Rheological Studies Research Articles

Rheological insights into the degradation behavior of PP/HDPE blends

The (re-)processing and degradation behavior of polypropylene (PP) blends with high-density polyethylene (HDPE) is a crucial topic in mechanical recycling due to the prevalence of PP/HDPE mixtures. In particular, small amounts of cross-contamination (below 10.0 wt.%) between these polyolefins are quite common. While much empirical data is available, systematic studies on such blends are scarce and rarely account for the polymers’ chain structure. This study employs time-resolved rheology, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and chemiluminescence techniques to study the degradation of different PP types containing 0.5 to 10.0 wt.% of HDPE. It is observed that the addition of small amounts of HDPE can result in a prominent change in the viscoelastic properties of PP during the thermo-oxidative degradation. The substantial evolution of elasticity in the blends is mainly related to the gelation of fine PE particles dispersed within the PP matrix. It is also shown that a smaller viscosity ratio between the blend components can lead to a more significant degradation through morphology alterations. Remarkably, time-resolved rheology studies revealed that even a small amount of HDPE (2.5 wt.%) can lead to a reduction in the thermo-oxidative stability of the PP/HDPE blend through excessive branching/crosslinking of the HDPE phase. This effect was particularly more pronounced when the PP contained an ethylene comonomer in its backbone. The finer morphology of PE particles in PP copolymer can exacerbate the thermo-oxidative stability of the blend. These insights are essential in designing new life cycles for recycled PP cross-contaminated with HDPE, typically found in the light fraction of municipal solid plastic waste.

Impact of chickpea hummus on postprandial blood glucose, insulin and gut hormones in healthy humans combined with mechanistic studies of food structure, rheology and digestion kinetics

Slowing the rate of carbohydrate digestion leads to low postprandial glucose and insulin responses, which are associated with reduced risk of type 2 diabetes. There is increasing evidence that food structure plays a crucial role in influencing the bioaccessibility and digestion kinetics of macronutrients. The aims of this study were to compare the effects of two hummus meals, with different degrees of cell wall integrity, on postprandial metabolic responses in relation to the microstructural and rheological characteristics of the meals. A randomised crossover trial in 15 healthy participants was designed to compare the acute effect of 27 g of starch, provided as hummus made from either intact chickpea cells (ICC) or ruptured chickpea cells (RCC), on postprandial metabolic responses. In vitro starch digestibility, microstructural and rheological experiments were also conducted to evaluate differences between the two chickpea hummus meals. Blood insulin and GIP concentrations were significantly lower (P < 0.02, P < 0.03) after the consumption of the ICC meal than the meal containing RCC. In vitro starch digestion for 90 min was slower in ICC than in RCC. Microscopic examination of hummus samples digested in vitro for 90 min revealed more intact chickpea cells in ICC compared to the RCC sample. Rheological experiments showed that fracture for ICC hummus samples occurred at smaller strains compared to RCC samples. However, the storage modulus for ICC was higher than RCC, which may be explained by the presence of intact cells in ICC. Food structure can affect the rate and extent of starch bioaccessibility and digestion and may explain the difference in the time course of metabolic responses between meals. The rheological properties were measured on the two types of meals before ingestion, showing significant differences that may point to different breakdown mechanisms during subsequent digestion.This trial was registered at clinicaltrial.gov as NCT03424187.

Structure-properties relationships of defined CNF single-networks crosslinked by telechelic PEGs

The high structural anisotropy and colloidal stability of cellulose nanofibrils' enable the creation of self-standing fibrillar hydrogel networks at very low solid contents. Adding methacrylate moieties on the surface of TEMPO oxidized CNFs allows the formation of more robust covalently crosslinked networks by free radical polymerization of acrylic monomers, exploiting the mechanical properties of these networks more efficiently. This technique yields strong and elastic networks but with an undefined network structure. In this work, we use acrylate-capped telechelic polymers derived from the step-growth polymerization of PEG diacrylate and dithiothreitol to crosslink methacrylated TEMPO-oxidized cellulose nanofibrils (MATO CNF). This combination resulted in flexible and strong hydrogels, as observed through rheological studies, compression and tensile loading. The structure and mechanical properties of these hydrogel networks were found to depend on the dimensions of the CNFs and polymer crosslinkers. The structure of the networks and the role of individual components were evaluated with SAXS (Small-Angle X-ray Scattering) and photo-rheology. A thorough understanding of hybrid CNF/polymer networks and how to best exploit the capacity of these networks enable further advancement of cellulose-based materials for applications in packaging, soft robotics, and biomedical engineering.

