Slope-Dependent Cell Motility Enhancements at the Walls of PEG-Hydrogel Microgroove Structures

In recent years, research utilizing micro- and nanoscale geometries and structures on biomaterials to manipulate cellular behaviors, such as differentiation, proliferation, survival, and motility, have gained much popularity; however, how the surface microtopography of 3D objects, such as implantable devices, can affect these various cell behaviors still remains largely unknown. In this study, we discuss how the walls of microgroove topography can influence the morphology and the motility of unrestrained cells, in a different fashion from 2D line micropatterns. Here adhesive substrates made of tetra­(polyethylene glycol) (tetra-PEG) hydrogels with microgroove structures or 2D line micropatterns were fabricated, and cell motility on these substrates was evaluated. Interestingly, despite being unconstrained, the cells exhibited drastically different migration behaviors at the edges of the 2D micropatterns and the walls of microgroove structures. In addition to acquiring a unilamellar morphology, the cells increased their motility by roughly 3-fold on the microgroove structures, compared with the 2D counterpart or the nonpatterned surface. Immunostaining revealed that this behavior was dependent on the alignment and the aggregation of the actin filaments, and by varying the slope of the microgroove walls, it was found that relatively upright walls are necessary for this cell morphology alterations. Further progress in this research will not only deepen our understanding of topography-assisted biological phenomena like cancer metastasis but also enable precise, topography-guided manipulation of cell motility for applications such as cancer diagnosis and cell sorting

Dynamic Covalent Star Poly(ethylene glycol) Model Hydrogels: A New Platform for Mechanically Robust, Multifunctional Materials

We develop a new platform of dynamic covalent model polymer networks comprising two types of four-armed star poly­(ethylene glycol)­s (tetraPEG), one end-functionalized with benzaldehyde groups and the other with benzaacyl­hydrazides, resulting in hydrazone cross-links. These materials, henceforth to be called tetraPEG DYNAgels, display remarkable mechanical properties, much superior to those based on randomly cross-linked analogues. Fast aqueous gel formation takes place both at acidic and, unexpectedly, at alkaline conditions, with gel formation times covering 4 orders of magnitude in the pH range from 2.0 to 12.5 and a maximum gelation time appearing at pH 8.5. Frequency-dependent oscillatory rheology indicates a finite lifetime of the cross-links in tetraPEG DYNAgels at acidic conditions. Furthermore, these materials exhibit self-healing ability and reversibility under acidic and moderately acidic conditions; however, these properties can be canceled by chemical reduction of the cross-links. The system is highly modular, allowing the facile incorporation of other functionalities, e.g., hydrophobicity or amphiphilicity, introduced via polymers bearing terminal benzaldehyde groups

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles

Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Probe Diffusion of Sol–Gel Transition in an Isorefractive Polymer Solution

The sol–gel transition of tetrafunctional polymers with mutual reactive end-groups was investigated by analyzing the dynamics of probe particles via dynamic light scattering. The dynamics of probe particles was exclusively observed by matching the refractive index of the solvent and the polymers. The sol–gel transition point, decreasing of sol fraction and increasing of gel fraction with the reaction, the onset of formation of closed structure inside branched polymer clusters, and a piece of evidence for the decrease of the local viscosity in postgel regime were observed via the dynamics of probe particles. In addition, a scaling relationship η_eff ∼ ε^{–1.13±0.06} was found in a wide range of cross-linking conversion (<i>p</i>) before the gel point, where η_eff is the effective viscosity estimated from probe particles’ dynamics and ε ≡ |<i>p</i> – <i>p</i>_c|/<i>p</i>_c is the relative distance from the sol–gel transition point (<i>p</i>_c is the cross-linking conversion at gel point)

Migration Behavior of Rodlike dsDNA under Electric Field in Homogeneous Polymer Networks

We investigated the migration behavior of rodlike dsDNA in polymer gels and polymer solutions. Tetra-PEG gel, which has a homogeneous network structure, was utilized as a model system, allowing us to systematically tune the polymer volume fraction and molecular weight of network strand. Although we examined the applicability of the existing models, all the models failed to predict the migration behavior. Thus, we proposed a new model based on the Ogston model, which well explained the experimental data of polymer solutions and gels. The polymer volume fraction determined the maximum mobility, while the network strand governed the size sieving effect. From these results, we conclude that the polymer network with lower polymer volume fraction and smaller network strand is better in terms of size separation. The homogeneous polymer network is vital for understanding of particles’ dynamics in polymer network and a promising material for high-performance size separation

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles