Active Gel Research Articles

Novel in situ growing carbon nanocoils onto steel mesh as positive electrode and hexagonal-MoO3 micro-rod array onto carbon fabric as negative electrode for assembling dual-asymmetric supercapacitors with redox active gel eleectrolyte

Intrinsically functionalized carbon nanocoils (CNCs) are in-situ grown onto the microwire surface of stainless steel mesh (SS) in an alcohol flame. The CNCs are deposited without using any additional catalysts and the flame growth mechanism is proposed. Such a unique structure with functionalized CNCs directly growing onto SS micro-wires in the mesh current collector makes it an excellent binder-free CNC/SS electrode. It exhibits ultrahigh capacitance in a iron ion based redox active electrolyte, where an remarkable areal capacitance of 4160 mF/cm 2 at 20 mA/cm 2 can be achieved. Meanwhile, hexagonal MoO 3 microrods are grown vertically onto carbon fibers and their electrochemical behaviors in normal H 2 SO 4 electrolyte are investigated. Finally, novel dual-asymmetric supercapacitors (DASCs) with the configuration of CNC/H 2 SO 4 +PVA + Fe 2+/3+ //H 2 SO 4 +PVA/h-MoO 3 are assembled. The device exhibits an excellent areal capacitance of 1502 mF/cm 2 at 3 mA/cm 2 , and a remarkable ultrahigh energy density of 252.4 μW h/cm 2 at the power energy of 1.6 mW/cm 2 as well. The research is expected to promote the development of SCs with high energy density through the design and assembly of all their main components, including the direct growth of active materials onto current collectors and the appropriate utilizing the redox active gel electrolyte. • A facile method for growing carbon nanocoils on stainless steel mesh was developed. • The flame catalytic growth mechanism of CNCs on stainless steel mesh was proposed. • Arrays of vertical h-MoO 3 hexagonal micro-rods was grown onto carbon fabric. • Novel dual-asymmetric supercapacitor with redox active gel electrolyte was assembled. • Remarkable capacitance of 1.5F/cm 2 and energy density of 252.4 μWh/cm 2 was realized.

DNA-Controlled Spatiotemporal Patterning of a Cytoskeletal Active Gel.

Living cells move and change their shape because signaling chemical reactions modify the state of their cytoskeleton, an active gel that converts chemical energy into mechanical forces. To create life-like materials, it is thus key to engineer chemical pathways that drive active gels. Here we describe the preparation of DNA-responsive surfaces that control the activity of a cytoskeletal active gel composed of microtubules: A DNA signal triggers the release of molecular motors from the surface into the gel bulk, generating forces that structure the gel. Depending on the DNA sequence and concentration, the gel forms a periodic band pattern or contracts globally. Finally, we show that the structuration of the active gel can be spatially controlled in the presence of a gradient of DNA concentration. We anticipate that such DNA-controlled active matter will contribute to the development of life-like materials with self-shaping properties.

Permeation Instabilities in Active Polar Gels.

We present a theory of active, permeating, polar gels, based on a two-fluid model. An active relative force between the gel components creates a steady-state current. We analyze its stability, while considering two polar coupling terms to the relative current: a permeation-deformation term, which describes network deformation by the solvent flow, and a permeation-alignment term, which describes the alignment of the polarization field by the network deformation and flow. Novel instability mechanisms emerge at finite wave vectors, suggesting the formation of periodic domains and mesophases. Our results can be used to determine the physical conditions required for various types of multicellular migration across tissues.

Hesperetin loaded proposomal gel for topical antioxidant activity

The present study was aimed at formulating and evaluating hesperetin-loaded proposomal gel for topical antioxidant activity. Hesperetin-loaded proposomes were first formulated and optimized with the central composite design and were characterized for particle size, polydispersity index, zeta potential and entrapment efficiency. In vitro release studies were also performed for the formulation. Various polymeric gel bases were assessed and one of them was selected to formulate the proposomal gel. The gels were characterized for their appearance, content uniformity, viscosity, spreadability and swelling index. In vitro diffusion studies were also carried out on the proposomal gel. Finally, in vitro antioxidant potentials of hesperetin and the proposomal formulation was determined using the 2,2- diphenyl-1-picrylhydrazyl hydrate (DPPH) assay. The optimized proposomal formulation showed enhanced in vitro drug release with a release of 95.51 ± 8.85% after 84 h compared to the hesperetin dispersion which released only 34.00 ± 1.71%. 1% carbopol was selected as a suitable gel base for the proposomal gel. The proposomal gel formulated showed good properties and was able to further sustain the drug release from the proposomes by releasing 42.63 ± 2.11% of the drug after 144 h. Finally, hesperetin and hesperetin-loaded proposomes showed comparable in vitro antioxidant activities with IC50 values of 82.15 μg/mL and 88.07 μg/mL, respectively. We can conclude that hesperetin-loaded proposomal gel can be an effective formulation with a controlled release profile and could be used to treat topical oxidative conditions.

