Gel Materials Research Articles

Intranasal Insulin Delivery: Microparticle Formulations Consisting of Aloe vera Polysaccharides for Advanced Delivery across Excised Olfactory and Respiratory Nasal Epithelial Tissues

Aloe vera gel and whole leaf materials, as well as polysaccharides, precipitated from the gel, have previously been shown to enhance macromolecular drug delivery across epithelial tissues. This study investigated the effectiveness of microparticle formulations prepared from A. vera polysaccharides for nasal delivery of insulin across excised sheep olfactory and respiratory nasal epithelial tissues. An emulsion-solvent evaporation technique was used to prepare two insulin microparticle formulations, namely one containing Eudragit® L100 and A. vera polysaccharides and one containing A. vera polysaccharides only. In addition, an ionic gelation technique was used to prepare an insulin microparticle formulation with A. vera polysaccharides, where calcium chloride was used as a cross-linker. The microparticle formulations were evaluated in terms of drug content (assay), particle size, drug release (dissolution), ex vivo drug permeation, and histology. The microparticle formulations exhibited statistically significantly higher insulin delivery across excised sheep olfactory and respiratory nasal epithelial tissues compared to that of the control group (insulin alone). In conclusion, the use of A. vera polysaccharides in microparticle formulations significantly improved nasal insulin delivery. Therefore, A. vera polysaccharide containing microparticles showed high potential to enhance systemic bioavailability and delivery into the brain of macromolecular drugs such as insulin after intranasal administration.

In situ formation of injectable organogels for punctal occlusion and sustained release of therapeutics: design, preparation, in vitro and in vivo evaluation

The treatment of dry eye mainly includes instillation of cyclosporine A (CsA) nanoemulsion or the use of punctal plugs. Therefore, in this study, a novel injectable in situ organogel plug was developed using CsA as a model drug, stearic acid, injectable soybean oil, and N-methyl-2-pyrrolidinone (NMP) (1.25:10:0.6, w/v/v) as gel materials, to provide a dual mechanism for dry eye treatment. The formulated CsA injectable in situ organogel (CsA-OG) was evaluated in terms of stability, in vitro release, rheology, ocular irritation, punctal occlusion tests, and ocular distribution assessment. In vivo ocular distribution investigations showed that CsA-OG achieved considerably higher Cmax (1.94, 1.92 and 1.97-fold respectively) and AUC0-72h in the cornea, conjunctiva, and sclera (2.49, 2.27 and 2.15-fold respectively) than ciclosporin eye drops (p < 0.05). In vitro model evaluation demonstrated significant decrease in flow flux to 52.78 % at 2 min after CsA-OG injection. According to evaluation of the in vivo model, the organogel plug can completely block the lacrimal passages and greatly decrease the lacrimal drainage rate (p < 0.05). The above results suggest that these intracanalicular CsA-OG plugs can offer more extensive clinical applications than existing lacrimal drainage plugs and may act as a drug delivery system.

Barnacle inspired high-strength hydrogel for adhesive.

Barnacle exhibits high adhesion strength underwater for its glue with coupled adhesion mechanisms, including hydrogen bonding, electrostatic force, and hydrophobic interaction. Inspired by such adhesion mechanism, we designed and constructed a hydrophobic phase separation hydrogel induced by the electrostatic and hydrogen bond interaction assembly of PEI and PMAA. By coupling the effect of hydrogen bond, electrostatic force and hydrophobic interaction, our gel materials show an ultrahigh mechanical strength, which is up to 2.66 ± 0.18MPa. Also, benefit from the coupled adhesion forces, as well as the ability to destroy the interface water layer, the adhesion strength on the polar materials can be up to 1.99 ± 0.11MPa underwater, while that of the adhesion strength is about 2.70 ± 0.21MPa under silicon oil. This work provides a deeper understanding of the underwater adhesion principle of barnacle glue. Furthermore, our bioinspired strategy would provide an inspiration for the fabrication of high mechanical gel materials, and the rapid strong adhesive used in both water and organic solvents.

