Transparency Of Gels Research Articles

Formation of a transparent soy protein hydrogel: Controlled thermal aggregation of protein using glutaminase

Plant protein-based hydrogels have enormous potential applications, and their great functional properties and sustainability are considered the best alternatives to reduce the environmental burden of animal protein resources. However, heat-induced plant protein-based hydrogels often exhibit a rough and opaque network structure, limiting their application in various scenarios where gel transparency is crucial. In this study, transparent hydrogels were successfully prepared using deamidated soy protein isolate (SPI) modified by protein-glutaminase (PG). Compared with the non-transparent SPI hydrogel, the deamidated SPI hydrogel possessed a soft and intricate chain-like network, exhibiting excellent light transmittance and certain mechanical strength. The results indicated that deamidation treatment unfolded the structure of SPI, shifting the protein conformation from ordered to disordered, and leading to the transformation of large insoluble protein aggregates into small soluble aggregates. In addition, deamidation treatment effectively inhibited the thermal aggregation rate and aggregation counts of SPI. This was attributed to the conversion of glutamine to glutamic acid, which enhanced the electrostatic repulsion between protein molecules. The present work offers a promising approach for preparing highly transparent plant protein-based hydrogels, which are conducive to developing the next generation of plant protein-based functional materials to replace existing petroleum-based materials.

Translucency mechanism of heat-induced pigeon egg white gel

In this study, the properties of pigeon egg white (PEW) and chicken egg white (CEW) thermal gels were compared, with the aim of revealing the mechanisms involved in the high transparency of PEW thermal gels. Results demonstrated that PEW gels exhibited higher transparency than CEW gels. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that PEW gels formed a fine chain gel network structure with an average diameter of thermal aggregates (89.84 ± 7.13 nm). The molecular properties of PEW proteins, such as higher content of β-sheet structures (32.73 %), reactive groups (free sulfhydryl groups, hydrophobic groups), and absolute zeta potential (−3.563 mV), were found to contribute to the formation of smaller thermal aggregates during thermal denaturation. The microrheology measurements showed that these features allowed PEW proteins to interact less with each other and form smaller thermal aggregates during thermal denaturation, which facilitated the formation of fine chain gel networks and thus improved the transparency of the gels. The present study initially reveals the molecular basis of the high transparency of PEW thermal gels and provides a theoretical reference for the development of new highly transparent protein materials.

Structural and functional properties and digital image texture analysis of gelatin, pectin, and carrageenan gels with honey addition.

Gels combined with honey might generate new possibilities of textures in food development. This work explores the structural and functional properties of gelatin (5 g/100 g), pectin (1 g/100 g), and carrageenan (1 g/100 g) gels with different content of honey (0-50 g/100 g). Honey decreased the transparency of gels and made them more yellow-greenish; all of them were firm and uniform, especially at the highest honey content. The water holding capacity increased (63.30-97.90 g/100 g) and moisture content, water activity (0.987-0.884) and syneresis (36.03-1.30 g/100 g) decreased with the addition of honey. This ingredient modified mainly the textural parameters of gelatin (Hardness: 0.82-1.35 N) and carrageenan gels (Hardness: 2.46-2.81 N), whereas only the adhesiveness and the liquid like-behavior were increased in the pectin gels. Honey increased the solid behavior of gelatin gels (G': 54.64-173.37 Pa) but did not modify the rheological parameters of the carrageenan ones. Honey also had a smoothing effect on the microstructure of gels as observed in the scanning electron microscopy micrographs. This effect was also confirmed by the results of the gray level co-occurrence matrix and fractal model's analysis (fractal dimension: 1.797-1.527; lacunarity: 1.687-0.322). The principal component and cluster analysis classified samples by the hydrocolloid used, except the gelatin gel with the highest content of honey, which was differentiated as a separate group. Honey modified the texture, rheology, and microstructure of gels indicating that it is possible to generate new products to be used in other food matrices as texturizers.

Comparison of the Physicochemical Properties of Carboxymethyl Agar Synthesized by Microwave-Assisted and Conventional Methods.

