Alginate Type Research Articles

Controlling the size and elastic modulus of in-aqueous alginate micro-beads.

The fabrication of microgels, particularly those ranging from tens to hundreds of micrometers in size, represents a thriving area of research, particularly for biologists seeking controlled and isotropic media for cell encapsulation. In this article, we present a novel and robust method for producing structurally homogeneous alginate beads with a reduced environmental footprint, employing a co-flow focusing microfluidic device. These beads can be easily recovered in an oil-free aqueous medium, making the fabrication method highly suitable for diverse applications. We demonstrate precise control over the production of perfectly spherical beads across a wide range of diameters, from about 30 to 300 μm. We then measure Young's moduli of the beads, revealing a wide accessible range from 90 Pa to 11 kPa, contingent upon controlling the type (e.g. chain length) and concentration of alginate.

Correlation between gastroesophageal reflux disease lung volumes and exacerbation of bronchial asthma: Italian pilot observational retrospective study GERDAS.

Reflux asthma is an entity characterized by typical symptoms and, in some cases, is "silent"; it is more dangerous when associated with obesity and sleep apnea syndrome. Numerous studies demonstrate its high prevalence in the general population, particularly in the pediatric population, where, despite medical specialists' treatment, asthma symptoms remain poorly controlled with a high risk of acute exacerbations. This clinical study aims to show how the addition of a particular type of alginate (Deflux Plus sachets) containing hyaluronic acid and melatonin at low doses administered over a prolonged period of 6 months causes a reduction in vagal reflex stimulation of the esophagus and pulmonary microaspiration reflexes by regulating lower esophageal sphincter motility in asthmatic patients, improving the asthma control test (ATC) score. In the reported statistical analysis, receiver operating characteristic curves were performed for sensitivity and specificity for the analyzed parameters, including the ACT score, with statistically significant data p<0.0001. We conclude that combining conventional therapy for reflux asthma with alginates may improve the risk of acute asthma exacerbations and dynamic lung volumes.

Microencapsulation of a Pickering Oil/Water Emulsion Loaded with Vitamin D3.

The ionotropic gelation technique was chosen to produce vitamin D3-loaded microparticles starting from oil-in-water (O/W) Pickering emulsion stabilized by flaxseed flour: the hydrophobic phase was a solution of vitamin D3 in a blend of vegetable oils (ω6:ω3, 4:1) composed of extra virgin olive oil (90%) and hemp oil (10%); the hydrophilic phase was a sodium alginate aqueous solution. The most adequate emulsion was selected carrying out a preliminary study on five placebo formulations which differed in the qualitative and quantitative polymeric composition (concentration and type of alginate selected). Vitamin D3-loaded microparticles in the dried state had a particle size of about 1 mm, 6% of residual water content and excellent flowability thanks to their rounded shape and smooth surface. The polymeric structure of microparticles demonstrated to preserve the vegetable oil blend from oxidation and the integrity of vitamin D3, confirming this product as an innovative ingredient for pharmaceutical and food/nutraceutical purposes.

Centrifugally spun poly(D,L-lactic acid)-alginate composite microbeads for drug delivery and tissue engineering

This work was based on medium-viscosity alginate as a minor constituent in composites with poly lactic acid (PLA) with the objective to prepare compositional variants through Forcespinning® (FS); for future medical applications. Composites within 0.08–0.25 wt% medium-viscosity alginate were used, at fixed PLA, 6.6 wt%, compared with a study using 0.17–0.48 wt% low-viscosity alginate (same PLA), starting from water-in-oil emulsions, before FS. The presence of alginate is proposed here to influence the high surface tension existing at the emulsion water/oil interface, reducing the total energy at this interface, and/or facilitating the particles in the amphiphilic blend to lie-flat (re-orient) for better fit to the PLA curvature. The study revealed a direct correlation of the inner-phase size (alginate/water ratio), to the change in the morphology and structure of the resultant composites before and after FS. The change in the alginate type, revealed characteristics better suited for medical applications by the medium-viscosity alginate. Composites at alginate- medium-viscosity; ≤0.25 wt%, and low-viscosity; ≤0.48 wt%, had fiber networks interwoven with micro-beads, with characteristics better suited for controlled-release drug delivery applications. Alternatively, each alginate type at 1.1 wt%, composites with PLA at 6.6 wt% could bring about homogenous fibrous materials better suited for wound dressing.