A Three-Dimensional Numerical Model of an Active Cell Cortex in the Viscous Limit

The cell cortex is a highly dynamic network of cytoskeletal filaments in which motor proteins induce active cortical stresses which in turn drive dynamic cellular processes such as cell motility, furrow formation or cytokinesis during cell division. Here, we develop a three-dimensional computational model of a cell cortex in the viscous limit including active cortical flows. Combining active gel and thin shell theory, we base our computational tool directly on the force balance equations for the velocity field on a discretized and arbitrarily deforming cortex. Since our method is based on the general force balance equations, it can easily be extended to more complex biological dependencies in terms of the constitutive laws or a dynamic coupling to a suspending fluid. We validate our algorithm by investigating the formation of a cleavage furrow on a biological cell immersed in a passive outer fluid, where we successfully compare our results to axi-symmetric simulations. We then apply our fully three-dimensional algorithm to fold formation and to study furrow formation under the influence of non-axisymmetric disturbances such as external shear. We report a reorientation mechanism by which the cell autonomously realigns its axis perpendicular to the furrow plane thus contributing to the robustness of cell division under realistic environmental conditions.

FORMULATION DEVELOPMENT AND EVALUATION OF TRANSFERSOMES OF ECONAZOLE FOR EFFECTIVE FUNGAL TREATMENT

The aim of the present work is to formulate and characterize Econazole loaded transfersomal gel for antifungal activity. Econazole is a broad-spectrum imidazole antifungal agent that belongs to BCS Class II. Due to poor solubility, Econazole is incompletely absorbed after oral administration and bioavailability vary among individuals. Topical treatment of fungal infections is usually preferred, but the barrier is to cross stratum corneum, so formulating the drug in Transfersomes solved this problem. Prepared formulations of transfersomes were optimized on basis of vesicle size, shape, surface charge and entrapment efficiency. In order to predict and correlate the in vitro econazole permeation behavior from these transfersomes through semi-permeable membrane, it is necessary to fit into a suitable mathematical model. The in vitro drug permeation data from formulation F-12 containing econazole through semi-permeable membrane was evaluated kinetically by various mathematical models like zero-order, first-order, Higuchi, and Korsmeyer-Peppas Model. The results were obtained which showed that transfersomal gel was a promising candidate for transdermal delivery with targeted and prolonged release of a drug.

Condensation tendency and planar isotropic actin gradient induce radial alignment in confined monolayers.

A monolayer of highly motile cells can establish long-range orientational order, which can be explained by hydrodynamic theory of active gels and fluids. However, it is less clear how cell shape changes and rearrangement are governed when the monolayer is in mechanical equilibrium states when cell motility diminishes. In this work, we report that rat embryonic fibroblasts (REF), when confined in circular mesoscale patterns on rigid substrates, can transition from the spindle shapes to more compact morphologies. Cells align radially only at the pattern boundary when they are in the mechanical equilibrium. This radial alignment disappears when cell contractility or cell-cell adhesion is reduced. Unlike monolayers of spindle-like cells such as NIH-3T3 fibroblasts with minimal intercellular interactions or epithelial cells like Madin-Darby canine kidney (MDCK) with strong cortical actin network, confined REF monolayers present an actin gradient with isotropic meshwork, suggesting the existence of a stiffness gradient. In addition, the REF cells tend to condense on soft substrates, a collective cell behavior we refer to as the 'condensation tendency'. This condensation tendency, together with geometrical confinement, induces tensile prestretch (i.e. an isotropic stretch that causes tissue to contract when released) to the confined monolayer. By developing a Voronoi-cell model, we demonstrate that the combined global tissue prestretch and cell stiffness differential between the inner and boundary cells can sufficiently define the cell radial alignment at the pattern boundary.

