Adaptive Liquid Interfacially Assembled Protein Nanosheets for Guiding Mesenchymal Stem Cell Fate

A Versatile Approach to Stabilize Liquid-Liquid Interfaces using Surfactant Self-Assembly

Stabilizing liquid-liquid interfaces, whether between miscible or immiscible liquids, is crucial for a wide range of applications, including energy storage, microreactors, and biomimetic structures. In this study, a versatile approach for stabilizing the water-oil interface is presented using the morphological transitions that occur during the self-assembly of anionic, cationic, and nonionic surfactants mixed with fatty acid oils. The morphological transitions underlying this approach are characterized and extensively studied through small-angle X-ray scattering (SAXS), rheometry, and microscopy techniques. Dissipative particle dynamics (DPD) as a simulation tool is adopted to investigate these morphological transitions both in the equilibrium ternary system as well as in the dynamic condition of the water-oil interface. Such a versatile strategy holds promise for enhancing applications such as liquid-in-liquid 3D printing. Moreover, it has the potential to revolutionize a wide range of fields where stabilizing liquid-liquid interfaces not only offers unprecedented opportunities for fine-tuning nanostructural morphologies but also imparts interesting practical features to the resulting liquid shapes. These features include perfusion capabilities, self-healing, and porosity, which could have significant implications for various industries.

Liquid Interfacial Gating of Superhydrophobic Plasmonic Metal-Organic Frameworks for Three-in-One Separation, Enrichment, and Recognition in Bacterial Quorum Sensing

Poor adsorption properties of nonadsorbing targets and competing adsorption of nontargets at a liquid interface always hamper the development of interface sensing techniques. There is a need to fabricate materials that are applicable to various interface assemblies and, meanwhile, could be employed as interfacial gating to improve the performance of interface sensing by separating, enriching, and recognizing targets at the liquid interface. Here, superhydrophobic zeolite imidazole frameworks-8@gold nanoparticles-1H,1H,2H,2H-perfluorodecanethiol (ZIF-8@GNPs-PFDT) with a static water contact angle (WCA) of 155° was constructed via electrostatic self-assembly and surface graft modification. The plasmonic metal-organic framework (PMOF) nanohybrid realized all-purpose self-assembly at air/liquid and liquid/liquid interfaces and also facilely assembled on the surface of liquid droplets, hydrogels, and foams. The self-assembled porous materials displayed the capability for separating, enriching, and recognizing analytes at various oil/water interfaces and thus could be used to adsorb nonadsorbing targets and block the competing adsorption of nontargets. The self-assembled ZIF-8@GNPs-PFDT structures were employed as a three-in-one interfacial gating to endow the excellent surface-enhanced Raman scattering (SERS) sensing capability and has become a promising tool for dye molecular analysis, oil/water separation, organic phase identification, and in situ cultivation and monitoring of bacterial quorum sensing (QS).

Formulate Adaptive Biphasic Scaffold via Sequential Protein-Instructed Peptide Co-Assembly

To ensure compositional consistency while mitigating potential immunogenicity for stem cell therapy, synthetic scaffolds have emerged as compelling alternatives to native extracellular matrix (ECM). Substantial progress has been made in emulating specific natural traits featuring consistent chemical compositions and physical structures. However, recapitulating the dynamic responsiveness of the native ECM involving chemical transitions and physical remodeling during differentiation, remains a challenging endeavor. Here, the creation of adaptive scaffolds is demonstrated through sequential protein-instructed molecular assembly, utilizing stage-specific proteins, and incorporating in situ assembly technique. The procedure is commenced by introducing a dual-targeting peptide at the onset of stem cell differentiation. In response to highly expressed integrins and heparan sulfate proteoglycans (HSPGs) on human mesenchymal stem cell (hMSC), the peptides assembled in situ, creating customized extracellular scaffolds that adhered to hMSCs promoting osteoblast differentiation. As the expression of alkaline phosphatase (ALP) and collagen (COL-1) increased in osteoblasts, an additional peptide is introduced that interacts with ALP, initiating peptide assembly and facilitating calcium phosphate (CaP) deposition. The growth and entanglement of peptide assemblies with collagen fibers efficiently incorporated CaP into the network resulting in an adaptive biphasic scaffold that enhanced healing of bone injuries.

Ultimately Adaptive Fluid Interfacial Phospholipid Membranes Unveiled Unanticipated High Cellular Mechanical Work

Living cells actively interact biochemically and mechanically with the surrounding extracellular matrices (ECMs) and undergo dramatic morphological and dimensional transitions, concomitantly remodeling ECMs. However, there is no suitable method to quantitatively discuss the contribution of mechanical interactions in such mutually adaptive processes. Herein, a highly deformable "living" cellular scaffold is developed to evaluate overall mechanical energy transfer between cell and ECMs. It is based on the water-perfluorocarbon interface decorated with phospholipids bearing a cell-adhesive ligand and fluorescent tag. The bioinert nature of the phospholipid membranes prevents the formation of solid-like protein nanofilms at the fluid interface, enabling to visualize and quantify cellular mechanical work against the ultimately adaptive model ECM. A new cellular wetting regime is identified, wherein interface deformation proceeds to cell flattening, followed by its eventual restoration. The cellular mechanical work during this adaptive wetting process is one order of magnitude higher than those reported with conventional elastic platforms. The behavior of viscous liquid drops at the air-water interface can simulate cellular adaptive wetting, suggesting that overall viscoelasticity of the cell body predominates the emergent wetting regime and regulates mechanical output. Cellular-force-driven high-energy states on the adaptive platform can be useful for cell fate manipulation.

2D Materials Nanoarchitectonics for 3D Structures/Functions

It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the post-nanotechnology concept of nanoarchitectonics. However, nanoarchitectonics, which creates intricate three-dimensional functional structures, is not always easy. Two-dimensional nanoarchitectonics based on reactions and arrangements at the surface may be an easier target to tackle. A better methodology would be to define a two-dimensional structure and then develop it into a three-dimensional structure and function. According to these backgrounds, this review paper is organized as follows. The introduction is followed by a summary of the three issues; (i) 2D to 3D dynamic structure control: liquid crystal commanded by the surface, (ii) 2D to 3D rational construction: a metal-organic framework (MOF) and a covalent organic framework (COF); (iii) 2D to 3D functional amplification: cells regulated by the surface. In addition, this review summarizes the important aspects of the ultimate three-dimensional nanoarchitectonics as a perspective. The goal of this paper is to establish an integrated concept of functional material creation by reconsidering various reported cases from the viewpoint of nanoarchitectonics, where nanoarchitectonics can be regarded as a method for everything in materials science.