Mechanical, rheological, thermal and morphological properties of pistachio shell powder reinforced / linear low-density polyethylene/polyolefin elastomer biocomposites

In the present study, 20 wt% ENGAGE (a polyolefin elastomer) is melt blended with 80 wt% linear low-density polyethylene (LLDPE) followed by composite preparation with pistachio shell powder (PSP) in various compositions (40 wt% to 70 wt%). The effect of variation of PSP content on mechanical properties is studied. The processability of composites is improved because of the unique processability of ENGAGE. Consequently, filler-containing capability of the LLDPE/ENGAGE (LE82) blend is also enhanced considerably due to extra space generated by amorphous ENGAGE. Again, blending of 20 wt% ENGAGE with 80 wt% LLDPE is helpful for maintaining mechanical properties of LLDPE/ENGAGE/PSP composite in useful range. The rheological study confirms that complex viscosity (η), storage modulus (G’) and loss modulus (G”) remain almost unchanged with the incorporation of a high quantity of PSP into the LE82 blend system for all the composites in the entire frequency range. From the rheological study, it is seen that the thermoplastic nature of the composites is maintained. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) show the structural integrity of LE82 blend-based composites revealing the thermal stability of the organic filler and consequently the composites. SEM also shows uniform dispersion of PSP into the LLDPE/ENGAGE blend matrix. Such biocomposite with 70 wt% biodegradable component and reliable mechanical properties is attractive for wide spread applications.

Improved biodistribution and enhanced immune response of subunit vaccine using a nanostructure formed by self-assembly of ascorbyl palmitate

New adjuvant strategies are needed to improve protein-based subunit vaccine immunogenicity. We examined the potential to use nanostructure of 6-O-ascorbyl palmitate to formulate ovalbumin (OVA) protein and an oligodeoxynucleotide (CpG-ODN) (OCC). In mice immunized with a single dose, OCC elicited an OVA-specific immune response superior to OVA/CpG-ODN solution (OC). Rheological studies demonstrated OCC's self-assembling viscoelastic properties. Biodistribution studies indicated that OCC prolonged OVA and CpG-ODN retention at injection site and lymph nodes, reducing systemic spread. Flow-cytometry assays demonstrated that OCC promoted OVA and CpG-ODN co-uptake by Ly6ChiCD11bhiCD11c+ monocytes. OCC and OC induced early IFN-γ in lymph nodes, but OCC led to higher concentration. Conversely, mice immunized with OC showed higher serum IFN-γ concentration compared to those immunized with OCC. In mice immunized with OCC, NK1.1+ cells were the IFN-γ major producers, and IFN-γ was essential for OVA-specific IgG2c switching. These findings illustrate how this nanostructure improves vaccine's response.

Supramolecular Gels Based on C3-Symmetric Amides: Application in Anion-Sensing and Removal of Dyes from Water.

