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In this work, we present basic research on developing thermogel carriers containing high amounts of model antibody immunoglobulin G (IgG) with potential use as injectable molecules. The quantities of IgG loaded into the gel were varied to evaluate the possibility of tuning the dose release. The gel materials were based on blends of thermoresponsive and degradable ABA-type block copolymers composed of poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) or poly(lactide-co-caprolactone)-b-poly(ethylene glycol)-b-(lactide-co-caprolactone) (PLCL–PEG–PLCL). Primarily, the gels with various amounts of IgG were obtained via thermogelation, where the only factor inducing gel formation was the change in temperature. Next, to control the gels' mechanical properties, degradation rate, and the extent of antibody release, we have tested two approaches. The first one involved the synergistic physical and chemical crosslinking of the copolymers. To achieve this, the hydroxyl groups located at the ends of the PLGA–PEG–PLGA chain were modified into acrylate groups. In this case, the thermogelation was accompanied by chemical crosslinking through the Michael addition reaction. Such an approach increased the dynamic mechanical properties of the gels and simultaneously prolonged their decomposition time. An alternative solution was to suspend crosslinked PEG–polyester nanoparticles loaded with IgG in a PLGA–PEG–PLGA gelling copolymer. We observed that loading IgG into thermogels lowered the gelation temperature (TGEL) value and increased the storage modulus of the gels, as compared with gels without IgG. The prepared gel materials were able to release the IgG from 8 up to 80 days, depending on the gel formulation and on the amount of loaded IgG. The results revealed that additional, chemical crosslinking of the thermogels and also suspension of particles in the polymer matrix substantially extended the duration of IgG release. With proper matching of the gel composition, environmental conditions, and the type and amount of active substances, antibody-containing thermogels can serve as effective IgG delivery materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Thermally-induced in-situ gelation of polymers and nanogels is of significant importance for injectable non-invasive tissue engineering and delivery systems of drug delivery system. In this study, we for the first time demonstrated that the interpenetrating (IPN) nanogel with two networks of poly (N-isopropylacrylamide) (PNIPAM) and poly (N-Acryloyl- l -phenylalanine) (PAphe) underwent a reversible temperature-triggered sol-gel transition and formed a structural color gel above the phase transition temperature (Tp). Dynamic light scattering (DLS) studies confirmed that the Tp of IPN nanogels are the same as that of PNIPAM, independent of Aphe content of the IPN nanogels at pH of 6.5 ∼ 7.4. The rheological and optical properties of IPN nanogels during sol-gel transition were studied by rheometer and optical fiber spectroscopy. The results showed that the gelation time of the hydrogel photonic crystals assembled by IPN nanogel was affected by temperature, PAphe composition, concentration, and sequence of interpenetration. As the temperature rose above the Tp, the Bragg reflection peak of IPN nanogels exhibited blue shift due to the shrinkage of IPN nanogels. In addition, these colored IPN nanogels demonstrated good injectability and had no obvious cytotoxicity. These IPN nanogels will open an avenue to the preparation and thermally-induced in-situ gelation of novel NIPAM-based nanogel system. [ABSTRACT FROM AUTHOR]

The lifetime and application of electrochemical storage devices are always threatened by thermal runaway. Intelligent self-protecting gel electrolytes can be designed using temperature-responsive polymers. However, the mechanisms and factors affecting protective behavior are unclear. Here, we fabricated supercapacitors using temperature-responsive polyacrylamide-2-hydroxyethyl acrylate (PNIPAM-co-HEA) hydrogel polyelectrolytes. It was found that the polymer changed from hydrophilic to hydrophobic with increasing temperature, and the physical cross-linking of the polymer molecular strands in the electrolyte was enhanced, thus restricting conductive ion migration and closing the ion transportation pathway. The hydrophilic–hydrophobic transition on the gel surface also contributed to the suppression of the specific capacitance of the supercapacitor. This self-protection feature is repeatable. In addition, we investigated the effect of methyl groups in the main chain structure on the electrochemical properties using poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNIPAM-co-HEMA). Methylene enhanced the hydrophobicity of the polymer at room temperature and reduced the thermo-protective effect. The methyl group in the main chain also reduced the thermal response temperature of the polymer. This study explores the mechanism by which temperature-responsive polymers inhibit thermal runaway in supercapacitors and provides support for the design of more rational and efficient temperature-sensitive electrolytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Introducing TBA provides steric hindrance to achieve thermally induced physical crosslinking in nano-gels. • Introducing Aphe can enable the nano-gels to maintain structural color above the phase transition point. • Introducing BISS imparts redox activity to PNTA-BISS due to the disulfide bonds in the structure. • There are significant differences in the rheological properties of PNTA nano-gels when crosslinkers BAC and BISS are used. Thermally induced physical hydrogels formed through the sol–gel transition of nanogels usually lose structural color above phase transition temperature (T p). Herein, temperature/pH/redox-responsive nanogels that undergo sol–gel transition still keep structural colors above the T p have been synthesized and studied. N -isopropylacrylamide (NIPAm) was copolymerized with N - tert -butylacrylamide (TBA) and N -acrylamido- l -phenylalanine (Aphe) to form P(NIPAm/TBA/Aphe) nanogel crosslinked with N,N'-bis(acryloyl)cystine (BISS) (referred to as PNTA-BISS). PNTA-BISS nanogel with a broad range of biodegradable crosslinker BISS content can achieve a reversible sol–gel transition above the T p , surprisingly, while PNTA nanogels with a comparable content of biodegradable N,N'-Bis(acryloyl)cystam (BAC) crosslinker (referred to as PNTA-BAC) didn't form sol–gel transition. Although BISS and BAC possess same disulfide bonds with redox properties, BISS, unlike BAC, is water-soluble and features two carboxyl groups. The mechanism by which PNTA-BISS nanogels form hydrogel photonic crystals has been deeply explored with temperature-variable NMR. The results showed the introduction of Aphe with both steric hindrance and carboxyl groups greatly slowed down the shrinkage of PNTA-BISS nanogels. Therefore, PNTA-BISS nanogels can form sol–gel transition and further structural color of hydrogel photonic crystals due to carboxyl groups above the T p. Furthermore, the properties of biodegradable hydrogel photonic crystals above the T p were investigated for the first time, attributed to the presence of the strong reducing agent 1,4-dithiothreitol (DTT). When loaded with doxorubicin (DOX), PNTA-BISS exhibited favorable degradation properties under the influence of DTT. In summary, the PNTA-BISS nanogel, in addition to its in-situ gelation capabilities, demonstrated degradability, potentially providing a novel nanoplatform for applications in drug delivery, biotechnology, and related fields. [ABSTRACT FROM AUTHOR]

A combination of Poloxamer 407 (P407) and hydroxypropyl methylcellulose (HPMC) hydrosols is proposed as an in situ thermo-gelling vehicle for the nasal drug delivery of chlorhexidine–silver nanoparticles conjugates (SN-CX). Optimization of the formulation was carried out by applying varying ratios of P407 and HPMC in the presence and absence of SN-CX so that gelation would occur in the temperature range of the nasal cavity (30–34 °C). Mechanisms for the observed gelation phenomena were suggested based on viscosimetry, texture analysis, and dynamic light scattering. Tests were carried out for sprayability, washout time, in vitro drug release, ex vivo permeation, and antimicrobial activity. When applied separately, HPMC was found to lower the P407 gelation temperature (Tg), whereas SN-CX increased it. However, in the presence of HPMC, SN-CX interfered with the P407 micellar organization in a principally contrasting way while leading to an even further decrease in Tg. SN-CX-loaded nasal formulations composed of P407 16% and HPMC 0.1% demonstrated a desired gelation at 31.9 °C, good sprayability (52.95% coverage of the anterior nasal cavity), mucoadhesion for 70 min under simulated nasal clearance, expedient release and permeation, and preserved anti-infective activity against seasonal Influenza virus and beta-coronavirus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and other pathogens. Our findings suggest that the current development could be considered a potential formulation of a protective nasal spray against respiratory infections. [ABSTRACT FROM AUTHOR]

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Nanoporous aerogel fibers enjoy the luxury of being one of the most attractive nanomaterials. However, the representative fabrication pathways have faced up with low production rates due to significant speed mismatch between slow sol–gel transition and as fast as possible spinning in the same period. Herein, a novel gas‐blows‐liquid spinning (GS) strategy with a spinning speed of 300–700 m s−1 is developed to get the high‐speed and high‐efficiency production of aerogel fibers/fabrics. The spinning speed of the GS strategy is 900 times higher than various techniques reported for aerogel fibers. The resulting aerogel fibers exhibit a high specific surface area (180 m2 g−1). In comparison, the aerogel fiber possesses the highest tensile strength (58.7±3.9 MPa) among its counterparts and aerogel fabric with surprising water‐absorption and microparticle‐blocking performances exhibits the application prospect for better hemostasis than that of commercial gauze and cotton ball. Besides, the GS aerogel fabrics with hierarchical aligned structures show better thermal insulation (≈0.035 Wm−1K−1) than wet spinning aerogel fabric and commercial insulation felts. This work has provided inspiration for fast fabricating more aerogel fibers/fabrics with this GS strategy, and the resulting aerogel fibers/fabrics may find significant application in the fields of 5G smart phones, wound hemostasis, etc. [ABSTRACT FROM AUTHOR]

The objective of this study is to enhance the comprehension of the mechanism of enzymatic gelation in milk by investigating statistically significant changes in milk viscosity and carrying out corresponding electron microscopic studies of the process of structure formation at the enzymatic stage of coagulation using various enzyme preparations. Employing a non-destructive method (Hot-Wire) to monitor viscosity, we were able to confirm a decrease in viscosity during the middle of this stage and identify a previously undescribed peak in viscosity change at the end of the enzymatic stage. By conducting parallel studies utilizing transmission electron microscopy and various methods of specimen preparation, it was possible to discover that a hierarchical transformation process in the protein component of milk started at the end of the enzymatic stage of gelation in milk. This process is triggered by a cooperative conformational transition in casein micelle clusters, which leads to a series of increasingly energy-intensive reactions resulting in the transformation of loosely bound micelle clusters into denser aggregates. The final structure of the milk gel primarily consists of the previously formed individual micelle aggregates. It was noted that no changes in the microstructure of the milk gel were observed during the enzymatic stage of gelation when milk-clotting enzymes (MCEs) of animal, plant, and microbial (GMO) origins were used. Furthermore, investigations into the molecular weight distribution of soluble protein substances in samples generated with different types of MCEs revealed that the enzyme derived from the fungi of Rhizomucor miehei had a greater proteolytic effect on milk proteins compared to other variants of MCEs. [ABSTRACT FROM AUTHOR]

The work studied the effect of structuring of gelatin solution with a different content of acetic acid on the stability of electrospinning process and obtained nanofibers morphology. Using the method of dynamic light scattering and analysis using the Arrhenius equation, it was found that the process of formation of gelatin sol is thermally activated, and the activation energy of the process increases from 70.2 to 102.2 kJ/mol with the introduction of 10 vol.% acetic acid. Using dynamic mechanical analysis of viscoelastic properties, it was found that when the solution concentration is more than 15 wt.% in the presence of 10 vol.% acid, a structure of the solution close to a gel is formed. It has also been shown that as the fraction of acid increases to 25 vol.% and higher solutions are characterized by a sol state with an increase in the elastic component after 24 h of solution settling. It was found that the structuring of the solution during settling affects the stability of electrospinning. Statistical analysis of the morphology of gelatin nanofibers showed that with an acid content of 25 vol.% the average diameter of nanofibers increases by 2 times during settling of 24 h. When using an acetic acid content in a gelatin solution of more than 50 vol.%, a significant increase in the stability of the electrospinning process and in the average diameter of nanofibers were observed, regardless of the settling time. [ABSTRACT FROM AUTHOR]

Quasi‐solid zinc‐ion batteries using hydrogel electrolytes show great potential in energy storage devices owing to their intrinsic safety, fewer side reactions and wide electrochemical windows. However, the dendrite issues on the zinc anodes cannot be fundamentally eliminated and the intrinsic anode‐electrolyte interfacial interspace is rarely investigated. Here, we design a dynamically healable gelatin‐based hydrogel electrolyte with a highly reversible sol‐gel transition, which can construct a conformal electrode‐electrolyte interface and further evolve into a stable solid‐solid interface by in situ solidification. The unique helical gelatin chain structure provides a uniform channel for zinc ion transport by the bridging effect of sulfate groups. As a consequence, the dynamically healable interface enables dendrite‐free zinc anodes and repeatedly repairs the anode‐electrolyte interfacial interspaces by the reversible sol‐gel transition of gelatin electrolyte to retain long‐lasting protection for sustainable zinc‐ion batteries. [ABSTRACT FROM AUTHOR]

In this work, we present basic research on developing thermogel carriers containing high amounts of model antibody immunoglobulin G (IgG) with potential use as injectable molecules. The quantities of IgG loaded into the gel were varied to evaluate the possibility of tuning the dose release. The gel materials were based on blends of thermoresponsive and degradable ABA-type block copolymers composed of poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) or poly(lactide-co-caprolactone)-b-poly(ethylene glycol)-b-(lactide-co-caprolactone) (PLCL–PEG–PLCL). Primarily, the gels with various amounts of IgG were obtained via thermogelation, where the only factor inducing gel formation was the change in temperature. Next, to control the gels’ mechanical properties, degradation rate, and the extent of antibody release, we have tested two approaches. The first one involved the synergistic physical and chemical crosslinking of the copolymers. To achieve this, the hydroxyl groups located at the ends of the PLGA–PEG–PLGA chain were modified into acrylate groups. In this case, the thermogelation was accompanied by chemical crosslinking through the Michael addition reaction. Such an approach increased the dynamic mechanical properties of the gels and simultaneously prolonged their decomposition time. An alternative solution was to suspend crosslinked PEG–polyester nanoparticles loaded with IgG in a PLGA–PEG–PLGA gelling copolymer. We observed that loading IgG into thermogels lowered the gelation temperature (TGEL) value and increased the storage modulus of the gels, as compared with gels without IgG. The prepared gel materials were able to release the IgG from 8 up to 80 days, depending on the gel formulation and on the amount of loaded IgG. The results revealed that additional, chemical crosslinking of the thermogels and also suspension of particles in the polymer matrix substantially extended the duration of IgG release. With proper matching of the gel composition, environmental conditions, and the type and amount of active substances, antibody-containing thermogels can serve as effective IgG delivery materials.