Ionic Liquid Interface as a Cell Scaffold

In sharp contrast to conventional solid/hydrogel platforms, water-immiscible liquids, such as perfluorocarbons and silicones, allow the adhesion of mammalian cells via protein nanolayers (PNLs) formed at the interface. However, fluorocarbons and silicones, which are typically used for liquid cell culture, possess only narrow ranges of physicochemical parameters and have not allowed for a wide variety of cell culturing environments. In this paper, it is proposed that water-immiscible ionic liquids (ILs) are a new family of liquid substrates with tunable physicochemical properties and high solvation capabilities. Tetraalkylphosphonium-based ILs are identified as non-cytotoxic ILs, whereon human mesenchymal stem cells are successfully cultured. By reducing the cation charge distribution, or ionicity, via alkyl chain elongation, the interface allows cell spreading with matured focal contacts. High-speed atomic force microscopy observations of the PNL formation process suggest that the cation charge distribution significantly altered the protein adsorption dynamics, which are associated with the degree of protein denaturation and the PNL mechanics. Moreover, by exploiting dissolution capability of ILs, an ion-gel cell scaffold is fabricated. This enables to further identify the significant contribution of bulk subphase mechanics to cellular mechanosensing in liquid-based culture scaffolds.

An extracellular matrix-mimicking magnetic microrobot for targeted elimination of circulating cancer cells

Cancer cells disseminate through the bloodstream, leading to metastasis in distant sites within the body. One promising strategy to prevent metastasis is to eliminate circulating tumor cells. However, this remains challenging due to the lack of an active and targeted biomedical tool for efficient cancer cell elimination. Here, we developed a magnetic microrobot by using natural materials derived from the extracellular matrix (ECM) to mimic the ligand-receptor interaction between cancer cells and the ECM, offering targeted elimination of cancer cells. The ECM-mimicking microrobot is designed with a biodegradable hydrogel matrix, incorporating a cancer cell ligand and magnetic microparticles for cancer cell capture and active locomotion. This microrobot was fabricated based on an interface-shearing method, enabling controllable magnetic response and size scalability (30 μm-500 μm). The presented ECM-mimicking microrobot can actively approach and capture single cancer cells and cell clusters under the control of specific magnetic fields. The experiment was conducted in a blood vessel-mimicking simulator. The microrobot demonstrates an outstanding elimination efficacy of 92.3% on MDA-MB-231 cancer cells and a stable transport capability of the captured cells over long distances to a designed recycling site, inhibiting cell metastasis. This magnetic ECM-mimicking microrobot based on a bioinspired binding mechanism represents a promising candidate for the efficient elimination of cancer cells and other biological waste in the blood.

Co-Surfactant-Free Bioactive Protein Nanosheets for the Stabilization of Bioemulsions Enabling Adherent Cell Expansion

Bioemulsions are attractive platforms for the scalable expansion of adherent cells and stem cells. In these systems, cell adhesion is enabled by the assembly of protein nanosheets that display high interfacial shear moduli and elasticity. However, to date, most successful systems reported to support cell adhesion at liquid substrates have been based on coassemblies of protein and reactive cosurfactants, which limit the translation of bioemulsions. In this report, we describe the design of protein nanosheets based on two globular proteins, bovine serum albumin (BSA) and β-lactoglobulin (BLG), biofunctionalized with RGDSP peptides to enable cell adhesion. The interfacial mechanics of BSA and BLG assemblies at fluorinated liquid-water interfaces is studied by interfacial shear rheology, with and without cosurfactant acyl chloride. Conformational changes associated with globular protein assembly are studied by circular dichroism and protein densities at fluorinated interfaces are evaluated via surface plasmon resonance. Biofunctionalization mediated by sulfo-succinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC) is studied by fluorescence microscopy. On the basis of the relatively high elasticities observed in the case of BLG nanosheets, even in the absence of cosurfactant, the adhesion and proliferation of mesenchymal stem cells and human embryonic kidney (HEK) cells on bioemulsions stabilized by RGD-functionalized protein nanosheets is studied. To account for the high cell spreading and proliferation observed at these interfaces, despite initial moderate interfacial elasticities, the deposition of fibronectin fibers at the surface of corresponding microdroplets is characterized by immunostaining and confocal microscopy. These results demonstrate the feasibility of achieving high cell proliferation on bioemulsions with protein nanosheets assembled without cosurfactants and establish strategies for rational design of scaffolding proteins enabling the stabilization of interfaces with strong shear mechanics and elasticity, as well as bioactive and cell adhesive properties. Such protein nanosheets and bioemulsions are proposed to enable the development of new generations of bioreactors for the scale up of cell manufacturing.

Manipulating the Dynamic Adaptivity of a Fluid Interface to Maintain the Multipotency of Mesenchymal Stromal Cells

The native extracellular matrix is highly dynamic with continuous mutual feedback between cells being responsible for many important cell function regulators. However, establishing bidirectional interaction between complex adaptive microenvironments and cells remains elusive. Herein an adaptive biomaterial based on lysozyme monolayers self-assembled at a perfluorocarbon FC40-water interface is reported. The dynamic adaptivity of interfacially assembled protein nanosheets is modulated independently of bulk mechanical properties by covalent crosslinking. This provides a scenario to establish bidirectional interactions of cells with liquid interfaces of varying dynamic adaptivity. This is found that growth and multipotency of human mesenchymal stromal cells (hMSCs) are enhanced at the highly adaptive fluid interface. The multipotency retention of hMSCs is mediated by low cell contractility and metabolomic activity involving the continuous mutual feedback between the cells and materials. Consequently, an understanding of the cells' response to dynamic adaptivity has substantial implications for regenerative medicine and tissue engineering.

