Gelation Mechanism Research Articles

Research and functionalization of konjac glucomannan and its hydrogel in wound dressing

Abstract In the last decade, polysaccharide dressings have become a popular research area owing to their low toxicities, good biocompatibilities, and their abilities to modulate and accelerate wound healing. Konjac glucomannan (KGM) is a naturally occurring, neutral polysaccharide that is biocompatible and highly modifiable. In addition, KGM-based hydrogels are innovative wound dressings that effectively promote the healing of injured blood vessels and wound fibres. In this review, we summarise how KGM has been modified and used in hydrogel wound-dressing applications, starting with its material properties and gelation mechanism. We then discuss recent advances in the study of systems for enhancing KGM hydrogels and KGM hydrogel wound dressings, emphasising the special benefits of such hydrogels in terms of antimicrobial and anti-inflammatory properties, their wound-healing capabilities, as drug carriers and growth promoters, as well as their functionalisation. Finally, this paper discusses the primary obstacles and potential avenues for the advancement of wound dressings with the aim of establishing a theoretical foundation and point of reference for future research into KGM functional materials.

Lignin nanoparticle/MXene-based conductive hydrogel with mechanical robustness and strain-sensitivity property via rapid self-gelation process towards flexible sensor.

Conductive hydrogels have been showcased with substantial potential for soft wearable devices. However, the tedious preparation process and poor trade-off among overall properties, i.e., mechanical and sensing performance, severely limits flexibility of electronics' applications. Herein, we have developed a rapid self-gelation system for achieving high-performance conductive hydrogel within several minutes at ambient condition. The rapid gelation mechanism is attributed to the hydroxyl radical species generated with the help of lignin nanoparticle-Mn+1 (Ag+, Ca2+, Mg2+, Al3+ and Fe3+) based on reversible redox reaction and MXene activization effect. By adjusting the material components, the cross-linked polymer network can be highly strengthened by multiple physical interactions and nano-reinforcement, strongly supporting the mechanical performance. Comparatively, Fe3+-based conductive hydrogel displays integrated merits of mechanical robustness, high stretchability and good electrical conductivity. Meanwhile, due to excellent mechanical and electrical performance, such hydrogel-based sensor possesses good sensing performance, i.e., high sensitivity (maximum GF: 1.08), cyclic reliability and wide work window (0-860%), displaying promising application in strain-induced detection. Our sensors also produce stable and reliable signal output for signature/vocal recognition. Apparently, the strategy developed herein sets up an innovative concept for highly-efficient green fabricating advanced hydrogel materials for emerging wearable electronics.

Xanthan‐Induced Gelation in Cellulose Nanocrystal Suspensions: Altering Self‐Assembly and Optical Purity

AbstractCellulose nanocrystals are charged rod‐like nanoparticles that can spontaneously organize into cholesteric mesophases upon evaporation to produce photonic films with circular polarization. In this study, it is demonstrated that through the modulation of gelation and kinetics of phase separation via the addition of a strong gelating agent, xanthan gum, the cellulose nanocrystals produce flexible photonic films with improved optical purity in terms of circular reflection. The work reveals the self‐assembly behavior as a function of xanthan gum through the volume depletion mechanism, quenching of the tactoids at the early stages of the self‐assembly, and evaporation into cholesteric films. In dried films, this leads to significant reduction in the domain size and the absence of domain folding which is usually caused by the merger of large tactoids. Despite the reduction in metallic iridescence caused by the entrapment of cellulose nanocrystal tactoids, the films exhibit improved macroscopic color uniformity across 30–60° observation angles, which implies a combined effect of surface texturing and scattering of visible light induced by incorporating xanthan gum within the co‐assembled structure. Overall the work provides new insights into the gelation mechanism in hybrid cellulose nanocrystal systems and presents an efficient approach to control the self‐assembly and macroscopic color appearance.

Spectroscopic Investigation of Hydrogels Formed from Phenylalanine.