Reversible chemical covalency provides a path to materials that can degrade and recombine with appropriate stimuli and which can be used for tissue regeneration and repair. However, designing and preparing efficient and quickly self-healing materials has always been a challenge. The preparation strategies of photoresponsive gels attract a lot of attention due to their precise spatial and temporal control and their predetermined response to light stimulation. In this work, the linear copolymer PAC was synthesized via precipitation polymerization of acrylic acid and 7-(2-acrylate-ethoxylated)-4-methylcoumarin. The coumarin groups on the copolymer PAC side chains provide a reversible chemical cross-linking via photostimulation, which achieves reversible regulation of the gel network structure. The concentration of 18 wt% PAC solution produces gelation under irradiation with 365 nm. In contrast, PAC gel is restored to soluble copolymers under irradiation with 254 nm. Meanwhile, the mechanical and self-healing properties of the gel were also explored. It is demonstrated that the cracks of the gel can be repaired simply, quickly, and efficiently. Furthermore, the PAC copolymer shows an excellent adhesion property based on the reversible sol–gel transition. Thus, the PAC gel has considerable potential for applications in engineering and biomedical materials. [ABSTRACT FROM AUTHOR]

A simple model is introduced to describe phase behaviours of binary mixtures of a thermoreversible gel and a low-molecular-weight liquid crystal (LC). We predict novel phase diagrams on the temperature–concentration plane, including sol–gel transition, nematic–isotropic phase transition, and phase separation. At high temperatures, the phase separation between the isotropic sol and gel phases appears. As the temperature decreases, we have the phase separation between nematic sol and isotropic gel phases, in which the nematic domains are dispersed in the isotropic gel phase. We suggest that thermoreversible gelation of reactive molecules mixed with LCs will become one of the new classes of polymer-dispersed liquid crystals. [ABSTRACT FROM AUTHOR]

We describe a mechanism of pre-transition process near the sol-gel transition temperature in the sol-phase of water solutions of rigid-chain polymers. During this process the water boundary layer is disordered, and voids are formed in it. The variation of density of the hydroxypropyl methylcellulose with temperature is measured experimentally for temperatures between 25 and 80 °C. The experiment supports the proposed mechanism. [ABSTRACT FROM AUTHOR]

A combination of Poloxamer 407 (P407) and hydroxypropyl methylcellulose (HPMC) hydrosols is proposed as an in situ thermo-gelling vehicle for the nasal drug delivery of chlorhexidine–silver nanoparticles conjugates (SN-CX). Optimization of the formulation was carried out by applying varying ratios of P407 and HPMC in the presence and absence of SN-CX so that gelation would occur in the temperature range of the nasal cavity (30–34 °C). Mechanisms for the observed gelation phenomena were suggested based on viscosimetry, texture analysis, and dynamic light scattering. Tests were carried out for sprayability, washout time, in vitro drug release, ex vivo permeation, and antimicrobial activity. When applied separately, HPMC was found to lower the P407 gelation temperature (Tg), whereas SN-CX increased it. However, in the presence of HPMC, SN-CX interfered with the P407 micellar organization in a principally contrasting way while leading to an even further decrease in Tg. SN-CX-loaded nasal formulations composed of P407 16% and HPMC 0.1% demonstrated a desired gelation at 31.9 °C, good sprayability (52.95% coverage of the anterior nasal cavity), mucoadhesion for 70 min under simulated nasal clearance, expedient release and permeation, and preserved anti-infective activity against seasonal Influenza virus and beta-coronavirus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and other pathogens. Our findings suggest that the current development could be considered a potential formulation of a protective nasal spray against respiratory infections.

Tissue engineering is emerging as an effective and alternate strategy for healing the impaired bones. This study reports the development of potential and novel bone tissue regenerating matrices from the avian eggshell membrane derived collagen dispersed in poly-(vinyl alcohol) (PVA). The concentration of the aqueous collagen dispersions within the PVA solution were varied from 0.5 % to 2 % (w/V); and the sols were subjected to varying freeze-thaw cycles to achieve gelation; leading to the fabrication of hydrogel matrices. The developed hydrogels were investigated for their physico-chemical characteristics through the ATR-FTIR, XRD, FESEM and biocompatibility measurements. The ATR-FTIR results showed the presence of amide A, amide I and hydroxyl groups; which were further reinstated by the XRD studies. The morphological and topological analysis of the different hydrogel groups was made through FESEM. It comprised of the measurements of pore dimensions ranging (3.98 ± 1.84 µm to 9.24 ± 5.55 µm), percentage porosity (47 %–97 %), and average surface roughness (21–39 µm); thus, indicating them to be analogous support systems for bone tissue regeneration. Further, L929 mouse fibroblasts grown over these support systems showed excellent cell viability, thus hinting towards its competitive features and application towards remedial bone regeneration. [ABSTRACT FROM AUTHOR]

Sol-gel is a modern technological process that is widely used in the production of inorganic sorbents, catalysts and catalyst carriers, synthetic zeolites, inorganic binders, ceramics with select physical, optical, magnetic, and electrical properties, glass, glass ceramics, fibers, etc. The creation of models of this process will make it possible to fine-tune the properties of the resulting materials. The sol-gel transition is a process of sol-particle association accompanied by the formation of "an infinite aggregate". Two ways of constructing mathematical models are suggested. The first approach is based on the methods of statistical thermodynamics, and the second one is hydrodynamical. Both methods make it possible to obtain the inter-consistent equations describing the relationship between the gelation time and the macroscopic parameters. [ABSTRACT FROM AUTHOR]

There are various types of gel materials used in a wide range of fields, and their gelation mechanisms are extremely diverse. Furthermore, in the case of hydrogels, there exist some difficulties in understanding complicated molecular mechanisms especially with water molecules interacting through hydrogen bonding as solvents. In the present work, the molecular mechanism of the structural formation of fibrous super-molecular gel by the low molecular weight gelator, N-oleyl lactobionamide/water mixture was elucidated using the broadband dielectric spectroscopy (BDS) method. The dynamic behaviors observed for the solute and water molecules indicated hierarchical structure formation processes in various time scales. The relaxation curves obtained at various temperatures in the cooling and heating processes showed relaxation processes respectively reflecting the dynamic behaviors of water molecules in the 10 GHz frequency region, solute molecules interacting with water in MHz region, and ion-reflecting structures of the sample and electrode in kHz region. These relaxation processes, characterized by the relaxation parameters, showed remarkable changes around the sol–gel transition temperature, 37.8 °C, determined by the falling ball method and over the temperature range, around 53 °C. The latter change suggested a structure formation of rod micelles appearing as precursors before cross-linking into the three-dimensional network of the supramolecular gels. These results clearly demonstrate how effective relaxation parameter analysis is for understanding the gelation mechanism in detail. [ABSTRACT FROM AUTHOR]