細胞核はどこにあるか――アクティブ・ゲルと配置対称性の制御原理

細胞核はどこにあるか――アクティブ・ゲルと配置対称性の制御原理

Aggregation‐Induced Emissive Carbon Dots Gels for Octopus‐Inspired Shape/Color Synergistically Adjustable Actuators

AbstractSome living organisms such as the octopus have fantastic abilities to simultaneously swim away and alter body color/morphology for disguise and self‐protection, especially when there is a threat perception. However, it is still quite challenging to construct artificial soft actuators with octopus‐like synergistic shape/color change and directional locomotion behaviors, but such systems could enhance the functions of soft robotics dramatically. Herein, we proposed to utilize unique hydrophobic carbon dots (CDs) with rotatable surficial groups to construct the aggregation‐induced emission (AIE) active glycol CDs polymer gel, which could be further employed to be interfacially bonded to an elastomer to produce anisotropic bilayer soft actuator. When putting the actuator on a water surface, glycol spontaneously diffused out from the gel layer to allow water intake, resulting in a color change from a blue dispersion fluorescence to red AIE and a shape deformation, as well as a large surface tension gradient that can promote its autonomous locomotion. Based on these findings, artificial soft swimming robots with octopus‐like synergistic shape/color change and directional swimming motion were demonstrated. This study provides an elegant strategy to develop advanced multi‐functional bio‐inspired intelligent soft robotics.

Activated carbon from composite of palm bio-waste as electrode material for solid-state electric double layer capacitor

This work explores the synergistic advantage of the lignocellulose chemistry of oil palm fiber, empty fruit bunch, and oil palm shell as a composite in activated carbon preparation using physical and chemical activation methods. Using coin cell CR2032–3 V, supercapacitors were fabricated with the prepared activated carbon composite as electrode active material and H3PO4-based gel electrolyte. At a specific power density of 50 WKg−1, electric double-layer capacitors derived from chemically and physically activated carbon composite shows a specific energy density of 8.6 WhKg−1 and 5.8 WhKg−1, respectively. These results were observed to be better than the results of supercapacitors fabricated using liquid electrolytes. Apart from the better performance, the solid-state electric double layer capacitor is relatively lighter, allows miniaturization, flexibility, and mitigates liquid electrolyte leakage.

Aqueous high-voltage all 3D-printed micro-supercapacitors with ultrahigh areal capacitance and energy density

With the rapid development of integrated and miniaturized electronics, the planar energy storage devices with high capacitance and energy density are in enormous demand. Hence, the advanced manufacture and fast fabrication of microscale planar energy units are of great significance. Herein, we develop aqueous planar micro-supercapacitors (MSCs) with ultrahigh areal capacitance and energy density via an efficient all-3D-printing strategy, which can directly extrude the active material ink and gel electrolyte onto the substrate to prepare electrochemical energy storage devices. Both the printed active carbon/exfoliated graphene (AC/EG) electrode ink and electrolyte gel are highly processable with outstanding conductivity (~97 S cm−1 of electrode; ~34.8 mS cm−1 of electrolyte), thus benefiting the corresponding shaping and electrochemical performances. Furthermore, the 3D-printed symmetric MSCs can be operated stably at a high voltage up to 2.0 V in water-in-salt gel electrolyte, displaying ultrahigh areal capacitance of 2381 mF cm−2 and exceptional energy density of 331 μWh cm−2, superior to previous printed micro energy units. In addition, we can further tailor the integrated 3D-printed MSCs in parallel and series with various voltage and current outputs, enabling metal-free interconnection. Therefore, our all-3D-printed MSCs place a great potential in developing high-power micro-electronics fabrication and integration.

Optogenetic control of intracellular flows and cell migration: A comprehensive mathematical analysis with a minimal active gel model.

The actin cytoskeleton of cells is in continuous motion due to both polymerization of new filaments and their contraction by myosin II molecular motors. Through adhesion to the substrate, such intracellular flow can be converted into cell migration. Recently, optogenetics has emerged as a new powerful experimental method to control both actin polymerization and myosin II contraction. While optogenetic control of polymerization can initiate cell migration by generating protrusion, it is less clear if and how optogenetic control of contraction can also affect cell migration. Here we analyze the latter situation using a minimal variant of active gel theory into which we include optogenetic activation as a spatiotemporally constrained perturbation. The model can describe the symmetrical flow of the actomyosin system observed in optogenetic experiments, but not the long-lasting polarization required for cell migration. Motile solutions become possible if cytoskeletal polymerization is included through the boundary conditions. Optogenetic activation of contraction can then initiate locomotion in a symmetrically spreading cell and strengthen motility in an asymmetrically polymerizing one. If designed appropriately, it can also arrest motility even for protrusive boundaries.