Preparation of compact alginate films for 2D in vitro studies: Challenges and strategies for improvement

Alginate-based hydrogels show high biocompatibility and therefore are broadly used for cell cultivation and tissue engineering approaches in general. When hydrogel films for cell seeding were prepared by following published protocols, attached but inhomogeneously distributed cells were observed, which was attributed to the fact that casted hydrogel films were uneven and irregularly shaped. The causes of these irregularities resulting in an inhomogeneous cell distribution, e.g., due to accumulation of cells in cracks, were investigated. This study established a universal protocol for preparing planar hydrogel films that allow a homogenous cell distribution by varying several parameters such as alginate type, freezing, and crosslinking conditions. This finding can be applied to investigations of two-dimensional cell-material interactions of advanced alginate-based materials, e.g., when coupled with peptides.

Development of MXene-decorated sodium alginate/SiO2@n-docosane hierarchical phase-change microcapsules for solar-driven sustainable seawater desalination

A novel type of MXene-decorated and sodium alginate (SA)-coated phase-change microcapsules (hereafter named “MXene/SA/SiO2-MEPCM”) was designed as a bifunctional solar absorber for the interfacial evaporator to realize sustainable seawater desalination. The MXene/SA/SiO2-MEPCM was fabricated by encapsulating n-docosane as a phase change material (PCM) in the SiO2 shell, followed by depositing a SA layer and decorating MXene nanosheets. An innovative integration of SA and MXene nanosheets enables the microcapsules to achieve a high light absorption capability of over 97 % together with good wettability, promoting a high evaporation rate of 2.11 kg·m−2·h−1 under one-sun illumination. The MXene/SA/SiO2-MEPCM exhibits a high latent heat capacity of over 150 J·g−1 for consecutive and high-efficient evaporation under intermittent solar illumination. Compared to the evaporator without a PCM core, the MXene/SA/SiO2-MEPCM-based evaporator achieved an increase in evaporation mass by 1.4 kg·m−2 through 5-cycle consecutive evaporation processes under solar illumination and natural cooling. Furthermore, its total water production was increased by 1.01 kg·m−2 under natural solar illumination for 7.5 h on a semi-cloudy day. The MXene/SA/SiO2-MEPCM also exhibits good recyclability for long-term use in solar-driven seawater desalination thanks to the good structural stability of its shell and highly stable reversible phase transitions of its PCM core.

Research on enhancing the mechanical strength of polyvinyl alcohol/sodium alginate gel beads applied in biological wastewater treatment

This study investigated a new type of polyvinyl alcohol-sodium alginate (PVA/SA) gel beads for immobilization of activated sludge biomass. Gel beads are made from PVA, SA, and graphene oxide (GO) with different concentrations of GO (0.02, 0.2; 2; 20 and 200 mg/L). The results showed that the basic properties, including the roundness and expansion rate of the gel beads, did not differ significantly between the GO concentrations. At the same time, the higher the concentration of go, the more it improves the mechanical strength of the gel beads. The highest strength was when GO levels reached 200 mg/L. At the same concentration, the gel beads achieved the highest methylene blue absorption capacity (91.2%) and the fastest oxygen consumption rate (0.31 mg/L/min) compared to PVA/SA gel beads without GO. This result initially demonstrated that the addition of GO is an effective way to enhance the mechanical strength of PVA/SA gel beads.

The effect of contact time between alginate impression material and type III dental stone on the surface properties of stone casts

Background: Alginate impression material is the irreversible hydrocolloid material that is widely used in dentistry. The contact time between alginate and gypsum cast could have a detrimental effect on the properties of the gypsum cast. The objective of this study is to evaluate the impact of various contact time intervals of Alginate impressions &amp; type III dental stone on surface properties of stone cast. Materials and Methods: Time intervals tested were 1hour, 6 hours and 9 hours. Surface properties of stone cast evaluated were surface detail reproduction, hardness and roughness. Surface detail reproduction was determined using cylindrical brass test block in accordance with ISO 1563. Surface roughness was measured by profilometer and hardness was measured by Durometer (Shore D). Results: The detail reproduction showed significant difference (P&lt;0.05), at 6 hr., and 9 hr. showed better results. While surface roughness significantly decreased (p&lt;0.01) with prolonged contact time. However, surface hardness increased significantly (p&lt;0.01) with increased contact time. Conclusions: Surface detail reproduction increased with increasing the contact time and this was noticed at (6, 9 hours). However, 1hour time interval showed decreased surface detailed reproduction. Roughness decreased when the contact time was increased between type III dental stone and alginate impression whereas, hardness was improved significantly with increasing contact time.