Flexible batteries based on gel electrolytes with high safety are promising power solutions for wearable electronics but suffer from vulnerable electrode‐electrolyte interfaces especially upon complex deformations, leading to irreversible capacity loss or even battery collapse. Here, a supramolecular sol‐gel transition electrolyte (SGTE) that can dynamically accommodate deformations and repair electrode‐electrolyte interfaces through its controllable rewetting at low temperatures is designed. Mediated by the micellization of polypropylene oxide blocks in Pluronic and host‐guest interactions between α‐cyclodextrin (α‐CD) and polyethylene oxide blocks, the high ionic conductivity and compatibility with various salts of SGTE afford resettable electrode‐electrolyte interfaces and thus constructions of a series of highly durable, flexible aqueous zinc batteries. The design of this novel gel electrolyte provides new insights for the development of flexible batteries. [ABSTRACT FROM AUTHOR]

Thermally-induced gelling systems based on Poloxamer 407 (PL) and polysaccharides are known for their biomedical applications; however, phase separation frequently occurs in mixtures of poloxamer and neutral polysaccharides. In the present paper, the carboxymethyl pullulan (CMP) (here synthesized) was proposed for compatibilization with poloxamer (PL). The miscibility between PL and CMP in dilute aqueous solution was studied by capillary viscometry. CMP with substitution degrees higher than 0.5 proved to be compatible with PL. The thermogelation of concentrated PL solutions (17%) in the presence of CMP was monitored by the tube inversion method, texture analysis and rheology. The micellization and gelation of PL in the absence or in the presence of CMP were also studied by dynamic light scattering. The critical micelle temperature and sol–gel transition temperature decrease with the addition of CMP, but the concentration of CMP has a peculiar influence on the rheological parameters of the gels. In fact, low concentrations of CMP decrease the gel strength. With a further increase in polyelectrolyte concentration, the gel strength increases until 1% CMP, then the rheological parameters are lowered again. At 37 °C, the gels are able to recover the initial network structure after high deformations, showing a reversible healing process. [ABSTRACT FROM AUTHOR]

Hydrocolloids are long-chain biopolymers that can form viscous solutions or gels when dissolved in water. They are employed as rheological modifiers in various manufacturing processes or finished products. Due to its unique gelation properties, animal gelatin is one of the most widely used hydrocolloids, finding applications in several fields such as food, pharmaceutical, and photographic. Nowadays, the challenge of finding valid alternatives to animal products has become a crucial issue, for both ethical and environmental reasons. The aim of this work, is to propose a green hydrocolloidal network, able to reproduce the gelation features of animal gelatin gels. κ-carrageenan gels may be an interesting alternative to gelatin, due to their attractive gelling features. We investigate the thermorheological behavior of κ-carrageenan aqueous solutions at various concentrations, focusing on gel features such as transition temperature and gel strength. To improve the viscoelastic response of such gels, we add a viscosity-enhancing hydrocolloid, i.e., xanthan gum. The results show that the gel strength increases exponentially with xanthan concentration, thus suggesting a synergistic interaction between the two networks. We also study the effect of sucrose on the thermal and mechanical properties of modified gels, finding a marked increase in transition temperatures and gel elasticity. In recent years, three-dimensional (3D) food printing has been extensively studied in the food industry, due to its many advantages, such as customized food design, personalized nutrition, simplified supply chain, and the expansion of available food materials. In view of this growing interest for additive manufacturing, we also study the printability of the complete formulation composed of κ-carrageenan, xanthan gum and sucrose. [ABSTRACT FROM AUTHOR]

Psoriasis is a chronic inflammatory skin disease characterized by erythema, scaling, and skin thickening. Topical drug application is recommended as the first-line treatment. Many formulation strategies have been developed and explored for enhanced topical psoriasis treatment. However, these preparations usually have low viscosity and limited retention on the skin surface, resulting in low drug delivery efficiency and poor patient satisfaction. In this study, we developed the first water-responsive gel (WRG), which has a distinct water-triggered liquid-to-gel phase transition property. Specifically, WRG was kept in a solution state in the absence of water, and the addition of water induced an immediate phase transition and resulted in a high viscosity gel. Curcumin was used as a model drug to investigate the potential of WRG in topical drug delivery against psoriasis. In vitro and in vivo data showed that WRG formulation could not only extend skin retention but also facilitate the drug permeating across the skin. In a mouse model of psoriasis, curcumin loaded WRG (CUR-WRG) effectively ameliorated the symptoms of psoriasis and exerted a potent anti-psoriasis effect by extending drug retention and facilitating drug penetration. Further mechanism study demonstrated that the anti-hyperplasia, antiinflammation, anti-angiogenesis, anti-oxidation, and immunomodulation properties of curcumin were amplified by enhanced topical drug delivery efficiency. Notably, neglectable local or systemic toxicity was observed for CUR-WRG application. This study suggests that WRG is a promising formulation for topically psoriasis treatment. [ABSTRACT FROM AUTHOR]

Nanocomposite hydrogels were elaborated by the addition of citrated magnetic nanoparticles (MNPs) in sodium alginate aqueous solutions ionically crosslinked by in situ release of calcium ions from calcium carbonate (CaCO3) with gradual hydrolysis of d-glucono-δ lactone (GDL). The sol-gel transition was studied by time-resolved mechanical spectroscopy (TRMS) in the linear viscoelastic region. The power law frequency dependence of the storage and loss moduli allowed to determine the gelation time (tg), the power law relaxation exponent (Δ), and the gel stiffness (S) at the critical gel (gel at tg) for different calcium and MNP concentrations. The effect of an applied magnetic field on these parameters was also studied for the first time. The obtained results show an effect of the concentration of both calcium and MNPs on the kinetics (tg) and properties at the critical gel (S and Δ) obtaining faster kinetics and harder critical gels for higher calcium and lower MNP concentrations. Moreover, the application of the magnetic field allows to modulate the viscoelastic properties before the gel point, but no effect was observed on the structural properties of the critical gel. Finally, this work highlights how the shear viscoelastic, compressive, and swelling properties of totally gelled nanocomposite hydrogels can be successfully modulated when MNPs are introduced in the calcium alginate matrices with a good agreement between all these properties and with the properties of the critical gels. [ABSTRACT FROM AUTHOR]