The microwave-assisted carboxymethylation of agar to improve its physicochemical properties was investigated. Microwave power, reaction time, and temperature, ethanol concentration, and amounts of chloroacetic acid and sodium hydroxide were assessed for their effects on synthetic yield and degree of substitution (DS). All factors were positively correlated with DS within a certain range. Using optimized conditions, samples with different DS were prepared, and the physicochemical properties of unmodified and carboxymethyl agars prepared by microwave and conventional methods were compared. Carboxymethylation significantly changed the physicochemical properties of the agar, improving gel transparency and reducing dissolution temperature, gel strength, gel hardness, molecular weight, and molecular size; DS was the key factor. Specifically, higher DS values resulted in greater changes. The microwave-assisted method significantly shortened the reaction time and preserved molecular weight, gel strength, and texture hardness of the agar. Therefore, as an environmentally friendly method, microwave-assisted synthesis shows great promise for producing carboxymethyl agar.

Gel properties transition from mono-succinylation to cross-linking of agar by attemperation with succinic anhydride

Chemical modification is often used to improve the gel properties of agar but inevitably weakens gel strength in practical applications. This study achieved a breakthrough in improving the gel properties of agar without reducing its gel strength through modification with succinic anhydride. Fourier transform infrared spectroscopy and carbon nuclear magnetic resonance analyses showed that succinic anhydride could be mono-succinylated, cross-linked, and desulfurized with agar. The transition from mono-succinylation to cross-linking of agar was achieved by attemperation. Interestingly, the gel transparency of mono-succinylated agar increased from 55% to 89%, but its gel strength remarkably decreased from 1073 g/cm2 to 188 g/cm2. Cross-linking endowed agar with a higher gel strength (815 g/cm2) and gel transparency (85.3%). Agar succinylation demonstrated more beneficial effects and further enhanced the water-retention capacity of agar powder (18.1 g/g), the swelling ratio of agar film (1736.2%), and the freeze–thaw stability of agar gel (30.3%, 7th).

Synthesis and properties of maleic anhydride-modified agar with reversibly controlled gel strength

Agar is modified by chemical methods to improve its functional properties and meet the increasing demand of the market. Some of the functional properties of agar are improved after chemical modification, while other properties are reduced, especially gel strength. This study aimed to comprehensively improve the functional properties of agar through acylation and crosslinking by reacting with maleic anhydride. 13C NMR indicated the maleylation reaction was preferred at the C2 hydroxyl group of D-galactose, and the crosslinking reactions occurred at the C2 and C6 hydroxyl groups of D-galactose in different agar chains. Interestingly, the maleylated agar monoester had higher gel transparency (1.5%, w/v) of up to 76% than the native agar (58%). However, it showed a significant decrease in gel strength from 783 g/cm2 to 403 g/cm2, while crosslinking endowed agar with higher gel strength (845 g/cm2) and gel transparency (78.4%). The high transparency of the modified agar plate made colony observation and colony counting easy. Maleylation of agar further enhanced the freeze–thaw stability of agar gel (24.8%, 7th freeze–thaw cycles). Overall, the maleylated agar possessed superior functional properties, and it could be used as food, bacteriological, and biotechnological agar.

Optimization of Agar Preparation Based on Transparency

To meet the requirement for high transparency of agar gel used in tissue culture, bacteriological applications, and high-quality cosmetics and food, this study on improving the transparency of agar products was carried out by using activated carbon for decolorization and perlite for aiding filtration. The results showed that the pre-coating filtration method was better than that of the mixed slurry filtration, so an orthogonal experiment optimization was conducted using the pre-coating filtration method based on the single factor experimental results. The experimental results showed that the optimal process conditions based on the transparency index were: concentration of agar of 1.30%, activated carbon dosage of 0.80%, processing temperature of 95 °C, and treatment time of 20 min. Agar products with gel transparency of 58.93% and blue-ray whiteness value of 93.82 could be obtained under these experimental conditions. The order of the factors influencing the decolorization ratio of agar was as follows: activated carbon dosage > concentration of agar > processing temperature > treatment time. The experimental results provided effective procession methods for the production enterprises based on transparency and increased economic benefits, and it was of practical significance.