Modulation of the clinically accessible gelation time using glucono-d-lactone and pyridoxal 5′-phosphate for long-acting alginate in situ forming gel injectable

The purpose of this study was to design alginate in situ forming gel (ISFG) injectable with clinically acceptable gelation time and controlled release of hydrophobic drug. Milled or unmilled paliperidone palmitate (PPP) was used. The gelation time was controlled by varying the ratios of glucono-d-lactone (GDL) and pyridoxal 5′-phosphate (PLP) in prefilled alginate solution mixtures (ASMs) containing PPP, CaCO3, GDL and PLP for clinically acceptable injectability. However, the gelation time was varied by the alginate type (M/G ratio), storage condition, and drug solubilizers. This ISFG exhibited 32.15 kPa of the maximal compressive stress without causing pain and stiffness. The ISFG containing conically milled PPP released PPP in a controlled manner without exhibiting any initial burst release for 4 weeks. The current alginate ISFG injectable using new combination of PLP and GDL could be used to deliver long-acting injectable drugs.

Effect of sodium alginate molecular structure on electrospun membrane cell adhesion

Alginate-based electrospun nanofibers prepared via electrospinning technique represent a class of materials with promising applications in the biomedical and pharmaceutical industries. However, to date, the effect of alginate molecular mass and block composition on the biological response of such systems remains to some extent unclear. As such, in the present work, three alginates (i.e., M.pyr, L.hyp, A.nod) with different molecular features are employed to prepare nanofibers whose ability to promote cell adhesion is explored by using both skin and bone cell lines. Initially, a preliminary investigation of the raw materials is carried out via rheological and zeta-potential measurements to determine the different grade of polyelectrolyte behaviour of the alginate samples. Specifically, both the molecular mass and block composition are found to be important factors affecting the alginate response, with long chains and a predominance of guluronic moieties leading to a marked polyelectrolyte nature (i.e., lower dependence of the solution viscosity upon the polymer concentration). Subsequently, physically crosslinked alginate nanofibrous mats are first morphologically characterized via both scanning electron and atomic force microscopy, which show a homogenous and defect-free structure, and their biological response is then evaluated. Noticeably, fibroblast and keratinocyte cell lines do not show significant differences in terms of cell adhesion on the three mats (i.e., 30–40% and 10–20% with respect to the seeded cells, respectively), with the formers presenting a greater affinity toward the alginate-based nanofibers. Conversely, both the investigated osteoblast cells are characterized by a distinct behaviour depending on the alginate type. Specifically, polysaccharide samples with an evident polyelectrolyte nature are found to better promote cell viability (i.e., cell adhesion in the range 15–36% with respect to seeded cells) compared to the ones displaying a nearly neutral behaviour (i.e., cell adhesion in the range 5–25% with respect to seeded cells). Therefore, the obtained results, despite being preliminary, suggest that the alginate type (i.e., molecular structure properties) may play a topical role in conditioning the efficiency of healing patches for bone reparation, but it has a negligible effect in the case of skin regeneration.

Integrated powdered activated carbon and quorum quenching strategy for biofouling control in industrial wastewater membrane bioreactor

Microbial quorum quenching (QQ) has been shown as a promising technology for biofouling control in membrane bioreactors (MBRs). However, QQ technology has never been applied in the industrial wastewater MBR due to the complex water properties. In this study, a type of novel alginate (polyvinyl alcohol)-powdered activated carbon-quorum quenching bacteria beads (APQ beads) was introduced, and the anti-biofouling potential was investigated in an MBR treating semi-conductor wastewater (rich in ethanolamine and diethylene glycol butyl ether). The results show that APQ strategy could significantly alleviate MBR biofouling by extending 4.5 times operating period as compared to the Control-MBR (R1) without APQ beads. The APQ strategy effectively reduced the extracellular polymeric substance (EPS) content and N-acyl homoserine lactones (AHL) concentration in biocake. EPS concentration was reduced by 33.8% and AHLs almost disappeared, probably retarded the adhesion rate of biofilm on the membrane surface, thus displayed a high biofouling mitigation potential. With APQ addition, cake layer membrane resistance was also greatly reduced by 37.22% compared to that of Control-MBR (R1). The QQ activity batch tests confirmed that the used APQ beads still displayed a high AHL-degrading activity and can be employed for long-term operation.