A base-catalysed methyltrimethoxysilane (MTMS) colloidal gel formation was implemented as a cellular automaton (CA) system, specifically diffusion and/or reaction-limited aggregation. The initial characteristic model parameters were determined based on experimental synthesis of MTMS-based, ambient-pressure-dried aerogels. The applicability of the numerical approach to the prediction of gels' condensation kinetics and their structure was evaluated. The developed model reflects the kinetics properly within the investigated chemical composition range (in strongly reaction-limited aggregation conditions) and, to a slightly lesser extent, the structural properties of aggregates. Ultimately, a relatively simple numerical model reflecting silica-based gel formation was obtained and verified experimentally. The CA simulations have proved valid for understanding the relation between the initial chemical composition and kinetics constants of MTMS-based synthesis and their impact on secondary particle aggregation process kinetics. [ABSTRACT FROM AUTHOR]

In this study, diclofenac sodium (DS) is post-loaded directly into thermo-sensitive hydrogels fabricated from chitosan and β-glycerophosphate (GP) for temperature-controlled-release application at the inflammatory sites. Experiments analyzing the effect of GP concentration and simulated physiological temperature show that the hydrogels have a compatible heat-sensitive response through sol-gel and swelling behaviors. The hydrogels are soluble at 25 °C and rapidly gel above 37 °C with a decrease in the gelation time from 4 to 1 min when the temperature rises to 41 °C. Specific surface area, pore size, and pore volume of developed chitosan hydrogels are respectively 16.91–34.62 m2/g, 4.16–4.61 nm, and 0.08–0.28 cm3/g. Moreover, all hydrogels exhibit adaptive swelling to temperature changes as evidenced by the increase in equilibrium swelling ratio from 18.4–66.0% (25 °C) to 34.8–88.5% (37 °C) and 56.0–108.4% (39 °C). In terms of DS delivery, the highest loading capacity of the developed hydrogel is achieved at 8.81 mg/g with the GP content of 25 w/v%, the initial drug concentration of 2000 µg/ml, and the drug dissolution solvent being water, indicating the 23.8 times higher DS loading capacity compared with co-crosslinked chitosan/GP/genipin hydrogels in the previous work. About 87 and 95% of the loaded DS amount is released from the prepared chitosan hydrogels after 5 h at 37 and 39 °C correspondingly. The findings demonstrate that the ability to carry and release the anti-inflammatory DS of the thermo-sensitive chitosan hydrogels is significantly influenced by many subjective (composition) and objective (media temperature, initial drug concentration, and drug dissolution solvent) factors which can be adjusted to monitor the DS delivery at the right time and the right dose as required. Highlights: Diclofenac sodium is directly post-loaded into thermo-sensitive chitosan hydrogel. The hydrogel is soluble at 25 °C and rapidly becomes gel at 39 °C in 4 min. The highest swelling ratio of the hydrogel is 108.4% at 39 °C. The maximum drug loading of the hydrogel is 8.81 mg/g. 87% and 95% of drug-loaded is released after 5 h at 37 °C and 39 °C, respectively. [ABSTRACT FROM AUTHOR]

A simple model is introduced to describe phase behaviours of binary mixtures of a thermoreversible gel and a low-molecular-weight liquid crystal (LC). We predict novel phase diagrams on the temperature–concentration plane, including sol–gel transition, nematic–isotropic phase transition, and phase separation. At high temperatures, the phase separation between the isotropic sol and gel phases appears. As the temperature decreases, we have the phase separation between nematic sol and isotropic gel phases, in which the nematic domains are dispersed in the isotropic gel phase. We suggest that thermoreversible gelation of reactive molecules mixed with LCs will become one of the new classes of polymer-dispersed liquid crystals.

Reversible chemical covalency provides a path to materials that can degrade and recombine with appropriate stimuli and which can be used for tissue regeneration and repair. However, designing and preparing efficient and quickly self-healing materials has always been a challenge. The preparation strategies of photoresponsive gels attract a lot of attention due to their precise spatial and temporal control and their predetermined response to light stimulation. In this work, the linear copolymer PAC was synthesized via precipitation polymerization of acrylic acid and 7-(2-acrylate-ethoxylated)-4-methylcoumarin. The coumarin groups on the copolymer PAC side chains provide a reversible chemical cross-linking via photostimulation, which achieves reversible regulation of the gel network structure. The concentration of 18 wt% PAC solution produces gelation under irradiation with 365 nm. In contrast, PAC gel is restored to soluble copolymers under irradiation with 254 nm. Meanwhile, the mechanical and self-healing properties of the gel were also explored. It is demonstrated that the cracks of the gel can be repaired simply, quickly, and efficiently. Furthermore, the PAC copolymer shows an excellent adhesion property based on the reversible sol–gel transition. Thus, the PAC gel has considerable potential for applications in engineering and biomedical materials.

Coal fires, most of which are triggered by the spontaneous combustion of coal, cause a huge waste of resources and release poisonous and harmful substances into the environment, seriously threatening the safety of industrial production. Gel flame retardant plays a core role in coal fire prevention and extinguishing. Most gel flame retardants used in coal fires possess good sealing and oxygen isolation properties, but it is difficult for them to flow deep into fire areas due to their low fluidity. Some fire extinguishing agents with good fluidity lack leak-blocking performance. In order to simultaneously improve the fluidity, leakage sealing, and oxygen isolation effects of coal fire extinguishing colloids, a novel, pH-sensitive, sol-gel transition colloid was prepared using low methoxyl pectin (LMP), calcium bentonite (Ca-Bt), sodium bentonite (Na-Bt), and water as the main components. When the initial sol-state colloid absorbed acid gas products from coal combustion, the pH value decreased and a large amount of Ca2+ in Ca-Bt precipitated, thus immediately growing calcium bridges with LMP molecules that formed a three-dimensional network structure for gelation. The optimum ratio of the new colloid was determined through X-ray diffraction, tube inversion, shock shear-temperature scanning, and genetic algorithm. By testing the fire extinguishing performance of the colloid, the findings proved that the product had good oxygen isolation performance, strong adhesion ability, high thermal stability, and strong inhibition effects on coal combustion. [ABSTRACT FROM AUTHOR]

Vat‐photopolymerization‐based 3D printing enables on‐demand construction of customized objects with scalable production capacity and high precision. Herein, the sol‐gel process for aerogels with digital light processing 3D printing to produce advanced functional materials possessing hierarchical pore structures and complex shapes is combined. It has revealed the temporal evolution of the photorheological behavior of acrylate‐modified silica sols in an acid‐base catalytic procedure, and confirmed that silica aerogels can be fabricated with very low acrylate content. The resulting aerogels are thermostable with intrinsic silica contents, skeletal densities, and physical characteristics similar to those of commercial silica aerogels yet distinct mechanical behaviors. More importantly, the printed silica aerogels can be used as a versatile nanoengineering platform to produce high‐performance and multifunctional interpenetrating phase nanocomposites with complex shapes through programmable post‐printing processes. Epoxy‐based nanocomposites possessing excellent mechanical performance, ionogel‐based conductive nanocomposites with decoupled electrical and mechanical properties, and anti‐swelling hydrogel‐based nanocomposites are demonstrated. The results of this study offer new guidelines for the design and fabrication of novel materials by additive manufacturing. [ABSTRACT FROM AUTHOR]