Effects of ultrasound, freeze-thaw pretreatments and drying methods on structure and functional properties of pectin during the processing of okra

Although, okra has features of high moisture content, rich nutrients, and pectin, it has extremely short shelf life, so deteriorate easily. Simple drying can prolong okra's shelf life but takes considerable time and is not cost-effective. Therefore, suitable pretreatments are usually employed to improve the drying efficiency and reduce the costs. This study showed that ultrasound (US) and freeze-thawing (FT) pretreatments, as well as three drying methods including vacuum pulsed drying (VPD), vacuum freeze-drying (VFD) and hot air drying (HD) have effects on structure and functional characteristics of okra pectin. The results indicated that drying methods affected differently the structure and chain conformation of the pectin molecular main chain. The thermal drying processes reduced molecular weight and increased viscosity, oxidation resistance, thermal stability, cohesion, and resilience. Particularly, the VPD pectin samples had lower molecular weight, higher antioxidant activity, better retention of the homogalacturonan (HG) main chain, thermal stability, emulsification activity, cohesiveness, resilience and weaker hardness and gel strength. The pretreatments had little effect on molecular weight, improved the antioxidant activity and emulsification activity of samples, and increased the viscosity of cold processed samples. US pretreatment retained pectin molecular chains, and FT pretreatment aggravated molecular chain debranching. In summary, VPD and US/FT pretreatments are beneficial to the development and utilization of pectin products.

Application of an active oxygen (blue®m) with free connective graft technique for root coverage – a case report

Gingival recession occurs due to the migration of the gingiva in the apical direction, leading to compromising local aesthetics and root hypersensitivity. Connective tissue graft is the gold standard treatment in these cases improving both functional and aesthetics aspects.The purpose of this case is to report root coverage using the free connective tissue graftingtechnique (CTG) associated with topical application of active oxygen oral gel and mouthwash (blue®m). A 27-year-old female sought care with the main complaint of root hypersensitivity and the presence of gingival recession in the anterior region of the mandible. Clinical examination revealed the presence of type 1 gingival recession in the left mandibular central incisor. The treatment of choice was a modified graft (free connective graft). The graft and recipient bed received applications of blue®m oral gel. The patient was instructed to use blue®m mouthwash and blue®m oral gel after the surgery for 10 days. At 60 days, the patient showed satisfactory healing in the area of the free CTG, with gain of keratinized tissue and partial covering of the gingival recession. Free CTG with the support of the gel and the mouthwash with active oxygen release makes the technique viable, preventing graft necrosis and achieving root coverage and keratinized tissue.

Thermosensitive and mucoadhesive in situ ocular gel for effective local delivery and antifungal activity of itraconazole nanocrystal in the treatment of fungal keratitis

Itraconazole is a lipophilic drug, which limits its absorption for ocular administration. This study focused on the incorporation of itraconazole into nanocrystalline carrier system with stabilizer Pluronic® F127 and was further formulated into thermosensitive in situ ocular gel. Itraconazole nanocrystals (ITZ-NCs) were fabricated using media milling method with ultra-small-scale device. The obtained nanocrystals were observed to have a better in vitro activity against C. albicans (CA) compared to free itraconazole suspension in water. Furthermore, the optimization of the thermosensitive ocular gel formula was carried out with a central composite design, using three types of polymers, namely Pluronic® F127, Pluronic® F68, and hydroxypropyl methylcellulose (HPMC). After being dispersed into the optimized thermosensitive gel base, ITZ-NCs did not alter in terms of physical characteristics. Ex vivo ocularkinetic studies on infected porcine eye models showed a better profile of the optimized formula of thermosensitive in situ ocular gel when compared to standard gel base. Importantly, the ex vivo antifungal activity of these preparations was also increased, with a 93% decrease in the CA population observed after 48 h in infected porcine eye model. Altogether, this work has provided evidence of a novel approach in developing more advanced treatments for fungal keratitis.

Rheology of active emulsions with negative effective viscosity

ABSTRACT We numerically study by lattice Boltzmann simulations the rheological properties of an active emulsion made of a suspension of an active polar gel embedded in an isotropic passive background. We find that the hexatic equilibrium configuration of polar droplets is highly sensitive to both active injection and external forcing and may either lead to asymmetric unidirectional states which break top-bottom symmetry or symmetric ones. In this latter case, for large enough activity, the system develops a shear thickening regime at low shear rates. Importantly, for larger external forcing a regime with stable negative effective viscosity is found. Moreover, at intermediate activity a region of multistability is encountered and we show that a maximum entropy production principle holds in selecting the most favorable state.

