flexibility of the hydrogen-bonding network in the interfacial region during detachment of the epoxy resin from the hydrophilic silica surface. © 2018 Wiley Periodicals, Inc.     

Probing Deviation of Adhered Membrane Dynamics between Reconstituted Liposome and Cellular System

The dynamics of cell‐cell adhesion are complicated due to complexities in cellular interactions and intra‐membrane interactions. In the present work, we have reconstituted a liposome‐based model system to mimic the cell‐cell adhesion process. Our model liposome system consists of one fluorescein‐tagged and one TRITC (tetramethyl‐rhodamine isothiocyanate)‐tagged liposome, adhered through biotin‐neutravidin interaction. We monitored the adhesion process in liposomes using Förster Resonance Energy Transfer (FRET) between fluorescein (donor) and TRITC (acceptor). Occurrence of FRET is confirmed by the decrease in donor lifetime as well as distinct rise time of the acceptor fluorescence. Interestingly, the acceptor's emission exhibits fluctuations in the range of ≈3±1 s. This may be attributed to structural oscillations associated in two adhered liposomes arising from the flexible nature of biotin‐neutravidin interaction. We have compared the dynamics in a cell‐mimicking liposome system with that in an in vitro live cell system. In the adhered live cell system, we used CPM (7‐diethylamino‐3‐(4‐maleimido‐phenyl)‐4‐methylcoumarin, donor) and nile red (acceptor), which are known to stain the membrane of CHO (Chinese Hamster Ovary) cells. The dynamics of the adhered membranes of two live CHO cells were observed through FRET between CPM and nile red. The acceptor fluorescence intensity exhibits an oscillation in the time‐scale of ≈1±0.75 s, which is faster compared to the reconstituted liposome system, indicating the contributions and involvement of multiple dynamic protein complexes around the cell membrane. This study offers simple reconstituted model systems to understand the complex membrane dynamics using a FRET‐based physical chemistry approach.     

A chimeric antibody to L1 cell adhesion molecule shows therapeutic effect in an intrahepatic cholangiocarcinoma model

Intrahepatic cholangiocarcinoma (ICC), a malignant tumor derived from the intrahepatic bile duct epithelium, has a poor prognosis and is refractory to conventional chemotherapy and radiation therapy. Thus, there is an urgent need to develop new effective therapeutic strategies for this disease. We previously found that L1 cell adhesion molecule (L1CAM) plays an important role in tumor progression of ICC, and we generated a murine mAb, A10-A3 (IgG1), that binds to the Ig1 domain of L1CAM. In the present study, we further characterized A10-A3, constructed a chimeric A10-A3 antibody (cA10-A3) containing the constant regions of human IgG1, and evaluated the therapeutic potential in a human ICC xenograft nude mice model. The affinities (KD) of A10-A3 and cA10-A3 for soluble L1CAM were 1.8 nM and 1.9 nM, respectively, as determined by competition ELISA. A10-A3 inhibited L1CAM homophilic binding and was slowly internalized into the tumor cells, but it did not significantly inhibit proliferation of ICC cells in vitro. cA10-A3 mediated antibody- dependent cell-mediated cytotoxicity in vitro and displayed anti-tumor activity in the ICC animal model. These results suggest that the humanized A10-A3 antibody may have potential as an anticancer agent for the treatment of ICC.     

纳米粒子与细胞相互作用的力学-化学偶联研究进展

纳米粒子在生物医学和大气环境领域的广泛研究使得其生物安全性越来越受到重视。目前已经有许多研究关注纳米粒子与细胞的相互作用及细胞毒性问题。本综述从细胞力学-化学偶联的角度总结了近五年来有关纳米粒子与细胞相互作用的研究进展。首先介绍了与细胞力学-化学偶联性质相关的分子基础以及目前检测细胞机械性质的纳米技术,然后重点讨论了纳米粒子对细胞粘附、骨架、刚度和迁移性质的影响。在此基础上,进一步指出了纳米生物力学-化学偶联的挑战与展望。     

Engineering Substrate Topography at the Micro‐ and Nanoscale to Control Cell Function

The interaction of mammalian cells with nanoscale topography has proven to be an important signaling modality in controlling cell function. Naturally occurring nanotopographic structures within the extracellular matrix present surrounding cells with mechanotransductive cues that influence local migration, cell polarization, and other functions. Synthetically nanofabricated topography can also influence cell morphology, alignment, adhesion, migration, proliferation, and cytoskeleton organization. We review the use of in vitro synthetic cell–nanotopography interactions to control cell behavior and influence complex cellular processes, including stem‐cell differentiation and tissue organization. Future challenges and opportunities in cell–nanotopography engineering are also discussed, including the elucidation of mechanisms and applications in tissue engineering.     