Structure and physicochemical properties of amphiphilic agar modified with octenyl succinic anhydride

A novel amphiphilic agar with high transparency and freeze-thaw stability was prepared using octenyl succinic anhydride (OSA). Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed that the hydrophobic OS groups were successfully introduced in OSA-modified agar (OSAR) backbone. The OSAR showed higher emulsion stability and oil loading capacity than the native agar (NA). Compared with gel transparency (47.1 %), syneresis (42.1 %) of NA, OSAR exhibited high gel transparency (80 %) and low syneresis (3.3 %) when the degree of substitution (DS) was 0.06 and 0.12, respectively. Meanwhile, the OSAR showed a decreased interface tension and average molecular weight after modification. Thermogravimetric analysis indicated the thermal stability of OSAR was decreased, while texture profile analysis showed the springiness of the OSAR gel was enhanced. Dynamic rheology measurements revealed the OSAR with low gel strength displayed more liquid-like properties. Moreover, the OSAR exhibited lower turbidity and melting temperatures than the NA.

Transparency of Temperature-responsive Shape-memory Gels Tuned by a Competition between Crystallization and Glass Transition

Transparency is often an important property in the practical applications of temperature-responsive shape-memory gels. We investigated the mechanism of significant transparency improvement upon a change in two copolymer gels with their molar ratios between stearyl acrylate and N, N-dimethylacrylamide from 1:1 to 0.75:1. By means of Flash DSC measurement, we made the thermal analysis characterization of crystallization and glass transition in two copolymer gels and compared the results to the parallel experiments of corresponding homopolymers. The results showed that the slightly lower content of stearyl acrylate sequences suppresses crystallization in their side chains due to the chemical confinement of comonomers on copolymer crystallization; meanwhile it shifts up the glass transition temperature of the backbone N, N-dimethylacrylamide sequences. Eventually on cooling, crystallization gives its priority position to glass transition in copolymer gels, resulting in a higher transparency of the gel without losing the shape-memory performance. To confirm the chemical confinement, we further compared the isothermal crystallization kinetics of stearyl acrylate side chains in the copolymer gel to that of their homopolymer. Our observations facilitate the rational design of the temperature-responsive shape-memory gels for the transparency property.

In situ-forming hyaluronic acid hydrogel through visible light-induced thiol-ene reaction

Here we present hyaluronic acid (HA) hydrogels crosslinked via thiol-ene reaction initiated by visible blue light exposure in the presence of riboflavin phosphate (RFP). The gelation procedure is rapid and proceeds as effectively with exposure to blue light as it does with UV light. We successfully initiated the thiol-ene reaction by RFP with blue light, which triggered gelation that proceeds over about 5 min at 36 °C after an initial small change in modulus upon light exposure. Gel transparency was also evaluated, and the HA gel exhibited over 80% transmittance in the visible spectrum. The degradation and protein release kinetics of the photo-crosslinked HA hydrogel are also presented. The capacity of blue light to initiate thiol-ene reaction was equal to or more effective than UV light of the same energy. The cytocompatibility of hydrogels was evaluated using corneal fibroblasts, and the light-induced fabrication procedure and resultant gel materials did not affect cell viability. The results indicate that an RFP-based, BL-initiated photo-reaction to gelate HA may be an effective and promising modality for applications where in situ gelation is desired.