Liquid-Liquid Interfacial Nanoarchitectonics

Science in the small world has become a crucial key that has the potential to revolutionize materials technology. This trend is embodied in the postnanotechnology concept of nanoarchitectonics. The goal of nanoarchitectonics is to create bio-like functional structures, in which self-organized and hierarchical structures are working efficiently. Liquid-liquid interface like environments such as cell membrane surface are indispensable for the expression of biological functions through the accumulation and organization of functional materials. From this viewpoint, it is necessary to reconsider the liquid-liquid interface as a medium where nanoarchitectonics can play an active role. In this review, liquid-liquid interfacial nanoarchitectonics is classified by component materials such as organic, inorganic, carbon, and bio, and recent research examples are discussed. Examples discussed in this paper include molecular aggregates, supramolecular polymers, conductive polymers film, crystal-like capsules, block copolymer assemblies, covalent organic framework (COF) films, complex crystals, inorganic nanosheets, colloidosomes, fullerene assemblies, all-carbon π-conjugated graphite nanosheets, carbon nanoskins and fullerphene thin films at liquid-liquid interfaces. Furthermore, at the liquid-liquid interface using perfluorocarbons and aqueous phases, cell differentiation controls are discussed with the self-assembled structure of biomaterials. The significance of liquid-liquid interfacial nanoarchitectonics in the future development of materials will then be discussed.

Guideline for design of substrate stiffness for mesenchymal stem cell culture based on heterogeneity of YAP and RUNX2 responses

Mesenchymal stem cells (MSCs) have the potential for self-renewal and multipotency to differentiate into various lineages. Thus, they are of great interest in regenerative medicine as a cell source for tissue engineering. Substrate stiffness is one of the most extensively studied exogenous physical factors; however, consistent results have not always been reported for controlling MSCs. Conventionally used stiff culture substrates, such as tissue-culture polystyrene and glass, enhance nuclear localization of a mechanotransducer YAP and a pre-osteogenic transcription factor RUNX2, and bias MSCs towards the osteogenic lineage, even without osteogenic-inducing soluble factors. The mechanosensitive nature and intrinsic heterogeneity present challenges for obtaining reproducible results. This review summarizes the heterogeneity in human MSC response, specifically, nuclear/cytoplasmic localization changes in the mechanotransducer yes-associated protein (YAP) and the osteogenic transcription factor RUNX2, in response to substrate stiffness. In addition, a perspective on the intracellular factors attributed to response heterogeneity is discussed. The optimal range of stiffness parameters, Young's modulus, for MSC expansion culture to suppress osteogenic differentiation bias through the suppression of YAP and RUNX2 nuclear localization, and cell cycle progression is likely to be surprisingly narrow for a cell population from an identical donor and vary among cell populations from different donors. We believe that characterization of the heterogeneity of MSCs and understanding their biological meaning is an exciting research direction to establish guidelines for the design of culture substrates for the sophisticated control of MSC properties.

Mesenchymal Stem Cells Sense the Toughness of Nanomaterials and Interfaces

Stem cells are known to sense and respond to the mechanical properties of biomaterials. In turn, cells exert forces on their environment that can lead to striking changes in shape, size and contraction of associated tissues, and may result in mechanical disruption and functional failure. However, no study has so far correlated stem cell phenotype and biomaterials toughness. Indeed, disentangling toughness-mediated cell response from other mechanosensing processes has remained elusive as it is particularly challenging to uncouple Youngs' or shear moduli from toughness, within a range relevant to cell-generated forces. In this report, it is shown how the design of the macromolecular architecture of polymer nanosheets regulates interfacial toughness, independently of interfacial shear storage modulus, and how this controls the expansion of mesenchymal stem cells at liquid interfaces. The viscoelasticity and toughness of poly(l-lysine) nanosheets assembled at liquid-liquid interfaces is characterised via interfacial shear rheology. The local (microscale) mechanics of nanosheets are characterised via magnetic tweezer-assisted interfacial microrheology and the thickness of these assemblies is determined from in situ ellipsometry. Finally, the response of mesenchymal stem cells to adhesion and culture at corresponding interfaces is investigated via immunostaining and confocal microscopy.

Supercharged Protein Nanosheets for Cell Expansion on Bioemulsions

Cell culture at liquid-liquid interfaces, for example, at the surface of oil microdroplets, is an attractive strategy to scale up adherent cell manufacturing while replacing the use of microplastics. Such a process requires the adhesion of cells at interfaces stabilized and reinforced by protein nanosheets displaying not only high elasticity but also presenting cell adhesive ligands able to bind integrin receptors. In this report, supercharged albumins are found to form strong elastic protein nanosheets when co-assembling with the co-surfactant pentafluorobenzoyl chloride (PFBC) and mediate extracellular matrix (ECM) protein adsorption and cell adhesion. The interfacial mechanical properties and elasticity of supercharged nanosheets are characterized by interfacial rheology, and behaviors are compared to those of native bovine serum albumin, human serum albumin, and α-lactalbumin. The impact of PFBC on such assembly is investigated. ECM protein adsorption to resulting supercharged nanosheets is then quantified via surface plasmon resonance and fluorescence microscopy, demonstrating that the dual role supercharged albumins are proposed to play as scaffold protein structuring liquid-liquid interfaces and substrates for the capture of ECM molecules. Finally, the adhesion and proliferation of primary human epidermal stem cells are investigated, at pinned droplets, as well as on bioemulsions stabilized by corresponding supercharged nanosheets. This study demonstrates the potential of supercharged proteins for the engineering of biointerfaces for stem cell manufacturing and draws structure-property relationships that will guide further engineering of associated systems.

Viscoelastic Liquid Matrix with Faster Bulk Relaxation Time Reinforces the Cell Cycle Arrest Induction of the Breast Cancer Cells via Oxidative Stress

The reactivating of disseminated dormant breast cancer cells in a soft viscoelastic matrix is mostly correlated with metastasis. Metastasis occurs due to rapid stress relaxation owing to matrix remodeling. Here, we demonstrate the possibility of promoting the permanent cell cycle arrest of breast cancer cells on a viscoelastic liquid substrate. By controlling the molecular weight of the hydrophobic molten polymer, poly(ε-caprolactone-co-D,L-lactide) within 35-63 g/mol, this study highlights that MCF7 cells can sense a 1000 times narrower relaxation time range (80-290 ms) compared to other studies by using a crosslinked hydrogel system. We propose that the rapid bulk relaxation response of the substrate promotes more reactive oxygen species generation in the formed semi-3D multicellular aggregates of breast cancer cells. Our finding sheds light on the potential role of bulk stress relaxation in a viscous-dominant viscoelastic matrix in controlling the cell cycle arrest depth of breast cancer cells.

