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Cells continuously sense external forces from their microenvironment, the extracellular matrix (ECM). In turn, they generate contractile forces, which stiffen and remodel this matrix. Although this bidirectional mechanical exchange is crucial for many cell functions, it remains poorly understood. Key challenges are that the majority of available matrices for such studies, either natural or synthetic, are difficult to control or lack biological relevance. Here, we use a synthetic, yet highly biomimetic hydrogel based on polyisocyanide (PIC) polymers to investigate the effects of the fibrous architecture and the nonlinear mechanics on cell-matrix interactions. Live-cell rheology was combined with advanced microscopy-based approaches to understand the mechanisms behind cell-induced matrix stiffening and plastic remodeling. We demonstrate how cell-mediated fiber remodeling and the propagation of fiber displacements are modulated by adjusting the biological and mechanical properties of this material. Moreover, we validate the biological relevance of our results by demonstrating that cellular tractions in PIC gels develop analogously to those in the natural ECM. This study highlights the potential of PIC gels to disentangle complex bidirectional cell-matrix interactions and to improve the design of materials for mechanobiology studies. ispartof: Proc Natl Acad Sci U S A vol:120 issue:15 pages:e2216934120- ispartof: location:United States status: published

Glyco‐assemblies derived from amphiphilic sugar‐decorated block copolymers (ASBCs) have emerged prominently due to their wide application, for example, in biomedicine and as drug carriers. However, to efficiently construct these glyco‐assemblies is still a challenge. Herein, we report an efficient technology for the synthesis of glyco‐inside nano‐assemblies by utilizing RAFT polymerization of a galactose‐decorated methacrylate for polymerization‐induced self‐assembly (PISA). Using this approach, a series of highly ordered glyco‐inside nano‐assemblies containing intermediate morphologies were fabricated by adjusting the length of the hydrophobic glycoblock and the polymerization solids content. A specific morphology of complex vesicles was captured during the PISA process and the formation mechanism is explained by the morphology of its precursor and intermediate. Thus, this method establishes a powerful route to fabricate glyco‐assemblies with tunable morphologies and variable sizes, which is significant to enable the large‐scale fabrication and wide application of glyco‐assemblies., Glyco‐inside nano‐assemblies containing numerous intermediate morphologies are fabricated by leveraging RAFT polymerization of a galactose‐decorated monomer for polymerization‐induced self‐assembly. This method establishes a powerful route to fabricate glyco‐inside nano‐assemblies with tunable morphologies and variable sizes, which is significant to expand the large‐scale fabrication and wide application of glyco‐assemblies.

A new concept named “rotating magnetocaloric effect (RMCE)” has been proposed and attracted more attention recently. Unlike the traditional MCE that is achieved by moving the magnetic refrigerant in and out of magnetic field, RMCE can be realized by rotating the anisotropic material within the static field, thus implying the possible higher efficiency and simpler device. However, most studies on RMCE are concentrated on single crystals, which are generally more expensive and difficult to prepare in comparison with polycrystals. Therefore, it is highly desirable to search polycrystalline materials with high RMCE. Here, the textured HoNiSi polycrystal is reported to show a giant RMCE, e.g., the rotating magnetic entropy change (−ΔSR) are 18.5 and 26.7 J/kg K and rotating adiabatic temperature change (ΔTR) are 7.0 and 13.4 K under 2 and 5 T, respectively. This giant RMCE over a wide temperature range especially under low field suggests textured HoNiSi as promising material for practical application of rotary magnetic refrigeration. Moreover, the large magnetic anisotropy of HoNiSi is explained by the single-ion magnetic anisotropy theory, and the coherent orientation of crystallographic texture and rare-earth ion moments leads to the large RMCE in the textured HoNiSi polycrystal. This work reveals that the strongly coherent orientation of crystallographic texture and rare-earth ion moments is a key to realize large RMCE in polycrystalline materials.

Hepatocellular carcinoma development is closely related to the changes in tissue mechanics induced by excess collagen deposition and crosslinking, which leads to liver fibrosis and malignant progression. The role of matrix stiffness has been widely assessed using various linearly elastic materials. However, the liver, like many soft tissues, also exhibits nonlinear elasticity by strain-stiffening, allowing cells to mechanically interact with their micromilieus which has attracted much attention in cellular processes recently. Here, we use a biomimetic hydrogel grafting of GRGDS peptide with tunable nonlinear mechanical properties, polyisocyanides (PIC), to investigate the influence of strain-stiffening on HepG2 liver cancer cell behavior by tuning PIC polymer length. Compared to short PIC polymer with lower critical stress, PIC hydrogels composed of long polymer with higher critical stress promote the motility and invasiveness of HepG2 cells, and induce more actin stress fibers and higher expression level of mechanotransducer YAP and its nuclear translocation. Strikingly, the expression of calcium-activated potassium channel KCa3.1, an important biomarker in hepatocellular carcinoma, is also affected by the mechanical property of PIC hydrogels. It was also shown that downregulating the KCa3.1 channel can be achieved by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC hydrogels affects the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation, and ultimately influences the liver carcinoma cell functional response. STATEMENT OF SIGNIFICANCE: The effect of nonlinear elasticity by strain-stiffening, is assessed in HepG2 liver cancer cell behavior by using a biomimetic hydrogel with tunable mechanical properties, polyisocyanides (PIC). PIC gels with higher critical stress promote the motility and invasiveness of HepG2 cells and induce upregulated expression levels of KCa3.1 potassium channel and YAP, but which can be suppressed by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC gels influences the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation and, ultimately affects the liver carcinoma cell functional response. ispartof: ACTA BIOMATERIALIA vol:148 pages:152-162 ispartof: location:England status: published