Supramolecular hydrogels assembled from amino acids, particularly offer promising prospects as biomimetic three-dimensional extracellular matrices. Phenylalanine, an aromatic amino acid, can self-assemble via hydrophobic interactions, notably through 𝜋 - 𝜋 stacking between phenyl rings. Although the self-assembly processes have been studied, the gelation mechanism of phenylalanine as an individual amino acid has received limited attention in the literature. This study focuses on investigating the gelation behavior of phenylalanine. Fluorescence spectroscopy, along with UV- Visible spectroscopy, and Fourier-transform infrared spectroscopy, were employed to elucidate the molecular interactions and the self-assembly process responsible for hydrogel formation. By leveraging fluorescence spectroscopy, this study aims to elucidate the mechanisms underlying the hydrogelation process. The fluorescence properties of the synthesized hydrogels are extensively examined, providing insights into their structural organization and stability, In this study, we employed a simple heating-cooling method for preparing phenylalanine hydrogel resulting in the formation of opaque hydrogels. Spectral analyses revealed the molecular interactions and structural organization, highlighting the relationship between concentration, opacity, and gel properties. Through this study, we investigated the gelation mechanism of a simple molecule using fluorescence spectroscopy, which provides a foundation for exploring the use of the same in other hydrogel-forming systems.

Mechanisms of Low Temperature Thickening of Different Materials for Deepwater Water-Based Drilling Fluids.

During deepwater drilling, the low mudline temperatures and narrow safe density window pose serious challenges to the safe and efficient performance of deepwater water-based drilling fluids. Low temperatures can lead to physical and chemical changes in the components of water-based drilling fluids and the behavior of low temperature gelation. As a coarse dispersion system, water-based drilling fluid has a complex composition of dispersed phase and dispersing medium. Further clarification of low temperature gelation would be helpful in developing technical approaches to enhance the flat rheology performance of deepwater water-based drilling fluids. In this paper, different components are separated in order to comprehensively analyze the gelation behavior of different materials in water-based drilling fluids at low temperatures. In the first place, the rheological and hydrodynamic radius alterations of inorganic salts, bentonite, and additives in aqueous solutions were examined at low temperatures. The effects of inorganic salts, bentonite, and additives on the purified water system were investigated at low (4 °C)-normal (25 °C)-high (75 °C) temperatures. The low temperature gelation of different materials in pure water systems are fully clarified. The mud containing 4% bentonite with weak low temperature gelation commonly used in deepwater water-based drilling fluids was selected as the basic test system. Inorganic salts, additives, and solid-phase materials were added to the mud containing 4% bentonite. The effects of the interactions between different materials and bentonite particles on the low temperature gelation behavior of mud were analyzed. The higher the bentonite dosage, the stronger the low temperature gelation behavior of mud. The higher the addition of inorganic salts, the more serious the low temperature gelation behavior of mud. Inorganic salts should be avoided as much as possible to add too much. The low temperature gelation behavior of mud with low-viscosity additives is weak. However, the viscosity of mud with high-viscosity additives has a small change in viscosity with increasing temperature. The low temperature gelation of mud with the addition of solid-phase particulate materials with reactive groups on the surface is strong, and the low temperature gelation with the addition of inert particles is weak. This paper elucidates the low temperature gelation mechanism of bentonite, inorganic salts, additives, and solid-phase materials in deepwater water-based drilling fluids. The conclusion can also be used to guide the construction of a drilling fluid system, which is of great significance for the research and development of deepwater water-based drilling fluid additives and the safe and efficient performance of deepwater drilling fluids.

Gelation and post-gelation mechanism of methylcellulose in an aqueous medium: 1H NMR and dynamic compressive rheological studies.

Methylcellulose (MC) has become crucial in 3D bioprinting in the last decade. Researchers investigated MC aqueous solutions blended with biopolymers at room temperature, focusing on rheological studies. Even at low concentrations, the gel state of MC, which provides structural strength through hydrophilic and hydrophobic associations, was explored for injection-based 3D printability. Post-gelation phenomena were examined at 80°C using a dynamic mechanical analyzer (DMA), revealing increased storage and loss moduli with frequency, indicating a robust gel network structure. Optical microscopy reveals that upon heating from 40 to 80°C, the structural strength is enhanced via the formation of hydrophobic confirmations, starting from the micro-helical structure to the associated microarray. These microarrays are further synchronized to withstand the high frequency of the DMA probe. Compressive rheology outcomes allow us to elaborate on the possibility of injection-based 3D printability of aqueous MC gel at 80°C. 1H and 13C NMR studies probed hydrophobic interactions among MC chains, showing evidence of H-bonding through temperature-dependent shifts. UV/Vis experiments traced gel formation, depicting a time-dependent network formation process. Overall experiments indicated that adjusting temperature could control gelation time, allowing precise tuning of the printing process and achieving fine layers (10μm) in the printed membrane with maximum hydrophobic clusters.