Static and photoresponsive dynamic materials to dissect physical regulation of cellular functions

Recent progress in mechanobiology has highlighted the importance of physical cues, such as mechanics, geometry (size), topography, and porosity, in the determination of cellular activities and fates, in addition to biochemical factors derived from their surroundings. In this review, we will first provide an overview of how such fundamental insights are identified by synchronizing the hierarchical nature of biological systems and static materials with tunable physical cues. Thereafter, we will explain the photoresponsive dynamic biomaterials to dissect the spatiotemporal aspects of the dependence of biological functions on physical cues.

Materials nanoarchitectonics in a two-dimensional world within a nanoscale distance from the liquid phase

Promoted understanding of nanotechnology has enabled the construction of functional materials with nanoscale-regulated structures. Accordingly, materials science requires one-step further innovation by coupling nanotechnology with the other materials sciences. As a post-nanotechnology concept, nanoarchitectonics has recently been proposed. It is a methodology to architect functional material systems using atomic, molecular, and nanomaterial unit-components. One of the attractive methodologies would be to develop nanoarchitectonics in a defined dimensional environment with certain dynamism, such as liquid interfaces. However, nanoarchitectonics at liquid interfaces has not been fully explored because of difficulties in direct observations and evaluations with high-resolutions. This unsatisfied situation in the nanoscale understanding of liquid interfaces may keep liquid interfaces as unexplored and attractive frontiers in nanotechnology and nanoarchitectonics. Research efforts related to materials nanoarchitectonics on liquid interfaces have been continuously made. As exemplified in this review paper, a wide range of materials can be organized and functionalized on liquid interfaces, including organic molecules, inorganic nanomaterials, hybrids, organic semiconductor thin films, proteins, and stem cells. Two-dimensional nanocarbon sheets have been fabricated by molecular reactions at dynamically moving interfaces, and metal-organic frameworks and covalent organic frameworks have been fabricated by specific interactions and reactions at liquid interfaces. Therefore, functions such as sensors, devices, energy-related applications, and cell control are being explored. In fact, the potential for the nanoarchitectonics of functional materials in two-dimensional nanospaces at liquid surfaces is sufficiently high. On the basis of these backgrounds, this short review article describes recent approaches to materials nanoarchitectonics in a liquid-based two-dimensional world, i.e., interfacial regions within a nanoscale distance from the liquid phase.

Two-Dimensional Metal-Organic Framework-Based Cellular Scaffolds with High Protein Adsorption, Retention, and Replenishment Capabilities

Metal-organic frameworks (MOFs) are porous materials with adsorption, storage, and separation capabilities due to their high specific surface areas and large pore volumes. MOFs are thus used in biomedical applications, and MOF nanoparticles have been widely studied as nanocarriers for drug delivery systems. Several research groups recently reported that specific MOF nanoparticles can adsorb and retain proteins, suggesting to us that MOF nanoparticles may have advantages as novel cell culture scaffolds. However, MOF nanoparticles cannot be used as two-dimensional scaffolds for cells. We therefore established a bottom-up technique to construct two-dimensional MOFs [MIL-53 (Al)] on polymer films. The developed two-dimensional MIL-53 (Al) film [fMIL-53 (Al)] exhibited high serum protein adsorption, retention, and replenishment capabilities as compared to conventional cell culture scaffolds. β-Galactosidase, used as a model protein, adsorbed on fMIL-53 (Al) exhibited original enzymatic activity, indicating that proteins are not denatured during the adsorption process. The viability of mouse myoblast cells (C2C12) cultured on fMIL-53 (Al) was 100%, indicating the cell compatibility of fMIL-53 (Al). Importantly, C2C12 cells cultured on serum protein-preadsorbed fMIL-53 (Al) exhibited excellent long-term adhesion, morphology, and proliferation even in a medium lacking serum proteins, demonstrating an important advantage of fMIL-53 (Al) as a cell culture scaffold, given that conventional cell culture scaffolds typically require a serum-containing medium to support stable cell adhesion and proliferation. To our knowledge, this is the first report regarding the application of MOFs as cell culture scaffolds and will serve as a starting point for studying two- and three-dimensional MOF-based cellular scaffolds for cell culture systems and for in vitro and in vivo tissue engineering.

Constructing ECM-like Structure on the Plasma Membrane via Peptide Assembly to Regulate the Cellular Response

This feature article introduces the design of self-assembling peptides that serve as the basic building blocks for the construction of extracellular matrix (ECM)-like structure in the vicinity of the plasma membrane. By covalently conjugating a bioactive motif, such as membrane protein binding ligand or enzymatic responsive building block, with a self-assembling motif, especially the aromatic peptide, a self-assembling peptide that retains bioactivity is obtained. Instructed by the target membrane protein or enzyme, the bioactive peptides self-assemble into ECM-like structure exerting various stimuli to regulate the cellular response via intracellular signaling, especially mechanotransduction. By briefly summarizing the properties and applications (e.g., wound healing, controlling cell motility and cell fate) of these peptides, we intend to illustrate the basic requirements and promises of the peptide assembly as a true bottom-up approach in the construction of artificial ECM.

Bioactive 2D nanomaterials for neural repair and regeneration

Biomaterials have provided promising strategies towards improving the functions of injured tissues of the nervous system. Recently, 2D nanomaterials, such as graphene, layered double hydroxides (LDHs), and black phosphorous, which are characterized by ultrathin film structures, have attracted much attention in the fields of neural repair and regeneration. 2D nanomaterials have extraordinary physicochemical properties and excellent biological activities, such as a large surface-area-to-thickness ratio, high levels of adhesion, and adjustable flexibility. In addition, they can be designed to have superior biocompatibility and electrical or nano-carrier properties. To date, many 2D nanomaterials have been used for synaptic modulation, neuroinflammatory reduction, stem cell fate regulation, and injured neural cell/tissue repair. In this review, we discuss the advances in 2D nanomaterial technology towards novel neurological applications and the mechanisms underlying their unique features. In addition, the future outlook of functional 2D nanomaterials towards addressing the difficult issues of neuropathy has been explored to introduce a promising strategy towards repairing and regenerating the injured nervous system.

