A review of extractions of seaweed hydrocolloids: Properties and applications

Agar-gelatin Maillard conjugates used for Pickering emulsion stabilization

A few protein- and polysaccharide-based particles have shown promising potential as stabilizers in multi-phase food systems. By incorporating polymer-based particles and modifying the wettability of colloidal systems, it is possible to create particle-stabilized emulsions with excellent stability. A Pickering emulsifier (AGMs) with better emulsifying properties was obtained by the Maillard reaction between acid-hydrolysed agar and gelatin. Laser confocal microscopy imaging revealed that AGMs particles can be used as solid emulsifiers to produce a typical O/W Pickering emulsion, with AGMs adsorbing onto the droplet surface to form a dense interfacial layer. Cryo-scanning electron microscopy analysis showed that AGMs self-assembled into a three-dimensional network structure, which prevented droplets aggregation through strong spatial site resistance, contributing to emulsion stabilization. These emulsions exhibited stability within a pH range of 1 to 11, NaCl concentrations not exceeding 300 mM, and at temperatures below 80 °C. The most stable emulsion oil-water ratio was 6:4 at a particle concentration of 0.75 % (w/v). AGMs-stabilized Pickering emulsion was utilized to create a semi-solid mayonnaise as a replacement for hydrogenated oil. Rheological analysis demonstrated that low-fat mayonnaise stabilized with AGMs exhibited similar rheological behavior to traditional mayonnaise, offering new avenues for the application of Pickering emulsions in the food industry.

Seaweed-based biopolymers for food packaging: A sustainable approach for a cleaner tomorrow

With the increasing environmental and health consequences of uncontrolled plastic use, the scientific community is progressively gravitating toward biodegradable and ecofriendly packaging alternatives. Seaweed polysaccharides have attracted attention recently because of their biodegradability, nontoxicity, antioxidant properties, and superior film-forming ability. However, it has some limitations for packaging applications, such as low tensile strength, water solubility, and only modest antimicrobial properties. The incorporation of biopolymers, nanoparticles, or organic active ingredients enhances these characteristics. This review encapsulates the contemporary research landscape pivoting around the role of seaweed polysaccharides in the development of bioplastics, active packaging solutions, edible films, and protective coatings. A meticulous collation of existing literature dissects the myriad food application avenues for these marine biopolymers, emphasizing their multifaceted physical, mechanical, thermal, and functional attributes, including antimicrobial and antioxidant. A key facet of this review spotlights environmental ramifications by focusing on their biodegradability, reinforcing their potential as a beacon of sustainable innovation. This article delves into the prevalent challenges that stymie large-scale adoption and commercialization of seaweed-centric packaging, offering a comprehensive perspective on this burgeoning domain.

Chemical and Antioxidant Properties of Solvent and Enzyme-Assisted Extracts of Fucus vesiculosus and Porphyra dioica

Extraction strategies impact the efficiency and nature of extracted compounds. This work assessed the chemical composition and antioxidant capacity of ethanolic, hydroethanolic, and aqueous versus enzyme-assisted extracts (isolated or with the sequential use of alcalase®, cellulase®, and viscozyme®) of the macroalgae Fucus vesiculosus (brown, Phaeophyceae) and Porphyra dioica (red, Rhodophyta. For both macroalgae, enzyme-assisted extraction (EAE) was the most efficient process compared to solvent-assisted extraction (SAE), independent of solvent. Fucus vesiculosus extraction yields were higher for EAE than for SAE (27.4% to 32.2% and 8.2% to 30.0%, respectively). Total phenolics content (TPC) was at least 10-fold higher in EAE extracts (229.2 to 311.3 GAE/gextract) than in SAE (4.34 to 19.6 GAE/gextract) counterparts and correlated well with antioxidant capacity (ABTS and ORAC methods), with EAE achieving values up to 8- and 2.6-fold higher than those achieved by SAE, respectively. Porphyra dioica followed F. vesiculosus's trend for extraction yields (37.5% to 51.6% for EAE and 5.7% to 35.1% for SAE), TPC, although of a lower magnitude, (0.77 to 8.95 GAE/gextract for SE and 9.37 to 14.73 GAE/gextract for EAE), and antioxidant capacity. Aqueous extracts registered the highest DPPH values for both macroalgae, with 2.3 µmol TE/gextract and 13.3 µmol TE/gextract for F. vesiculosus and P. dioica, respectively. EAE was a more efficient process in the extraction of soluble protein and reducing sugars in comparison to SAE. Furthermore, an improved effect of enzyme-assisted combinations was observed for almost all analyzed parameters. This study shows the promising application of enzyme-assisted extraction for the extraction of valuable compounds from F. vesiculosus and P.dioica, making them excellent functional ingredients for a wide range of health and food industrial applications.

A High Andean Hydrocolloid Extracted by Microatomization: Preliminary Optimization in Aqueous Stability

Aqueous suspensions rely on electrostatic interactions among suspended solids, posing a significant challenge to maintaining stability during storage, particularly in the food and pharmaceutical industries, where synthetic stabilizers are commonly employed. However, there is a growing interest in exploring new materials derived from natural and environmentally friendly sources. This study aimed to optimize the stability parameters of a novel Altoandino Nostoc Sphaericum hydrocolloid (NSH) extracted via micro atomization. Suspensions were prepared by varying the pH, gelatinization temperature and NSH dosage using a 23 factorial arrangement, resulting in eight treatments stored under non-controlled conditions for 20 days. Stability was assessed through turbidity, sedimentation (as sediment transmittance), ζ potential, particle size, color and UV-Vis scanning. Optimization of parameters was conducted using empirical equations, with evaluation based on the correlation coefficient (R2), average relative error (ARE) and X2. The suspensions exhibited high stability throughout the storage period, with optimized control parameters identified at a pH of 4.5, gelatinization temperature of 84.55 °C and NSH dosage of 0.08 g/L. Simulated values included turbidity (99.00%), sedimentation (72.34%), ζ potential (-25.64 mV), particle size (300.00 nm) and color index (-2.00), with simulated results aligning with practical application. These findings suggest the potential use of NSH as a substitute for commercial hydrocolloids, albeit with consideration for color limitations that require further investigation.

Insights on updates in sodium alginate/MXenes composites as the designer matrix for various applications: A review

Advancements in two-dimensional materials, particularly MXenes, have spurred the development of innovative composites through their integration with natural polymers such as sodium alginate (SA). Mxenes exhibit a broad specific surface area, excellent electrical conductivity, and an abundance of surface terminations, which can be combined with SA to maximize the synergistic effect of the materials. This article provides a comprehensive review of state-of-the-art techniques in the fabrication of SA/MXene composites, analyzing the resulting structural and functional enhancements with a specific focus on advancing the design of these composites for practical applications. A detailed exploration of SA/MXene composites is provided, highlighting their utility in various sectors, such as wearable electronics, wastewater treatment, biomedical applications, and electromagnetic interference (EMI) shielding. The review identifies the unique advantages conferred by incorporating MXene in these composites, examines the current challenges, and proposes future research directions to understand and optimize these promising materials thoroughly. The remarkable properties of MXenes are emphasized as crucial for advancing the performance of SA-based composites, indicating significant potential for developing high-performance composite materials.

Arabinoxylan-based psyllium seed hydrocolloid: Single-step aqueous extraction and use in tissue engineering

Biomacromolecules derived from natural sources offer superior biocompatibility, biodegradability, and water-holding capacity, which make them promising scaffolds for tissue engineering. Psyllium seed has gained attention in biomedical applications recently due to its gel-forming ability, which is provided by its polysaccharide-rich content consisting mostly of arabinoxylan. This study focuses on the extraction and gelation of Psyllium seed hydrocolloid (PSH) in a single-step water-based protocol, and scaffold fabrication using freeze-drying method. After characterization of the scaffold, including morphological, mechanical, swelling, and protein adsorption analyses, 3D cell culture studies were done using NIH-3 T3 fibroblast cells on PSH scaffold, and cell viability was assessed using Live/Dead and Alamar Blue assays. Starting from day 1, high cell viability was obtained, and it reached 90 % at the end of 15-day culture period. Cellular morphology on PSH scaffold was monitored via SEM analysis; cellular aggregates then spheroid formation were observed throughout the study. Collagen Type-I and F-actin expressions were followed by immunostaining revealing a 9- and 10-fold increase during long-term culture. Overall, a single-step and non-toxic protocol was developed for extraction and gelation of PSH. Obtained results unveiled that PSH scaffold provided a favorable 3D microenvironment for cells, holding promise for further tissue engineering applications.

Chemical characterization of polysaccharides from Gracilaria gracilis from Bizerte (Tunisia)

Polysaccharides were extracted from Gracilaria gracilis collected from Manzel Jemil Lake in Bizerte Tunisia, with two different solvents (water and NaOH 0.3 M). Different assays were performed on samples (total sugars, neutral sugars, uronic acids, anhydrogalactose, proteins, sulphates, pyruvates), followed by high performance anion-exchange chromatography (HPAEC) to observe the monosaccharide composition, high pressure size exclusion chromatography with multi-angle laser light scattering (HPSEC-MALS) to obtain the molecular mass, Fourier transform infrared spectroscopy (FTIR), and 1D and 2D nuclear magnetic resonance (NMR) to access to structural data. Results have shown that the polysaccharide extracted from Gracilaria gracilis collected from Manzel Jemil Lake in Bizerte Tunisia, is of agar type but with high molecular mass and some original structural features. Hence, the sample was found to contain 9 % of pyruvate groups and is partly sulphated at the C4 of β-d-galactose and methylated on C2 of anhydro-α-l-galactose. The polymer from G. gracilis from Bizerte thus presents a never described structure that could be interesting for further rheological or biological activities applications.

Physicochemical and Functional Properties of Citrullus mucosospermus, Citroides, and Moringa oleifera Seeds' Hydrocolloids

Hydrocolloids form gel-like structures when dispersed in water and have garnered significant attention for their diverse applications in food, pharmaceuticals, and other industries. The extraction of hydrocolloids from natural sources, such as seeds, presents an intriguing avenue due to the potential diversity in composition and functionality. Utilising seeds from Citrullus lanatus mucosospermus, lanatus citroides, and Moringa aligns with the growing demand for natural and sustainable ingredients in various industries. This research investigated hydrocolloids extracted from Citrullus mucosospermus (CMS), lanatus citroides, and Moringa oleifera seeds, highlighting their versatile physicochemical and functional attributes. Hydrocolloids were extracted from the seeds and subjected to analysis of their proximate composition, particle size distribution, and interfacial tension using the hot water extraction method. Protein content variation was observed among the raw oilseed (CMS, Citroides, and Moringa oleifera) flours. The protein content of the hydrocolloids surpassed that of raw oilseeds, significantly enhancing the amino acid profile. Furthermore, the hydrocolloid ash contents ranged from 4.09% to 6.52% w/w dry weight, coupled with low fat levels. The particle size distribution revealed predominantly fine particles with a narrow size distribution. All three hydrocolloids demonstrated remarkable oil- and water-holding capacities, highlighting their suitability for efficient stabilisation and emulsification in food formulations. These findings suggest the potential utilisation of these hydrocolloids as valuable ingredients across a spectrum of applications, encompassing food, pharmaceuticals, and industry, thus contributing to the development of sustainable and functional products. The unique attributes presented herein mark a noteworthy advancement in the understanding and application of novel hydrocolloids from CMS, Citroides, and Moringa oleifera.

Intelligent carboxymethyl cellulose composite films containing Garcinia mangostana shell anthocyanin with improved antioxidant and antibacterial properties

In this study, anthocyanin from Garcinia mangostana shell extract (Mse) was used as pH indicator to prepare intelligent carboxymethyl cellulose (CMC) based composite films. The structure and properties of the CMC-based composite films were characterized and discussed in detail. Results showed that the CMC-based composite films with Mse had excellent mechanical, antibacterial and antioxidant abilities. Especially, the carboxymethyl cellulose/corn starch/Garcinia mangostana shell extract (CMC/Cst/Mse) composite film had best mechanical properties (20.62 MPa, 4.06 % EB), lowest water vapor permeability (1.80 × 10-12 g·cm/(cm2·s·Pa)), excellent ultraviolet (UV) blocking performance, and the best antibacterial and antioxidant abilities. The pH sensitivity of composite films which had Mse obviously changed with time when the fish freshness was monitored at 25 °C. Given the good pH sensitivity of the composite films, it had significant potential for application of intelligent packaging film as a food packaging material to indicate the freshness of fish.

Three-Dimensional Printing of Red Algae Biopolymers: Effect of Locust Bean Gum on Rheology and Processability

Seaweeds, rich in high-value polysaccharides with thickening/gelling properties (e.g., agar, carrageenan, and alginate), are extensively used in the food industry for texture customization and enhancement. However, conventional extraction methods for these hydrocolloids often involve potentially hazardous chemicals and long extraction times. In this study, three red seaweed species (Chondrus crispus, Gelidium Corneum, and Gracilaria gracilis) commercialized as food ingredients by local companies were chosen for their native gelling biopolymers, which were extracted using water-based methodologies (i.e., (1) hydration at room temperature; (2) stirring at 90 °C; and (3) centrifugation at 40 °C) for production of sustainable food gels. The potential use of these extracts as bioinks was assessed employing an extrusion-based 3D printer. The present work aimed to study the gelation process, taken place during printing, and assess the effectiveness of the selected green extraction method in producing gels. To improve the definition of the printed gel, two critical printing parameters were investigated: the addition of locust bean gum (LBG) at different concentrations (0, 0.5, 1, 1.5, 2, and 2.5%) and printing temperature (30, 40, 60, and 80 °C). Rheological results from a controlled-stress rheometer indicated that gels derived from G. corneum and G. gracilis exhibited a lower gel strength (lower G' and G″) and excessive material spreading during deposition (lower viscosity) than C. crispus. Thus, G' was around 5 and 70 times higher for C. crispus gels than for G. corneum and G. gracilis, respectively. When increasing LBG concentration (0.5 to 2.5% w/w) and lowering the printing temperature (80 to 30 °C), an enhanced gel matrix definition for G. corneum and G. gracilis gels was found. In contrast, gels from C. crispus demonstrated greater stability and were less influenced by these parameters, showcasing the potential of the seaweed to develop sustainable clean label food gels. Eventually, these results highlight the feasibility of using algal-based extracts obtained through a green procedure as bioinks where LBG was employed as a synergic ingredient.

Stability in Aqueous Solution of a New Spray-Dried Hydrocolloid of High Andean Algae Nostoc sphaericum

There is a growing emphasis on seeking stabilizing agents with minimal transformation, prioritizing environmentally friendly alternatives, and actively contributing to the principles of the circular economy. This research aimed to assess the stability of a novel spray-dried hydrocolloid from high Andean algae when introduced into an aqueous solution. Nostoc sphaericum freshwater algae were subject to atomization, resulting in the production of spray-dried hydrocolloid (SDH). Subsequently, suspension solutions of SDH were meticulously prepared at varying pH levels and gelling temperatures. These solutions were then stored for 20 days to facilitate a comprehensive evaluation of their stability in suspension. The assessment involved a multifaceted approach, encompassing rheological analysis, scrutiny of turbidity, sedimentation assessment, ζ-potential, and measurement of particle size. The findings from these observations revealed that SDH exhibits a dilatant behavior when in solution, signifying an increase in with higher shear rate. Furthermore, it demonstrates commendable stability when stored under ambient conditions. SDH is emerging as a potential alternative stabilizer for use in aqueous solutions due to its easy extraction and application.

Structure-activity relationships of bioactive polysaccharides extracted from macroalgae towards biomedical application: A review

Macroalgae are valuable and structurally diverse sources of bioactive compounds among marine resources. The cell walls of macroalgae are rich in polysaccharides which exhibit a wide range of biological activities, such as anticoagulant, antioxidant, antiviral, anti-inflammatory, immunomodulatory, and antitumor activities. Macroalgae polysaccharides (MPs) have been recognized as one of the most promising candidates in the biomedical field. However, the structure-activity relationships of bioactive polysaccharides extracted from macroalgae are complex and influenced by various factors. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with MPs. In line with these challenges and knowledge gaps, this paper summarized the structural characteristics of marine MPs from different sources and relevant functional and bioactive properties and particularly highlighted those essential effects of the structure-bioactivity relationships presented in biomedical applications. This review not only focused on elucidating a particular action mechanism of MPs, but also intended to identify a novel or potential application of these valued compounds in the biomedical field in terms of their structural characteristics. In the last, the challenges and prospects of MPs in structure-bioactivity elucidation were further discussed and predicted, where they were emphasized on exploring modern biotechnology approaches potentially applied to expand their promising biomedical applications.

Temperature-sensitive multifunctional intelligent responsive hydrogel based on carboxymethyl agarose and N-isopropylacrylamide: Controlled drug release and accelerated wound healing

Wound healing remains challenging due to posttraumatic pain. At present, most wound dressings ignore the importance of wound pain. In this study, a temperature-sensitive multifunctional intelligent hydrogel patch (CPAG) containing lidocaine has developed for wound healing. CPAG hydrogel was prepared by grafting N-isopropylacrylamide and acrylamide onto carboxymethyl agarose (CMA) modified by agarose and encapsulating gallic acid and lidocaine. FTIR, 1H NMR spectroscopy, SEM and rheology were used to investigate its structure and temperature-sensitive properties. The contraction force generated by the temperature response characteristics of CPAG at 30 °C can accelerate wound healing. In vitro release assays demonstrated that CPAG directly controlled the same amount of lidocaine release at different temperatures through the competition between polymer-polymer and polymer-water interactions. In addition, MTT, H&E staining and stimulation test further proved its biological safety. The pain behavior study showed that the pain inhibition rates of the lidocaine cataplasms and LID@CPAG were 51.16 % and 67.83 %, respectively. In vitro and in vivo studies have shown that compared with the blank group, the bleeding volume of LID@CPAG decreased by 54.3 %, and the wound healing rate reached 97 %. CPAG hydrogel can play a comprehensive therapeutic role in accelerating wound closure by controlling drug release, analgesia, antioxidation and hemostasis.

An Overview of Recent Developments in the Management of Burn Injuries

According to the World Health Organization (WHO), around 11 million people suffer from burns every year, and 180,000 die from them. A burn is a condition in which heat, chemical substances, an electrical current or other factors cause tissue damage. Burns mainly affect the skin, but can also affect deeper tissues such as bones or muscles. When burned, the skin loses its main functions, such as protection from the external environment, pathogens, evaporation and heat loss. Depending on the stage of the burn, the patient's condition and the cause of the burn, we need to choose the most appropriate treatment. Personalization and multidisciplinary collaboration are key to the successful management of burn patients. In this comprehensive review, we have collected and discussed the available treatment options, focusing on recent advances in topical treatments, wound cleansing, dressings, skin grafting, nutrition, pain and scar tissue management.

Improving the thermostability of a novel PL-6 family alginate lyase by rational design engineering for industrial preparation of alginate oligosaccharides

Alginate is degraded into alginate oligosaccharides with various biological activities by enzymes. However, the thermostability of the enzyme limits its industrial application. In this study, a novel PL-6 alginate lyase, AlyRm6A from Rhodothermus marinus 4252 was expressed and characterized. In addition, an efficient comprehensive strategy was proposed, including automatic design of heat-resistant mutants, multiple computer-aided ΔΔGfold value calculation, and conservative analysis of mutation sites. AlyRm6A has naturally high thermostability. Compared with the WT, T43I and Q216I kept their original activities, and their half-lives were increased from 3.68 h to 4.29 h and 4.54 h, melting point temperatures increased from 61.5 °C to 62.9 °C and 63.5 °C, respectively. The results of circular dichroism showed that both the mutants and the wild type had the characteristic peaks of β-sheet at 195 nm and 216 nm, which indicated that there was no significant effect on the secondary structure of the protein. Molecular dynamics simulation (MD) analyses suggest that the enhancement of the hydrophobic interaction network, improvement of molecular rigidity, and denser structure could improve the stability of AlyRm6A. To the best of our knowledge, our findings indicate that AlyRm6A mutants exhibit the highest thermostability among the characterized PL-6 alginate lyases, making them potential candidates for industrial production of alginate oligosaccharides.

Seaweed polysaccharide nanocomposite films: A review

A million tonnes of plastic produced each year are disposed of after single use. Biodegradable polymers have become a promising material as an alternative to petroleum-based polymers. Utilising biodegradable polymers will promote environmental sustainability which has emerged with potential features and performances for various applications in different sectors. Seaweed-derived polysaccharides-based composites have been the focus of numerous studies due to the composites' renewability and sustainability for industries (food packaging and medical fields like tissue engineering and drug delivery). Due to their biocompatibility, abundance, and gelling ability, seaweed derivatives such as alginate, carrageenan, and agar are commonly used for this purpose. Seaweed has distinct film-forming characteristics, but its mechanical and water vapour barrier qualities are weak. Thus, modifications are necessary to enhance the seaweed properties. This review article summarises and discusses the effect of incorporating seaweed films with different types of nanoparticles on their mechanical, thermal, and water barrier properties.

A Review on the Cytotoxicity and Antibacterial Effect of Marine Organisms of Persian Gulf

Marine organisms contain several natural products and bioactive compounds, including hydrolyzed proteins, antioxidant peptides, gelatin, collagen, ω-3 unsaturated fatty acids, vitamin A, vitamin D, calcium phosphate, hydroxyapatite, chitosan, lectin, and various toxins. They can inhibit diverse diseases, be used in pharmaceutical compounds, or as antibiotics and pigments. In this regard, these microorganisms are of crucial medicinal and economical importance. Thanks to new technologies and advanced laboratory methods, bioactive compounds can be extracted from aquatic organisms. In this review study, the cytotoxicity (IC50) and antibacterial effect of various extracts from marine organisms of the Persian Gulf are explored, compiled, and compared. Due to their easy accessibility, most of the studies are green, red, and brown algae.

Bioaccumulation of titanium dioxide nanoparticles in green (Ulva sp.) and red (Palmaria palmata) seaweed

A bioaccumulation study in red (Palmaria palmata) and green (Ulva sp.) seaweed has been carried out after exposure to different concentrations of citrate-coated titanium dioxide nanoparticles (5 and 25 nm) for 28 days. The concentration of total titanium and the number and size of accumulated nanoparticles in the seaweeds has been determined throughout the study by inductively coupled plasma mass spectrometry (ICP-MS) and single particle-ICP-MS (SP-ICP-MS), respectively. Ammonia was used as a reaction gas to minimize the effect of the interferences in the 48Ti determination by ICP-MS. Titanium concentrations measured in Ulva sp. were higher than those found in Palmaria palmata for the same exposure conditions. The maximum concentration of titanium (61.96 ± 15.49 μg g-1) was found in Ulva sp. after 28 days of exposure to 1.0 mg L-1 of 5 nm TiO2NPs. The concentration and sizes of TiO2NPs determined by SP-ICP-MS in alkaline seaweed extracts were similar for both seaweeds exposed to 5 and 25 nm TiO2NPs, which indicates that probably the element is accumulated in Ulva sp. mainly as ionic titanium or nanoparticles smaller than the limit of detection in size (27 nm). The implementation of TiO2NPs in Ulva sp. was confirmed by electron microscopy (TEM/STEM) in combination with energy dispersive X-Ray analysis (EDX).

Algal Phycocolloids: Bioactivities and Pharmaceutical Applications

Seaweeds are abundant sources of diverse bioactive compounds with various properties and mechanisms of action. These compounds offer protective effects, high nutritional value, and numerous health benefits. Seaweeds are versatile natural sources of metabolites applicable in the production of healthy food, pharmaceuticals, cosmetics, and fertilizers. Their biological compounds make them promising sources for biotechnological applications. In nature, hydrocolloids are substances which form a gel in the presence of water. They are employed as gelling agents in food, coatings and dressings in pharmaceuticals, stabilizers in biotechnology, and ingredients in cosmetics. Seaweed hydrocolloids are identified in carrageenan, alginate, and agar. Carrageenan has gained significant attention in pharmaceutical formulations and exhibits diverse pharmaceutical properties. Incorporating carrageenan and natural polymers such as chitosan, starch, cellulose, chitin, and alginate. It holds promise for creating biodegradable materials with biomedical applications. Alginate, a natural polysaccharide, is highly valued for wound dressings due to its unique characteristics, including low toxicity, biodegradability, hydrogel formation, prevention of bacterial infections, and maintenance of a moist environment. Agar is widely used in the biomedical field. This review focuses on analysing the therapeutic applications of carrageenan, alginate, and agar based on research highlighting their potential in developing innovative drug delivery systems using seaweed phycocolloids.

Modification, 3D printing process and application of sodium alginate based hydrogels in soft tissue engineering: A review

Sodium alginate (SA) is an inexpensive and biocompatible biomaterial with fast and gentle crosslinking that has been widely used in biological soft tissue repair/regeneration. Especially with the advent of 3D bioprinting technology, SA hydrogels have been applied more deeply in tissue engineering due to their excellent printability. Currently, the research on material modification, molding process and application of SA-based composite hydrogels has become a hot topic in tissue engineering, and a lot of fruitful results have been achieved. To better help readers have a comprehensive understanding of the development status of SA based hydrogels and their molding process in tissue engineering, in this review, we summarized SA modification methods, and provided a comparative analysis of the characteristics of various SA based hydrogels. Secondly, various molding methods of SA based hydrogels were introduced, the processing characteristics and the applications of different molding methods were analyzed and compared. Finally, the applications of SA based hydrogels in tissue engineering were reviewed, the challenges in their applications were also analyzed, and the future research directions were prospected. We believe this review is of great helpful for the researchers working in biomedical and tissue engineering.

Synthesis, characterization, antibacterial and emulsifying properties of agar benzoate

Agar benzoate (AB) with different degrees of substitution (DS) was synthesized by the esterification of agar and benzoic anhydride in aqueous solution. The DS could be regulated by adjusting composition ratio, pH, and temperature. Its chemical structure was determined by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). ¹³C NMR spectrum of the AB suggested the main substitution occurred at the C-6 in the d-galactopyranose. Cryo-scanning electron microscopy (Cryo-SEM) showed that the aperture of AB was larger than that of agar. The thermal performance of AB decreased slightly, but this did not affect its performance. AB showed the highest relative antibacterial activity against Escherichia coli, S. aureus and Alternaria alternata, reaching 100 % (AB 20 g/L), 100 % (AB 40 g/L) and 19.35 % (7 d incubation), respectively. Moreover, the obtained AB possessed good emulsion stability. These antibacterial AB have broad application prospects in the field of fruit and vegetable preservation.

Super absorbent glutaric anhydride-modified agar: Structure, properties, and application in biomaterial delivery

Agar was modified with glutaric anhydride (GA) in this study to expand its application in food and medicine. Glutaric anhydride-modified agar (GAR) can maintain high gel strength (1247.4 g/cm²) and improved transparency (82.7 %). The esterified agar formed by GA further formed a cross-linking molecule structure by increasing the reaction temperature. Notably, excellent freeze-thaw stability (24.1 %) and swelling property (3116.6 %) of GAR indicated that the carboxyl-terminal of modified agar improves its affinity with water. Therefore, satisfactory water permeability and expansive stone enable agar films to achieve high water absorption. Furthermore, GAR films exhibit a specific absorption capacity of tetracycline hydrochloride in weak acid solution, thereby suggesting its potential application as a sustainable drug delivery carrier. Finally, the structure of the modified agar was analyzed to explain the mechanism of binding water. Cryo-scanning electron microscopy (SEM) depicted the porous structure of the agar gel responsible for swelling, drug loading, and release. Low-field NMR results showed that GA improves agar gel's binding and free water content. According to our research results, these GAR hydrogel membranes with excellent properties have the potential to be used as effective drug delivery materials.

Pyropia yezoensis-derived porphyran attenuates acute and chronic colitis by suppressing dendritic cells

Porphyran is known to inhibit immune cell function. Previously, porphyran was shown to prevent lipopolysaccharide-induced sepsis in mice. However, studies on the inhibitory effects of porphyran during colitis are currently lacking. In this study, we evaluated the effects of Pyropia yezoensis-derived porphyran on dextran sodium sulfate (DSS)-induced acute and chronic colitis. The oral or intraperitoneal administration of porphyran inhibited the progression of DSS-induced colitis in mice, with the former also preventing immune cell infiltration in the colon. The levels of intracellular interferon-γ and interleukin-17 in T cells decreased when porphyran was administered orally. Porphyran inhibited T cell activation by suppressing dendritic cells (DCs) and macrophages. Porphyran prevented pathogen-associated molecular pattern and damage-associated molecular pattern-dependent DC and macrophage activation. Finally, porphyran attenuated chronic colitis caused via the long-term administration of DSS. These findings indicate that the oral administration of porphyran can inhibit DSS-induced colitis by suppressing DC and macrophage activation.

Biomolecules from Macroalgae-Nutritional Profile and Bioactives for Novel Food Product Development

Seaweed is in the spotlight as a promising source of nutrition for humans as the search for sustainable food production systems continues. Seaweed has a well-documented rich nutritional profile containing compounds such as polyphenols, carotenoids and polysaccharides as well as proteins, fatty acids and minerals. Seaweed processing for the extraction of functional ingredients such as alginate, agar, and carrageenan is well-established. Novel pretreatments such as ultrasound assisted extraction or high-pressure processing can be incorporated to more efficiently extract these targeted ingredients. The scope of products that can be created using seaweed are wide ranging: from bread and noodles to yoghurt and milk and even as an ingredient to enhance the nutritional profile and stability of meat products. There are opportunities for food producers in this area to develop novel food products using seaweed. This review paper discusses the unique properties of seaweed as a food, the processes involved in seaweed aquaculture, and the products that can be developed from this marine biomass. Challenges facing the industry such as consumer hesitation around seaweed products, the safety of seaweed, and processing hurdles will also be discussed.

Ultrasound-assisted extraction of alginic acid from Sargassum angustifolium harvested from Persian Gulf shores using response surface methodology

In this study, the extraction and characterization of alginic acid, the most abundant compound among brown algae were investigated. The used algae were Sargassum angustifolium from the family of brown algae native to the coasts of the Persian Gulf. The effect of temperature, time, algae mass to solvent volume ratio, and ultrasonic power on the extraction yield and ratio of monomers (M/G) was investigated using the central composite design method. Moreover, the effect of the mentioned parameters on the poly dispersity index and cytotoxic effects against breast cancer cells were also investigated. The maximum obtained extraction yield was 46 %, which was higher than those reported for algae in tropical climates. This shows the effectiveness of ultrasound in facilitating the extraction process. In addition, the minimum monomer ratio was 0.45, the minimum poly dispersity index was 2.5 and the maximum cytotoxicity for using the extract on breast cancer cell line (MCF-7) was 20.3 % (with alginic acid concentration of 250 micrograms per milliliter).

Coffee Waste Macro-Particle Enhancement in Biopolymer Materials for Edible Packaging

Plastic pollution has raised interest in biodegradable and sustainable plastic alternatives. For edible food packaging, seaweed biopolymers have been studied for their film-forming properties. In this study, packaging films were developed using the solvent casting technique from natural red seaweed (Kappaphycus alvarezii) and coffee waste product. The physico-chemical and thermal properties of seaweed/coffee biopolymer films was obtained using dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transmission irradiation (FT-IR), water contact angle measurement (WCA) and thermogravimetric analysis (TGA). The characterization study was carried out to improve the film's morphological, thermal, and mechanical properties. The average particle size of coffee waste was found to be between 1.106 and 1.281 µm, with a zeta potential value of -27.0 mV indicating the compound's strong negative charge. The SEM analysis revealed that the coffee filler was evenly dispersed in the polymer matrix, improving the film's structural properties. The FT-IR result shows that coffee waste was successfully incorporated over the film matrix with the presence of a N-H bond. The hydrophobic property of the film was enhanced with the incorporation of coffee filler, indicating increased water contact angle compared to the neat film. The tensile properties of the biopolymer film were significantly improved at 4 wt% coffee powder with optimum tensile strength (35.47 MPa) with the addition of coffee waste powder. The incorporation of coffee waste into the seaweed matrix increased the functional properties of the fabricated biopolymer film. Thus, seaweed/coffee biopolymer film has the potential to be used in food packaging and other applications.

Novel Technologies for Seaweed Polysaccharides Extraction and Their Use in Food with Therapeutically Applications—A Review

The use of seaweed for therapeutic purposes is ancient, but only in the last decade, with advanced technologies, has it been possible to extract seaweed’s bioactive compounds and test their potential properties. Algal metabolites possess nutritional properties, but they also exhibit antioxidant, antimicrobial, and antiviral activities, which allow them to be involved in several pharmaceutical applications. Seaweeds have been incorporated since ancient times into diets as a whole food. With the isolation of particular seaweed compounds, it would be possible to develop new types of food with therapeutically properties. Polysaccharides make up the majority of seaweed biomass, which has triggered an increase in interest in using seaweed for commercial purposes, particularly in the production of agar, carrageenan, and alginate. The bio-properties of polysaccharides are strictly dependent to their chemical characteristics and structure, which varies depending on the species, their life cycles, and other biotic and abiotic factors. Through this review, techniques for seaweed polysaccharides extraction are reported, with studies addressing the advantages for human health from the incorporation of algal compounds as dietary supplements and food additives.

Agar Biopolymer Films for Biodegradable Packaging: A Reference Dataset for Exploring the Limits of Mechanical Performance

This article focuses on agar biopolymer films that offer promise for developing biodegradable packaging, an important solution for reducing plastics pollution. At present there is a lack of data on the mechanical performance of agar biopolymer films using a simple plasticizer. This study takes a Design of Experiments approach to analyze how agar-glycerin biopolymer films perform across a range of ingredients concentrations in terms of their strength, elasticity, and ductility. Our results demonstrate that by systematically varying the quantity of agar and glycerin, tensile properties can be achieved that are comparable to agar-based materials with more complex formulations. Not only does our study significantly broaden the amount of data available on the range of mechanical performance that can be achieved with simple agar biopolymer films, but the data can also be used to guide further optimization efforts that start with a basic formulation that performs well on certain property dimensions. We also find that select formulations have similar tensile properties to thermoplastic starch (TPS), acrylonitrile butadiene styrene (ABS), and polypropylene (PP), indicating potential suitability for select packaging applications. We use our experimental dataset to train a neural network regression model that predicts the Young's modulus, ultimate tensile strength, and elongation at break of agar biopolymer films given their composition. Our findings support the development of further data-driven design and fabrication workflows.

Conventional vs. Innovative Protocols for the Extraction of Polysaccharides from Macroalgae

Macroalgae are one of the most environmentally friendly resources, and their industrial by-products should also be sustainable. Algal polysaccharides represent valuable products, and the definition of new eco-sustainable extraction processes, ensuring a safe and high-quality product, is a new goal in the context of reducing the carbon footprint. The aim of the present work was to determine the influence of the extraction methodology on the properties and structure of the polysaccharides, comparing conventional and innovative microwave-assisted methods. We focused on extraction times, yield, chemical composition and, finally, biological activities of raw polymers from three macroalgal species of Chlorophyta, Rhodophyta and Phaeophyceae. The main objective was to design a sustainable process in terms of energy and time savings, with the aim of developing subsequent application at the industrial level. Extraction efficacy was likely dependent on the physico-chemical polysaccharide properties, while the use of the microwave did not affect their chemical structure. Obtained results indicate that the innovative method could be used as an alternative to the conventional one to achieve emulsifiers and bacterial antiadhesives for several applications. Natural populations of invasive algae were used rather than cultivated species in order to propose the valorization of unwanted biomasses, which are commonly treated as waste, converting them into a prized resource.

An Overview of the Alternative Use of Seaweeds to Produce Safe and Sustainable Bio-Packaging

In modern times, seaweeds have become widely involved in several biotechnological applications due to the variety of their constituent bioactive compounds. The consumption of seaweeds dates to ancient times; however, only from the last few decades of research can we explain the mechanisms of action and the potential of seaweed-derived bioactive compounds, which has led to their involvement in food, cosmetic, pharmaceutical, and nutraceutical industries. Macroalgae-derived bioactive compounds are of great importance as their properties enable them to be ideal candidates for the production of sustainable “green” packaging. Diverse studies demonstrate that seaweed polysaccharides (e.g., alginates and carrageenans) not only provide health benefits, but also contribute to the production of biopolymeric film and biodegradable packaging. The dispersion of plastics and microplastics in the oceans provoke serious environmental issues that influence ecosystems and aquatic organisms. Thus, the sustainable use of seaweed-derived biopolymers is now crucial to replace plasticizers with biodegradable materials, and thus preserve the environment. The present review aims to provide an overview on the potential of seaweeds in the production of bioplastics which might be involved in food or pharmaceutical packaging.

Comparison Study of an Optimized Ultrasound-Based Method versus an Optimized Conventional Method for Agar Extraction, and Protein Co-Extraction, from Gelidium sesquipedale

Agar is a hydrocolloid found in red seaweeds, which has been of industrial interest over the last century due to its multiple applications in the food, cosmetic, and medical fields. This polysaccharide, extracted by boiling for several hours, is released from the cell wall of red seaweeds. However, the environmental impact coming from the long processing time and the energy required to reach the targeted processing temperature needs to be reduced. In this study, a response surface methodology was employed to optimize both conventional extraction and ultrasound-assisted extractions. Two different models were successfully obtained (R² = 0.8773 and R² = 0.7436, respectively). Additionally, a further re-extraction confirmed that more agar could be extracted. Protein was also successfully co-extracted in the seaweed residues. Optimized conditions were obtained for both the extractions and the re-extraction of the two methods (CE: 6 h, 100 °C; and UAE: 1 h, 100% power). Finally, FT-IR characterization demonstrated that the extracts had a similar spectrum to the commercial agar. Compared to commercial samples, the low gel strength of the agar extracts shows that these extracts might have novel and different potential applications.

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

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

An Overview of Potential Seaweed-Derived Bioactive Compounds for Pharmaceutical Applications

Nowadays, seaweeds are widely involved in biotechnological applications. Due to the variety of bioactive compounds in their composition, species of phylum Ochrophyta, class Phaeophyceae, phylum Rhodophyta and Chlorophyta are valuable for the food, cosmetic, pharmaceutical and nutraceutical industries. Seaweeds have been consumed as whole food since ancient times and used to treat several diseases, even though the mechanisms of action were unknown. During the last decades, research has demonstrated that those unique compounds express beneficial properties for human health. Each compound has peculiar properties (e.g., antioxidant, antimicrobial, antiviral activities, etc.) that can be exploited to enhance human health. Seaweed's extracted polysaccharides are already involved in the pharmaceutical industry, with the aim of replacing synthetic compounds with components of natural origin. This review aims at a better understanding of the recent uses of algae in drug development, with the scope of replacing synthetic compounds and the multiple biotechnological applications that make up seaweed's potential in industrial companies. Further research is needed to better understand the mechanisms of action of seaweed's compounds and to embrace the use of seaweeds in pharmaceutical companies and other applications, with the final scope being to produce sustainable and healthier products.

Chondrus crispus treated with ultrasound as a polysaccharides source with improved antitumoral potential

Ultrasound-assisted extraction was used to recover gelling biopolymers and antioxidant compounds from Chondrus crispus with improved biological potential. The optimal processing conditions were evaluated using a Box-Behnken design, and the impact on the biological and thermo-rheological properties of the carrageenan fraction and on the bioactive features of the soluble extracts were studied. The optimum extraction parameters were defined by extraction time of ~34.7 min; solid liquid ratio of ~2.1 g/100 g and ultrasound amplitude of ~79.0% with a maximum power of 1130 W. The dependent variables exhibited maximum carrageenan yields (44.3%) and viscoelastic modulus (925.9 Pa) with the lowest gelling temperatures (38.7 °C) as well as maximum content of the extract in protein (22.4 mg/g), gallic acid (13.4 mg/g) and Trolox equivalents antioxidant capacity (182.4 mg TEAC/g). Tested hybrid carrageenans exhibited promising biological activities (% of growth inhibition around 91% for four human cancer cellular lines: A549; A2780; HeLa 229; HT-29).

Impact of Various Essential Oils and Plant Extracts on the Characterization of the Composite Seaweed Hydrocolloid and Gac Pulp (Momordica cochinchinensis) Edible Film

Edible films and coatings have currently received increasing interest because of their potential in food applications. This study examined the effect of incorporated essential oils and natural plant extracts on the characteristics of the composite seaweed hydrocolloid and gac pulp films. Films were prepared by a casting technique, followed by measurement of physical, optical, barrier, mechanical, and structural properties. The results showed that adding plant oils and extracts significantly affected the physical, optical, mechanical, and structural properties of the composite films. Incorporation of the essential oils resulted in a reduction in moisture content and opacity while increasing values for Hue angle and elongation at break of the composite films. Besides, incorporation of the plant extracts showed increases in thickness, opacity, ΔE, Chroma, and elongation at the break, while there is a decrease in the Hue angle values of the composite films. In conclusion, incorporating plant essential oils and extracts into composite seaweed hydrocolloid and gac pulp films can enhance film properties, which can potentially be applied in food products.

Marine Polysaccharides for Wound Dressings Application: An Overview

Wound dressings have become a crucial treatment for wound healing due to their convenience, low cost, and prolonged wound management. As cutting-edge biomaterials, marine polysaccharides are divided from most marine organisms. It possesses various bioactivities, which allowing them to be processed into various forms of wound dressings. Therefore, a comprehensive understanding of the application of marine polysaccharides in wound dressings is particularly important for the studies of wound therapy. In this review, we first introduce the wound healing process and describe the characteristics of modern commonly used dressings. Then, the properties of various marine polysaccharides and their application in wound dressing development are outlined. Finally, strategies for developing and enhancing marine polysaccharide wound dressings are described, and an outlook of these dressings is given. The diverse bioactivities of marine polysaccharides including antibacterial, anti-inflammatory, haemostatic properties, etc., providing excellent wound management and accelerate wound healing. Meanwhile, these biomaterials have higher biocompatibility and biodegradability compared to synthetic ones. On the other hand, marine polysaccharides can be combined with copolymers and active substances to prepare various forms of dressings. Among them, emerging types of dressings such as nanofibers, smart hydrogels and injectable hydrogels are at the research frontier of their development. Therefore, marine polysaccharides are essential materials in wound dressings fabrication and have a promising future.

Synthesis of C6-amino agarose and evaluation of its antibacterial activity

In this paper, the biologically inert agarose was selectively modified at C6 of β-d-Galp units to produce an amino derivative with antibacterial property. The synthetic route involved the preparation of tosyl and azido agarose intermediates. All the polysaccharide derivatives were characterized by mono- and bidimensional 1H and 13C NMR and FT-IR analysis. A water-soluble amino polymer (Mw = 39,000 g mol-1, DSamino = 0.50) was produced by partial acid hydrolysis showing bactericidal and bacteriostatic activity against P. aeruginosa (ATCC 9027), S. aureus (ATCC 6538), and E. coli (ATCC 25922), with MIC values lower than 2.5 mg mL-1 and MBC values ranging from 2.5 to 5.0 mg mL-1.

Seaweed polysaccharides: Emerging extraction technologies, chemical modifications and bioactive properties

Nowadays, consumers are increasingly aware of the relationship between diet and health, showing a greater preference of products from natural origin. In the last decade, seaweeds have outlined as one of the natural sources with more potential to obtain bioactive carbohydrates. Numerous seaweed polysaccharides have aroused the interest of the scientific community, due to their biological activities and their high potential on biomedical, functional food and technological applications. To obtain polysaccharides from seaweeds, it is necessary to find methodologies that improve both yield and quality and that they are profitable. Nowadays, environmentally friendly extraction technologies are a viable alternative to conventional methods for obtaining these products, providing several advantages like reduced number of solvents, energy and time. On the other hand, chemical modification of their structure is a useful approach to improve their solubility and biological properties, and thus enhance the extent of their potential applications since some uses of polysaccharides are still limited. The present review aimed to compile current information about the most relevant seaweed polysaccharides, available extraction and modification methods, as well as a summary of their biological activities, to evaluate knowledge gaps and future trends for the industrial applications of these compounds.Key teaching pointsStructure and biological functions of main seaweed polysaccharides.Emerging extraction methods for sulfate polysaccharides.Chemical modification of seaweeds polysaccharides.Potential industrial applications of seaweed polysaccharides.Biological activities, knowledge gaps and future trends of seaweed polysaccharides.

Antiviral Activity of Carrageenans and Processing Implications

Carrageenan and carrageenan oligosaccharides are red seaweed sulfated carbohydrates with well-known antiviral properties, mainly through the blocking of the viral attachment stage. They also exhibit other interesting biological properties and can be used to prepare different drug delivery systems for controlled administration. The most active forms are λ-, ι-, and κ-carrageenans, the degree and sulfation position being determined in their properties. They can be obtained from sustainable worldwide available resources and the influence of manufacturing on composition, structure, and antiviral properties should be considered. This review presents a survey of the antiviral properties of carrageenan in relation to the processing conditions, particularly those assisted by intensification technologies during the extraction stage, and discusses the possibility of further chemical modifications.

Perspective on the Therapeutic Applications of Algal Polysaccharides

Abstract

Algae are an enormous source of polysaccharides and have gained much interest in human flourishing as organic drugs. Algal polysaccharides have aroused interest in the health sector owing to the various bioactivities namely anticancer, antiviral, immunoregulation, antidiabetic and antioxidant effects. The research community has comprehensively described the importance of algal polysaccharides regarding their extraction, purification, and potential use in various sectors. However, regardless of all the intriguing properties and potency in the health sector, these algal polysaccharides deserve detailed investigation. Hence, the present review emphasizes extensively on the previous and latest developments in the extraction, purification, structural properties and therapeutic bioactivities of algal polysaccharides to upgrade the knowledge for further advancement in this area of research. Moreover, the review also addresses the challenges, prospective research gaps and future perspective. We believe this review can provide a boost to upgrade the traditional methods of algal polysaccharide production for the development of efficacious drugs that will promote human welfare.

Graphic Abstract