Effects of TGase on the rheological behaviors, structural properties and molecular forces of cowpea protein isolate and cowpea albumin gels.

The effects of TGase on hardness, water holding capacity (WHC), molecular forces, structural properties, microstructure and rheological behaviors of TGase-induced cowpea protein isolate gel (T-CPIG) and cowpea albumin gel (T-CPAG) were investigated. TGase significantly increased the hardness of gels and the most stable three-dimensional network structures were formed by adding 20 U/g and 28 U/g. Not only the non-network structure proteins of gels and free sulfhydryl groups were fewer but also the β-fold and β-angle relative contents were higher than cowpea protein isolate (CPI) and cowpea albumin (CPA). Hydrophobic interaction and the disulfide bond played main roles in the formation of T-CPIG and T-CPAG. Scanning electron microscopy and rheological properties of the gel suggested that the TGase addition significantly influenced the fundamental structure and mechanical properties of the T-CPIG and T-CPAG. Taken together, the findings shed light on the gelation mechanisms of TGase cowpea proteins.

Stimuli-responsive hydrogels for skin wound healing and regeneration

AbstractSkin wounds are not only an aesthetic concern but also pose great risks to quality of life and general health. As the most promising biomaterial, hydrogels are three-dimensional polymeric networks and have attracted intense research attention. Hydrogels have developed a diverse range of biomedical and biopharmaceutical applications, owing to their large water content, biocompatibility, tunable mechanical properties, and stimuli-responsiveness. Stimuli-responsive hydrogels are smart materials which exhibit gelation, structural, degradation, performance and function changes when treated with external stimulations. Using these hydrogels to prepare wound dressing is a rapidly growing research area and has exhibited encouraging healing outcomes in small animal models, especially for the treatment of chronic wounds, diabetic wounds, and persistent skin inflammations. The present work gives a detailed and critical analysis on the design strategies, gelation mechanisms, materials selection, stimuli-responsiveness, hydrogel degradation, drug release profiles, and treatment outcomes of wound dressings prepared by the hydrogels with sensitivity to temperature, pH, reactive oxygen species (ROS), glucose, enzymes, and lights. We summarize, analyze, and critically evaluate the most recent publications in this area to explain, compare, and assess why and how various synthetic and bio-polymers are utilized by materials scientists to develop the next generation of skin wound dressing and regeneration. Graphical abstract

Chemical composition, rheological properties and calcium-induced gelation mechanism of Premna microphylla Turcz polysaccharide

The aim of this study was to investigate the chemical composition, molecular weight (Mw), and monosaccharide composition of Premna microphylla Turcz polysaccharide (PMP) and revealed the effects of calcium ions (Ca2+) on the rheological properties, thermal stability, texture properties, and structural properties of PMP gels. Additionally, the gelation mechanism of PMP was proposed. The results revealed that PMP was a negative charge acidic polysaccharide primarily composed of glucose, galactose and rhamnose. The results of small and large amplitude oscillatory shear experiments illustrated that the storage modulus (G′), loss modulus (G″), relaxation modulus (G(t)) of PMP gels showed a positive correlation with Ca2+ concentration, indicating the addition of Ca2+ improved the viscoelasticity and shear thinning capacity of PMP gels. Furthermore, the gel strength, hardness, and thermal stability of PMP gels were enhanced with increase of Ca2+ concentration. The microstructure of PMP gel was changed obviously after adding Ca2+, generating the lamellar and lump-like structure due to the PMP aggregation. The results of Zeta potential, X-ray diffraction, and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that electrostatic interactions played a crucial role in the formation of PMP gel and three-dimensional structure. These results suggested that PMP had great potential for application in the food industry due to their excellent gelation properties.