We modified C3-symmetric benzene-1,3,5-tris-amide (BTA) by introducing flexible linkers in order to generate an N-centered BTA (N-BTA) molecule. The N-BTA compound formed gels in alcohols and aqueous mixtures of high-polar solvents. Rheological studies showed that the DMSO/water (1:1, v/v) gels were mechanically stronger compared to other gels, and a similar trend was observed for thermal stability. Powder X-ray analysis of the xerogel obtained from various aqueous gels revealed that the packing modes of the gelators in these systems were similar. The stimuli-responsive properties of the N-BTA towards sodium/potassium salts indicated that the gel network collapsed in the presence of more nucleophilic anions such as cyanide, fluoride, and chloride salts at the MGC, but the gel network was intact when in contact with nitrate, sulphate, acetate, bromide, and iodide salts, indicating the anion-responsive properties of N-BTA gels. Anion-induced gel formation was observed for less nucleophilic anions below the MGC of N-BTA. The ability of N-BTA gels to act as an adsorbent for hazardous anionic and cationic dyes in water was evaluated. The results indicated that the ethanolic gels of N-BTA successfully absorbed methylene blue and methyl orange dyes from water. This work demonstrates the potential of the N-BTA gelator to act as a stimuli-responsive material and a promising candidate for water purification.

A high performance triboelectric nanogenerator using assembled sugar naphthalimides for self-powered electronics and sensors

A new class of N-glycosyl naphthalimide ricinoleate (NGNR) amphiphiles were generated using environmentally friendly reaction conditions in good yields. To investigate the potential applications of NGNR amphiphiles within the realm of supramolecular materials, molecular self-assembly experiments were conducted extensively across a diverse range of solvents and oils and observed the gel formation. Molecular-level interactions and assembly patterns were investigated by employing FTIR, SAXRD, UV–vis, and fluorescence spectroscopy, and a plausible assembly mechanism was proposed. The morphology of the supramolecular architecture was identified by scanning electron microscopy. Additionally, rheological studies provided insight into these soft materials' strength and processability. Further, in the process of fabricating a triboelectric nanogenerator (TENG) device, silicone rubber serves as an electron acceptor and assembled NGNR serves as an electron donor. The developed TENG demonstrated a significant improvement in performance over TENG made with amorphous NGNR, with output voltage, current, and power density of 410 V, 100 µA, and 5.1 W/m2, respectively, highlighting the importance of the assembly process. Furthermore, TENG is used to continuously power up small electronic device (calculator), which is useful in building self-powered electronic devices. Lastly, due to its high sensitivity and stability, the TENG was used to detect the humidity of the environment in the food processing, textile, and agriculture sectors. The change in TENG response is notably significant up to 70 % relative humidity (RH). This work showcases the development of self-powered humidity sensors.

Miscibility of Amorphous Solid Dispersions: A Rheological and Solid-State NMR Spectroscopy Study

Miscibility is critical in the prediction of stability against crystallization of amorphous solid dispersions (ASDs) in the solid state. However, currently available approaches for its determination are limited by both theoretical and practical considerations. Recently, a rheological approach guided by the polymer overlap concentration (c*) has been proposed for miscibility quantification of ASDs [J. Pharm. Sci., 112 (2023) 204−212] and shown to be useful in predicting both accelerated and long term physical stability in the absence of moisture. However, this approach can only be performed at high temperatures (slightly above the melting temperature, Tm, of drugs), and little is known about the difference in miscibility between high and low temperatures (e.g., below the glass transition temperature, Tg). Here we compare the miscibility of nifedipine (NIF)/polyvinylpyrrolidone (PVP) ASDs as determined by the rheological approach at 175°C (∼3°C above Tm of NIF) and solid state NMR (ssNMR) 1H T1 and T1ρ relaxation times at -20°C (∼66°C below Tg of NIF). Our results indicate agreement between the two methods. For low molecular weight (Mw) PVP, T1ρ measurements are more consistent with the rheological approach, while T1 measurements are closer for relatively high Mw PVP. Our findings support the use of the c* based rheological approach for inferring miscibility of deeply cooled ASDs.