Adaptive liquid interfaces induce neuronal differentiation of mesenchymal stem cells through lipid raft assembly

Stem cells and their microenvironment interact cooperatively to dictate their fates. Biomaterials are dynamically remodeled by stem cells, and stem cells sense and translate the changes into cell fate decisions. We have previously reported that adaptive biomaterials composed of fibronectin inserted into protein nanosheets at a liquid interface enhance neuronal differentiation of human mesenchymal stem cells (hMSCs). However, we could not decouple clearly the effect of ligand density from that of fibrillary structure on cellular function and fate. Here we present an adaptive biomaterial based on two-dimensional networks of protein nanofibrils at a liquid–liquid interface. Compared with flat protein nanosheets, this biomaterial enhances neuronal differentiation of hMSCs through a signaling mechanism involving focal adhesion kinase. Lipid raft microdomains in plasma membrane are found to play a central role in which hMSCs rapidly adapt to the dynamic microenvironment at the fluid interface. Our finding has substantial implications for regenerative medicine and tissue engineering.

In this work the authors report how human mesenchymal stem cells rapidly adapt to dynamic microenvironment through lipid raft in membrane microdomains that direct neurogenesis.

Mechano-Nanoarchitectonics: Design and Function

Mechanical stimuli have rather ambiguous and less-specific features among various physical stimuli, but most materials exhibit a certain level of responses upon mechanical inputs. Unexplored sciences remain in mechanical responding systems as one of the frontiers of materials science. Nanoarchitectonics approaches for mechanically responding materials are discussed as mechano-nanoarchitectonics in this review article. Recent approaches on molecular and materials systems with mechanical response capabilities are first exemplified with two viewpoints: i) mechanical control of supramolecular assemblies and materials and ii) mechanical control and evaluation of atom/molecular level structures. In the following sections, special attentions on interfacial environments for mechano-nanoarchitectonics are emphasized. The section entitled iii) Mechanical Control of Molecular System at Dynamic Interface describes coupling of macroscopic mechanical forces and molecular-level phenomena. Delicate mechanical forces can be applied to functional molecules embedded at the air-water interface where operation of molecular machines and tuning of molecular receptors upon macroscopic mechanical actions are discussed. Finally, the important role of the interfacial media are further extended to the control of living cells as described in the section entitled iv) Mechanical Control of Biosystems. Pioneering approaches on cell fate regulations at liquid-liquid interfaces are discussed in addition to well-known mechanobiology.

Biomimetic and Biological Nanoarchitectonics

A post-nanotechnology concept has been assigned to an emerging concept, nanoarchitectonics. Nanoarchitectonics aims to establish a discipline in which functional materials are fabricated from nano-scale components such as atoms, molecules, and nanomaterials using various techniques. Nanoarchitectonics opens ways to form a more unified paradigm by integrating nanotechnology with organic chemistry, supramolecular chemistry, material chemistry, microfabrication technology, and biotechnology. On the other hand, biological systems consist of rational organization of constituent molecules. Their structures have highly asymmetric and hierarchical features that allow for chained functional coordination, signal amplification, and vector-like energy and signal flow. The process of nanoarchitectonics is based on the premise of combining several different processes, which makes it easier to obtain a hierarchical structure. Therefore, nanoarchitectonics is a more suitable methodology for creating highly functional systems based on structural asymmetry and hierarchy like biosystems. The creation of functional materials by nanoarchitectonics is somewhat similar to the creation of functional systems in biological systems. It can be said that the goal of nanoarchitectonics is to create highly functional systems similar to those found in biological systems. This review article summarizes the synthesis of biomimetic and biological molecules and their functional structure formation from various viewpoints, from the molecular level to the cellular level. Several recent examples are arranged and categorized to illustrate such a trend with sections of (i) synthetic nanoarchitectonics for bio-related units, (ii) self-assembly nanoarchitectonics with bio-related units, (iii) nanoarchitectonics with nucleic acids, (iv) nanoarchitectonics with peptides, (v) nanoarchitectonics with proteins, and (vi) bio-related nanoarchitectonics in conjugation with materials.

The Past and the Future of Langmuir and Langmuir-Blodgett Films

The Langmuir-Blodgett (LB) technique, through which monolayers are transferred from the air/water interface onto a solid substrate, was the first method to allow for the controlled assembly of organic molecules. With its almost 100 year history, it has been the inspiration for most methods to functionalize surfaces and produce nanocoatings, in addition to serving to explore concepts in molecular electronics and nanoarchitectonics. This paper provides an overview of the history of Langmuir monolayers and LB films, including the potential use in devices and a discussion on why LB films are seldom considered for practical applications today. Emphasis is then given to two areas where these films offer unique opportunities, namely, in mimicking cell membrane models and exploiting nanoarchitectonics concepts to produce sensors, investigate molecular recognitions, and assemble molecular machines. The most promising topics for the short- and long-term prospects of the LB technique are also highlighted.

Exploiting Molecular Dynamics in Composite Coatings to Design Robust Super-Repellent Surfaces

Fluorinated motifs are promising for the engineering of repellent coatings, however, a fundamental understanding of how to effectively bind these motifs to various substrates is required to improve their stability in different use scenarios. Herein, the binding of fluorinated polyhedral oligomeric silsesquioxanes (POSS) using a cyanoacrylate glue (binder) is computationally and experimentally evaluated. The composite POSS-binder coatings display ultralow surface energy (≈10 mJ m^-2 ), while still having large surface adhesions to substrates (300-400 nN), highlighting that super-repellent coatings (contact angles >150°) can be readily generated with this composite approach. Importantly, the coatings show super-repellency to both corrosive liquids (e.g., 98 wt% H₂ SO₄ ) and ultralow surface tension liquids (e.g., alcohols), with ultralow roll-off angles (<5°), and tunable resistance to liquid penetration. Additionally, these coatings demonstrate the potential in effective cargo loading and robust self-cleaning properties, where experimental datasets are correlated with both relevant theoretical predictions and systematic all-atom molecular dynamics simulations of the repellent coatings. This work not only holds promise for chemical shielding, heat transfer, and liquid manipulations but offers a facile yet robust pathway for engineering advanced coatings by effectively combining components for their mutually desired properties.