Synthesis and Electrochemical Properties of Fluorine-Containing Hydrophobic Ionic Liquid Gels with Low-Molecular Gelators

INTRODUCTION Ionic liquid is a general term for salts with melting points below 100 °C. In particular, the substances that become liquid at room temperature and pressure are being considered for applications in electrochemical devices and CO2 sorption materials. [1] In previous studies, protic ionic liquids (PILs), which obtained by neutralization of Brønsted acid and Brønsted base, are expected to be used application for next-generated electrolytes for fuel cells, [2] however, they can dissolve in water (i.e., they have hydrophilicity). In contrast, we have reported that PILs for CO2 sorption materials were synthesized by neutralization of aromatic amine (e.g., dialkylpyridines and N,N-dimethylaniline) and Tf2NH. [3] Furthermore, we have reported that some rod-shaped low-molecular compounds containing fluoroalkyl chains can gelatinize some organic solvents and/or ionic liquids. [3,4] The formed gels are physical gels that undergo sol–gel transition by heating and cooling. Interestingly, their compounds are self-assembled by intermolecular interaction without hydrogen bonds since hydrogen-bonding groups (H-groups) such as hydroxy (–OH) and amide (–CONH–) groups are not contained. Generally, low-molecular gelators contain H-groups, which cause a strong intermolecular interaction then easily cause self-assembly to form fibrous aggregates then trapped solvents, resulting in gelation. [5] H-groups have been considered difficult to apply to electrolytes of Li-ion battery and fuel cells because of theirs effect on electrochemical properties. Therefore, low-molecular gelators without H-groups are very interested studies.In this study, hydrophobic PILs based on diethylanilines, and rod-shaped phenyl benzoates containing fluoroalkyl chains as gelators (Figure 1) were synthesized and evaluated physicochemical properties of PILs and their gels such as thermal and rheological properties, and ionic conductivity. EXPERIMENTAL Hydrophobic PILs were synthesized by neutralization of anilines and Tf2NH without solvents. Compounds 1 and 2 were synthesized by esterification of 1H,1H,2H,2H-tridecafluorooctyl 4-hydroxybenzoate and corresponding to 4-substitutedbenzoic acids. Thermal properties of PILs were analyzed with DSC and these of gels were evaluated visually as described in [4]. Rheological properties of gels were evaluated by a steady flow viscosity. Ionic conductivity was calculated from inverse of solution resistance, which was recorded on an AC impedance spectroscopy with a Solartron 1280C. RESULTS AND DISCUSSION Synthesized PILs exhibited hydrophobicity since these were phase-separated with water and 1-octanol–water partition coefficients, which was determined by a HPLC system, were more than 0. In addition, ionic conductivities at 120 ºC were ca. 20 mS cm–1, so ionic conduction may not be related to humidity. Figure 2 shows gel–sol transition temperatures (T gel-sol) of [N,N-Et2AN][TFSA] and [N,N,2,6-Et4AN][TFSA] gels. T gel-sol of 5wt% [N,N-Et2AN][TFSA] gels formed by compounds 1 and 2 were 63 ºC and 102 ºC, respectively. It is suggested that this is due to the fact that the electrostatic repulsion of fluorine atoms reduces solubility, making it easier for the self-assembly to exist as a metastable state rather than a stable state, which predominantly facilitates the construction of fibrous aggregates compared to crystallization. Meanwhile, compound 1 was not able to gelatinize [N,N,2,6-Et4AN][TFSA] rather than compound 2 was able to gelatinize.Figure 3 shows steady flow viscosity of 5wt% [N,N-Et2AN][TFSA] gel formed by compound 2. The gel exhibited thixotropy because of same viscosities before and after shear. Generally, self-assembly phenomena of gelation are the interaction between compounds (i.e., the solvent does not relate to gelatinize) then the gels are pseudoplastic fluids (i.e., viscosity of gel is decreased after shere) [6]. The gelation mechanism of 5wt% [N,N-Et2AN][TFSA] gels formed by compounds 2 is specific one since exhibiting thixotropy may be caused by intermolecular interaction between gelators and solvents.Figure 4 shows Arrhenius plots of ionic conduction for [N,N-Et2AN][TFSA] and its 5wt% gel formed by compounds 2. The activation energy of ionic conduction, obtained by the least-squares method using the Vogel-Fulcher-Tammann equation (σ(T) = AT –1/2 exp [–B/R(T – T 0)], where σ(T), A, B, T 0, and R indicate ionic conducticvity at T, pre-exponential factor, activation energy, ideal glass transition temperature, and gas constant, respectively), showed a slight increase after gelation compared to before gelation, suggesting that cation or anion may be trapped in the gelator molecules. Acknowledgement This work is financially supported by JST SPRING [JPMJSP2111], JSPS KAKENHI [22H03781, 23K25035], Paloma environmental technology development foundation, and Iketani Science and Technology Foundation.