Advances Toward Sustainable Lignin-based Gel for Energy Storage and Smart Sensing

Polymers obtained from biomass are promising alternatives to petro-based polymers owing to their low cost, biocompatibility, and biodegradability. Lignin, a complex aromatic polymer containing several functional hydrophilic and active groups including hydroxyls, carbonyls, and methoxyls, is the second most abundant biopolymer in plants. In particular, sustainable lignin-based gels are emerging as an appealing material platform for developing energy- and sensing-related applications owing to their attractive and tailorable physiochemical properties. This study describes the preparation strategies of lignin-based gels according to previously reported methods, with significant attention on the diverse performance of lignin-derived gel materials. Additionally, a detailed review of lignin-based gels utilized as an important resource in diverse fields is provided. Finally, a future vision on challenges and their possible solutions is presented.

Improving the Quality of Set Yoghurt Using Milk Fat Globule Membrane Fragments

Lacprodan®PL20, a dairy ingredient that is rich in protein and polar lipids, was added into set yoghurts produced from nonhomogenized raw milk. The set yoghurts were prepared using concentrations of 2%, 4%, and 6% Lacprodan®PL20, while the control sample was only supplemented with skim milk powder. The effect of Lacprodan®PL20 concentrations on the physical and chemical properties, rheology, and microstructure of set yoghurt was thoroughly investigated to determine some likely improvement or changes in quality. Consequently, Lacprodan®PL20 showed a gradual improvement in the set yoghurt nutritive values, water holding capacity, and apparent viscosity. The results indicated that the firmness of set yoghurt was altered which steadily improved the gel strength, especially at 4% and 6% concentrations. The fermentation process was slightly delayed at 4% and 6% concentrations and pH values were raised as Lacprodan®PL20 concentration increased. The microstructures of the set yoghurts produced with Lacprodan®PL20, as examined by scanning electron microscopy, revealed compacted structures with fewer and smaller holes in the gel matrices. Also, a slight color change was observed in set yoghurt using a colorimeter. These results vividly showed that Lacprodan®PL20, an enriched milk fat globule membrane fragment, has the potential to improve set yoghurt quality by reducing some defects associated with set yoghurt, such as low gel strength, low dry solids, and the likes.

Shear response behavior of SSE/Kevlar composite fabric before and after shear interlocking effect

Shear stiffening gel (SSG) material was obtained by high-temperature polymerization with boric acid and hydroxyl silicone oil, shear stiffening elastomer (SSE) material was enhanced by vulcanization, and the rheological properties were analyzed. SSG and SSE/Kevlar composite fabric was obtained by “dip–dry” and “hot-pressing” process, and a picture frame test was performed on neat fabric and composite fabrics under three loading rates. The in-plane shear deformation behaviors of the fabrics were characterized by the DIC marker method, and the shear deformation mechanism of braided cells was analyzed theoretically. The results show that the SSG material has superior shear stiffening characteristics, whereas the SSE material has a much higher initial degree of crosslinking and does not have cold-flow characteristics. The fabrics experience typical shear interlocking behavior in shear deformation, and different shear deformation stiffness and energy absorption capacity before and after the shear interlocking was observed, which is caused by the different resistance mechanisms of braided cell to external shear force. The strain rate phase-change characteristics of SSG and SSE materials make the composite fabric have higher shear deformation stiffness and energy absorption at high speed, and SSE material significantly reduces the contact force between adjacent yarns after shear interlocking.

Effect of Polymer Hydrophobicity in the Performance of Hybrid Gel Gas Sensors for E-Noses.

Relative humidity (RH) is a common interferent in chemical gas sensors, influencing their baselines and sensitivity, which can limit the performance of e-nose systems. Tuning the composition of the sensing materials is a possible strategy to control the impact of RH in gas sensors. Hybrid gel materials used as gas sensors contain self-assembled droplets of ionic liquid and liquid crystal molecules encapsulated in a polymeric matrix. In this work, we assessed the effect of the matrix hydrophobic properties in the performance of hybrid gel materials for VOC sensing in humid conditions (50% RH). We used two different polymers, the hydrophobic PDMS and the hydrophilic bovine gelatin, as polymeric matrices in hybrid gel materials containing imidazolium-based ionic liquids, [BMIM][Cl] and [BMIM][DCA], and the thermotropic liquid crystal 5CB. Better accuracy of VOC prediction is obtained for the hybrid gels composed of a PDMS matrix combined with the [BMIM][Cl] ionic liquid, and the use of this hydrophobic matrix reduces the effect of humidity on the sensing performance when compared to the gelatin counterpart. VOCs interact with all the moieties of the hybrid gel multicomponent system; thus, VOC correct classification depends not only on the polymeric matrix used, but also on the IL selected, which seems to be key to achieve VOCs discrimination at 50% RH. Thus, hybrid gels' tunable formulation offers the potential for designing complementary sensors for e-nose systems operable under different RH conditions.

Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel.

Predicting the mechanical response of soft gel materials under external deformation is of paramount importance in many areas, such as foods, pharmaceuticals, solid-liquid separations, cosmetics, aerogels, and drug delivery. Most of the understanding of the elasticity of gel materials is based on the concept of fractal scaling with very few microscopic insights. Previous experimental observations strongly suggest that the gel material loses the fractal correlations upon deformation and the range of packing fraction up to which the fractal scaling can be applied is very limited. In addition, correctly implementing the fractal modeling requires identifying the elastic backbone, which is a formidable task. So far, there is no clear understanding of the gel's elasticity at high packing fractions or the correct length scale that governs its mechanical response. In this work, we undertake extensive numerical simulations to elucidate the different aspects of stress transmission in gel materials. We observe the existence of two percolating networks of compressive and tensile normal forces close to the gel point. We also find that the probability distribution for the compressive and tensile parts normalized by their respective mean shows a universal behavior irrespective of various values of interaction potential and thermal energy and different particle size distributions. Interestingly, there are also a large number of contacts with zero normal force, and, consequently, a peak in the normal force distribution is observed at fn ≈ 0 even at higher pressures. We also identify the critical internal state parameters, such as the mean normal force, force anisotropies, and the average coordination number, and propose simple constitutive relations that relate different components of stress to internal state parameters. The agreement between our model prediction and the simulation observation is excellent. It is shown that the anisotropy in the force networks gives rise to the normal stress difference in soft gel materials. Our results strongly demonstrate that the mechanical response of the gel system is governed mainly by the particle length scale phenomena, with a complex interplay between the compressive and tensile forces at the particle contact.

Bioinspired Multiscale Micro-/Nanofiber Network Design Enabling Extremely Compressible, Fatigue-Resistant, and Rapidly Shape-Recoverable Cryogels.

Cryogels with extreme mechanical properties such as ultrahigh compressibility, fatigue resistance, and rapid recovery are attractive in biomedical, environmental remediation, and energy storage applications, which, however, are difficult to achieve in man-made materials. Here, inspired by the multiscale macro-/microfiber network structure of spider web, we construct an ultraelastic chitosan cryogel with interconnected hybrid micro-/nanofibers (CMNF cryogels) via freeze-induced physicochemical cross-linking. Chitosan chains are directionally assembled into high-aspect-ratio microfibers and nanofibers under shear-flow induction, which are further assembled into an interconnected three-dimensional (3D) network structure with staggered microfibers and nanofibers. In this multiscale network, nanofibers connecting the microfibers improve the stability, while microfibers improve the elasticity of the CMNF cryogels through long-range interaction. The synergy of the two-scale fibers endows the CMNF cryogel with extraordinary mechanical properties in comparison to those assembled with single-scale fibers, including its ultrahigh ultimate strain (97% strain with 50 cycles), excellent fatigue resistance (3200 compressing-releasing cycles at 60% compression strain), and rapid water-triggered shape recovery (recovering in ∼1 s). Moreover, the fibrous CMNF cryogel shows excellent functionalization capability via the rapid assembly of nanoscale building blocks for flexible electronics and environmental remediation. Our work thereby demonstrates the potential of this bioinspired strategy for designing gel materials with extreme mechanical properties.

Efficient strategies for preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa.

