Characterisation of xanthan gum solutions using dynamic light scattering and rheology

Carboxymethyl hydroxypropyl guar gum physicochemical properties in dilute aqueous media

We investigate carboxymethyl hydroxypropyl guar gum (CMHPG) solution properties in water and NaCl, KCl, and CaCl2 aqueous solutions. The Huggins, Kraemer, and Rao models were applied by fitting specific and relative viscosity of CMHPG/water and CMHPG/salt/water to determine the intrinsic viscosity [η]. The Rao models yielded better results (R2 = 0.779-0.999) than Huggins and Kraemer equations. [η] decreased up to 84% in salt solution over the range 0.9-100 mM compared to water. Salt effects screened the CMHPG charged side groups chains leading to a compacted structure. In 0.9 mM NaCl(aq), the hydrodynamic coil radius (Rcoil) was 28% smaller and 45% smaller in 100 mM NaCl solution relative to water. Similar decreases were seen in KCl and CaCl2 solutions. KCl and CaCl2 were more effective than NaCl. CMHPG is salt-tolerant and shows comparatively less viscosity change than native guar gum, with modest reduced viscosity increases with CMHPG dilution at all salt concentrations. The electrostatic interactions were effective up to 100 mM salt. The activation energy of viscous flow for CMHPG solutions was computed and compared to measured xanthan gum and several literature values. These data show that the barrier to CMHPG flow is higher than for xanthan gum.

Physicochemical properties and stability of oil-in-water emulsions stabilized by soy protein isolate and xanthan gum

The aim of this work was to determine rheological and disperse characteristics and stability of oil-in-water emulsions stabilized by soy protein isolate (SPI) and xanthan gum (XG), as natural components. The effects of their combination on emulsion stabilization have not been investigated yet. The existence of interactions between the two macromolecules were indicated by the influence of XG on SPI surface hydrophobicity and surface tension values. Increase in SPI concentration from 1 to 3 % shift of distribution curves towards smaller particle size, while the opposite effects of further increase of SPI was obtained. The emulsions stabilized by SPI showed shear-thinning flow behavior, which changed to thixotropic at 5 % of SPI concentration. The presence of XG in emulsions at low concentrations did not affect the size distribution of the droplets, while at 0.1 % of XG Sauter mean diameter value raised and distribution curves were shifted towards a higher particle size. The presence of XG at higher concentration resulted in thixotropic flow behavior of emulsions. Also, increase in XG concentration led to the increase in consistency index and extent of non-Newtonian behavior of emulsions and enhanced the influence of the elastic modulus and creaming stability of the systems.

Cutaneous Delivery and Biodistribution of Cannabidiol in Human Skin after Topical Application of Colloidal Formulations

The objective of this study was to investigate the cutaneous delivery of cannabidiol (CBD) from aqueous formulations developed for the targeted local treatment of dermatological conditions. CBD was formulated using a proprietary colloidal drug delivery system (VESIsorb®) into an aqueous colloidal solution at 2% (ACS 2%) and two colloidal gels (CG 1% and CG 2%, which contained 1% and 2% CBD, respectively). Two basic formulations containing CBD (5% in propylene glycol (PG 5%) and a 6.6% oil solution (OS 6.6%)) and two marketed CBD products (RP1 and RP2, containing 1% CBD) were used as comparators. Cutaneous delivery and cutaneous biodistribution experiments were performed using human abdominal skin (500-700 µm) under infinite- and finite-dose conditions with 0.5% Tween 80 in the PBS receiver phase. The quantification of CBD in the skin samples was performed using a validated UHPLC-MS/MS method and an internal standard (CBD-d3). The cutaneous deposition of CBD under finite-dose conditions demonstrated the superiority of CG 1%, CG 2%, and ACS 2% over the marketed products; CG 1% had the highest delivery efficiency (5.25%). Cutaneous biodistribution studies showed the superiority of the colloidal systems in delivering CBD to the viable epidermis, and the upper and lower papillary dermis, which are the target sites for the treatment of several dermatological conditions.