Investigating the role of lemon peel fiber in the casein gelation mechanism of low-fat yogurt

Incorporation of insoluble dietary fibers (IDFs) into yogurt can serve as both a nutritional supplement and texture modifier. However, the understanding of the interaction between IDFs and casein particles in yogurt, as well as their effect on the gelation mechanism of casein particles, remains limited. This study investigated the impact of varying contents of insoluble lemon peel fiber (LPF) on the casein gelation in low-fat yogurt. The gelation process of casein was monitored via oscillatory rheology, and the critical gel point was determined from time sweep curves. The post-gelation process was analyzed through the percolation model, and the topological structure after gelation was quantified using skeleton analysis. The incorporation of moderate content of LPF was found to reduce fermentation time (with the highest decrease being up to 1.2 h). This effect could be attributed to the enhanced main intermolecular forces (hydrophobic interactions and disulfide bonds), as well as the formation of casein-LPF-casein linked clusters with an elevated gelation rate exponent (α) value. These factors facilitated gel formation. Moreover, a moderate content of LPF facilitated cross-linking between caseins through a bridging effect, resulting in the development of a densely interconnected network with enhanced link density (88.25%) and reduced pore fraction (7.71%). Consequently, this led to a significant 17.6% inhibition in wheying off rate compared to low-fat yogurt without LPF during a 21-day storage time. However, the formation of weak or coarse gels was observed when the LPF content was low or high, the gelation rate was excessively rapid (exponent α = 3.05), or the presence of steric hindrance effect was present. The findings offered valuable insights for the application of insoluble particulate components in the food industry.

Formation and physical properties of skimmed milk/low-acyl gellan gum double gels: Influence of gelation sequence

Low-acyl gellan gum (LA) is a typical cold- and Ca2+-set gelation polysaccharide and is widely used to improve the stability of yoghurt. Acid and endogenous calcium can induce the formation of skimmed milk (SM)/LA double gels. However, the effect of acidification temperature on the formation and physical properties of SM/LA double gels has not been elucidated. In this study, temperature above and below the LA transition temperature (38 °C) were used as acidification temperatures, which adjusted the gelation sequence of SM and LA. The LA gel prior to the SM gel formed at acidification temperature of 37 °C, exhibiting the highest WHC and G′ among all samples. Moreover, SM/LA-37 double gels showed two networks: one was a porous network and the other was a dense network. By contrast, SM/LA mixtures acidified at 42 °C formed double networks during the cooling stage, and the previously formed SM gel hindered the formation of the LA gel. Consequently, SM/LA-42 double gels showed lower WHC and G′ compared with SM/LA-37 double gels. Overall, gelation sequence substantially affected the physical properties of SM/LA double gels. Our findings provide basis for adopting optimal methods to improve yoghurt quality and revealing the gelation mechanism involved in SM/LA double gels.

