Soft Matter最新文献

Hydrogel-forming peptides, including matrix metalloproteinase (MMP)-degradable motifs, have been employed to investigate cell-extracellular matrix interactions in vitro. However, their potential in 3D cancer models has been explored only in a few studies. In this study, we used modified MMP-2 degradable motifs (VSLRA or ASLRA) in the design of EDP1 (RVSLRADARVSLRADA) and EDP2 (RASLRADARASLRADA) peptide hydrogelators. The peptides self-assembled into nanofibrillar hydrogels with storage moduli between ∼300 and ∼400 Pa. MMP-2 degradation properties of the peptides were confirmed, and a slightly higher MMP-2 responsiveness of the EDP1 hydrogel was observed. The hydrogels were used in the encapsulation of A549 lung adenocarcinoma cancer cells and MRC-5 human lung fibroblast cells. The designed hydrogels supported the proliferation of these cells with high viability and induced cluster formation of encapsulated A549 cells similar to that observed with the RADA hydrogel. However, the hydrogel network structure affected the morphology of the migrated cells in the absence of curcumin. The addition of curcumin decreased the migration and invasion of A549 cells, resulting in a round cell morphology independent of the hydrogel matrices. Anticancer drug tests indicated that cell viability after drug treatment was higher in the 3D hydrogels than in 2D cultures. It was also confirmed that the combinational therapy of doxorubicin and curcumin decreased the cell proliferation and colonization to a greater extent compared to doxorubicin monotherapy. Thus, the hydrogels developed in this study can be used for 3D cancer models or other tissue engineering applications as an alternative to the RADA hydrogel by exploiting the MMP-2 degradation properties.

Active fluids generate internal active stress and exhibit unique responses to external forces such as superfluid-like flow and self-yielding transitions. However, how confinement geometry influences these responses remains poorly understood. Here, we investigate microtubule-kinesin active fluids under external shear stresses in three geometries. In a thin slab-like container with a translating wall, we observed a kinematic transition from activity-dominated chaotic flow to lid-driven cavity flow when the applied shear stress exceeds ∼1.5 mPa, comparable to the intrinsic active stress magnitude. Simulations supported the conclusion that this transition arises from competition between internal active stress and imposed shear stress. In contrast, in a ratcheted toroidal confinement, the imposed shear remains localized near the driven boundary and does not propagate through the bulk. Nevertheless, this localized perturbation cooperatively couples with internal active stress to reverse the global circulation. This cooperative mechanism is further demonstrated in a connected-toroid geometry: driving one toroid reorganizes flow in a second, indirectly connected toroid, while no such influence occurs in a passive fluid. Together, these findings show that the response of active fluids to external forcing depends not only on the magnitude of applied stress but also on how confinement geometry mediates whether stresses interact through bulk competition or local-to-global cooperative reorganization, revealing a new approach to combining static geometrical design with dynamic external stimuli for real-time modulation of flow patterns. Such strategies may be applied to microfluidics, where micromechanical actuators dynamically tune active fluid behavior within fixed geometries, enabling transitions between chaotic and coherent flows for mixing, sorting, or transport.

This work investigates the calcium-induced formation and properties at the nanoscale of hydrogels of structural extracellular polymeric substances (EPS) extracted from aerobic granular sludge (AGS) during wastewater treatment. By comparing EPS with model polymers representing the key biochemical families present in EPS—alginate for polysaccharides and bovine serum albumin (BSA) for proteins—we aim to elucidate their respective contributions to the overall hydrogel formation with calcium cations. Nanoscale characterization techniques (MP-SPR, QCM-D, and AFM) were employed to assess how divalent cations influence hydrogel formation and properties. Our findings revealed that polysaccharides played a dominant role in hydrogel formation through ionic crosslinking, as well as in hydrogel softness and water retention, while proteins contributed to the modulation of structure and viscoelasticity. The nanoscale structural analysis conducted in this study lays a valuable foundation for further understanding the macroscopic properties of EPS hydrogels, enhancing their potential applications in bio-based materials science.

Correction for ‘Errors matter when measuring Poisson's ratio of nearly incompressible elastomers’ by Robert D. Nedoluha et al., Soft Matter, 2025, 21, 6689–6696, https://doi.org/10.1039/D5SM00535C.

Hydrodynamics is known to have strong effects on the kinetics of phase separation. There exist open questions on how such effects manifest in systems under confinement. Here, we have undertaken extensive studies of the kinetics of phase separation in a two-component fluid that is confined inside pores of cylindrical shape. Using a hydrodynamics-preserving thermostat, we carry out molecular dynamics simulations to obtain results for domain growth and aging for varying temperature and pore width. We find that all systems freeze into a morphology where stripes of regions rich in one or the other component of the mixture coexist. Our analysis suggests that, irrespective of the temperature the growth of the average domain size, ℓ(t), prior to the freezing into stripped patterns, follows the power law ℓ(t) ∼ t^2/3, suggesting an inertial hydrodynamic growth, which typically is applicable for bulk fluids only in the asymptotic limit. Similarly, the aging dynamics, probed by the two-time order-parameter autocorrelation function, also exhibits a temperature-independent power-law scaling with an exponent λ ≃ 2.55, much smaller than what is observed for a bulk fluid.