Efficient strategies for the preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa using preparative high-performance liquid chromatography combined with appropriate pretreatment technologies were developed. Four fractions (Fr.1-1, Fr.1-2, Fr.1-3, and Fr.2-1) were firstly isolated from the crude extract of Hedyotis diffusa by column chromatography with C18, resin, and silica gel materials, respectively. Then, corresponding separation strategies were developed according to the polarity and chemical constituents. High-polar compounds of Fr.1-1 were purified by hydrophilic reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography mode. The combination of C18 and phenyl columns realized the complementary separation of iridoid glycosides in Fr.1-2. Meanwhile, the improved selectivity caused by the change of organic solvent in the mobile phase was utilized to realize the purification of flavonoid glycosides in Fr.1-3 and Fr. 2-1. Finally, 27 compounds (purity>95%) mainly involving nine iridoid glycosides and five flavonoid glycosides were obtained. A complete strategy was established for the separation of a complex sample with a wide polarity range, to jointly solve the problems of enrichment of target components and separation of structural analogs.

Formation of Alginate/Chitosan Interpenetrated Networks Revealed by EPR Spectroscopy.

This study analyzes the physico-chemical properties of interpenetrated polymer networks (IPNs) and semi-IPN resulting from cross-linking chitosan with glutaraldehyde and alginate with Ca2+ cations, as a function of the order in which the cross-linking agents are added to the polymer mixture. Three physico-chemical methods were used to assess the differences between systems: rheology, IR spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. While rheology and IR spectroscopy are commonly used to characterize gel materials, EPR spectroscopy is rarely used, but has the advantage of providing local information about the dynamics of a system. The rheological parameters, which describe the global behavior of the samples, show that semi-IPN systems have a weaker gel behavior and the order of introducing the cross-linker in the polymer systems plays a role. The IR spectra of samples resulting by adding only Ca2+ or Ca2+ as the first cross-linker are similar to that of the alginate gel, while the spectra of samples in which glutaraldehyde is firstly added resemble the chitosan gel spectrum. Using spin-labeled alginate and spin-labeled chitosan, we monitored the changes occurring in the dynamic of the spin labels due to the formation of IPN and semi-IPN. The results show that the order of adding the cross-linking agents influences the dynamic of the IPN network, and that the formation of the alginate network determines the characteristics of the entire IPN system. The EPR data were correlated with the rheological parameters and IR spectra of the analyzed samples.

"Smart" Stimuli-responsive Injectable Gels for Bone Tissue Engineering Application.

Bone grafting, as the current gold-standard for large scaled bone damage of various causes, has faced challenges from both the source and appliance. Emerging new tissue engineering substitutes are demonstrating more options and possibilities, with their improved biocompatibility, accessibility, and customizable function. Amongst them, injectable gels (IGs) are a class of gel material displaying astonishing non-invasive properties and surgical viability. While possessing responsiveness toward specific stimuli, they change their physical form in vivo, thus serving as wonderful biomaterials and drug delivery systems. In this review, the mechanics of stimuli-responsive IGs developed during the past decade are illustrated. Two branches of crosslinked gels - co-valent and non-covalent crosslinked IGs and their composition and customization are introduced. In conclusion, the present trend in bone tissue engineering research is summarized and made an outlook for future. It is hoped that this comprehensive review can provide a proper reference for the development of new IGs.

Textural landscapes of VOC-sensitive chiral liquid crystal-based materials

Liquid crystal-based materials, in which liquid crystal molecules are confined and ordered in compartments, are dynamic materials yielding a variety of optical textures that can be tuned as a response to physical and chemical stimuli. While nematic and smectic-based gel materials have been reported as dynamic optical sensors to report volatile organic compounds (VOCs), chiral systems are less explored despite having the potential to yield extremely rich optical landscapes. Here, we report for the first time the confinement of chiral liquid crystal formulations by an interface formed by ionic liquid molecules. The resultant self-assembled ionic liquid/liquid crystal droplets are simultaneously immobilized on a gelatin matrix. The droplets feature a rich variety of unique topological states. We explored, by means of polarizing optical microscopy, the various droplet optical textures and categorized them with regard to their relative chirality parameter. We further investigated their optical response in the presence of gas analytes and discussed their potential utilization as dynamic liquid crystal-based optical VOC sensors. The newly generated soft materials with semi-selective VOC sensing capabilities can be further utilized in arrays of liquid crystal-based gas sensors for the analysis of complex gas samples using artificial olfaction approaches.