Control of Three‐Dimensional Cell Adhesion by the Chirality of Nanofibers in Hydrogels

In the three‐dimensional (3D) extracellular matrix (ECM), the influence of nanofiber chirality on cell behavior is very important; the helical nanofibrous structure is closely related to the relevant biological events. Herein, we describe the use of the two enantiomers of a 1,4‐benzenedicarboxamide phenylalanine derivative as supramolecular gelators to investigate the influence of the chirality of nanofibers on cell adhesion and proliferation in three dimensions. It was found that left‐handed helical nanofibers can increase cell adhesion and proliferation, whereas right‐handed nanofibers have the opposite effect. These effects are ascribed to the mediation of the stereospecific interaction between chiral nanofibers and fibronectin. The results stress the crucial role of the chirality of nanofibers on cell‐adhesion and cell‐proliferation behavior in 3D environments.     

Novel recognition mechanisms in biological adhesion

Molecular recognition is generally thought of in terms of bond formation between unique sites on host and complementary guest molecules, but recent studies have revealed new complexities in biological recognition at cell. Adhesion between cell surfaces similarly involves specific interactions between analogous ligands and receptors. Recent force measurements, however, suggest that cell adhesion proteins may bind via multiple interaction sites that can form in a sequential manner. Other studies further show that in some instances, the principal recognition event may not be receptor–ligand docking, but the assembly of a complex pattern of many receptors and ligands.     

Effects of an avidin-biotin binding system on chondrocyte adhesion and growth on biodegradable polymers

Cell adhesion to a scaffold is a prerequisite for tissue engineering. Many studies have been focused on enhancing cell adhesion to synthetic materials that are used for scaffold fabrication. In this study, we applied an avidin-biotin binding system to enhance chondrocyte adhesion to biodegradable polymers. Biotin molecules were conjugated to the cell membrane of chondrocytes, and mediated cell adhesion to avidin-coated surfaces. We demonstrated that immobilization of biotin molecules to chondrocyte surfaces enhanced cell adhesion to avidin-coated biodegradable polymers such as poly(L-lactic acid), poly(D,L-lactic acid), and polycaprolactone, compared to the adhesion of normal chondrocytes to the same type of biodegradable polymer. The biotinylated chondrocytes still maintained their proliferation ability. This study showed the promise of applying the avidin-biotin system in cartilage tissue engineering. [diagram in text].     

Molecular modeling of class I and II alleles of the major histocompatibility complex in <Emphasis Type="Italic">Salmo salar</Emphasis>

Knowledge of the 3D structure of the binding groove of major histocompatibility (MHC) molecules, which play a central role in the immune response, is crucial to shed light into the details of peptide recognition and polymorphism. This work reports molecular modeling studies aimed at providing 3D models for two class I and two class II MHC alleles from Salmo salar (Sasa), as the lack of experimental structures of fish MHC molecules represents a serious limitation to understand the specific preferences for peptide binding. The reliability of the structural models built up using bioinformatic tools was explored by means of molecular dynamics simulations of their complexes with representative peptides, and the energetics of the MHC-peptide interaction was determined by combining molecular mechanics interaction energies and implicit continuum solvation calculations. The structural models revealed the occurrence of notable differences in the nature of residues at specific positions in the binding groove not only between human and Sasa MHC proteins, but also between different Sasa alleles. Those differences lead to distinct trends in the structural features that mediate the binding of peptides to both class I and II MHC molecules, which are qualitatively reflected in the relative binding affinities. Overall, the structural models presented here are a valuable starting point to explore the interactions between MHC receptors and pathogen-specific interactions and to design vaccines against viral pathogens.     

Multivalency as a Chemical Organization and Action Principle

Multivalent interactions can be applied universally for a targeted strengthening of an interaction between different interfaces or molecules. The binding partners form cooperative, multiple receptor–ligand interactions that are based on individually weak, noncovalent bonds and are thus generally reversible. Hence, multi‐ and polyvalent interactions play a decisive role in biological systems for recognition, adhesion, and signal processes. The scientific and practical realization of this principle will be demonstrated by the development of simple artificial and theoretical models, from natural systems to functional, application‐oriented systems. In a systematic review of scaffold architectures, the underlying effects and control options will be demonstrated, and suggestions will be given for designing effective multivalent binding systems, as well as for polyvalent therapeutics.     