Preliminarily revealing rheological behaviors of mesoscale collagen fibrils in suspension

Using natural mesoscopic collagen as the structural unit has gradually emerged as a promising processing strategy for the preparation of high-performance collagen materials. These mesoscopic collagen fibrils (CAs) are exfoliated from biological tissues and dispersed in liquid media to prepare subsequent materials. The present work explores the effects of solid content, size, and temperature on the rheological behavior of collagen fibril suspensions under shearing through steady-state and dynamic rheological studies. Suspensions tend to exhibit shear-thinning and gel-like behavior, attributed to mesoscopic collagen forming a rigid network. Suspensions with large-size collagen fibers (aspect ratio > 100) exhibit high resistance to shear deformation at low solid contents (0.5 wt%) due to the intensive physical entanglement. The viscosity of the suspension was temperature-dependent and decreased rapidly near the hydrated thermal denaturation temperature of collagen. This work reveals the interactions between mesoscale collagen's surface interfaces and provides the necessary theoretical basis for collagen processing.

Development of Rheology in the Area of High-Performance Concrete – A Review

Abstract The rheological or flow quality high-performance concrete (HPC) are significant as they affect several parameters, including ease of placing, compatibility, durability and strength. For the selection of component materials and prediction of the fresh and hardened characteristics of HPC, an adequate understanding of rheology is required. This literature review gives a gist of the works done in the field of rheological study of HPC. The flow models and equations to explain the flow behaviour of HPC mixes as proposed by the researchers are presented. Yield stress and plastic viscosity are the basic rheological parameters that are used in these equations. Various rheometers developed to measure and estimate these rheological parameters of HPC are also presented in this paper. This review provides a thorough analysis of the effects of various constituent materials on the rheological properties of HPC. This includes aggregates, cement, various supplementary cementitious materials like fly ash silica fume, slag etc. Also, the effect of mineral admixtures like superplasticizers and viscosity modifying agents along with the synergic effects is discussed. Finally, the prospects of the study on the unexplored areas and future challenges in the field of study are discussed.

Synthesis and Rheological Analysis of Non-Isocyanate Polyurethanes Blended with Poly(vinyl alcohol)

This study investigated the blending of non-isocyanate polyurethanes (NIPUs) with poly(vinyl alcohol) (PVA) at various ratios, with specific emphasis on ratios such as 20%, 50%, 80%, and 100% NIPU content. Focus has been made on assessing their rheological behaviour, mechanical performance, and thermal stability. As the NIPU content surpassed 50%, a shear-thickening trend emerged, suggesting a highly interwoven molecular structure. Rheological studies demonstrate viscosity variations dependent on blend composition and shear rate, with pure NIPU solution exhibiting shear thickening behaviour suggestive of network formation facilitated by the application of shear. Dynamic modulus analysis revealed viscoelastic properties in blends containing 50% and 100% NIPU. Thixotropic analysis showcased a remarkable structural recovery of 99% in solutions with over 20% NIPU, emphasizing the resilience of NIPU-rich blends to shear-induced alterations. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrate thermal stability and crystallinity, with blends exhibiting intermediate behaviour and reduced crystallinity compared to pure PVA due to NIPU incorporation. Blends exceeding 10% PVA displayed reduced consistency and diminished PVA crystallization ability, corroborated by DSC and wide-angle X-ray diffraction (WXRD) results. Thermal stability increased with NIPU integration, and blends demonstrated intermediate thermal behaviour between the pure polymers. Notably, the PU2PVA8 blend demonstrates the highest miscibility and a unique combination of amorphous and crystalline nature, showcasing its potential for tailored material design with enhanced structural and thermal properties.

Production and characterization of a blood analogue based on alginate microparticles

This work addresses the need for a universal blood substitute by focusing on developing alginate-based microparticles engineered to replicate the mechanical properties of red blood cells (RBCs). Alginate, known for its biocompatibility and tunable mechanical properties, is used to create microparticles that closely resemble RBCs in size and shape. These alginate microparticles are produced through premix membrane emulsification (PME), ensuring a uniform size distribution. The viscosity ratio and the size of the filter pores influence the final size of the microparticles. Filters with pores of 20 µm were used to produce 5 wt% alginate microparticles with a diameter of 7.81 µm ± 0.77, and filters with pores of 30 µm were used to produce 0.5 wt% alginate microparticles with a diameter of 8.69 µm ± 3.30. The Deformability Index (DI) of the alginate microparticles follows the correlation that microparticles with higher elastic modulus exhibit lower DI values. The DI found for 0.5 wt% alginate microparticles solution is higher than the DI found for 5 wt% alginate microparticles. The DI of RBCs is higher than the ones found for the alginate microparticles, however the value is in the range of the experimental error. Rheological studies reveal that suspensions of 25–30 wt% alginate microparticles exhibit a shear-thinning behavior similar to human blood. The DI of the alginate microparticles shows little influence on the rheology of the suspensions. Furthermore, the Cell-Free Layer (CFL) of alginate microparticles is close to that of RBCs, reinforcing the potential of alginate as a suitable material for blood substitute development. The alginate microparticles produced in this work show a great potential to contribute to creating a blood-mimicking fluid for applications in medical treatments and research.