Bio-interactive nanoarchitectonics with two-dimensional materials and environments

Like the proposal of nanotechnology by Richard Feynman, the nanoarchitectonics concept was initially proposed by Masakazu Aono. The nanoarchitectonics strategy conceptually fuses nanotechnology with other research fields including organic chemistry, supramolecular chemistry, micro/nanofabrication, materials science, and bio-related sciences, and aims to produce functional materials from nanoscale components. In this review article, bio-interactive nanoarchitectonics and two-dimensional materials and environments are discussed as a selected topic. The account gives general examples of nanoarchitectonics of two-dimensional materials for energy storage, catalysis, and biomedical applications, followed by explanations of bio-related applications with two-dimensional materials such as two-dimensional biomimetic nanosheets, fullerene nanosheets, and two-dimensional assemblies of one-dimensional fullerene nanowhiskers (FNWs). The discussion on bio-interactive nanoarchitectonics in two-dimensional environments further extends to liquid-liquid interfaces such as fluorocarbon-medium interfaces and viscous liquid interfaces as new frontiers of two-dimensional environments for bio-related applications. Controlling differentiation of stem cells at fluidic liquid interfaces is also discussed. Finally, a conclusive section briefly summarizes features of bio-interactive nanoarchitectonics with two-dimensional materials and environments and discusses possible future perspectives.

Regulation of stem cell fate and function by using bioactive materials with nanoarchitectonics for regenerative medicine

Nanoarchitectonics has emerged as a post-nanotechnology concept. As one of the applications of nanoarchitectonics, this review paper discusses the control of stem cell fate and function as an important issue. For hybrid nanoarchitectonics involving living cells, it is crucial to understand how biomaterials and their nanoarchitected structures regulate behaviours and fates of stem cells. In this review, biomaterials for the regulation of stem cell fate are firstly discussed. Besides multipotent differentiation, immunomodulation is an important biological function of mesenchymal stem cells (MSCs). MSCs can modulate immune cells to treat multiple immune- and inflammation-mediated diseases. The following sections summarize the recent advances of the regulation of the immunomodulatory functions of MSCs by biophysical signals. In the third part, we discussed how biomaterials direct the self-organization of pluripotent stem cells for organoid. Bioactive materials are constructed which mimic the biophysical cues of in vivo microenvironment such as elasticity, viscoelasticity, biodegradation, fluidity, topography, cell geometry, and etc. Stem cells interpret these biophysical cues by different cytoskeletal forces. The different cytoskeletal forces lead to substantial transcription and protein expression, which affect stem cell fate and function. Regulations of stem cells could not be utilized only for tissue repair and regenerative medicine but also potentially for production of advanced materials systems. Materials nanoarchitectonics with integration of stem cells and related biological substances would have high impacts in science and technology of advanced materials.

A Topologically Engineered Gold Island for Programmed In Vivo Stem Cell Manipulation

E ven a well-designed system can only control stem cell adhesion, release, and differentiation, while other cell manipulations such as in situ labeling and retention in target tissues, are difficult to achieve in the same system. Herein, native ligand cluster-mimicking islands, composed of topologically engineered ligand, anchoring point AuNP, nuclease mimetics Ce IV complexes and magnetic core Fe 3 O 4 , are designed to facilitate comprehensive cell manipulations in a programmable manner. Three islands with different amounts of AuNPs are constructed, which means tunable interligand spacing within a cluster. These nanostructures are chemically coupled to a substrate using DNA tethers. Under tissue-penetrative magnetic field, this integrated system promotes stem cell adhesion, proliferation, mechanosensing, differentiation, detachment, in situ effective magnetic labeling and retention both in vitro and in vivo , offering fascinating opportunities for biomimetic matrix in regenerative medicine.

Developing biomaterials to mediate the spatial distribution of integrins

Innovation in material design to regulate cell behavior and function is one of the primary tasks in materials science. Integrins, a family of cell surface-adhesion receptors that mechanically connect the extracellular matrix (ECM) to the intracellular cytoskeleton, have long served as primary targets for the design of biomaterials because their activity is not only critical to a wide range of cell and tissue functions but also subject to very tight and complex regulations from the outside environment. To review the recent progress of material innovations targeting the spatial distribution of integrins, we first introduce the interaction mechanisms between cells and the ECM by highlighting integrin-based cell adhesions, describing how integrins respond to environmental stimuli, including variations in ligand presentation, mechanical cues, and topographical variations. Then, we overview the current development of soft materials in guiding cell behaviors and functions via spatial regulation of integrins. Finally, we discuss the current limitations of these technologies and the advances that may be achieved in the future. Undoubtedly, synthetic soft materials that mediate the spatial distribution of integrins play an important role in biomaterial innovations for advancing biomedical applications and addressing fundamental biological questions.

Long term expansion profile of mesenchymal stromal cells at protein nanosheet-stabilised bioemulsions for next generation cell culture microcarriers

Tremendous progress in the identification, isolation and expansion of stem cells has allowed their application in regenerative medicine and tissue engineering, and their use as advanced in vitro models. As a result, stem cell manufacturing increasingly requires scale up, parallelisation and automation. However, solid substrates currently used for the culture of adherent cells are poorly adapted for such applications, owing to their difficult processing from cell products, relatively high costs and their typical reliance on difficult to recycle plastics and microplastics. In this work, we show that bioemulsions formed of microdroplets stabilised by protein nanosheets displaying strong interfacial mechanics are well-suited for the scale up of adherent stem cells such as mesenchymal stromal cells (MSCs). We demonstrate that, over multiple passages (up to passage 10), MSCs retain comparable phenotypes when cultured on such bioemulsions, solid microcarriers (Synthemax II) and classic 2D tissue culture polystyrene. Phenotyping (cell proliferation, morphometry, flow cytometry and differentiation assays) of MSCs cultured for multiple passages on these systems indicate that, although stemness is lost at late passages when cultured on these different substrates, stem cell phenotypes remained comparable between different culture conditions, at any given passage. Hence our study validates the use of bioemulsions for the long term expansion of adherent stem cells and paves the way to the design of novel 3D bioreactors based on microdroplet microcarriers.