Development and characterization of ultrastable emulsion gels based on synergistic interactions of xanthan and sodium stearoyl lactylate

Emulsion gels with the mixtures of low-molecular-weight emulsifier (LME) and polymer have attracted much attention in food; however, the LME-polymer interactions in emulsion system are complex and unclear. Here, the interactions between SSL and xanthan in emulsions and the mechanisms of stabilizing emulsions were investigated by using tensiometry, zeta potential, Fourier transform infrared spectroscopy (FTIR), confocal laser scanning microscopy (CLSM), cryo-scanning electron microscopy (cryo-SEM) and rheology. SSL was more efficiently adsorbed on the oil-water interface than xanthan. Interestingly, the honeycomb structure was formed in emulsion gels, which firmly immobilized oil droplets. Furthermore, electrostatic repulsion and hydrophobic interactions between xanthan and SSL facilitated the efficient bonding at interface and in bulk. Both linear and nonlinear rheology strongly supported the fact that the interactions between xanthan and SSL enhanced gel-like viscoelastic structure of emulsion gels. This structure endows excellent stability of emulsion gels under high temperature storage, sealed conditions and pH change.

Rheological Assessment of Oil-Xanthan Emulsions in Terms of Complex, Storage, and Loss Moduli

This experimental assessment was carried out to study the viscoelastic performance of crude oil-xanthan emulsions employing a RheoStress RS100 rheometer. Crude oil with a concentration range of 0−75% by volume was used to prepare the oil-gum emulsions. Two xanthan gums of Sigma and Kelzan were added in the emulsions with concentration ranges of 0−104 ppm. The linear viscoelastic ranges of all the tested oil-gum emulsions were found in the range of 0.1−10 Pa. Thus, the experimental tests were completed within the linear viscoelastic range of 1 Pa. The complex modulus increased gradually and steadily with frequency and gum concentration for all the examined emulsions. The addition of crude oil into the lighter xanthan concentration of <103 ppm provided almost the same behavior as the xanthan solution, whereas the presence of crude oil within the higher xanthan concentrations significantly stimulated the measured values of the complex modulus. For lower gum concentrations of up to 1000 ppm, oil concentration displayed no effect on both the storage and loss moduli, whereas for gum concentrations higher than 1000 ppm, both moduli increased gradually with crude oil concentration.

Viscoelastic Behavior of Crude Oil-Gum Emulsions in Enhanced Oil Recovery

The experimental study of the Creep-recovery examination is necessary to understand the viscoelastic behavior of crude oil-Xanthan gum emulsions. The experimental measurements and analysis of these tests were completed using RheoStress RS100 under controlled stress CS-mode. Rheometers with CS-mode allow for a useful and direct technique for the experimental measurements of creep and recovery stages. This investigation covers a wide range of crude oil concentration of 0–75% by volume, Xanthan concentration range of 0–10⁴ ppm, and two types of Xanthan gums are used and investigated. The creep-recovery measurements of crude oil-Xanthan gums emulsions were extensively investigated. It was important to find the linear viscoelastic range for the examined crude oil-Xanthan gum emulsions. The experimental measurements and analysis of the creep-recovery examinations showed that the linear viscoelastic range was up to 1 Pa. The experimental investigation showed that the higher the concentration of the used gum and crude oil, the lower the compliance of the emulsions. For the Xanthan concentrations of less than 10³ ppm, the crude oil-gum emulsion exhibited viscous behavior. However, for the Xanthan concentration of higher than 10³, the examined emulsions displayed viscoelastic behavior.

Effect on Rheological Properties and 3D Printability of Biphasic Calcium Phosphate Microporous Particles in Hydrocolloid-Based Hydrogels

The production of patient-specific bone substitutes with an exact fit through 3D printing is emerging as an alternative to autologous bone grafting. To the success of tissue regeneration, the material characteristics such as porosity, stiffness, and surface topography have a strong influence on the cell–material interaction and require significant attention. Printing a soft hydrocolloid-based hydrogel reinforced with irregularly-shaped microporous biphasic calcium phosphate (BCP) particles (150–500 µm) is an alternative strategy for the acquisition of a complex network with good mechanical properties that could fulfill the needs of cell proliferation and regeneration. Three well-known hydrocolloids (sodium alginate, xanthan gum, and gelatin) have been combined with BCP particles to generate stable, homogenous, and printable solid dispersions. Through rheological assessment, it was determined that the crosslinking time, printing process parameters (infill density percentage and infill pattern), as well as BCP particle size and concentration all influence the stiffness of the printed matrices. Additionally, the swelling behavior on fresh and dehydrated 3D-printed structures was investigated, where it was observed that the BCP particle characteristics influenced the constructs’ water absorption, particle diffusion out of the matrix and degradability.

