Higher Alginate Concentrations Research Articles

Alendronate releasing silk fibroin 3D bioprinted scaffolds for application in bone tissue engineering: Effects of alginate concentration on printability, mechanical properties and stability

3D bioprinting uses biomaterials combined with cells to develop living constructs. This study explores the optimization of natural polymers, including silk fibroin, gelatin, and alginate, as bioink for 3D bioprinting in bone tissue engineering. The physicochemical properties of the bioink were thoroughly examined, revealing high water uptake and reduced degradation rate due to the addition of silk fibroin. The compressive modulus increased with higher alginate concentration. Rheological analysis confirmed shear-thinning properties and viscoelasticity of the ink. Through meticulous parameter optimization, the ink achieved the highest print accuracy with 4 % w/v alginate content. The printed scaffolds exhibited both macro and micro porosity, making them suitable for bone tissue regeneration. Furthermore, the scaffolds remained stable in culture medium for 36 days. The optimal composition for the hydrogel was determined to be a blend of 5 % fibroin, 7 % gelatin, and 4 % alginate in equal ratios. The bioink demonstrated excellent biocompatibility and, when supplemented with alendronate, enhanced alkaline phosphatase activity in MG-63 osteoblast-like cells. This finding indicates the commitment of cells toward the osteoblastic phenotype. Overall, this study successfully optimized the bioink and bioprinting process for bone tissue engineering applications, highlighting its promising potential for future advancements in the field.

Designing an antimicrobial film for wound applications incorporating bacteriophages and ε-poly-l-lysine

Alginate-based dressings have been shown to promote wound healing, leveraging the unique properties of alginate. This work aimed to develop and characterize flexible individual and bilayered films to deliver bacteriophages (phages) and ε-Poly-l-lysine (ε-PLL). Films varied in different properties. The moisture content, swelling and solubility increased with higher alginate concentrations. The water vapour permeability, crucial in biomedical films to balance moisture levels for effective wound healing, reached optimal levels in bilayer films, indicating these will be able to sustain an ideal moist environment. The bilayer films showed improved ductility (lower tensile strength and increased elongation at break) compared to individual films. The incorporated phages maintained viability for 12 weeks under vacuum and refrigerated conditions, and their release was sustained and gradual. Antibacterial immersion tests showed that films with phages and ε-PLL significantly inhibited Pseudomonas aeruginosa PAO1 growth (>3.1 Log CFU/cm2). Particle release was influenced by the swelling degree and diffusional processes within the polymer network, providing insights into controlled release mechanisms for particles of varying size (50 nm to 6 μm) and charge. The films developed, demonstrated modulated release capabilities for active agents, and may show potential as controlled delivery systems for phages and wound healing adjuvants.

Biosynthesis of sustainable biodegradable bioplastics using alginate extracted from Padina pavonica, optimization and characterization

Plastic products requirements are increasing due to the over population. Petroleum-based plastics have a major impact on the environment including greenhouse gas emissions and water consumption. Therefore, innovations are needed to decrease the usage of petroleum-based plastics and to find eco-friendly alternatives to plastics. Macroalgal polymers have great prospects for biodegradable bioplastics manufacture. The use of seaweeds bio-polymers in bioplastics production has been shown to have a negligible effect on the food web. The brown seaweed, Padina pavonica, has been investigated for its high alginate content as a promising seaweed to produce bioplastics. Twenty experimental runs of a rotatable central composite design matrix were carried out for alginate-based bioplastic optimization. Using the desirability function, the optimal conditions for alginate-based bioplastics with the highest percentage of elongation were determined, and these conditions were confirmed experimentally. The best conditions for maximizing elongation percentage were determined to be alginate concentration 3 %, glycerol concentration 6 %, and CaCO3 concentration 6 %. Under these conditions, the highest actual value of the elongation percentage of the alginate-based bioplastics was 24.02. Moreover, biodegradation experiments were performed to assess the biodegradability of alginate-based bioplastic. It was found that 46.51 % of bioplastic was biodegraded on day 30, and full biodegradation was attained on day 45.