Activity pulses induce spontaneous flow reversals in viscoelastic environments.

Complex interactions between cellular systems and their surrounding extracellular matrices are emerging as important mechanical regulators of cell functions, such as proliferation, motility and cell death, and such cellular systems are often characterized by pulsating actomyosin activities. Here, using an active gel model, we numerically explore spontaneous flow generation by activity pulses in the presence of a viscoelastic medium. The results show that cross-talk between the activity-induced deformations of the viscoelastic surroundings and the time-dependent response of the active medium to these deformations can lead to the reversal of spontaneously generated active flows. We explain the mechanism behind this phenomenon based on the interaction between the active flow and the viscoelastic medium. We show the importance of relaxation time scales of both the polymers and the active particles and provide a phase space over which such spontaneous flow reversals can be observed. Our results suggest new experiments investigating the role of controlled pulses of activity in living systems ensnared in complex mircoenvironments.

Chemo-mechanical model of a cell as a stochastic active gel

While it is commonly observed that the shape dynamics of mammalian cells can undergo large random fluctuations, theoretical models aiming at capturing cell mechanics often focus on the deterministic part of the motion. In this paper, we present a framework that couples an active gel model of the cell mechanical scaffold with the complex cell metabolic system stochastically delivering the chemical energy needed to sustain an active stress in the scaffold. Our closure assumption setting the magnitude of the fluctuations is that the chemo-mechanical free energy of the cell is controlled at a target homeostatic value. Our model rationalizes the experimental observation that the cell shape fluctuations depend on the mechanical environment that constraints the cell. We apply our framework to the simple case of a cell migrating on a one dimensional track to successfully capture the different regimes of the cell mean square displacement along the track as well as the magnitude of the long time scale effective diffusive motion of the cell.

Efficacy and safety of a new vaginal gel for the treatment of symptoms associated with vulvovaginal atrophy in postmenopausal women: A double-blind randomized placebo-controlled study

ObjectiveThe aim of the present randomized placebo-controlled single-center study was to assess the efficacy and safety of a new vaginal gel (Meclon Idra - Alfasigma) in the treatment of vulvovaginal atrophy (VVA). The gel is composed of sea buckthorn (Hippophaë rhamnoides) oil, aloe vera, 18β-glycyrrhetic acid, hyaluronic acid and glycogen. The study assessed whether the gel can reduce VVA symptoms (vaginal dryness, itching, burning sensation) and improve sexual function in postmenopausal women over 12 weeks. Study DesignPostmenopausal women (n° = 60) reporting VVA symptoms were recruited and randomized in a 1:1 ratio to the gel or placebo. Active vaginal gel or placebo was applied for 14 days and then twice a week for 90 consecutive days. Main outcome measureThe Vaginal Health Index (VHI), including vaginal pH, was used to assess changes in objective signs, whereas the self-reported Female Sexual Function Index (FSFI) was used to investigate sexual function. ResultsMeclon Idra was effective in reducing vaginal pain, dyspareunia and vaginal pH, with the VHI showing significant improvement at day 90 (P < .0001), and in reducing each VVA symptom (vaginal dryness, vaginal itching, burning sensation) at weeks 2 and 4, and the end of the study (P < .0001). The analysis of FSFI scores showed, after the end of treatment, an improvement of sexual function in the active-treatment group, with a statistically significant increase (P < 0.001) in all domains scores and total score (P < 0.001). ConclusionsThe present single-center randomized clinical trial demonstrated the efficacy, tolerability and safety of 12-week treatment with a new vaginal gel in postmenopausal women with symptoms associated with VVA. Based on this trial, the gel seems to be a valid choice as a single, local agent for relieving VVA symptoms and improving sexual function, and to have good compliance.This trial is registered prospectively with the Clinical Trials Registry – India, number CTRI/2019/05/01911.

Activity-induced isotropic-polar transition in active liquid crystals

Active fluids are intrinsically out-of-equilibrium systems due to the internal energy injection of the active constituents. We show here that a transition from a motion-less isotropic state towards a flowing polar one can be possibly driven by the sole active injection through the action of polar-hydrodynamic interactions in absence of an ad hoc free energy which favors the development of an ordered phase. In particular, we propose an analytical argument and we perform lattice Boltzmann simulations where the appearance of large temporal fluctuations in the polar fraction of the system is observed at the transition point. We show that elastic absorption plays a relevant role in energy transfer dynamics, contrary to the case of the usual active gel theory where this term can be factually neglected.