Physiological fluid interfaces: Functional microenvironments, drug delivery targets, and first line of defense

Fluid interfaces, i.e. the boundary layer of two liquids or a liquid and a gas, play a vital role in physiological processes as diverse as visual perception, oral health and taste, lipid metabolism, and pulmonary breathing. These fluid interfaces exhibit a complex composition, structure, and rheology tailored to their individual physiological functions. Advances in interfacial thin film techniques have facilitated the analysis of such complex interfaces under physiologically relevant conditions. This allowed new insights on the origin of their physiological functionality, how deviations may cause disease, and has revealed new therapy strategies. Furthermore, the interactions of physiological fluid interfaces with exogenous substances is crucial for understanding certain disorders and exploiting drug delivery routes to or across fluid interfaces. Here, we provide an overview on fluid interfaces with physiological relevance, namely tear films, interfacial aspects of saliva, lipid droplet digestion and storage in the cell, and the functioning of lung surfactant. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe therapies and drug delivery approaches targeted at fluid interfaces. STATEMENT OF SIGNIFICANCE: Fluid interfaces are inherent to all living organisms and play a vital role in various physiological processes. Examples are the eye tear film, saliva, lipid digestion & storage in cells, and pulmonary breathing. These fluid interfaces exhibit complex interfacial compositions and structures to meet their specific physiological function. We provide an overview on physiological fluid interfaces with a focus on interfacial phenomena. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe novel therapies and drug delivery approaches targeted at fluid interfaces. This sets the scene for ocular, oral, or pulmonary surface engineering and drug delivery approaches.

Fluorinated Metal-Organic Coatings with Selective Wettability

Surface chemistry is a major factor that determines the wettability of materials, and devising broadly applicable coating strategies that afford tunable and selective surface properties required for next-generation materials remains a challenge. Herein, we report fluorinated metal-organic coatings that display water-wetting and oil-repelling characteristics, a wetting phenomenon different from responsive wetting induced by external stimuli. We demonstrate this selective wettability with a library of metal-organic coatings using catechol-based coordination and silanization (both fluorinated and fluorine-free), enabling sensing through interfacial reconfigurations in both gaseous and liquid environments, and establish a correlation between the coating wettability and polarity of the liquids. This selective wetting performance is substrate-independent, spontaneous, durable, and reversible and occurs over a range of polar and nonpolar liquids (60 studied). These results provide insight into advanced liquid-solid interactions and a pathway toward tuning interfacial affinities and realizing robust, selective superwettability according to the surrounding conditions.

Hyaluronan (HA) Immobilized on Surfaces via Self-Assembled Monolayers of HA-Binding Peptide Modulates Endothelial Cell Spreading and Migration through Focal Adhesion

The extracellular matrix (ECM) modulates a multitude of cell functions, and this regulation is provided by key ECM components forming a complex network. Hyaluronic acid (HA) is an abundant component of the ECM that binds to proteins and influences various activities of endothelial cells (ECs). Although the effect of soluble HA on cell spreading has been studied, the impact of peptide-bound HA has not yet been investigated in great detail. We aim to comprehensively study the roles of immobilized HA on the regulation of EC behavior compared to the more conventional use of soluble HA. A 2D model surface formed by self-assembled monolayers (SAMs) of a HA-binding peptide (Pep-1) is used as an anchor for HA immobilization. Mixed SAMs, consisting of thiolated Pep-1 and 1-octanethiol, are prepared and characterized by using ellipsometry and contact angle measurement. Full density Pep-1 SAMs are more hydrophilic and bind more HA than mixed SAMs. Cell spreading and migration are enhanced by immobilized low molecular weight (LMW) HA, which also facilitates cell alignment and elongation under laminar flow conditions and potentially drives directional migration. This effect is not mediated by the expression of CD44, and immobilized LMW HA is found to accelerate the assembly of focal adhesions. Such biomimetic surfaces provide new insights into the role of HA in regulating the spreading and phenotype of endothelial cells.

Nanoarchitectonics: what's coming next after nanotechnology?

In science and technology today, the crucial importance of the regulation of nanoscale objects and structures is well recognized. The production of functional material systems using nanoscale units can be achieved via the fusion of nanotechnology with the other research disciplines. This task is a part of the emerging concept of nanoarchitectonics, which is a concept moving beyond the area of nanotechnology. The concept of nanoarchitectonics is supposed to involve the architecting of functional materials using nanoscale units based on the principles of nanotechnology. In this focus article, the essences of nanotechnology and nanoarchitectonics are first explained, together with their historical backgrounds. Then, several examples of material production based on the concept of nanoarchitectonics are introduced via several approaches: (i) from atomic switches to neuromorphic networks; (ii) from atomic nanostructure control to environmental and energy applications; (iii) from interfacial processes to devices; and (iv) from biomolecular assemblies to life science. Finally, perspectives relating to the final goals of the nanoarchitectonics approach are discussed.

Investigations of Chirality Effects on Undifferentiated State of Mesenchymal Stem Cells Using Soft Nanofibrous Oligopeptide Hydrogels

Soft nanofibrous oligopeptide hydrogels consisting of self-assembled l- and d-form Fmoc-Phe-Phe-Cys networks photo-cross-linked by poly(ethylene glycol)-dimethacrylate, which are referred to as l- and d-gel, respectively, were developed for investigation of chirality effects on the undifferentiated state of mesenchymal stem cells. Encapsulated mesenchymal stem cells in d-gel showed slower growth and less spreading, resulting in higher maintenance of the undifferentiated state, compared to in l-gel. This indicates that d-form peptide materials might be useful as scaffold materials for regenerative medicine using stem cells.