Alginate-waterborne polyurethane 3D bioprinted scaffolds for articular cartilage tissue engineering

Articular cartilage defects comprise a spectrum of diseases associated with degeneration or damage of the connective tissue present in particular joints, presenting progressive osteoarthritis if left untreated. In vitro tissue regeneration is an innovative treatment for articular cartilage injuries that is attracting not only clinical attention, but also great interest in the development of novel biomaterials, since this procedure involves the formation of a neotissue with the help of material support. In this work, functional alginate and waterborne polyurethane (WBPU) scaffolds have been developed for articular cartilage regeneration using 3D bioprinting technology. The particular properties of alginate-WBPU blends, like mechanical strength, elasticity and moistening, mimic the original cartilage tissue characteristics, being ideal for this application. To fabricate the scaffolds, mature chondrocytes were loaded into different alginate-WBPU inks with rheological properties suitable for 3D bioprinting. Bioinks with high alginate content showed better 3D printing performance, as well as structural integrity and cell viability, being most suitable for scaffolds fabrication. After 28 days of in vitro cartilage formation experiments, scaffolds containing 3.2 and 6.4 % alginate resulted in the maintenance of cell number in the range of 104 chondrocytes/scaffold in differentiated phenotypes, capable of synthesizing specialized extracellular matrix (ECM) up to 6 μg of glycosaminoglycans (GAG) and thus, showing a potential application of these scaffolds for in vitro regeneration of articular cartilage tissue.

Processing of Sargassum binderi Seaweed for Supplementation in Poultry Diet

Sargassum binderi has been potentially used as laying hen feed since it contains bioactive compounds useful for poultry health. In addition, the high alginate content of S. binderi has made it inappropriate for the poultry diet. Therefore, the alginate content should be reduced before its use in poultry feed. This study aimed to reduce the alginate of S. binderi for use as laying hen feed. The experiment was performed in two phases in a completely randomized design. The first phase included heated S. binderi in the autoclave and the second phase entailed the immersion of S. binderi in whiting filtrate. The treatments in the physical method contained a control group, and four treatment groups heating for 15, 30, 45, and 60 minutes. The treatments in the chemical method had a control group and four treatment groups with immersion periods of 1, 2, 3, and 4 hours. Each treatment was repeated five times, and the investigated parameters were crude protein, total dry matter, organic matter, ash, and alginate, respectively. The heating durations of S. binderi in an autoclave and different immersion periods of S. binderi in whiting filtrate did not significantly affect total dry matter, organic matter, ash, alginate, and crude protein. The results of this study showed that physical treatment (heat treatment) and chemical treatments (whiting filtrate immersion) did not have a significant effect on the alginate content, crude protein, ash, dry matter, and organic matter. Keywords: Alginate, Heating, Laying hen, Sargassum binderi, Whiting filtrate

Cross-linked Alginate Beads of Montelukast Sodium Coated with Eudragit for Chronotherapy: Statistical Optimization, In vitro and In vivo Evaluation.

Chronotherapy is the administration of medication according to the biological rhythm to maximize pharmacological effects and minimize side effects. The objective of the current investigation is to prepare delayed-release beads (DRBs) containing montelukast sodium (MKS) for chronotherapy of asthma. Delayed-release beads of alginate were prepared using a simple method, i.e., ionotropic gelation. The effect of cross-linking agents (zinc or calcium ions) and the concentration of chitosan on the properties of the beads were investigated. The prepared beads were coated by a polymer having pHindependent solubility, i.e., Eudragit RSPO and Eudragit RLPO in different ratios to achieve the desired lag time of 4-5 h. Beads were evaluated for surface morphology, practical yield, encapsulation efficiency, XRD, and in vitro release study. The pharmacokinetic study was carried out on New Zealand white male rabbits. No major differences in the drug release profile were observed between Ca++ and Zn++ crosslinked beads. However, a slight slow release was seen in the case of chitosan-reinforced beads. MKS released from cross-linked alginate beads was slightly altered with sodium alginate concentration, crosslinking time, and talc. At a higher alginate concentration, slow drug release was observed, whereas the addition of talc to alginate increased the release rate. The in vitro release study showed that the optimal formulation of DRBs has a lag time of 4.5 h, and the release at 6 h was found to be 74.9%. In vivo pharmacokinetic study of the beads showed Tmax at 7 h with an initial lag time of 4 h. When dosed at sleep time, the prepared cross-linked beads may deliver montelukast sodium required to relieve early morning symptoms in asthmatic patients.