An Important Play Role of Polymer in Daily Life and Duration of Covid19

Abstract: In this article we are focused on specially application of polymers and what hazards effects will come in future . Because at present time polymer application day by day used in multifunctional work. Here we want to discuss type of polymer. Synthetic polymers having wide applications like as a electronic equipments ,aerospace application, Light equipment , Cardiac heart valves, Polymer base mesh used in prevent of hernia in human body, synthetic polymer rayon useful in textiles industries. Synthetic polymers are vast used in medical sectors ,like as drug delivery, many packing are easily transported from one palace to other palace self-healing, and molecular-recognition materials. Many researchers have synthesized gel materials by designing their molecular and macroscopic structure as well as the constituent materials from the perspective of organic chemistry, physical chemistry, and biochemistry, among others. In addition, the fact that pharmacy, biomedicine, molecular biology, biochemistry, and biophysics are the fields that polymers and polymer chemistry play a significant role in the development of their new areas. It is obvious why the study of giant molecules is one of the most attended and the fastest growing fields of science. Therefore, it seems that polymer is not a specialized interdisciplinary or branch of chemistry. Here I have mention one of the polymers made by me and focused on application of polymers.

A model for fracture of temperature-sensitive hydrogel with diffusion and large deformation

A model is formulated theoretically in this paper via the phase field method for simulation of fracture in temperature-sensitive hydrogels with consideration of diffusion coupled with large deformation, based on the finite-element analysis with analogies between the phase field evolution law and heat transfer as well as between the diffusion law and heat transfer. The model is implemented by the commercial finite-element code ABAQUS/Standard, through its in-built features to robustly simulate the 2D or 3D fracture process under various boundary conditions for the smart hydrogels at both equilibrium and transient states. In particular, no preset crack is required by the model with capability to simulate of the fracture for different types of temperature-sensitive hydrogels under various boundary conditions. Subsequently, the model is validated by comparison with the experimental fracture data of temperature-sensitive hydrogel published in open literature. After that, several parameter studies are carried out numerically to demonstrate the robustness of the model and to understand the influence of temperature and diffusion on the fracture process of the hydrogels. Finally, three case studies of fracture occurring in potential engineering are investigated. The provided source codes and the tutorials make it easy for practicing engineers and scientists to model crack propagation in soft gel materials.

A mechanically strong shape-memory organohydrogel based on dual hydrogen bonding and gelator-induced solidification effect

Shape-memory gel materials are widely used in smart drives and biological tissues due to their excellent flexibility and diverse stimuli responsiveness. In particular, shape-memory organohydrogel materials have rose intense interest recently owing to their sophisticated shape memory behavior. However, conventional mechanical enhancement strategies, either by introducing nanoparticles or double-network structure, employed in the preparation of organohydrogels require high energy input, leading to difficulties in emulsification for emulsion precursors of organohydrogels. These strategies are not suitable for large-scale production of high-strength organohydrogels. Herein，a high-strength shape-memory organohydrogel NL-H was prepared based on dual hydrogen bonding and gelator-induced solidification effect. The precursor was easily emulsified, as the aqueous phase involved no nanoparticles or highly viscous polymers. Moreover, the dual hydrogen bonds among the dual amide groups of N-acryloyl glycinamide (NAGA) monomers can endow the organohydrogel with high mechanical properties. Owing to the oil-solidification effect of gelator HSA, the mechanical properties could be greatly enhanced, showing a high Young's modulus of 188.04 kPa. Furthermore, by integrating a high elastic hydrogel matrix and reversible oil domains, the organohydrogel showed a thermo-softening and favorable shape-memory properties. Consequently, this work provides a new enhancement strategy for the preparation of organohydrogel with high mechanical properties and excellent shape memory capabilities. And the simple preparation process can also facilitate the large-scale fabrication.