Hybrid biomimetic hydrogels with enhanced reactive oxygen species (ROS)-generation efficiency under 600 nm light show high antibacterial activity. The hybrid gels are composed of helical tri(ethylene glycol)-functionalized polyisocyanides (PICs) and a conformation-sensitive conjugated polythiophene, poly(3-(3 '-N,N,N-triethylammonium-1 '-propyloxy)-4-methyl-2,5-thiophene chloride) (PMNT). The PIC polymer serves as a scaffold to trap and align the PMNT backbone into a highly ordered conformation, resulting in redshifted, new sharp bands in the absorption and fluorescence spectra. Similar to PIC, the hybrid closely mimics the mechanical properties of biological gels, such as collagen and fibrin, including the strain stiffening properties at low stresses. Moreover, the PMNT/PIC hybrids show much higher ROS production efficiency under red light than PMNT only, leading to an efficient photodynamic antimicrobial effect towards various pathogenic bacteria.

Graphene quantum dots (GQDs) have been successfully used as a highly sensitive probe for the sensing of formaldehyde (HCHO) in an aqueous solution. Through static quenching, the probe utilizes the interaction between HCHO and GQDs to trigger the “turn off” fluorescence response, and has good selectivity. The probe can detect HCHO in a pure aqueous solution, and it also can still detect HCHO in a complex environment with a pH range from 4 to 10. The concentration of HCHO and the fluorescence intensity of GQDs show a good linear relationship within the range of HCHO of 0–1 μg/mL, which was much more sensitive than previous reports. The limit of HCHO detection by GQDs is about 0.0515 μg/mL. In addition, we successfully applied it to the actual food inspection. It is proved to be a selective, sensitive and visualized method to check whether the concentration of HCHO in the foods exceeds the regulatory limit, which presents a potential application in food safety testing.

The effects of Cu substitution for Ni atoms on the magnetic and magnetocaloric properties have been investigated in Mn0.8Fe0.2Ni1-xCuxGe (x = 0.05–0.3) compounds. The substitution of Cu leads to the larger separation of Mn atoms, which stabilizes the hexagonal phase and thus reduces the structural transition temperature Tstr. Moreover, the larger separation of nearest-neighbor Mn atoms weakens the ferromagnetic (FM) coupling in TiNiSi-type orthorhombic phase and results in the spiral antiferromagnetic (AFM) and more antiparallel AFM state with increasing Cu content. Similarly, the Ni2In-type hexagonal phase also changes from FM state to weak-magnetic spin-glass-like state with the introduction of Cu. The x = 0.05 compound shows a conventional magnetocaloric effect (MCE) due to the magnetostructural transformation from PM hexagonal phase to FM orthorhombic phase. On the contrary, the x = 0.1 compound undergoes the antiferromagnetically magnetostructural transition from FM hexagonal phase to AFM orthorhombic phase, which leads to a high inverse MCE. This large inverse MCE could be utilized in novel magnetic refrigerator to improve the refrigeration efficiency and applied for magnetic refrigeration of natural gas liquefaction.

The magnetic and rotating magnetocaloric properties in textured Tb3NiGe2 compound were investigated. Two successive magnetic transitions, a ferrimagnetic to antiferromagnetic (AFM)-like transition at Tt = 130 K and an AFM to paramagnetic (PM)-like transition at TN = 144 K, are observed. Besides, a magnetic-field-induced antiferromagnetic-ferromagnetic metamagnetic transition occurs in the temperature range of Tt ∼ TN. Large rotating magnetic entropy changes, together with considerable adiabatic temperature changes and refrigeration capacity, are obtained in textured Tb3NiGe2 compound. Moreover, the equivalence of different calculation methods for rotating magnetocaloric effect (RMCE) is discussed mathematically. The large RMCE with excellent thermal and magnetic reversibility suggests textured Tb3NiGe2 compound as an attractive candidate for novel magnetic refrigerant.

Hybrid nanocomposites consisting of uniform Fe 3 O 4 nanoparticles and boron nitride (BN) nanospheres were synthesized via an ethanol-thermal reaction method. The spherical BN nanoparticles (BNNSs) with average diameter 150 nm have been uniformly coated with dense ultra-small Fe 3 O 4 nanoparticles (with average diameter of 10 nm), forming novel Fe 3 O 4 @BNNS nanocomposites. Magnetic measurement by using vibrating sample magnetometer (VSM) indicates that the Fe 3 O 4 coating is superparamagnetic, and the nanocomposites can be physically manipulated at a low magnetic field. Preliminary biocompatibility study has also been performed to evaluate the toxicity of the nanocomposites. The nanocomposites show cytocompatibility at low concentration and have little effect on cell viability of MCF-7, MCF-10 and Hela cell lines. The Fe 3 O 4 @BNNS nanocomposites may find a wide range of potential applications including water treatment, catalysts, carriers for boron neutron capture therapy and magnetic-targeted drug delivery.

Thermosensitive polymers show an entropy-driven transition from a well-solvated to a poorly solvated polymer chain, resulting in a more compact globular conformation. The transition at the lower critical solution temperature (LCST) is often sharp, which allows for a wide range of smart material applications. At the LCST, oligo(ethylene glycol)-substituted polyisocyanides (PICs) form soft hydrogels, composed of polymer bundles similar to biological gels, such as actin, fibrin and intermediate filaments. Here, we show that the LCST of PICs strongly depends linearly on the length of the ethylene glycol (EG) tails; every EG group increases the LCST and thus the gelation temperature by nearly 30 °C. Using a copolymerisation approach, we demonstrate that we can precisely tailor the gelation temperature between 10 °C and 60 °C and, consequently, tune the mechanical properties of the PIC gels.