Formation and characteristics of alginate and anthocyanin complexes

Sodium alginates with different mannuronate to guluronate units ratio ALG1 and ALG2 were employed in the formation of insoluble complexes with anthocyanins (ATC) extracted from Vaccinium myrtilus by exploiting the electrostatic interaction between carboxylate groups of sodium alginate (ALG) and flavylium cations of ATC. Monomer composition of ALG1 and ALG2 was determined from the 13C CP-MAS NMR spectra. The amount of ATC incorporated into the complex depended on the type of ALG used, the ALG to ATC weight ratio and the total concentration of the components in the solution. ALG1 having higher amount of G-blocks was favourable in the complex formation with ATC. At ALG to ATC weight ratio being 0.4 to 1 and total concentration of 0.66 g/L, about 1.54 g of ATC per gram of ALG1 and about 1.24 g of ATC per gram of ALG2 was incorporated into the complex. Thermogravimetric analysis showed that the rate of ALG and ATC complex decomposition also depended on the type of ALG used and was 2.5 times higher for ALG2 and ATC complex compared to ALG1 and ATC complex. Furthermore, ALG/ATC complexes showed prolonged antioxidant activity when compared to ATC.

Entrapment of glutaraldehyde‐crosslinked cells from Aspergillus oryzaeIPT‐301 in calcium alginate for high transfructosylation activity

AbstractBACKGROUNDFructooligosaccharides (FOS) are sweeteners produced through the use of enzymes called fructosyltransferases (FTases) (EC 2.4.1.9). However, FTase reuse is meagre and the cost of the enzyme production is high, making FOS production economically unfeasible. In order to address these issues, this study aims to immobilize cells from Aspergillus oryzae IPT‐301, containing FTase enzyme previously glutaraldehyde‐crosslinked, by means of entrapment in calcium alginate beads. The conditions to obtain the particles, such as alginate type, mycelium mechanical dispersion, degree of crosslinking, size of the beads, and their reflections on transfructosylation activity (AT) were evaluated previously.RESULTSThe highest AT used low‐viscosity alginate solution (4.0% w/w) crosslinked with calcium chloride (0.2 mol L−1) and beads of mean diameter 2.15 mm. The entrapment conditions were complemented by conducting the reaction under different temperatures, pH values, substrate concentrations and by reusing the beads. The highest transfructosylation activities were obtained under reaction conditions of 50 °C, pH 5.5 and substrate concentration 400 g L−1.CONCLUSIONThe AT levels found with the glutaraldehyde‐crosslinked and entrapped cells in calcium alginate were ≈70% higher than the ones obtained with free cells, not glutaraldehyde‐crosslinked. Moreover, the immobilized cells (crosslinked+entrapped) retained their AT up to the third cycle of total sucrose depletion in the reaction medium, attesting to the potential use of the beads in continuous FOS production. © 2020 Society of Chemical Industry

Effects of type and concentration of alginate on microencapsulation characteristics of lime essential oil (Citrus aurantifolia) produced by extrusion-dripping methods

The extrusion-dripping method to produce alginate-calcium beads for microencapsulation of lime oil (Citrus aurantifolia) was carried out in this study. The experimental range of alginate concentration was from 1 to 4%. Above 1% alginate concentration, viscosity was pseudoplastic behavior. The size (1.52 - 1.57 mm) and sphericity (above 95%) of the beads were maximum at alginate concentration of 2 - 3%. The extrusion-dripping method was not applicable when alginate concentration was over 3.5% due to the high viscosity resulting in low sphericity. The two types of alginates with a protein content of 9% (alg1) and 2% (alg2) had the same microencapsulation yield of 73 - 74%. However, the solid recovery of alg2 (98.99%) was much higher than that of alg1 (52.71%). This is because alg2 has a higher purity and if it is used in production, it is easier to control the content of active ingredients and reduce the amount of organic waste that is harmful to the environment compared to alg1.

Effect of Sodium Alginate Type on Drug Release from Chitosan-Sodium Alginate-Based In Situ Film-Forming Tablets.

Natural polymers are promising as the carrier of matrix-based sustained release tablets but limited by their diversity in source and structure properties. Our previous studies found that chitosan (CS)- and alginate (SA)-based tablets can form self-assembled polyelectrolyte complex (PEC) film on the surface, which controlled drug release with a novel mechanism. To elucidate whether PEC-based sustained drug delivery system could weaken the influence of single-matrix material diversity on drug release behavior, taking theophylline as a drug model, the effect of SA structure properties, including viscosity, G/M ratio, SA salt type, and degree of esterification on drug release profiles, swelling, and erosion of CS-SA composite system was investigated. The results showed that the viscosity, G content, salt type, and esterification degree of SA had a remarkable influence on drug release when SA alone was used as a matrix, but little effect of these parameters on drug release was observed in CS-SA combination system. SA of low viscosity is superior in controlling drug release from CS-SA combination system. Potassium, magnesium salt of SA, and esterified SA can help form PEC of higher thickness with different swelling and erosion extent. In conclusion, this study demonstrated that drug release diversity due to SA structure difference can be well eradicated by using CS-SA combination system, which is a promising strategy to manufacture natural polymer-based products with constant quality.

Studies on Surface Morphology of Irreversible Hydrocolloid Impression Material Based on Brown Algae Type Padina sp.

This study aimed to investigate the potential of brown algae (Padina sp.). The investigation focused on surface morphology of the brown algae as preparation for making sodium alginate-based impression materials to obtain standardized impression materials. The sample was a natural sodium alginate type Padina sp. taken from South Sulawesi, Indonesia. The extraction process was conducted to attain the sodium alginate extract. Subsequently, an irreversible hydrocolloid impression material was fabricated by mixing some of the impression material composition and sodium alginate from Padina sp. The test of physical characteristic was conducted by describing the surface morphology of impression materials using scanning electron microscope (SEM). The data analysis of the SEM images showed that there was a difference in the surface morphology structure of the impression materials of the brown algae of the type of Padina sp. and standard impression materials showing a rough surface. Furthermore, the particles had no binding with other particles for all samples.

Graphene oxide in zinc alginate films: Antibacterial activity, cytotoxicity, zinc release, water sorption/diffusion, wettability and opacity.

Alginate is considered an exceptional biomaterial due to its hydrophilicity, biocompatibility, biodegradability, nontoxicity and low-cost in comparison with other biopolymers. We have recently demonstrated that the incorporation of 1% graphene oxide (GO) into alginate films crosslinked with Ca2+ cations provides antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis, and no cytotoxicity for human keratinocyte HaCaT cells. However, many other reports in literature have shown controversial results about the toxicity of GO demanding further investigation. Furthermore, the synergic effect of GO with other divalent cations with intrinsic antibacterial and cytotoxic activity such as Zn2+ has not been explored yet. Thus, here, two commercially available sodium alginates were characterised and utilized in the synthesis of zinc alginate films with GO following the same chemical route reported for the calcium alginate/GO composites. The results of this study showed that zinc release, water sorption/diffusion and wettability depended significantly on the type of alginate utilized. Furthermore, Zn2+ and GO produced alginate films with increased water diffusion, wettability and opacity. However, neither the combination of GO with Zn2+ nor the use of different types of sodium alginates modified the antibacterial activity and cytotoxicity of the zinc alginates against these Gram-positive pathogens and human cells respectively.