Non-ideal behavior of binary aqueous mixtures of some urea derivatives and their capacity to induce lysozyme gelation

The urea derivatives, namely, ethylurea (EU), 1,3 dimethylurea (1,3-DMU) and 1,1 diethylurea (1,1-DEU), in the limiting regions of their solubilities in water, and tetramethylurea (TMU) at w≥0.65 were investigated in relation to their capacity of inducing hen egg white lysozyme (HEWL) physical (non-covalent) gelation. Protein transparent gels were generated out of TMU/H2O and 1,1-DEU/H2O, respectively, whereas an intensively turbid gel resulted from sol-gel transition taking place in EU/H2O. Oscillatory rheology revealed distinctions in the gels’ structural and dynamic characteristics. Hydration patterns of the derivatives in solution, sizes of their non-polar domains and supramolecular symmetry features played a central role in their capacity of gel formation and in the gels’ rheological behavior and morphology. Effects on gel characteristics of distinctively positioned ions in the Hofmeister series showed that SCN− disrupted water H-bonding interconnectivity in TMU lysozyme gel, strengthening gel structure, yet maintaining gel transparency. Citrate enhanced system elasticity albeit causing intense turbidity and leading to phase separation. Larger values of the storage modulus, G′, were verified for gels generated from binary mixtures containing urea derivatives with higher dipole moments.

Transparent Porous Polysaccharide Cryogels Provide Biochemically Defined, Biomimetic Matrices for Tunable 3D Cell Culture

Biomimetic scaffolds are desirable for 3D cell culture, yet optically transparent, macroporous, polysaccharide hydrogels have been limited. By incorporating soluble mono- and disaccharide additives during cryogelation, we synthesized biomimetic scaffolds and gained insight into the mechanism of their formation. The mono/disaccharide additives affect the size of ice crystal porogens and interact with polysaccharide polymers, altering cryogel pore size and mechanical properties. Importantly, gel transparency is maintained following removal of additives, enabling their use as biomimetic extracellular matrices. We demonstrate both optical transparency with 3D spatial control of immobilized bioactive growth factors using multiphoton patterning and cellular response to immobilized ligands.

Solvent-Dependent Properties and Higher-Order Structures of Aryl Alcohol + Surfactant Molecular Gels.

Molecular organogels, comprising small organic gelators in solvents, can be applied for dispersal of optical devices, such as emitters. Phenolic compounds and the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) are known examples of self-assembly organogels. However, conventional phenol + AOT gels in aromatic and acyclic alkane solvents are optically turbid, which is an obstacle for use as host materials in optical devices. In this study, a variety of aryl alcohol-AOT-solvent sets have been investigated systematically, and the correlation between the molecular architecture and optical transparency of the gels was considered. Accordingly, p-chlorophenol + AOT gels in cyclic alkane solvents were shown to form optically transparent gels. In contrast, aromatic and acyclic alkane solvents gave rise to turbid or opaque gels, even when utilizing the same gelators. AFM, NMR, SAXS, and FTIR were employed to determine the organogel structures. Consequently, we found that the gel transparency strongly depends on the size of the fibrous network of the gel, the structure of which is attributed to higher-order aggregates of the gelators. The average contour length and diameter of the fibrous network, lav and dav, respectively, were determined from AFM images. The transparent gels were shown to have lav = 4-9 μm and dav ≤ 0.3 μm, whereas the turbid gels had lav = 15 μm and dav = 0.4-0.6 μm. Such differences in the size of the fibrous network significantly affected the mechanical response of the gels, as shown by stress-strain measurements.

Osmocapillary phase separation

A covalent network of polymer can imbibe a solvent to form a gel. In a cavity on the surface of the gel, capillary force may suck the solvent out of the gel to form a pure liquid phase. We show that such osmocapillary phase separation occurs when capillarity balances osmosis, and when the diffusion of solvent in the gel prevails over the condensation of solvent from the vapor. Osmocapillary phase separation can occur even when the gel is isolated from the vapor, or when the solvent is nonvolatile. We relate osmocapillary phase separation to phenomena of practical significance, including the wettability of gels, the transparency of gels, the liquid bridge at the tip of an atomic force microscope, the adhesion between a gel and another substance, the surface morphology of gels, and the production of tight oil.