Sodium caseinate/gellan gum emulsion gels for zeaxanthin dipalmitate delivery: Preparation, characterization, and gelation mechanism

The emulsion gel composed of proteins and polysaccharides exhibits significant potential as a targeted delivery system for bioactives in the gastrointestinal tract. In this study, a composite emulsion was prepared by using sodium caseinate (NaCas) and gellan gum (GG), which was subsequently crosslinked with transglutaminase (TG), glucono-δ-lactone (GDL), and calcium ions (Ca2+) to form emulsion gels. The physicochemical properties of the NaCas/GG emulsion gels were characterized to verify the effects of zeaxanthin dipalmitate encapsulation and protection, and a possible mechanism was discussed. The appearance and microscopy analyses revealed that the Ca2+-induced NaCas/GG emulsion gel exhibited superior shape retention and a denser network structure compared to GDL or TG crosslinking methods. The rheological analysis demonstrated that the Ca2+-crosslinked emulsion gels had higher modulus and hardness than their TG- or GDL- crosslinked counterparts. Infrared spectroscopy, molecular docking, and gelling force analysis revealed that the gelation mechanism of these emulsion gels primarily involved carbonyl-amide group crosslinking reactions, hydrogen bonding, and hydrophobic interactions. Furthermore, the Ca2+-crosslinked emulsion gel encapsulating zeaxanthin dipalmitate exhibited excellent thermal stability, resistance to gastrointestinal conditions, and stability. Overall, the above findings highlight that using Ca2+ crosslinking in NaCas/GG composite emulsion yields edible composite materials with enhanced functional performance, thereby expanding the possibilities for food gel design strategies.

Recent opportunities and application of gellan gum based drug delivery system for intranasal route.

In the recent years, in-situ hydrogel based on gellan gum has been investigated for delivery of various drug molecules particularly to treat neurological disorders via intranasal route. The major objective of the present manuscript is to review the recent research studies exploring gellan gum as ionic triggered in-situ gel for intranasal administration to enhance absorption of drugs and to increase their therapeutic efficacy. This review include literature from 1982 to 2023 and were collected from various scientific electronic databases like Scopus, PubMed and Google Scholar to review source, chemistry, ionotropic gelation mechanism, and recent research studies for gellan gum based in-situ hydrogel for intransasl administration.Keywords such as gellan gum, in-situ hydrogel, intranasal administration and brain targeting were used to search literature. The present review included the research studies which explored gellan gum based in-situ gel for intranasal drug delivery. The findings have shown enhanced biavailability of various drugs upon intranasal administration using gellan-gum based in-situ hydrogel.Moreover, the review indicated that intranasal administration of in-situ hydrogel facilitate to overcome blood brain barrier effectively. Hence, significantly higher drug concentration was found to be achieved in brain tissues upon intranasal administration than that of other routes like oral and intravenous. The present work conducted a comprehensive review for gellan gum based in-situ hydrogel particularly for intransal administration to overcome BBB. The study concluded that gellan gum based in-situ hydrogel could be potential promising delivery system for intranasal administration to improve bioavailability and efficacy of drugs specifically to treat neurological disorders.

Effect of gel composition interaction on rheological, physicochemical and textural properties of methyl cellulose oleogels and lard replacement in ham sausage

Cellulose-derived edible vegetable oleogels can replace saturated/trans fats. The gelation mechanism relies on non-covalent interactions between gel components, influenced by their structure, concentration, and nature of the gelling factors. On the premise of preparing methyl cellulose (MC) with different viscosity, the effects of different gelling agents, MC, gelatin and oil concentration on the structure, physicochemical properties, oil binding capacity (OBC) and texture of emulsion and oleogels were studied. The oleogels were used as a lard substitute to study the effect on the texture, structure and sensory properties of the prepared ham sausage. We found that MC3 with gelatin had superior emulsification properties, inhibiting particle size and aggregation. Raising MC3 and gelatin concentrations to 1.5 wt% and 0.5 wt% led to oleogels with high OBC (>95 %), stability, and viscosity. The oleogels exhibited a dense structure and high mechanical strength with significantly enhanced structural hardness (199.55 g and 226.44 g). Higher oil concentration stabilized the emulsion but reduced oleogels stability after freeze-drying due to saturated oil absorption. The ratio of oleogels replacing lard was closely related to the texture of ham sausage. The texture properties of the ham sausage with 50 % lard replacement were closest to those of the control group.