Non-adsorbing macromolecules in plasma induce erythrocyte adhesion to the endothelium

Red blood cell (RBC) adhesion to the endothelium is usually insignificant. However, an enhanced adhesion can be observed in various pathological conditions such as diabetes mellitus or sickle cell disease, which is often accompanied by elevated levels of pro-adhesive plasma proteins such as fibrinogen. In the past, these proteins have only been considered to act as ligands, cross-linking the corresponding receptors on adjacent cells, but the detailed underlying mechanism often remained obscure. This work demonstrates that the presence of non-adsorbing polymers in plasma can also enhance the adhesion efficiency of RBCs to endothelial cells (ECs) through depletion interaction. Furthermore, adhesion of RBCs to ECs may be likewise promoted by the protein fibrinogen through depletion interaction. We propose an alternative mechanism for the pro-adhesive effects of plasma proteins and indicate that depletion interaction might play a significant role for the stabilization and destabilization of blood flow in health and disease.     

Structural and functional annotation of PR/SET Domain (PRDM) protein family: In-silico study elaborating role of PRDM12 mutation in congenital insensitivity to pain

Congenital insensitivity to pain (CIP), classified as a type of hereditary sensory and autonomic neuropathies, is a rare disease in which the affected individuals fail to perceive sensation of pain. One of the PR/SET Domain Proteins, PRDM12, has been identified in recent past as a candidate gene for congenital insensitivity to pain. In the present study, we performed whole exome sequencing in a Pakistani family with CIP phenotype to ascertain the causative mutation. We identified a previously described alanine repeat duplication in PRDM12 (Ala353_Ala359dup) in this family. After this, we performed structural annotations for PR/SET Domain (PRDM) containing protein family to prognosticate the potential hypothetical structure of PRDM proteins with physical and chemical parameters. Out of nineteen members of this family, four members (PRDM5, PRDM8, PRDM12 and PRDM13) were specially focused because of their role in neurological disorders. Predictions about structure and interactions of these proteins revealed novel interacting molecules and pathways. Detailed in silico analysis of PRDM12 was performed to elaborate importance of its domain structure in interaction with other proteins and its role in pain insensitivity phenotype. These results have substantially enhanced our understanding regarding the etiology of congenital pain insensitivity and would stimulate further research on therapy and prevention.     

Block Copolymer Brushes for Completely Decoupled Control of Determinants of Cell–Surface Interactions

The known determinants for cell–surface interactions, comprising biochemical cues, patterns, passivating functionality, and control of tether mechanical properties, are fully decoupled in tailored block copolymer brushes synthesized by surface‐initiated atom transfer radical polymerization. Exploiting sequential polymerization of a passivating underlying polyacrylamide (PAAm) block with defined cross‐linking followed by a second poly(acrylic acid) block, which can be conjugated with a selective adhesion peptide, hierarchically structured brushes that can be micro‐patterned by soft lithography were obtained. The interaction of NIH 3T3 fibroblasts and PaTu 8988t pancreatic tumor cells with brushes that differed only in the stiffness of the hidden PAAm block or only in the peptide ligand, while keeping all other parameters constant, revealing profound differences in cell adhesion and morphology. In particular, cells could only attach well to stiff RGD presenting brushes.     

The Cooperative Effect of Both Molecular and Supramolecular Chirality on Cell Adhesion

Although helical nanofibrous structures have great influence on cell adhesion, the role played by chiral molecules in these structures on cells behavior has usually been ignored. The chirality of helical nanofibers is inverted by the odd–even effect of methylene units from homochiral l ‐phenylalanine derivative during assembly. An increase in cell adhesion on left‐handed nanofibers and weak influence of cell behaviors on right‐handed nanofibers are observed, even though both were derived from l ‐phenylalanine derivatives. Weak and negative influences on cell behavior was also observed for left‐ and right‐handed nanofibers derived from d ‐phenylalanine, respectively. The effect on cell adhesion of single chiral molecules and helical nanofibers may be mutually offset.     

Peptide–Protein Interactions: From Drug Design to Supramolecular Biomaterials

The self-recognition and self-assembly of biomolecules are spontaneous processes that occur in Nature and allow the formation of ordered structures, at the nanoscale or even at the macroscale, under thermodynamic and kinetic equilibrium as a consequence of specific and local interactions. In particular, peptides and peptidomimetics play an elected role, as they may allow a rational approach to elucidate biological mechanisms to develop new drugs, biomaterials, catalysts, or semiconductors. The forces that rule self-recognition and self-assembly processes are weak interactions, such as hydrogen bonding, electrostatic attractions, and van der Waals forces, and they underlie the formation of the secondary structure (e.g., α-helix, β-sheet, polyproline II helix), which plays a key role in all biological processes. Here, we present recent and significant examples whereby design was successfully applied to attain the desired structural motifs toward function. These studies are important to understand the main interactions ruling the biological processes and the onset of many pathologies. The types of secondary structure adopted by peptides during self-assembly have a fundamental importance not only on the type of nano- or macro-structure formed but also on the properties of biomaterials, such as the types of interaction, encapsulation, non-covalent interaction, or covalent interaction, which are ultimately useful for applications in drug delivery.     