Semi-continuous production of xanthan in biofilm reactor using Xanthomonas campestris

Semi-continuous production of xanthan gum using self-immobilized Xanthomonas campestris cells in biofilm reactors was studied. Fermentation was carried out using two different designs of biofilm reactor equipped with a) stainless-steel support (SSS) and b) polyethylene support (PES). Fermentation was performed in three cycles with refreshing the media at the beginning of each: cycle 1, 0-27 h; cycle 2, 27-54 h; and cycle 3, 54-78.5 h. Results showed that the glucose consumption and the pH reduction in the PES biofilm reactor was faster compared to the SSS biofilm reactor. Scanning electron microscopy showed that the SSS was capable to immobilize more cells during the growth of X. campestris. The maximum concentration of xanthan gum in the SSS biofilm reactor obtained after 27 h (3.47 ± 0.71 g/L), while the maximum concentration of xanthan in the PES biofilm reactor obtained after 78.5 h (3.21 ± 0.68 g/L). Thermal stability analysis of xanthan using differential scanning calorimetry showed the presence of two fractures attributed to dehydration and degradation of polymer. The thermogram represented both endothermal and exothermal behaviour of xanthan polymer. Furthermore, the functional groups and molecular structure of the xanthan produced in this study was evaluated using Fourier transform infrared spectrometry and also proton nuclear magnetic resonance. in addition, the surface tension of (0.2 %, w/v) xanthan gum solution was in a range of 52.16-56.5 mN/m. Rheological analysis of xanthan showed that the G' values were higher than the G″ in all frequencies demonstrating a relatively high elasticity of the produced xanthan gum.

Impact of octenyl succinic anhydride (OSA) modified starch on the particle size distribution and rheological properties of xanthan gum in aqueous solutions

Effects of addition of octenyl succinate anhydride (OSA) starch on the structural, rheological and thermo-rheological properties of aqueous solutions of 0.5 (w/v %) xanthan gum were evaluated. Analysis by dynamic light scattering revealed the absence of complex formation in the mixed solution. However, it was noticed that an increase in the concentration of OSA starch (COSA) leads simultaneously to an increase of the number of micelles and their self-assembly within the network formed by the xanthan macromolecules. This same mechanism was observed during the evaluation of the rheological properties. For systems containing 0.5 (w/v %) of xanthan and for which COSA ≤ 4 (w/v %), a thermoreversible behavior was found similar to that of xanthan in solution. Furthermore, for COSA ≥ 5 (w/v %), the rheological behavior remained indifferent to the increase in temperature but, scored a spectacular rise in storage modulus when the cooling temperature begins near 70 °C.

Depletion-Induced Flocculation of Concentrated Emulsions Probed by Photon Density Wave Spectroscopy

Stable, creaming-free oil in water emulsions with high volume fractions of oil (ϕ = 0.05-0.40, density matched to water) and polysorbate 80 as an emulsifier were characterized without dilution by Photon Density Wave spectroscopy measuring light absorption and scattering behavior, the latter serving as the basis for droplet size distribution analysis. The emulsion with ϕ = 0.10 was used to investigate flocculation processes induced by xanthan as a semi-flexible linear nonabsorbing polymer. Different time regimes in the development of the reduced scattering coefficient μ_s' could be identified. First, a rapid, temperature-dependent change in μ_s' during the depletion process was observed. Second, the further decrease of μ_s' follows a power law in analogy to a spinodal demixing behavior, as described by the Cahn-Hilliard theory.

Recent trends on gellan gum blends with natural and synthetic polymers: A review

Gellan gum (GG), a linear negatively charged exopolysaccharide,is biodegradable and non-toxic in nature. It produces hard and translucent gel in the presence of metallic ions which is stable at low pH. However, GG has poor mechanical strength, poor stability in physiological conditions, high gelling temperature and small temperature window.Therefore,it is blended with different polymers such as agar, chitosan, cellulose, sodium alginate, starch, pectin, polyanaline, pullulan, polyvinyl chloride, and xanthan gum. In this article, a comprehensive overview of combination of GG with natural and synthetic polymers/compounds and their applications in biomedical field involving drug delivery system, insulin delivery, wound healing and gene therapy, is presented. It also describes the utilization of GG based materials in food and petroleum industry. All the technical scientific issues have been addressed; highlighting the recent advancement.

Polysaccharide matrices used in 3D in vitro cell culture systems

Polysaccharides comprise a diverse class of polymeric materials with a history of proven biocompatibility and continual use as biomaterials. Recent focus on new matrices appropriate for three-dimensional (3D) cell culture offers new opportunities to apply polysaccharides as extracellular matrix mimics. However, chemical and structural bases for specific cell-polysaccharide interactions essential for their utility as 3-D cell matrices are not well defined. This review describes how these naturally sourced biomaterials satisfy several key properties for current 3D cell culture needs and can also be synthetically modified or blended with additional components to tailor their cell engagement properties. Beyond their benign interactions with many cell types in cultures, their economical and high quality sourcing, optical clarity for ex situ analytical interrogation and in situ gelation represent important properties of these polymers for 3D cell culture applications. Continued diversification of their versatile glycan chemistry, new bio-synthetic sourcing strategies and elucidation of new cell-specific properties are attractive to expand the polysaccharide polymer utility for cell culture needs. Many 3D cell culture priorities are addressed with the portfolio of polysaccharide materials available and under development. This review provides a critical analysis of their properties, capabilities and challenges in 3D cell culture applications.

Effect of Xanthan Gum on the Rheological Behavior and Microstructure of Sodium Caseinate Acid Gels

The aim of this work was to study the effect of xanthan gum (XG) on the gelation process of bovine sodium caseinate (NaCAS) induced by acidification with glucono-δ-lactone (GDL) and on the mixed acid gel microstructure. Before GDL addition, segregative phase separation was observed in all the NaCAS-XG mixtures evaluated. The gelation process was analyzed by using a fractional factorial experimental design. The images of the microstructure of the mixed acid gels were obtained by conventional optical microscopy and the mean diameter of the interstices was determined. Both the elastic character and the microstructure of the gels depended on the concentrations of XG added. As XG concentration increased, the kinetics of the gelation process was modified and the degree of compactness and elasticity component of the gel network increased. The microstructure of gels depends on the balance among thermodynamic incompatibility, protein gelation and NaCAS-XG interactions.

Design and development of a nanoemulsion system containing extract of Clinacanthus nutans (L.) leaves for transdermal delivery system by D-optimal mixture design and evaluation of its physicochemical properties

C. nutansis a well-known medicinal plant in South-East Asia that has attracted attention for its therapeutic characteristics. In this work, nanoemulsion has been chosen to be a carrier in encapsulation ofC. nutansextract for its potential in nanotechnology application.

Introducing diffusing wave spectroscopy as a process analytical tool for pharmaceutical emulsion manufacturing

Emulsions are widely used for pharmaceutical, food, and cosmetic applications. To guarantee that their critical quality attributes meet specifications, it is desirable to monitor the emulsion manufacturing process. However, finding of a suitable process analyzer has so far remained challenging. This article introduces diffusing wave spectroscopy (DWS) as an at-line technique to follow the manufacturing process of a model oil-in-water pharmaceutical emulsion containing xanthan gum. The DWS results were complemented with mechanical rheology, microscopy analysis, and stability tests. DWS is an advanced light scattering technique that assesses the microrheology and in general provides information on the dynamics and statics of dispersions. The obtained microrheology results showed good agreement with those obtained with bulk rheology. Although no notable changes in the rheological behavior of the model emulsions were observed during homogenization, the intensity correlation function provided qualitative information on the evolution of the emulsion dynamics. These data together with static measurements of the transport mean free path (l*) correlated very well with the changes in droplet size distribution occurring during the emulsion homogenization. This study shows that DWS is a promising process analytical technology tool for development and manufacturing of pharmaceutical emulsions.