Transglutaminase–mucin binding dynamics in gastrointestinal mucus: Interfacial behaviour, thermodynamics and gelation mechanism

Transglutaminase, an enzyme present in epithelial cells and as a residual component in processed foods, is hypothesised to interact with gastrointestinal mucus, impacting its structure and function. To test the physical validity of this phenomenon, this study investigates the binding kinetics and thermodynamics between porcine gastric mucin (PGM) and microbial transglumatinse (TGM) in a model gastrointestinal mucus, followed by the rheological analysis of the resulting systems. At pH 7, TGM exhibited pronounced binding with the PGM interface, characterised by a high surface density (55.34 ± 1.86 µg/m−2) and a low dissociation constant (KD ∼ 4.03 ± 0.10 μM) as determined by surface plasma resonance (SPR). Conversely, at pH 3, TGM showed weak adhesion onto PGM, resulting in a less stable binding, reflected by a lower surface density (10.94 ± 0.67 µg/m−2) and a higher dissociation constant (KD ∼ 6.24 ± 0.22 μM). Regardless of the nature of interaction, the Hill coefficients (nH ≥ 1) indicated that the binding sites were markedly denser at pH 7 (1383.38 ± 46.47 pmol/m−2), than at pH 3 (273.68 ± 16.84 pmol/m−2). Fluorimetry analysis suggested temperature-dependent dynamic binding between PGM and TGM. The resulting Benesi – Hildebrand plots illustrated a linear correlation between PGM and increasing TGM concentration, suggesting a single-step interaction mechanism. The calculated thermodynamic parameters indicated spontaneous interaction between PGM and TGM (ΔG < 0) via endothermic (entropic) interactions (ΔH > 0). Notably, hydrophobic forces played a significant role in the network stabilisation of PGM−TGM complex (ΔS > 0). Rheometry analysis elucidates that the interaction maxima within TGM−PGM systems substantially elevate both shear viscosity (η), and the melting point (Tm), shifting from 6.75 ± 0.28 to 70.94 ± 2.21 (×10−3) Pa s (at 1 s−1), and 36.80 ± 0.80 to 48.20 ± 0.11 °C, respectively. Furthermore, the coexistence of these two macromolecular species results in a 3- to 4-fold dramatic increase in the viscoelastic moduli of the binary complex. These findings build a strong physicochemical basis for the interaction between TGM and PGM, with profound effects on the rhological behaviour of the latter; it also highlights the need to examine the biochemical/enzymatic aspects of said interactions, and their potential effects on mucosa and human physiology.

Internally-crosslinked alginate dialdehyde/alginate/gelatin-based hydrogels as bioprinting inks for prospective cardiac tissue engineering applications

Cardiovascular diseases represent a worldwide social and economic challenge, due to heart tissue limited regenerative capabilities. 3D bioprinted cell-laden constructs are a promising approach to develop patches for cardiac regeneration or in vitro models for new drug preclinical discovery and validation. However, the development of bioinks with optimal mechanical, rheological, and biological properties is still a challenge. Although alginate (Alg)-based bioinks have been extensively explored, such hydrogels lack cell adhesion properties and degradability. Additionally, 3D Alg structures are usually obtained by micro-extrusion bioprinting exploiting conventional external cross-linking methods, which introduce inhomogeneities and unpredictability in construct formation. This work exploits Alg internal ionic gelation mechanism to obtain homogeneous self-standing multilayered 3D printed constructs without employing support baths or post-printing crosslinking treatments, combining an insoluble calcium salt (calcium carbonate, CaCO3) with an acidifying agent (D-(+)-Glucono-1,5-lactone, GDL) to promote controlled release of calcium ions. Alg was blended with oxidized alginate (ADA) and gelatin (Gel) to achieve degradable and cell adhesive hydrogels for cardiac tissue engineering. Firstly, ADA/Alg bioink composition was tailored by varying polymer weight ratio (keeping ADA as the main component) and calcium ions concentration to achieve cardiac tissue-like viscoelastic properties. Then, the amount of Gel in ADA/Alg hydrogels was optimized to support adult human cardiac fibroblasts (AHCFs) adhesion, producing shear thinning inks with tunable viscoelastic properties (G&amp;rsquo; 650-1300 Pa) and degradation profile (40-80% weight loss after 21 days in phosphate buffered saline, PBS) by varying Gel concentration. ADA/Alg/Gel hydrogels showed a shear thinning behavior suitable for 3D bioprinting and dependent on ink stabilization time, due to the gradual pH-triggered release of calcium ions over time. AHCFs-laden ADA/Alg/Gel bioinks could be successfully printed producing scaffolds with high shape fidelity and good cell viability post-printing. Finally, 3D AHCF-laden and H9C2-laden ADA/Alg/Gel bioinks with the highest gelatin content (25% w/w) allowed cell adhesion after 24 hours of incubation, showing potential application for cardiac tissue modelling. This research presented a comprehensive framework for advancing the design of bioink formulations enabling the printing of cell-adhesive and self-supporting constructs.