Polyelectrolyte hydrogels, characterized by their charged networks, exhibit exceptional deformability and biocompatibility, making them ideal platforms for realizing multifunctional and intelligent material systems, yet the molecular origin of their pearl-necklace-like chains remains controversial. Here we develop a thermodynamic unbinding framework that treats the necklace as an assembly of compact polymeric blobs connected by worm-like spacers. The total free-energy density is decomposed into three additive contributions: (i) conformational entropy of the worm-like chains, (ii) electrostatic interaction, and (iii) interfacial unbinding of the blobs, the latter being modeled through a constrained-junction model that captures non-affine micro-deformation. Conceptualizing the pearl necklace as an assembly of distinct polymer blobs and connecting chains, this approach facilitates a detailed examination of its microstructure and complex mechanical response. Closed-form stress–elongation ratio relations are derived for arbitrary three-dimensional loading. The proposed blob-unbinding strategy offers a universal platform for rationalizing the mechanochemistry of polyelectrolyte networks. The uniaxial tensile data of 50 times deformed hyperelastic hydrogels, regular PAM hydrogels, and ring cross-linked hydrogels, and the planar extension data of PTHF hydrogels were analyzed to illustrate the effectiveness of the proposed model.

Investigation of the properties of membrane proteins (MPs) is essential to the successful development of medicines and biotechnology. However, their study is often complicated by denaturation caused by the use of detergents during conventional extraction methods. Copolymers of styrene and maleic acid (SMA) have shown promise in extracting MPs directly from cells while reconstituting lipid membranes into nanodiscs. Despite their potential, there remains a dearth of information on the precise interactions that take place between the copolymers and lipid membranes although they are known to be sensitive to small variations in copolymer composition or structure. We have used reversible addition–fragmentation chain transfer (RAFT) polymerisation to synthesise SMA copolymers with equivalent molar mass, but with inverted block sequences and end group termini. Through a range of experiments, including dynamic light scattering and small-angle neutron scattering (SANS) on SMA aggregates and nanodisc formation studies using UV-vis spectroscopy with both model DMPC lipids and E. coli membranes, the impact of both block distribution and end group chemistry on copolymer–membrane interactions was investigated. It was found that mismatched hydrophilic and hydrophobic end groups on the styrene block and alternating block, respectively, impeded membrane disruption and subsequent solubilisation. This highlights not only how the amphiphilic balance of these blocks is important for efficient nanodisc formation, but also how end groups influence these and may be optimised towards extraction of more challenging MPs. The work contributes to a better understanding of SMA behaviour and offers insight into how these nanomaterials may be better designed and tailored for specific applications.

Topological defects provide a unifying language to describe how orientational order breaks down in active and living matter. Considering cells as elongated particles confluent, epithelial tissues can be interpreted as nematic fields and their defects have been linked to extrusion, migration, and morphogenetic transformations. Yet, epithelial cells are not restricted to nematic order: their irregular shapes can express higher rotational symmetries, giving rise to p-atic order with p > 2. Here we introduce a framework to extract p-atic fields and their defects directly from experimental images. Applying this method to MDCK cells, we find that all symmetries from p = 2 to p = 6 generate defects. Surprisingly, the statistics reveal an even–odd asymmetry, with odd p producing more defects than even p, consistent with geometric frustration arguments based on tilings. In contrast, no strong positional or orientational correlations are found between nematic and hexatic defects, suggesting that different symmetries coexist largely independently. These results demonstrate that epithelial tissues should not be described by nematic order alone, but instead host a spectrum of p-atic symmetries. Our work provides experimental evidence for this multivalency of order and offers a route to test and refine emerging p-atic liquid crystal theories of living matter.

Complex memory effects under applied strain are a defining feature of glassy polymers in the strain hardening regime. We proposed recently a theory for plastic flow and strain hardening as controlled by two contributions to the free energy barriers in glassy polymers submitted to an applied deformation. Free energy barriers decrease under the effect of the stress, which leads to yielding and the onset of plastic flow. Conversely, monomer orientation increases the barriers. These two contributions have very different kinetics. The contribution related to the stress relaxes quickly as a function of the applied stress whereas the orientation contribution relaxes by rotational diffusion, which is very slow at depth in the glassy state. This description could account for the main feature of the Bauschinger effect when considering a stop of the deformation followed by a resuming of the deformation after some waiting time, or for describing deformation cycles, e.g. a tensile test followed by a compression, or the reverse. We show here that the same model allows for interpreting and explaining memory effects in complex deformation histories as regard the distribution of relaxation times, the evolution of tangent delta measured by dielectric spectroscopy and the kinetics of recovery of the reference curve as a function of the waiting time and allows for the interpretation of recent experimental results obtained by small probes reorientation dynamics and dielectric spectroscopy.

The activity of swimming bacteria fundamentally alters the transport properties of passive particles through active agitation. While particle diffusion enhancement is known to scale linearly with the active bacterial flux (the product of swimmer density and velocity), the factors controlling the proportionality coefficient β, which represents the efficiency of energy transfer per swimmer, remain unclear. Here, we systematically investigate how bacterial swimming behavior modulates diffusion enhancement using Escherichia coli and Pseudomonas aeruginosa suspensions. We compare wild-type and smooth-swimming E. coli strains to isolate the effect of tumbling, and we tune swimming velocities in both E. coli and P. aeruginosa to test generality across species with different motility phenotypes. Our results show that bacterial reorientation dynamics have little effect on β, as both wild-type and smooth-swimming E. coli exhibit similar enhancement. In contrast, swimming velocity has a pronounced effect on β in both species. Direct measurements reveal that bacteria-tracer interactions are confined to a radius of approximately 5 µm, with microsphere velocity decaying as r^−1.3 with distance from the nearest bacterium. These findings establish swimming velocity as a key determinant of diffusion enhancement in active suspensions, with implications for understanding nutrient transport and mixing in microbial environments.