Molecular Encryption and Reconfiguration for Remodeling of Dynamic Hydrogels

Dynamic materials have been widely studied for regulation of cell adhesion that is important to a variety of biological and biomedical applications. These materials can undergo changes mainly through one of the two mechanisms: ligand release in response to chemical, physical, or biological stimuli, and ligand burial in response to mechanical stretching or the change of electrical potential. This study demonstrates an encrypted ligand and a new hydrogel that are capable of inducing and inhibiting cell adhesion, which is controlled by molecular reconfiguration. The ligand initially exhibits an inert state; it can be reconfigured into active and inert states by using unblocking and recovering molecules in physiological conditions. Since molecular reconfiguration does not require the release of the ligand from the hydrogels, inhibiting and inducing cell adhesion on the hydrogels can be repeated for multiple cycles.     

利用表面上的小分子控制细胞黏附

细胞黏附是重要的生理过程,多细胞生物体中大部分种类的细胞都依赖于在表面的黏附而进行其正常生理活动。细胞的黏附需要固定在表面的有机分子（例如蛋白质或多肽）作配体。我们利用表面小分子模拟蛋白质或多肽作为配体,通过与细胞膜上受体结合,促进细胞黏附到表面。聚乙二醇（PEG）可以抵抗细胞在表面的黏附,我们利用含有PEG的表面小分子来调节细胞黏附。细胞表面的受体与胞外基质表面的配体结合是一个动态过程,在适宜时间和空间发生的时候,细胞就会产生运动和迁移,细胞的迁移也是重要的生理过程。本文主要介绍近年来利用小分子的表面化学和微纳米结构控制细胞在表面的黏附和迁移。     

Inflammatory mimetic microfluidic chip by immobilization of cell adhesion molecules for T cell adhesion

Leukocyte adhesion to adhesion molecules on endothelial cells is important in immune function, cancer metastasis and inflammation. This cell-cell binding is mediated via cell adhesion molecules such as E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) found on endothelial cells. Because these adhesion molecules on endothelial cells vary significantly across several disease conditions such as autoimmune diseases, inflammation or cancer metastasis, investigations of therapeutic agents that down-regulate leukocyte-endothelial interactions have been based on in vitro models using endothelial cell lines. Here we report a new model, an inflammatory mimetic microfluidic chip, which emulates leukocyte binding to cell adhesion molecules (CAM) by controlling the types and ratio of adhesion molecules. In our model, E-selectin was essential for the synergic binding of Jurkat T cells. Immunosuppressive drugs, such as tacrolimus (FK506) and cyclosporine A (CsA), were used to inhibit T cell interactions under the physiologic model of T cell migration at a ratio of 5?:?4.3?:?3.9 (E-selectin?:?ICAM-1?:?VCAM-1). Our results support the potential usefulness of the inflammatory mimetic microfluidic chip as a T cell adhesion assay tool with modified adhesion molecules for applications such as immunosuppressive drug screening. The inflammatory mimetic microfluidic chip can also be used as a biosensor in clinical diagnostics, drug efficacy tests and high throughput drug screening due to the dynamic monitoring capability of the microfluidic chip.     

Characterization of a hierarchical network of hyaluronic acid/gelatin composite for use as a smart injectable biomaterial

Hybrid HA/Ge hydrogel particles are embedded in a secondary HA network to improve their structural integrity. The internal microstructure of the particles is imaged through TEM. CSLM is used to identify the location of the Ge molecules in the microgels. Through indentation tests, the Young's modulus of the individual particles is found to be 22 ± 2.5 kPa. The overall shear modulus of the composite is 75 ± 15 Pa at 1 Hz. The mechanical properties of the substrate are found to be viable for cell adhesion. The particles' diameter at pH = 8 is twice that at pH = 5. The pH sensitivity is found to be appropriate for smart drug delivery. Based on their mechanical and structural properties, HA-Ge hierarchical materials may be well suited for use as injectable biomaterials for tissue reconstruction.