Rheological study of methane gas hydrates in the presence of micron-sized sand particles

Natural gas hydrates, intricate crystalline structures formed by water molecules and small gas molecules, have emerged as a significant and globally impactful clean energy resource. However, their commercial exploitation faces challenges, particularly operational disruptions caused by sand-related blockages. Understanding the rheological properties of hydrate slurry, especially in the presence of micron-sized sand particles, is imperative for ensuring the flow assurance of subsea hydrate exploitation. This study extensively investigates the rheological properties of sand-containing hydrate slurries. The findings reveal that these slurries exhibit non-Newtonian fluid characteristics, including yield stress, thixotropy, and shear-thinning behavior. Solid-like elastic features are observed in sand-containing hydrate slurries before yielding, transitioning to viscous behavior after yielding. Even with a minimal amount of sand, both static yield stress and yield strain experience substantial changes, correlating with the increase in sand concentration. The research conclusively establishes the thixotropic nature of sand–hydrate slurries, where the viscosity decay rate is directly influenced by the shear rate. These insights aim to contribute comprehensively to the development of effective flow assurance strategies, ensuring the safe and stable operation of subsea hydrate exploitation.

A comparative study of molecular structure, rheology, and thermal characteristics of deacetylated konjac glucomannan-treated gluten during frozen storage

Konjac glucomannan is extensively employed to enhance the quality of wheat-based products. Despite this, the utilization of natural KGM in the food industry is restricted due to its inadequate mechanical attributes, heightened susceptibility to humidity, and unappealing taste profile. In this study, the influence of deacetylated konjac glucomannan (DKGM) on the structure, rheology, and thermal characteristics of gluten during frozen storage was explored. Furthermore, the mechanism outlining the action between gluten and DKGM was analyzed. The secondary structure results showed that DKGM promoted the formation of α-helices and β-sheets in gluten. Scanning electron microscopy analysis confirmed that DKGM made the gluten network more stable. Moreover, DKGM provided a significant improvement in the rheological and thermal properties of frozen gluten. This is attributes to the fact that DKGM alters the hydrophobic residues in frozen gluten. Overall, this work indicates that the molecular structure and thermal properties of gluten are optimally substantial improvements at a substitution content of 1.5% D3 (deacetylation degree of 95%) in the dough. These findings provide a reference value for the application of DKGM in frozen wheat-based foods.

Synthesis of guar gum maleate under dry conditions: Reaction kinetics and characterization

In the present study, a novel environment friendly dry method for preparation of guar gum maleate (GGM) with varying degrees of substitution (DS; 0.02–1.04) was optimized. GGM with a maximum DS of 1.04 was successfully synthesized using guar gum (GG) and maleic anhydride (MA) in proportion of 1: 1 at 80 °C with 4 h of reaction time. The activation energy for the reaction was determined to be 36.91 ± 3.61 kJ mol−1 with pre-exponential factor of 1392 min−1. Esterification of GG was confirmed by FT-IR and 13C NMR. Analysis using size exclusion chromatography (SEC) indicated a decrease in weight average molecular weight (Mw) of the polymer with an increase in polydispersity index (PDI) due to esterification. In comparison with GG, GGM displayed increased hydrophobicity and reduced thermal stability, as analysed by differential scanning calorimetry (DSC). Rheological studies of GGM revealed that initial apparent viscosity decreased with increasing DS. For the first time, the study offered valuable insights on GGM synthesis under dry solvent-less reaction conditions enabling simpler and scalable synthesis process.