Impact of diverse mineral hardness in electrodialysis water on the ionotropic gelation mechanism of low methoxyl pectin

In this study, the effect of desalinated lava seawater via electrodialysis (ED water) on the formation and properties of low methoxyl pectin (LMP) gels was investigated. Additionally, the syneresis, microstructure, gelation mechanism, and thermostability of the gel samples were analyzed. When the ED water content exceeded 25 %, pectin gels with viscosities and textures that differed from those of the sol were formed. The highest gel hardness (9.38 N) was observed when 50 % ED water was mixed with LMP. However, when 75 % ED water was added, the pore size of the LMP gel became the largest, and excess water was released from the gel, resulting in a weak gel strength (4.98 N). The formation and properties of the gel structure were found to be mainly due to the ionic bonds between the minerals in the ED water and the free carboxyl groups of pectin, and it was confirmed that the hydrogen bonds within the pectin chains also had an effect. These results suggest that the interaction between the ED water and LMP can be widely used in various industrial fields, including low-sugar gels or viscosity-enhancing agents with diverse rheological properties.

Legume protein gelation: The mechanism behind the formation of homogeneous and fractal gels

Protein gelation can provide texture in plant-based foods and can be influenced by many factors, including protein extraction method and salt addition. However, the protein gelation mechanism is still not well understood for plant proteins, especially for isolates obtained using commercial protein extraction processes. Therefore, the structural changes that legume sources such as yellow pea, faba bean, and soybeans undergo during the gelation process to understand the differences in their gelation mechanisms was investigated herein by using small-angle neutron scattering. Among these protein sources, the commercial extraction method was found to play a major part in the gelation pathway. Intensive protein extraction methods involving isoelectric precipitation led to lower protein solubility (∼1–38% w/w), larger insoluble protein particle sizes (60–100 μm), and a gelation pathway that is dependent on the changes of the insoluble protein particles. In contrast, extraction using ultrafiltration instead of precipitation resulted in higher protein solubility (∼18–88% w/w) and smaller insoluble protein particle sizes (40–70 μm), and the structural changes observed during gelation involved the structural changes of both soluble proteins and insoluble proteins. SEM imaging also showed different gel networks, with fractal networks formed by insoluble proteins (for sources with low solubility) or more homogenous networks formed by the interactions between the soluble proteins (for sources with high solubility). Despite the differences observed in the gelation network and the protein solubility, the gelation strength exhibited by protein sources at low protein solubility were similar to the ones by protein sources at high protein solubility, demonstrating the potential of fractal gel networks in providing texture.

Mechanisms of gelation induced by laser irradiation for CaO powder dispersed in ethanol – Formation of calcium acetate and its role in gelation

Our recent study of gelation induced by laser ablation of CaO powders dispersed in ethanol proposed that CaO particle size composition would be an important factor affecting gelation because gelation is brought about by mixing a colloid composed of laser-fragmented particles and a raw CaO colloid. The present work was conducted to clarify this point. Results showed that, differing from our assumption, laser-fragmented particles are not necessary for gelation because gelation occurred even when laser-fragmented particles were removed from a laser-irradiated colloid before mixing it with a raw CaO colloid. Moreover, findings revealed that acetic acid generated by laser-induced oxidation of ethanol causes gelation, as confirmed by the fact that gelation also occurred when a proper amount of acetic acid was added to a raw CaO colloid. Results also revealed that nanofibers composed of calcium acetate hydrate play an important role in the gel structure formation. Results demonstrated that the gel structure and composition can be controlled simply by adjusting the amount of acetic acid without laser irradiation, suggesting that the results obtained from this study are useful as a newly developed and simple method of preparing calcium gel with various structures.