3D-Printed Gelatin-Alginate Hydrogel Dressings for Burn Wound Healing: A Comprehensive Study.

Burn wound treatment is still a clinical challenge due to the severity of tissue damage and dehydration. Among various wound dressings, hydrogel materials have gained significant attention for burn wound treatment in clinical practice due to their soothing and moisturizing activity. In this study, 3D-printed dressings were fabricated using clinically relevant hydrogels for deep partial-thickness burn (PTB) wounds. Different ratios of gelatin and alginate mixture were 3D-printed and examined in terms of rheological behavior, shear thinning behavior, mechanical properties, degradation rate, and hydration activity to tune the hydrogel composition for best functionality. The cell-laden dressings were bioprinted to evaluate the effect of the gelatin: alginate ratio on the proliferation and growth of human dermal fibroblasts. The present findings confirm that the higher alginate content is associated with higher viscosity and Young's modulus, while higher gelatin content is associated with faster degradation and higher cell viability. Together, the 3D-printed dressing with 75% gelatin and 25% alginate showed the best tradeoff between mechanical properties, hydration activity, and in vitro biological response. Findings from in vivo test using the most effective dressing showed the positive effect of 3D-printed porous pattern on wound healing, including faster wound closure, regenerated hair follicles, and non-traumatic dressing removal compared to the non-printed hydrogel with the same composition and the standard of care. Results from this research showed that 3D-printed dressings with an adequate gelatin: alginate ratio enhanced wound healing activity for up to 7 days of moisture retention on deep PTB wounds.

Protein Stabilization by Alginate Binding and Suppression of Thermal Aggregation.

Polymers designed to stabilize proteins exploit direct interactions or crowding, but mechanisms underlying increased stability or reduced aggregation are rarely established. Alginate is widely used to encapsulate proteins for drug delivery and tissue regeneration despite limited knowledge of its impact on protein stability. Here, we present evidence that alginate can both increase protein folding stability and suppress the aggregation of unfolded protein through direct interactions without crowding. We used a fluorescence-based conformational reporter of two proteins, the metabolic protein phosphoglycerate kinase (PGK) and the hPin1 WW domain to monitor protein stability and aggregation as a function of temperature and the weight percent of alginate in solution. Alginate stabilizes PGK by up to 14.5 °C, but stabilization is highly protein-dependent, and the much smaller WW domain is stabilized by only 3.5 °C against thermal denaturation. Stabilization is greatest at low alginate weight percent and decreases at higher alginate concentrations. This trend cannot be explained by crowding, and ionic screening suggests that alginate stabilizes proteins through direct interactions with a significant electrostatic component. Alginate also strongly suppresses aggregation at high temperature by irreversibly associating with unfolded proteins and preventing refolding. Both the beneficial and negative impacts of alginate on protein stability and aggregation have important implications for practical applications.

Effect of the addition of different sodium alginates on viscoelastic, structural features and hydrolysis kinetics of corn starch gels

Corn starch gels (1:4 w:w) were made with the addition (up to 2% w/w starch basis) of sodium alginates of different average molecular sizes and nature. Rheology of the starchy gels were characterized to evaluate their viscoelasticity. Gels were subjected to in vitro digestion to estimate the effect of alginates addition on glycemic response. Tested alginates significantly decreased the value of the elastic modulus of gels. The coordination number obtained from complex modulus indicated that in general, less compact structures were obtained in the presence of alginates. These results were confirmed by scanning electron micrographs, where significant differences in the structure of alginate-corn starch gels were observed, but molecular size of alginates was not critical. Hydrolysis rate decreased with the presence of alginates in corn starch gels by interactions of alginates with leached amylose. At high alginate content, slower hydrolysis rates were determined when the most hygroscopic alginates were added.