Interfacial control and dispersion characteristics of polylactic acid fiber/pulp fiber composites

AbstractTo solve the problem of the dispersibility of pulp fiber in polylactic acid (PLA)/pulp fiber composites, PLA fiber instead of PLA beads and pulp fiber were used for initial physical mixing, and then internal mixer‐melting was conducted. The dispersion of pulp fiber in PLA was improved compared with conventional composite preparation protocols. After the pulp fiber was treated with a silane coupling agent, the compatibility of the composite and the transparency of the material were also improved. When the pulp fiber content reached 30%, the mechanical properties and heat resistance of the composite were optimal: tensile fracture strength of 56.52 MPa, and thermal deformation temperature increase of 5°C. Rheological studies indicate that when the pulp fiber content reached 10%, the system exhibited a PLA‐pulp fiber network. When the pulp fiber content was ≥20%, the system exhibited a PLA–PLA and pulp fiber–pulp fiber dual‐network structure.Highlights The dispersion of filler in the matrix was improved by blending fiber with fiber. There was rheological percolation upon filling the pulp fiber in the PLA matrix. The coupling agent facilitated reactive compatibilization and PLA chain extension.

Double networks hybrid hydrogels of silica nanoparticles/polyacrylamide: Network stiffness, viscoelastic, mechanical and adhesion properties

Today, the challenge of enhancing the strength and adhesion of the polyacrylamide hydrogel network is still a major concern in many applications. This study investigates the effect of silica nanoparticle concentration on the cross-linked polyacrylamide hydrogel’s gelation, viscoelastic, structural, and adhesion properties. The hybrid hydrogels were evaluated using DSC, XRD, SEM, and rheological analysis to determine their enthalpy of cross-linking, crystallinity, morphology, and elastic properties. The results of kinetic analysis confirmed the catalytic effect of silica nanoparticles on the gelation kinetics. A deviation from the elastic behavior of the unfilled hydrogel was found from the rheological studies. Using the Weibull Model to describe the creep test results showed a significant increase in retardation time with increasing silica nanoparticles content up to the percolation threshold of 0.24 wt.%. This confirmed the development of a more viscous behavior due to the formation of a physical network of nano-silica particles. Based on the DSC energy of hydrogels, both chemical and physical tie points (approximately 19 covalent crosslinking points) were calculated. The hydrogel containing 9 wt.% of silica nanoparticles demonstrated significant improvement in density, and adhesion to the metal surface by about 100% and 350%, respectively. As a result of this study, the hydrogel containing 9 wt% of silica nanoparticles (H9) is suggested for various field studies, such as oil well plugging industries.

Versatile xanthan gum-based support bath material compatible with multiple crosslinking mechanisms: rheological properties, printability, and cytocompatibility study

Extrusion-based bioprinting is a promising technology for the fabrication of complex three-dimensional (3D) tissue-engineered constructs. To further improve the printing accuracy and provide mechanical support during the printing process, hydrogel-based support bath materials have been developed. However, the gel structure of some support bath materials can be compromised when exposed to certain bioink crosslinking cues, hence their compatibility with bioinks can be limited. In this study, a xanthan gum-based composite support material compatible with multiple crosslinking mechanisms is developed. Different support bath materials can have different underlying polymeric structures, for example, particulate suspensions and polymer solution with varying supramolecular structure) and these properties are governed by a variety of different intermolecular interactions. However, common rheological behavior can be expected because they have similar demonstrated performance and functionality. To provide a detailed exploration/identification of the common rheological properties expressed by different support bath materials from a unified perspective, benchmark support bath materials from previous studies were prepared. A comparative rheological study revealed both the structural and shear behavior characteristics shared by support bath materials, including yield stress, gel complex moduli, shear-thinning behavior, and self-healing properties. Gel structural stability and functionality of support materials were tested in the presence of various crosslinking stimuli, confirming the versatility of the xanthan-based support material. We further investigated the effect of support materials and the diameter of extrusion needles on the printability of bioinks to demonstrate the improvement in bioink printability and structural integrity. Cytotoxicity and cell encapsulation viability tests were carried out to confirm the cell compatibility of the xanthan gum-based support bath material. We propose and demonstrate the versatility and compatibility of the novel support bath material and provide detailed new insight into the essential properties and behavior of these materials that serve as a guide for further development of support bath-based 3D bioprinting.