Development of the composition and technology of a caries preventive gel

Prevention of dental caries involves remineralization of the tooth surfaces with calcium and phosphorus medicines, but the use of fluorine- containing remedies in the form of a cream, gel and varnish is more effective. The aim of our work was to substantiate the composition and technology of a gel with cetylpyridinium hexafluorosilicate having the caries preventive action. A gelling agent – hydroxyethyl cellulose that provides stability and the essential structural and mechanical properties of the gel has been selected experimentally. Microscopic studies have substantiated introduction of the solubilizer PEG-40 hydrogenated castor oil in the concentration of 0.5% that promotes dissolution of the peppermint essential oil with preserving the gel transparency. The use of 10% sorbitol has been substantiated to provide the moderate osmotic properties and to prevent the gel drying. Microbiological studies have shown the necessity of using sodium benzoate as a preservative in the concentration of 0.3%. The temperature regimen of cetylpyridinium hexafluorosilicate introduction in the composition of the gel base has been substantiated by thermogravimetric studies. The technology of gel has been developed.

Formulation and evaluation of clindamycin HCL in situ gel for vaginal application.

Objective:The vagina has been studied as a favorable site for the local and systemic delivery of drugs, for female associated conditions. Vaginal preparations, although generally perceived as safer most still associated with number of problems including multiple days of dosing, dripping, leakage and messiness, causing discomfort to users and expulsion due to the self-cleansing action of the vaginal tract. These limitations lead to poor patient compliance and failure of the desired therapeutic effects. For efficient vaginal delivery of drugs, the delivery system should reside at the site of infection for a prolonged period of time. In situ gel formulation which combines advantages of both gels and solution so that an accurate dose can be administered with ease. These formulations remain in solution state before administration and transforms to gel after administration in to vaginal cavity.Material and Methods:In these formulations we prepared clindamycin loaded hydroxypropyl methycellulose (0.1%) (bioadhesive) and gellan gum (ion activated gelling polymer) based in situ gel system for vaginal application. NaCl (0.9%) was added as an isotonic agent. The developed formulation was characterized for various in vitro parameters such as clarity, refractive index, pH, viscosity, drug release profile, statistical release kinetics, bioadhesive force, and microbial efficacy along with stability studies. To simulate vaginal conditions, synthetic membrane (cellophane hydrated with modified simulated vaginal fluid) was used as model membranes.Results and Discussion:The developed formulation was found to be nonirritant, bioadhesive with good retention properties. Formulations have satisfactory appearance, clarity and drug content in the range 98.1-101%. Refractive index of the gel is ranging from 1.335 to 1.337, proofing the transparency of gel. Furthermore, formulation displayed 33.3% cumulative drug release after 2 h. 67.4% after 6 h and 98.9% after 12 h.Conclusion:Developed formulation should be stable. Hence, formulation is thus a viable alternative to conventional vaginal dosage forms.

Physical and radiological properties of radiochromic gel as of its composition

In the research, we evaluated the use of leuco crystal violet (LCV) gel as a dosimeter for therapeutic radiation by investigating its optical characteristics at various component concentrations. We also investigated the aging effect of the LCV gel at different beam energies, doserates, and dosing times to evaluate the LCV’s applicability to radiation therapy. We confirmed that the optimal optical wavelength of the LCV gel dosimeter was 600 nm. The dose sensitivity increased with increasing concentration of LCV; however, the optimal concentration was 1 mM LCV because the transparency of the gel dosimeter is important for use in optical CT scanners. However, the dose sensitivity decreased with increasing concentration of trichloroacetic acid (TAA). Moreover, the transparency of LCV rapidly decreased because of the generation of a white precipitate at TAA concentrations below 25 mM. Thus, an optimal TAA concentration of 30 mM was used in this study. Triton X-100 (8 mM) was identified as the optimal reagent for determining the optimum gel transparency and dose sensitivity. Thus, we present an LCV gel dosimeter composed of 4% gelatin by mass, 1 mM LCV, 30 mM TAA, and 8-mM Triton X-100 for use with an optical CT scanner. We showed good dose linearity up to 30 Gy. There was a little doserate dependency at a beam energy of 6 MV while the doserate dependence was more than 4.2% at a beam energy of 10 MV. To evaluate the energy dependence of the LCV gel dosimeter, we irradiated it at 20 Gy by using 6 MV and 10 MV beams. At the high doserate, the difference in the dose energy dependence was relatively small at approximately 1%, but the difference increased to 4.6% at the low doserate. With respect to the radiation absorbance at a photon energy of 6 MV, the absorbance at an electron energy of 6 MeV decreased by 5.4%, and the absorbances at 9, 12, and 15 MeV increased by 3, 18.7, and 12.2%, respectively. Furthermore, the aging effect was larger in the low-dose group then in the high-dose group. Moreover, we observed that the absorbance between 24 and 48 h after irradiation increased by approximately 5% at 5 Gy. For gel groups tested at high doses, the aging effect was reduced by approximately 1%.