Dimensional Stability of Casts Derived from Three Types of Alginate at Different Times After Impression

Objective: To evaluate the dimensional changes in three types of alginate following three different delay times after casting. Material and Methods: In this laboratory study, a maxillary arch-shaped stainless steel model was prepared and three pins with similar and determined diameters and heights were placed (one at mid-line and two on the underside of the model) as reference points to compare the dimensional stability of the three types of alginates. A special metal tray was made from the main model. The main moldel was imprisoned by the metal tray, and these were kept for a specific time in a humid environment. Gypsum Type 4 was poured over the impression to obtain 90 gypsum casts for three types of alginate. The dimensions of casts obtained from each alginate were compared in two lateral and anterior-posterior dimensions, they were compared with each other, and the alginates were also compared to the main model. Results: At a time interval of 15 minutes, the dimensional accuracy of the casts obtained from the three types of alginates, with the main model in both anterior-posterior and transverse dimensions was not significantly different (p<0.05); but there was a significant difference at 60 minutes and 24 hours in both dimensions (p<0.05). Although there was no significant difference between the alginates in both dimensions and all three studied time periods, the least difference with the main model was related to Zhermack and the highest difference was related to Golchai alginates. Pairwise comparisons showed that none of the samples had a significant difference in terms of dimensions. Conclusion: The dimensional stability of alginate was a time-dependent type of alginate and had no significant effect on the dimensional accuracy of casts.

Viscoelastic properties of nanocellulose based inks for 3D printing and mechanical properties of CNF/alginate biocomposite gels

Inks for 3D printing based on cellulose nanofibrils (CNFs) or mixtures of CNFs and either cellulose nanocrystals (CNCs) or alginate were assessed by determining their viscoelastic properties i.e. complex viscosity and storage and loss moduli (G′ and G″). Two types of alginates were used, i.e. from Laminaria hyperborea stipe and Macrocystis pyrifera. Shape fidelity of 3D printed grids were qualitatively evaluated and compared to the viscoelastic properties of the inks. The biocomposite gels containing alginate were post stabilized by crosslinking with Ca2+. Mechanical properties of the crosslinked biocomposite gels were assessed. The complex viscosity, G′ and G″ of CNF suspensions increased when the solid content was increased from 3.5 to 4.0 wt%, but levelled off by further increase in CNF solid content. The complex viscosity at low angular frequency at 4 wt% was as high as 104 Pa·s. This seemed to be the necessary viscosity level for obtaining good shape fidelity of the printed structures for the studied systems. By replacing part of the CNFs with CNCs, the complex viscosity, G′ and G″ were reduced and so was also the shape fidelity of the printed grids. The changes in complex viscosity and moduli when CNFs was replaced with alginate depended on the relative amounts of CNFs/alginate. The type of alginate (from either L. hyp. stipe or M. pyr.) did not play a role for the viscoelastic properties of the inks, nor for the printed grids before post stabilization. Replacing CNFs with up to 1.5 wt% alginate gave satisfactory shape fidelity. The effect of adding alginate and subsequent crosslinking with Ca2+, strongly affected the strength properties of the gels. By appropriate choice of relative amounts of CNFs and alginate and type of alginate, the Young’s modulus and rupture strength could be controlled within the range of 30–150 kPa and 1.5–6 kg, respectively. The deformation at rupture was around 55%. The alginate from L. hyp. stipe yields higher Young’s modulus and lower syneresis compared to M. pyr. This shows that the choice of alginate plays a significant role for the mechanical properties of the final product, although it does not influence on the viscoelastic properties of the ink. The choice of alginate should be L. hyp. stipe if high strength is desired.

A material characterization and embodied energy study of novel clay-alginate composite aerogels

There is a growing incentive within the construction industry to design low energy buildings which incorporate increased levels of insulation whilst also encouraging the use of ‘green’ materials which have a low environmental impact and can contribute positively to sustainable building strategies. Silica aerogels have received an increasing amount of attention in recent years as a contemporary insulation material, but their wide-spread use is currently hindered by high costs and their high embodied energy. This research project explores the development of a composite insulation material proposed as an alternative to silica aerogel, which consists of natural components including clay and a biopolymer obtained from seaweed known as alginate. Prototype specimens have been developed and characterized in terms of their mechanical properties and microstructure allowing comparisons to be made between five alginate types, each obtained from a different seaweed source. Whilst all of the composites tested offered an improvement over the control sample, the results also demonstrated that the type of alginate used has a significant influence on the compressive strength and modulus values of the resulting composite materials. An analysis of the production process additionally demonstrated that the freeze-drying element can have a significant impact on both the environment and financial costs of producing such a material.