Poloxamers are negatively temperature-sensitive hydrogels and their hydrophilic groups interact with water molecules at lower temperatures (liquid phase) while their hydrophobic groups interact more strongly with increases in temperature causing gelation. To investigate the factors affecting the rheological properties of poloxamers, various parameters including different poloxamer P407 concentrations, poloxamers P407/P188 blending ratios and additives were examined. The results presented a clear trend of decreasing gelling temperature/time when P407 was at higher concentrations. Moreover, the addition of P188 enhanced the gelling temperature regardless of poloxamer concentration. Polysaccharides and their derivatives have been widely used as components of hydrogel and we found that alginic acid (AA) or carboxymethyl cellulose (CMC) reduced the gelling temperature of poloxamers. In addition, AA-containing poloxamer promoted cell proliferation and both AA -and CMC-containing poloxamer hydrogels reduced cell migration. This study investigated the intriguing characteristics of poloxamer-based hydrogel, providing useful information to compounding an ideal and desired thermo-sensitive hydrogel for further potential clinical applications such as development of sprayable anti-adhesive barrier, wound-healing dressings or injectable drug-delivery system for cartilage repair. [ABSTRACT FROM AUTHOR]

Abstract Vat‐photopolymerization‐based 3D printing enables on‐demand construction of customized objects with scalable production capacity and high precision. Herein, the sol‐gel process for aerogels with digital light processing 3D printing to produce advanced functional materials possessing hierarchical pore structures and complex shapes is combined. It has revealed the temporal evolution of the photorheological behavior of acrylate‐modified silica sols in an acid‐base catalytic procedure, and confirmed that silica aerogels can be fabricated with very low acrylate content. The resulting aerogels are thermostable with intrinsic silica contents, skeletal densities, and physical characteristics similar to those of commercial silica aerogels yet distinct mechanical behaviors. More importantly, the printed silica aerogels can be used as a versatile nanoengineering platform to produce high‐performance and multifunctional interpenetrating phase nanocomposites with complex shapes through programmable post‐printing processes. Epoxy‐based nanocomposites possessing excellent mechanical performance, ionogel‐based conductive nanocomposites with decoupled electrical and mechanical properties, and anti‐swelling hydrogel‐based nanocomposites are demonstrated. The results of this study offer new guidelines for the design and fabrication of novel materials by additive manufacturing.

The effects of non-solvent on the sol-gel transition of polyacrylonitrile (PAN) solution were investigated in thermodynamics and kinetics by the means of rheology method. The facilitating effects of non-solvent in thermodynamics was illustrated by the variety of viscoelasticity and gel transition temperature (Tgel). With the addition of non-solvent, the mobility of PAN molecular chains are limited due to its increased entanglement. As a result, the PAN solution with higher non-solvent content has lower conformation entropy to satisfy the occurrence of sol-gel transition at higher temperature. It means that less thermodynamic driving is demanded. The kinetical characteristics of PAN solution with different non-solvent content in sol-gel transition process were also discussed. The kinetic hindrance of non-solvent was proved by the gradually stronger time-dependence of loss tangent with the addition of non-solvent during sol-gel transition. This apparent extending of relaxation time is resulted from the more restriction of the mobility of PAN molecules. The gelation activation energy (Egel) was calculated according to Ozawa method. The results also indicated that the activity of PAN molecules in this transition became weaken with the addition of non-solvent since a relative tight connection between PAN molecules was there. Therefore, the formation of physical junction points for sol-gel transition was hindered due to the decreasing of the mobility of self-adjustment for PAN molecules. This is the fundamental reason for the kinetic hindrance role of non-solvent.

In recent years, intensive research has been carried out on the use of hydrogels obtained from natural polymers, mainly chitosan. These products are increasingly replacing solutions based on synthetic materials in medicine. This publication presents the results of studies on the sol-gel transition of chitosan solutions as the base material for the preparation of thermosensitive hydrogels for potential applications in tissue engineering. The measurements were carried out for systems consisting of chitosan lactate and chitosan chloride solutions using β-glycerol phosphate disodium salt pentahydrate and uridine 5′-monophosphate disodium salt as the cross-linking agents. The sol-gel transition point of the solutions was determined based on the rheological measurements in the cone-plate configuration of the rotational rheometer and experiments performed using the method of nuclear magnetic resonance. The obtained results showed a significant influence of the cross-linking agent on the course of the sol-gel transition of chitosan salt solutions, and the systems that consisted of chitosan lactate seemed to be especially interesting for biomedical applications. [ABSTRACT FROM AUTHOR]

Fricke-XO-Pluronic F-127 has recently been proposed as a 3D dosimeter for radiotherapy. It contains the typical ingredients of the Fricke ionizing radiation dosimeter, which are embedded in a physical gel of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127). The main reactions upon irradiation are the conversion of Fe+2 to Fe+3 and the formation of a colored complex with XO ([XO-Fe]+3). The study attempts to optimize the dosimeter in terms of its solution-to-gel transition temperature. In order to lower this temperature, the use of NaCl salt has been proposed. The new composition was characterized in order to obtain information on its thermal performance, storage stability, dose response to irradiation with a medical accelerator emitting different types of radiation, and tissue equivalence. The results obtained show an improvement in the sol-gel transition temperature and dose sensitivity compared to the composition without NaCl and broaden the knowledge of the Fricke-XO-Pluronic F-127. [ABSTRACT FROM AUTHOR]

Associating polymers developed by grafting a block copolymer of monomethoxy poly(ethylene glycol)‐b‐poly(caprolactone) (MPEG‐b‐PCL) onto poly(acrylic acid) undergo an irreversible sol–gel transition on heating. The influence of various physicochemical parameters on the thermoresponsive behaviour was examined by rheology and NMR studies. Pulsed field gradient NMR diffusion studies were performed to probe the mechanism of thermally induced gelation. Analysis of the diffusion data reveals the presence of loosely and strongly associated structures which respond differently to variation in temperature. It is observed that the polymer solution, which is visibly homogeneous, is heterogeneous on a mesoscopic scale with a distribution of domains. Detailed investigation of the thermally induced sol–gel transition shows that the mechanism of gelation involves irreversible alterations in the domain structure and size. © 2022 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Thermal-responsive hydrogels are developed as ion-conductive switchs for energy storage devices, however, the molecule mechanism of switch on/off remains unclear. Here, poly(N-isopropylacrylamide-co-acrylamide) hydrogel is synthesized as a model material and nanodiamond (ND) based quantum sensing for phase change study is developed. First, micro-scale phase separation with cross-linked mesh structure after sol-gel transition is visualized in situ and water molecules are trapped by polymer chains and on a chemically "frozen" state. Then, the nano-scale inhomogeneous distributions of viscosity, thermal conductivity and ionic mobility in hydrogel at high temperature are observed by measuring the rotation, translation and zero-field splitting of NDs. Besides, the ionic mobility of hydrogel is found to be dependent not only on temperature but also on polymer concentration. These observations suggested that the physical "wall" induced by inhomogeneous phase separation at microscopic scale blocked the ion conduction pathways, providing a potential intrinsic explanation for ion migration shut-down of ionic hydrogels at high temperature., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The progress of nanotechnology enables us to make use of the special properties of materials on the nanoscale and open up many new fields of biomedical research. Among them, thermosensitive nanomaterials stand out in many biomedical fields because of their “intelligent” behavior in response to temperature changes. However, this article mainly reviews the research progress of thermosensitive nanomaterials, which are popular in biomedical applications in recent years. Here, we simply classify the thermally responsive nanomaterials according to the types of polymers, focusing on the mechanisms of action and their advantages and potential. Finally, we deeply investigate the applications of thermosensitive nanomaterials in drug delivery, tissue engineering, sensing analysis, cell culture, 3D printing, and other fields and probe the current challenges and future development prospects of thermosensitive nanomaterials.