Globular protein assembly and network formation at fluid interfaces: effect of oil

The formation of viscoelastic networks at fluid interfaces by globular proteins is essential in many industries, scientific disciplines, and biological processes. However, the effect of the oil phase on the structural transitions of proteins, network formation, and layer strength at fluid interfaces has received little attention. Herein, we present a comprehensive study on the effect of oil polarity on globular protein networks. The formation dynamics and mechanical properties of the interfacial networks of three different globular proteins (lysozyme, β-lactoglobulin, and bovine serum albumin) were studied with interfacial shear and dilatational rheometry. Furthermore, the degree of protein unfolding at the interfaces was evaluated by subsequent injection of disulfide bonds reducing dithiothreitol. Finally, we measured the interfacial layer thickness and protein immersion into the oil phase with neutron reflectometry. We found that oil polarity significantly affects the network formation, the degree of interfacial protein unfolding, interfacial protein location, and the resulting network strength. These results allow predicting emulsion stabilization of proteins, tailoring interfacial layers with desired mechanical properties, and retaining the protein structure and functionality upon adsorption.

Nuclear Stiffness Decreases with Disruption of the Extracellular Matrix in Living Tissues

Reciprocal interactions between the cell nucleus and the extracellular matrix lead to macroscale tissue phenotype changes. However, little is known about how the extracellular matrix environment affects gene expression and cellular phenotype in the native tissue environment. Here, it is hypothesized that enzymatic disruption of the tissue matrix results in a softer tissue, affecting the stiffness of embedded cell and nuclear structures. The aim is to directly measure nuclear mechanics without perturbing the native tissue structure to better understand nuclear interplay with the cell and tissue microenvironments. To accomplish this, an atomic force microscopy needle-tip probe technique that probes nuclear stiffness in cultured cells to measure the nuclear envelope and cell membrane stiffness within native tissue is expanded. This technique is validated by imaging needle penetration and subsequent repair of the plasma and nuclear membranes of HeLa cells stably expressing the membrane repair protein CHMP4B-GFP. In the native tissue environment ex vivo, it is found that while enzymatic degradation of viable cartilage tissues with collagenase 3 (MMP-13) and aggrecanase-1 (ADAMTS-4) decreased tissue matrix stiffness, cell and nuclear membrane stiffness is also decreased. Finally, the capability for cell and nucleus elastography using the AFM needle-tip technique is demonstrated. These results demonstrate disruption of the native tissue environment that propagates to the plasma membrane and interior nuclear envelope structures of viable cells.

Lipid-Raft-Targeted Molecular Self-Assembly Inactivates YAP to Treat Ovarian Cancer

The Yes-associated protein (YAP) is a major oncoprotein responsible for cell proliferation control. YAP's oncogenic activity is regulated by both the Hippo kinase cascade and uniquely by a mechanical-force-induced actin remodeling process. Inspired by reports that ovarian cancer cells specifically accumulate the phosphatase protein ALPP on lipid rafts that physically link to actin cytoskeleton, we developed a molecular self-assembly (MSA) technology that selectively halts cancer cell proliferation by inactivating YAP. We designed a ruthenium-complex-peptide precursor molecule that, upon cleavage of phosphate groups, undergoes self-assembly to form nanostructures specifically on lipid rafts of ovarian cancer cells. The MSAs exert potent, cancer-cell-specific antiproliferative effects in multiple cancer cell lines and in mouse xenograft tumor models. Our work illustrates how basic biochemical insights can be exploited as the basis for a nanobiointerface fabrication technology which links nanoscale protein activities at specific subcellular locations to molecular biological activities to suppress cancer cell proliferation.

Molecular recognition at the air-water interface: nanoarchitectonic design and physicochemical understanding

Although molecular recognition at the air-water interface has been researched for over 30 years, investigations on its fundamental aspects are still active research targets in current science. In this perspective article, developments and future possibilities of molecular recognition at the air-water interface from pioneering research efforts to current examples are overviewed especially from the physico-chemical viewpoints. Significant enhancements of binding constants for molecular recognition are actually observed at the air-water interface although molecular interactions such as hydrogen bonding are usually suppressed in aqueous media. Recent advanced analytical strategies for direct characterization of interfacial molecules also confirmed the promoted formation of hydrogen bonding at the air-water interfaces. Traditional quantum chemical approaches indicate that modulation of electronic distributions through effects from low-dielectric phases would be the origin of enhanced molecular interactions at the air-water interface. Further theoretical considerations suggest that unusual potential changes for enhanced molecular interactions are available only within a limited range from the interface. These results would be related with molecular recognition in biomolecular systems that is similarly supported by promoted molecular interactions in interfacial environments such as cell membranes, surfaces of protein interiors, and macromolecular interfaces.

Interfacial nanoarchitectonics for responsive cellular biosystems

The living cell can be regarded as an ideal functional material system in which many functional systems are working together with high efficiency and specificity mostly under mild ambient conditions. Fabrication of living cell-like functional materials is regarded as one of the final goals of the nanoarchitectonics approach. In this short review article, material-based approaches for regulation of living cell behaviors by external stimuli are discussed. Nanoarchitectonics strategies on cell regulation by various external inputs are first exemplified. Recent approaches on cell regulation with interfacial nanoarchitectonics are also discussed in two extreme cases using a very hard interface with nanoarchitected carbon arrays and a fluidic interface of the liquid-liquid interface. Importance of interfacial nanoarchitectonics in controlling living cells by mechanical and supramolecular stimuli from the interfaces is demonstrated.

Nanoarchitectonics beyond Self-Assembly: Challenges to Create Bio-Like Hierarchic Organization

Incorporation of non-equilibrium actions in the sequence of self-assembly processes would be an effective means to establish bio-like high functionality hierarchical assemblies. As a novel methodology beyond self-assembly, nanoarchitectonics, which has as its aim the fabrication of functional materials systems from nanoscopic units through the methodological fusion of nanotechnology with other scientific disciplines including organic synthesis, supramolecular chemistry, microfabrication, and bio-process, has been applied to this strategy. The application of non-equilibrium factors to conventional self-assembly processes is discussed on the basis of examples of directed assembly, Langmuir-Blodgett assembly, and layer-by-layer assembly. In particular, examples of the fabrication of hierarchical functional structures using bio-active components such as proteins or by the combination of bio-components and two-dimensional nanomaterials, are described. Methodologies described in this review article highlight possible approaches using the nanoarchitectonics concept beyond self-assembly for creation of bio-like higher functionalities and hierarchical structural organization.