Sustainable highly stretchable and tough gelatin-alkali lignin hydrogels for scaffolding and 3D printing applications

Hydrogels and bioinks obtained from gelatin (Gel) generally present poor mechanical properties and require a series of time-consuming and stepwise chemical processes to exhibit improved elasticity and resistance to fatigue. Alkali lignin (AL) is an underutilized by-product of the paper and pulp industry. It is a widely available and inexpensive biomaterial that presents enormous potential for high-value applications owing to its ease of chemical modification and unique naturally occurring polyaromatic structure. This work aims to develop different GelAL hydrogel formulations with a single-step method that are innovative and sustainable. The results obtained from the mechanical, rheological, and degradation studies of the developed GelAL hydrogels demonstrated that their properties can be easily modified and tuned using straightforward processing techniques, allowing these stretchable and tough hydrogels to be used as bioinks in 3D printing. The modulation of mechanical properties through hydrogel formulations is a result of interactions between the Gel and AL which can be associated with the interplay of anionic sulfonates in AL and the arginine and lysine residues from Gel. The tensile stress at the break for the Gel20AL10 formulation was 32% higher than the value for Gel20AL5 and 157% higher than that of Gel10AL10. The elongation at break also decreased as it averaged 659 ± 149% for the Gel20AL10 formulation, which is 20% more than that of Gel20AL5 and 55% more than the average elongation at break of Gel10AL10. Further zeta potential measurements and quartz crystal microbalance with energy dissipation studies demonstrated that Gel and AL seem to form neutral complexes when mixed. These assays support the idea that AL and Gel are readily bound through weak interactions, and chemical crosslinking strategies need to be considered when degradability and mechanical properties tuning are envisioned. Altogether, these high-performance GelAL hydrogels display mechanical properties similar to soft tissues with high elasticity beyond that of natural hydrogels and fulfill the requirements of a broad range of biomedical and tissue engineering scaffolding applications.

Formulation and Characterization of Curcumin 12-Hydroxystearic Acid in Triacetin Organogel for Topical Administration

Background: Curcumin (CUR) and its derivatives have shown a wide variety of biological activities, such as anti-oxidant, anti-inflammatory, anti-tumor, antimicrobial and antiparasitic effects as well as for the treatment of skin diseases. Due to its physico-chemical limitations such as low aqueous solubility and low bioavailability, we developed curcumin organogel as a topical delivery system to overcome those limitations. The12-hydroxystearic acid (12-HSA) is well known as a low-molecular-weight organogelators (LMOGs) capable of gelling an organic liquid phase. Different concentrations of (12-HSA) in triacetin with 50 mg CUR were gelled and applied for various examinations: tabletop rheology, oil binding capacity, pH measurement, spreadability, in vitro drug release, antibacterial activity and oscillatory rheology studies. The results revealed that the organogels transition temperatures from solid to liquid were greater than the normal body temperature, this helped the organogels keep their shape; they had good spreadability,and the organogels pH levels were within the safe range for the skin . In vitro release data showed that 4% 12HSA+5%CUR +TA (4TA) gave us 100% release after 6 hours. The selected 4TA illustrated good viscoelastic properties in the amplitude sweep test and a frequency-independent as seen in the frequency sweep test. CUR has good antibacterial action against Staphylococcus aureus; Streptococcus pyrogen, Proteus mirabilis, and Escherichia coli, which prevail at the site of wound injury as this pointed out that 4TA organogel can be used for topical wound healing.