There are various types of gel materials used in a wide range of fields, and their gelation mechanisms are extremely diverse. Furthermore, in the case of hydrogels, there exist some difficulties in understanding complicated molecular mechanisms especially with water molecules interacting through hydrogen bonding as solvents. In the present work, the molecular mechanism of the structural formation of fibrous super-molecular gel by the low molecular weight gelator, N-oleyl lactobionamide/water mixture was elucidated using the broadband dielectric spectroscopy (BDS) method. The dynamic behaviors observed for the solute and water molecules indicated hierarchical structure formation processes in various time scales. The relaxation curves obtained at various temperatures in the cooling and heating processes showed relaxation processes respectively reflecting the dynamic behaviors of water molecules in the 10 GHz frequency region, solute molecules interacting with water in MHz region, and ion-reflecting structures of the sample and electrode in kHz region. These relaxation processes, characterized by the relaxation parameters, showed remarkable changes around the sol–gel transition temperature, 37.8 °C, determined by the falling ball method and over the temperature range, around 53 °C. The latter change suggested a structure formation of rod micelles appearing as precursors before cross-linking into the three-dimensional network of the supramolecular gels. These results clearly demonstrate how effective relaxation parameter analysis is for understanding the gelation mechanism in detail.

Postoperative adhesion is a serious and frequent complication, but there is currently no reliable anti-adhesive barrier available due to low tissue adhesiveness, undesirable chemical reactions, and poor operability. To overcome these problems, we report a single-syringe hotmelt tissue adhesive that dissolves upon warming over 40 °C and coheres at 37 °C as a postoperative barrier. Tendon-derived gelatin was conjugated with the ureidopyrimidinone unit to supramolecularly control the sol-gel transition behavior. This functionalization improved bulk mechanical strength, tissue-adhesive properties, and stability under physiological conditions through the augmentation of intermolecular hydrogen bonding by ureidopyrimidinone unit. This biocompatible adhesive prevented postoperative adhesion between cecum and abdominal wall in adhesion models of rats. This hotmelt tissue adhesive has enormous potential to prevent postoperative complications and may contribute to minimally invasive surgery. There is a strong need to develop medical tissue adhesives with high biocompatibility, tissue adhesiveness, and operatability to prevent postoperative complications. In this report, single syringe, hotmelt-type tissue adhesive was developed by controlling sol-gel transition behavior of gelatin through supramolecular approach. The functionalization of gelatin with quadruple hydrogen bonding improved key features necessary for anti-adhesive barrier including bulk mechanical strength, tissue adhesive property, stability under physiological conditions, and anti-adhesive property. The hotmelt tissue adhesive can be used for a sealant, hemostatic reagent, and wound dressing to prevent postoperative complications including delayed bleeding, perforation, and inflammation and contribute to minimally invasive surgery. [Display omitted] [ABSTRACT FROM AUTHOR]

In the recent years a considerable effort has been devoted to foster the understanding of the basic mechanisms underlying the dynamical arrest that is involved in glass forming in supercooled liquids and in the sol-gel transition. The elucidation of the nature of such processes represents one of the most challenging unsolved problems in the field of material science. In this context, two important theories have contributed significantly to the interpretation of these phenomena: the Mode-Coupling theory (MCT) and the Percolation theory (PT). These theories are rooted on the two pillars of statistical physics, universality and scale laws, and their original formulations have been subsequently modified to account for the fundamental concepts of Energy Landscape (EL) and of the universality of the fragile to strong dynamical crossover (FSC). In this review, we discuss experimental and theoretical results, including Molecular Dynamics (MD) simulations, reported in the literature for colloidal and polymer systems displaying both glass and sol-gel transitions. Special focus is dedicated to the analysis of the interferences between these transitions and on the possible interplay between MCT and PT. By reviewing recent theoretical developments, we show that such interplay between sol-gel and glass transitions may be interpreted in terms of the extended F13 MCT model that describes these processes based on the presence of a glass-glass transition line terminating in an A3 cusp-like singularity (near which the logarithmic decay of the density correlator is observed). This transition line originates from the presence of two different amorphous structures, one generated by the inter-particle attraction and the other by the pure repulsion characteristic of hard spheres. We show here, combining literature results with some new results, that such a situation can be generated, and therefore experimentally studied, by considering colloidal-like particles interacting via a hard core plus an attractive square well potential. In the final part of this review, scaling laws associated both to MCT and PT are applied to describe, by means of these two theories, the specific viscoelastic properties of some systems. [ABSTRACT FROM AUTHOR]

We investigate the rheological behavior of aqueous solutions containing animal gelatin, sugars and polyols. The aim is to study how the gelation kinetics, transition temperatures and gel strengths of an aqueous gelatin solution can be affected by the progressive addition of co-solutes. Aqueous solutions with a fixed mass percentage of gelatin of 6.8 wt% were prepared at various concentrations of sugars and polyols. Through Dynamic Temperature Ramp tests, performed at various ramp rates, and Dynamic Time Sweep and Dynamic Frequency Sweep tests, carried out at different temperatures, it was possible both to evaluate the transition temperatures and to monitor the gelation kinetics of the samples. It was found that the contribution of co-solutes positively affects both the gelation process and the thermal stability of the aqueous gelatin solution by reducing the gelation time and improving the mechanical properties of the gel in terms of network elasticity. [ABSTRACT FROM AUTHOR]

Developing fully rigid-chain polyimides with reversible sol-gel/gel-sol transitions is of great interest for designing high-performance materials. To date, few approaches have been employed to construct polyimide gels other than hydrogen bonding. Here, we report a polyimide-Zn(II) complex with thermo-responsive sol-gel/gel-sol transition behavior by introducing supramolecular coordination interactions. The tunable dynamic sol-gel behaviors of polyimide-Zn(II) complexes were confirmed using rheological methods. Microstructure analysis shows that coordination interactions occur between the benzimidazole molecules and Zn(II) ions. As a result, the apparent viscosity of the polyimide-Zn(II) complex even rises approximately four orders of magnitude higher than that of the PI-neat oligomer solution. Based on the 2D-correlation spectra and X-ray diffraction results, we deduced that the formation of dense chain stacking caused by coordination effects plays an essential part in the reversible sol-gel transition. As a preliminary experiment, this work gives a novel strategy to construct polyimide gels, showing application prospects in the fabrication of porous polyimide membranes, high-performance polyimide fibers, and aerogels, etc.