Aggregation Kinetics of Metal Chalcogenide Nanocrystals: Generation of Transparent CdSe(ZnS) Core(shell) Gels.

Transparent CdSe(ZnS) sol-gel materials have potential uses in optoelectronic applications such as light emitting diodes (LEDs) due to their strong luminescence properties and the potential for charge transport through the prewired nanocrystal (NC) network of the gel. However, typical syntheses of metal chalcogenide gels yield materials with poor transparency. In this work, the mechanism and kinetics of aggregation of two sizes of CdSe(ZnS) core(shell) NCs, initiated by removal of surface thiolate ligands using tetranitromethane (TNM) as an oxidant, were studied by means of time-resolved dynamic light scattering (TRDLS); the characteristics of the resultant gels were probed by optical absorption, transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). At low concentrations of NCs (ca. 4 × 10(-7) M), the smaller, green-emitting NCs aggregate faster than the larger, orange-emitting NCs, for a specific oxidant concentration. The kinetics of aggregation have a significant impact on the macroscopic properties (i.e. transparency) of the resultant gels, with the transparency of the gels decreasing with the increase of oxidant concentration due the formation of larger clusters at the gel point and a shift away from a reaction limited cluster aggregation (RLCA) mechanism. This is further confirmed by the analyses of the gel structures by SAXS and TEM. Likewise, the larger orange-emitting particles also produce larger aggregates at the gel point, leading to lower transparency. The ability to control the transparency of chalcogenide gels will enable their properties to be tuned in order to address application-specific needs in optoelectronics.

Acceptability of tenofovir gel as a vaginal microbicide by US male participants in a Phase I clinical trial (HPTN 050)

We studied the acceptability of tenofovir gel among HIV-infected and uninfected men who were exposed to it during vaginal intercourse. The gel was found to be highly acceptable to most men, the large majority indicating they would probably use it in the future if they were concerned about HIV and the product were available. Men liked the gel's transparency and odorless qualities, although reactions to its viscosity were more varied. Men acknowledged women's rights to self-determination concerning HIV-prevention, yet considered that women's covert use of the product was more acceptable in the context of ‘one-night-stands’ than in stable relationships, for which dialogue on protection measures was preferred. Restrictions to couples’ habitual sexual repertoire and the protocol requirement to use condoms resulted in complaints. Microbicide trials that do not require condom use from men who don't typically use them may provide a more accurate assessment of acceptability. Consistent microbicide use may be contingent on its ease of incorporation into typical sexual practices, type of sexual partnership and contextual issues.

Aqueous Dispersions of J-Aggregates and J-Aggregate-Doped Silica Bulk Gels

A preparation method of the aqueous dispersions of merocyanine J-aggregates was refined to achieve better transparency. By using these dispersions, the J-aggregates were doped in silica bulk gels by a sol–gel method. The obtained bulk gels also had a high transparency and J-aggregates were introduced uniformly into the silica matrix. The preparation procedures are precisely described together with the optical properties. By maintaining the bulk gel transparency and the uniformity of doping, we attempted to increase the concentration of the dye. The achieved concentration of 0.41 mmol/L was 6-fold higher than that reported previously.