Physicochemical properties of various alginate-based raft-forming antacid products: a comparative study

Background: Alginate-based, raft-forming antacid products with reflux suppressant activity are complex formulations expected to achieve effective raft formation and cause elimination or displacement of the acid pocket, which is typically manifested in gastroesophageal reflux disease (GERD).Methods: In the present study, six alginate-based raft-forming products commercially available in the Indian market were compared in terms of their acid neutralization properties, strength, resilience and structural and thermal properties of their rafts. Percent alginate content was also determined.Results: Rafts of products containing calcium-based antacids formed voluminous, porous and floating rafts within seconds of addition to the simulated gastric fluid (SGF) compared with the products that contained aluminium and magnesium-based antacids. Marked differences were not evident in the ANC (acid neutralization capacity) values of the various products. No correlation was observed between ANC and raft-forming capacity or duration of neutralization. Raft structures affected their neutralization profiles. Rafts of porous and absorbent nature could retain their ANC probably due to release of trapped antacids. Further, raft strengths of only two products were above the British Pharmacopoeia specification of not less than 7.5 g. Sodium alginate content was within specifications (85-115%) for three of the six products.Conclusions: Raft-forming formulations with higher alginate content and calcium-based antacids have better physicochemical properties such as ANC, neutralization profiles, raft strength and raft resilience than those with lower alginate content or those containing aluminium or magnesium-based antacids.

Oil-in-water emulsions stabilized by sodium alginate microgels

Abstract In this research, sodium alginate (ALG) microgels were prepared with different ALG concentrations, and physicochemical and emulsifying profiles of these hydrophilic microgels were comparatively analyzed. Results showed that these microgels possessed different size, hardness, and surface charge. All these microgels could stabilize an oil-in-water emulsion through the Mickering mechanisms, and smaller microgels had better emulsifying capacity. The surface hydrophobicity and interfacial tension of the microgels had no exact effects on their emulsifying behaviors. Compared with the harder microgels (prepared with high ALG concentration, e. g. 4 mg/mL), the emulsifying capacities of the softer ones (prepared with low ALG concentration, e.g. 1 mg/mL) were more sensitive to the high salt concentration (200 mM NaCl) but stable under acidic environment (pH 2.0). Our research would afford a new strategy for the manufacture and application of the novel polysaccharide-based emulsifiers.

Influence of sodium alginate on the gelatinization, rheological, and retrogradation properties of rice starch

Adding hydrocolloids into native starch is a secure and effective method of physical modification. In this study, the effect of sodium alginate (AG) on the gelatinization, rheological, and retrogradation properties of rice starch (RS) was investigated by measuring the pasting parameters, melting enthalpy (ΔH), rheological characteristic parameters, intensity ratio of 1047 cm−1 to 1022 cm−1 (R1047/1022), and relative crystallinity (RC) of RS–AG blends. Rapid visco analysis shows that AG could significantly change the gelatinization parameters of RS. Differential scanning calorimetry results show that the ΔH values of RS initially decreased in the low AG concentration range (0.10%–0.30%), but increased in the high AG concentration range (0.30%–0.50%). Dynamic rheological analysis reveals that the modulus (G′, G′′) and the loss tangent (tan δ) increased with the rise of the AG concentration from 0.10% to 0.50%. Fourier transform infrared spectroscopy and X-ray diffraction patterns collectively prove that the crystallinity of RS decreased with the addition of AG during the retrogradation periods. The interactions between AG and starch molecules in RS–AG blends were hypothesized to correlate with the aforementioned results.

How does counter-cation substitution influence inter- and intramolecular hydrogen bonding and electrospinnability of alginates

Despite numerous applications of nanofibrous alginate (Alg) mat, its facile fabrication via electrospinning is still challenging. The low alginate content compared to the carrier polymer and existence of impurities are the main drawbacks of existing approaches. The purpose of this research is both to study and improve alginate electrospinnability by focusing on the effect of inter- and intramolecular hydrogen bonding. Based on hard and soft acids and bases (HSAB) theory, the Na+ cations (carboxylate counter-cation) were substituted with a harder acid, Li+ cation, to increase the strength of ionic interaction and decrease the density of hydrogen bonding. Viscosity and electrical conductivity measurements as well as FTIR and 1H NMR revealed a lower intramolecular hydrogen bonding density in Li-Alg. SEM images showed improvement of alginate electrospinnability for Li-Alg compared to the salts of Na-Alg and K-Alg. This study sheds more light on underlying reasons hindering alginate electrospinning and introduces a simple method for fabrication of nanofibers with high alginate content.

Mucoadhesive wafers composed of binary polymer blends for sublingual delivery and preservation of protein vaccines

The objective of this study is to develop a simple biopolymer platform of mucoadhesive wafers that enables effective sublingual delivery and preservation of protein vaccines. The wafers were composed of a series of binary polymer blends of carboxymethylcellulose (CMC) and alginate (ALG). Varying the ratio between CMC and ALG resulted in wafers with different microstructure, mechanical properties, disintegration time, and release kinetics of model compounds. Wafers with high CMC content were highly mucoadhesive to sublingual mucosal tissue and could withstand extensive washing, leading to improved protein permeation into the tissue. On the other hand, wafers with high ALG content were not only mechanically robust, but also able to protect a model enzyme (β-galactosidase) against lyophilization and heat challenge. HIV gp140 protein loaded in wafers of the optimal composition could be stored and transported without cold chain, while maintaining antigen-specific immunogenicity after sublingual vaccination in mice. These findings established that the CMC/ALG binary blend polymer wafers have the potential to improve the sublingual delivery and storage stability of protein-based vaccines.

Physicochemical and swelling properties of composite gel microparticles based on alginate and callus cultures pectins with low and high degrees of methylesterification

Composite gel microparticles based on alginate and callus culture pectins with low and high degrees of methylesterification or apple pectin were produced. By varying the chemical composition of the pectic samples and the ratio of alginate to pectin, the gel strength, morphology, and swelling properties of composite microparticles can be altered. The inclusion of increasing concentrations of alginate in gel formulations promoted an increase in the microparticle gel strength and the formation of a smoother surface microrelief independently of the pectin chemical composition. Microparticles based on the pectin with a low degree of methylesterification (DM) and a higher concentration of alginate exhibited an increased swelling degree in the simulated digestive fluids. Microparticles based on the pectin with high DM and low alginate concentration were destroyed in the simulated intestinal fluid within 1 h due to the low Ca2+ content, gel strength, and grooved and rough surface of these microparticles. An increase in alginate concentration of gel formulations based on pectin with high DM led to increased stability of the microparticles in the simulated intestinal and colonic fluids due to increased Ca2+ content, microparticle gel strength and degree of crosslinking.

In vitro digestion behavior of (W1/O/W2) double emulsions incorporated in alginate hydrogel beads: Microstructure, lipolysis, and release

The aim of the present study was to illuminate the digestion behavior of (W1/O/W2) double emulsions incorporated in alginate hydrogel beads using a simulated in vitro gastrointestinal tract model. Swelling study and fluorescence microscopy observation showed that compact beads gradually became swollen and heterogeneous during intestinal digestion, and the swelling extent was dependent on the alginate concentration. Laser diffractometry and flow cytometry were conducted to characterize the oil droplet population released from beads. The incorporated oil droplets were gradually released from the hydrogel matrix along with the swelling of beads, which might prevent the coalescence. The microstructure transformation from (W1/O/W2) double emulsion droplets to empty emulsion droplets could occur within beads without the requirement of the droplet release from beads, and oil droplets were mainly released from beads in the form of empty emulsion droplets at high alginate concentration. The release profiles of free fatty acids indicated that the lipolysis of incorporated double emulsions was gentler than that of double emulsions. Furthermore, the lipolysis was delayed at high alginate concentration. The incorporation had no influence on the cumulative release amount of encapsulated hydrophilic dye from double emulsions into digestive fluid. These results provided useful data for the design of (W1/O/W2) double emulsions-based delivery system with controlled lipolysis and adequate release of encapsulated hydrophilic active ingredients.

Development of high alginate comprised hydrogels for removal of Pb(II) ions

Natural polymers have been used for the development of innovative hydrogels in order to improve their properties, principally, their swelling capacity. Herein, an alginate-acrylamide hydrogel was developed by employing a high proportion of alginate via a free-radical polymerization method. Water soluble alginate was extracted from Laminaria digitata and used for the development of alginate hydrogels in order to obtain superior hydrogels. Water adsorption capacity (swelling) and diffusion kinetics performance of the hydrogels were investigated. The hydrogel containing a high amount of alginate had the highest swelling capacity (109.3 g/g) and diffusion coefficient (3.5116 cm2 s−1), which has high water absorption capacity. This hydrogel exhibited super case II diffusion and other hydrogels showed anomalous diffusion water transport phenomena. Additionally, the hydrogel with high alginate content, showed high adsorption of Pb(II) ions. Owing to their swelling and adsorption capacity of Pb(II) ions, this hydrogel could serve as a strong absorbent material in water purification and agricultural applications.

Rheological Properties of Alginate–Essential Oil Nanodispersions

Due to its favorable structural properties and biocompatibility, alginate is recognized as a suitable versatile biopolymer for use in a broad range of applications ranging from drug delivery, wound healing, tissue engineering, and food formulations such as nanodispersions. Rheological analysis plays a crucial role in the design of suitable nanoemulsion based coatings. Different essential oil and alginate nanodispersion compositions stabilized by Tween 80 were analyzed for rheological and conductometric properties. The results confirmed that the nanoformulations shared a pseudoplastic non-Newtonian behavior that was more evident with higher alginate concentrations (2%). Nanodispersions made of alginate and essential oil exhibited a slight thixotropic behavior, demonstrating the aptitude to instantaneously recover from the applied stress or strain. Oscillatory frequency sweep tests showed a similar fluid-like behavior for 1% and 2% alginate nanodispersions. Finally, it was demonstrated that advantages coming with the use of the essential oil are added to the positive aspects of alginate with no dramatic modification on the flow behavior.

Development of mucoadhesive sericin/alginate particles loaded with ibuprofen for sustained drug delivery

A sericin/alginate blend was successfully applied as a matrix for incorporation of ibuprofen. This provided a sustained release formulation, which could improve the therapeutic efficacy of ibuprofen and patient adherence to treatment. Sericin increased the proportion of drug incorporated into the particles (i.e., the drug incorporation efficiency), with incorporation rates between 73.01%±1.70% and 94.15%±4.21%. Alginate affected the drug release, and the particles with the maximum alginate mass fraction tested (2.8%) showed sustained release through a dissolution mechanism, reaching equilibrium after about 1400min. Analysis of the incorporation efficiency and the drug release time showed the best results were for formulations with a high alginate content. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis were used for particle characterization to study the incorporation of ibuprofen. The particle size range was 0.80±0.13 to 1.08±0.11mm. The size distributions of sericin-containing particles showed a good fit with the Gaussian model.

Alginate-Mediated Mineralization for Ultrafine Hydroxyapatite Hybrid Nanoparticles.

The good bioactivity of hydroxyapatite (HA) makes it become a popular biomaterial, and so, the synthesis of HA has attracted much attention. However, a simple method to prepare well-dispersive and ultrafine HA nanoparticles (NPs) still needs to be explored. Here, needle-like hybrid HA NPs were synthesized in the presence of alginate (ALG) and the mechanism of ALG regulation on forming HA/ALG hybrid NPs was investigated. The size and crystallinity of HA/ALG NPs could be controlled simply by varying the amount of ALG. With a higher concentration of ALG, the size of HA/ALG NPs reduced and their dispersity was further improved. The assembly with ca. 3-6 nm thick nanoneedles was discernible in HA/ALG NPs. The results collected by Ca2+ concentration, pH, and conductometric measurements further provided the supportive data for ALG inhibition of calcium phosphate compound formation and thus modulation of HA crystallization. In addition, the good biocompatibility of synthesized HA/ALG NPs was indicated from the results of CCK-8 assays and CLSM observations after cultured with L929 cells. The needle-like HA NPs are promising for varied biomedical purposes, and their potential application as drug carriers would be further studied.