Study on Amino-functionalized Porous Carbon Materials for MB and Cr(VI) Adsorption

From the perspective of environmental protection, high removal rate, reusable and degradable, amino-functionalized porous hydrogel material P-(EA-β-CD/KHA/AC) was synthesized by introducing ethylamino cyclodextrin, humic acid, and activated carbon, using polyacrylic acid as the carrier. MB and Cr (VI) are common wastewater pollutants, thus, Such contaminants must be removed from the water. The gel materials before and after adsorption were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The removal of MB and Cr(VI) showed high adsorption capacity. At 298 K and pH 8, the adsorption capacities of P-(EA-β-CD/KHA/AC) hydrogel for MB and Cr(VI) were as high as 262.31 and 170.12 mg/g, respectively, and the removal rates were 98.96% and 70.27%, respectively. The adsorption behavior follows the pseudo-second-order kinetic equation, conforming to the Langmuir model; and through intermolecular forces, π–π conjugation, chelation, and other interactions, entropy-increasing, endothermic, and spontaneous process is formed. The regeneration and degradability experiments of P-(EA-β-CD/KHA/AC) hydrogel were conducted and its recycling performance was verified.

Ethyl Cellulose-Based Thermoreversible Organogel Photoresist for Sedimentation-Free Volumetric Additive Manufacturing.

Liquid photoresists are abundant in the field of light-based additive manufacturing (AM). However, printing unsupported directly into a vat of material in emerging volumetric AM technologies-typically a benefit due to fewer geometric constraints and less material waste-can be a limitation when printing low-viscosity liquid monomers and multimaterial constructs due to part drift or sedimentation. With ethyl cellulose (EC), a thermoplastic soluble in organic liquids, a simple three-component transparent thermoreversible gel photoresist with melting temperature of ≈64 °C is formulated. The physically crosslinked network of the gel leads to storage moduli in the range of 0.1-10kPa and maximum yield stress of 2.7kPa for a 10 wt% EC gel photoresist. Nonzero yield stress enables sedimentation-free tomographic volumetric patterning in low-viscosity monomer without additional hardware or modification of apparatus. In addition, objects inserted into the print container can be suspended in the gel material which enables overprinting of multimaterial devices without anchors connecting the object to the printing container. Flexural strength is also improved by 100% compared to the neat monomer for a formulation with 7 wt% EC.

Thermally-modulated shape transition at the interface of soft gel filament and hydrophobic substrate

A liquid filament may pinch off into different shapes on interacting with a soft surface, as modulated by the interplay of inertial, capillary, and viscous forces. While similar shape transitions may intuitively be realized for more complex materials such as soft gel filaments as well, their intricate controllability towards deriving precise and stable morphological features remains challenging, as attributed to the complexities stemming from the underlying interfacial interactions over the relevant length and time scales during the sol–gel transition process. Circumventing these deficits in the reported literature, here we report a new means of precisely-controlled fabrication of gel microbeads via exploiting thermally-modulated instabilities of a soft filament atop a hydrophobic substrate. Our experiments reveal that abrupt morphological transitions of the gel material set in at a threshold temperature, resulting in spontaneous capillary thinning and filament breakup. We show that this phenomenon may be precisely modulated by an alteration in the hydration state of the gel material that may be preferentially dictated by its intrinsic glycerol content. Our results demonstrate that the consequent morphological transitions give rise to topologically-selective microbeads as an exclusive signature of the interfacial interactions of the gel material with the deformable hydrophobic interface underneath. Thus, intricate control may be imposed on the spatio-temporal evolution of the deforming gel, facilitating the inception of highly ordered structures of specific shapes and dimensionalities on demand. This is likely to advance the strategies of long shelf-life analytical biomaterial encapsulations via realizing one-step physical immobilization of bio-analytes on the bead surfaces as a new route to controlled materials processing, without demanding any resourced microfabrication facility or delicate consumable materials.

Modulus watch: In situ determination of the gel modulus by timing the fluorescence color change

The gel modulus, a key parameter for gel materials, is traditionally determined by cumbersome rheometer. Recently, probe technologies occur to meet the requirements of in situ determination. Till now, in situ and quantitatively testing of gel materials with unabridged structure informations still remains a challenge. Here, we provide a facile, in situ approach to determine the gel modulus, by timing the aggregation of a doped fluorescence probe. The probe shows green emission during aggregation and shifts to blue once it forms aggregates. The higher modulus of the gel, the longer probe’s aggregation time. Furthermore, a quantitative correlation of gel modulus with the aggregation time is established. The in situ method not only facilitates the scientific researches in the field of gels, but also provides a new approach for spatiotemporal materials.