[Display omitted] • Smart hydrogels prepared using anionic surfactant and anionic photoresponsive additive. • Hydrogels prepared based on hydrogen bonding and steric hindrance regulation strategy. • Hydrogels exhibit the stimulus-responsiveness of both NaDC and trans -NaOMCA. • Bridging hydrogen bonds between DC− and trans -OMCA− lead to their synergistic effect. • Release of model drug from the prepared hydrogels was triggered by external stimuli. Developing natural biosurfactant-based smart hydrogels with low-toxicity, biocompatibility and multi-stimulus-responsiveness is of great importance in fundamental and applied science. Based on the strategy of hydrogen bonding and steric hindrance regulation, multi-stimulus-responsive hydrogels were constructed using electrostatically repulsive sodium deoxycholate (NaDC) and sodium salt of trans -ortho-methoxycinnamic acid (trans -NaOMCA). The rheological and DLS techniques, TEM, optical microscopy, 1H NMR, FT-IR and UV–vis spectrometers were used to investigate the stimulus-responsiveness and the controlled release of model drug. Molecular dynamics (MD) simulations were performed to provide molecular insights into the effect of stimuli on self-assembly, type and number of hydrogen bonds, etc. This study provides a new method to construct multi-stimulus-responsive hydrogels using anionic surfactant and anionic photoresponsive additive. The NaDC/ trans -NaOMCA/H 2 O mixed system exhibits reversible pH- and CO 2 -responses. FT-IR and 1H NMR spectra results and MD simulations reveal that, the formation and breaking of bridging hydrogen bonds involving H 3 O+ (including the acid salt structures) play key roles in reversible sol ⇌ gel transition, and the bridging hydrogen bonds between DC− and trans -OMCA− lead to a synergistic effect during the formation of HAc- and CO 2 -induced hydrogels. In addition, the HAc-induced hydrogels are thermosensitive and photoresponsive, exhibiting the stimulus-responsiveness of both NaDC and trans -NaOMCA. The stimulus-responsive mechanism has been proposed. The investigation of the release of methylene blue from the prepared hydrogels will provide guidance for practical applications. [ABSTRACT FROM AUTHOR]

The rheological and morphological characteristics of Ca-crosslinked alginate hydrogels with two different M/G ratios, α-L-guluronate (G)-rich and β-D-mannuronate (M)-rich, each with one alginic acid concentration, were investigated. It was found that the stiffness and elasticity of alginate hydrogels are derived from the thickness and density of the fibril network structures. In aqueous alginate solution, ball-like aggregates of alginates are present. Time-resolved small-angle X-ray scattering and time-domain nuclear magnetic resonance measurements suggest that the disaggregation of alginate aggregates and loose fibrillation occur in the early stage of the sol-gel transition. After these induction stage, direct gelation is finally caused by the formation of the egg-box junction. G-rich alginate hydrogel has a higher stiffness and a thicker and denser fibril network structure than M-rich alginate hydrogel. The former also exhibits faster and more significant changes in physical properties during the sol-gel transition. [ABSTRACT FROM AUTHOR]

Hydrocolloids are long-chain biopolymers that can form viscous solutions or gels when dissolved in water. They are employed as rheological modifiers in various manufacturing processes or finished products. Due to its unique gelation properties, animal gelatin is one of the most widely used hydrocolloids, finding applications in several fields such as food, pharmaceutical, and photographic. Nowadays, the challenge of finding valid alternatives to animal products has become a crucial issue, for both ethical and environmental reasons. The aim of this work, is to propose a green hydrocolloidal network, able to reproduce the gelation features of animal gelatin gels. κ-carrageenan gels may be an interesting alternative to gelatin, due to their attractive gelling features. We investigate the thermorheological behavior of κ-carrageenan aqueous solutions at various concentrations, focusing on gel features such as transition temperature and gel strength. To improve the viscoelastic response of such gels, we add a viscosity-enhancing hydrocolloid, i.e., xanthan gum. The results show that the gel strength increases exponentially with xanthan concentration, thus suggesting a synergistic interaction between the two networks. We also study the effect of sucrose on the thermal and mechanical properties of modified gels, finding a marked increase in transition temperatures and gel elasticity. In recent years, three-dimensional (3D) food printing has been extensively studied in the food industry, due to its many advantages, such as customized food design, personalized nutrition, simplified supply chain, and the expansion of available food materials. In view of this growing interest for additive manufacturing, we also study the printability of the complete formulation composed of κ-carrageenan, xanthan gum and sucrose.

Thermally-induced gelling systems based on Poloxamer 407 (PL) and polysaccharides are known for their biomedical applications; however, phase separation frequently occurs in mixtures of poloxamer and neutral polysaccharides. In the present paper, the carboxymethyl pullulan (CMP) (here synthesized) was proposed for compatibilization with poloxamer (PL). The miscibility between PL and CMP in dilute aqueous solution was studied by capillary viscometry. CMP with substitution degrees higher than 0.5 proved to be compatible with PL. The thermogelation of concentrated PL solutions (17%) in the presence of CMP was monitored by the tube inversion method, texture analysis and rheology. The micellization and gelation of PL in the absence or in the presence of CMP were also studied by dynamic light scattering. The critical micelle temperature and sol–gel transition temperature decrease with the addition of CMP, but the concentration of CMP has a peculiar influence on the rheological parameters of the gels. In fact, low concentrations of CMP decrease the gel strength. With a further increase in polyelectrolyte concentration, the gel strength increases until 1% CMP, then the rheological parameters are lowered again. At 37 °C, the gels are able to recover the initial network structure after high deformations, showing a reversible healing process.

The influence of chitosan on orientation–micellar association of Pluronic F-127 in an aqueous medium in the temperature range of 4–37°C has been studied by polarization microscopy and rotational viscometry. It is established that, with an increase in temperature, this amphiphilic copolymer undergoes a phase transition to a shape-stable hydrogel, characterized by optical dichroism and rheograms of viscosity with the yield stress. Chitosan additive suppresses the effect of optical anisotropy and influences the gel-formation time and viscoelastic characteristics of the binary mixture with implementation of flow curves of dilatant fluids or structured compositions with different degrees of micellar ordering. The optical texture of the macroscopic gel phase of Pluronic F-127 and its mixtures with chitosan is found to correlate with the viscoelastic properties of the polymer system. [ABSTRACT FROM AUTHOR]