Modified alginates have a wide range of applications, including in the manufacture of dressings and scaffolds used for regenerative medicine, in systems for selective drug delivery, and as hydrogel ...materials. This literature review discusses the methods used to modify alginates and obtain materials with new or improved functional properties. It discusses the diverse biological and functional activity of alginates. It presents methods of modification that utilize both natural and synthetic peptides, and describes their influence on the biological properties of the alginates. The success of functionalization depends on the reaction conditions being sufficient to guarantee the desired transformations and provide modified alginates with new desirable properties, but mild enough to prevent degradation of the alginates. This review is a literature description of efficient methods of alginate functionalization using biologically active ligands. Particular attention was paid to methods of alginate functionalization with peptides, because the combination of the properties of alginates and peptides leads to the obtaining of conjugates with properties resulting from both components as well as a completely new, different functionality.
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Alginate hydrogel particles are promising delivery systems for protein encapsulation and controlled release because of their excellent biocompatibility, biodegradability, and mild ...gelation process. In this study, a facile microfluidic approach is developed for making uniform core-shell hydrogel microparticles. To address the challenge of protein retention within the alginate gel matrix, poly(ethyleneimine) (PEI)- and chitosan-coated alginate microparticles were fabricated demonstrating improved protein retention as well as controlled release. Furthermore, a model protein ovalbumin was loaded along with delta inulin microparticulate adjuvant into the water-core of the alginate microparticles. Compared to those microparticles with only antigen loaded, the antigen + adjuvant loaded microparticles showed a delayed and sustained release of antigen. This microfluidic approach provides a convenient method for making well-controlled alginate microgel particles with uniform size and controlled properties, and demonstrates the ability to tune the release profiles of proteins by engineering microparticle structure and properties.
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Recent advances in three-dimensional (3-D) printing offer an excellent opportunity to address critical challenges faced by current tissue engineering approaches. Alginate hydrogels ...have been used extensively as bioinks for 3-D bioprinting. However, most previous research has focused on native alginates with limited degradation. The application of oxidized alginates with controlled degradation in bioprinting has not been explored. Here, a collection of 30 different alginate hydrogels with varied oxidation percentages and concentrations was prepared to develop a bioink platform that can be applied to a multitude of tissue engineering applications. The authors systematically investigated the effects of two key material properties (i.e. viscosity and density) of alginate solutions on their printabilities to identify a suitable range of material properties of alginates to be applied to bioprinting. Further, four alginate solutions with varied biodegradability were printed with human adipose-derived stem cells (hADSCs) into lattice-structured, cell-laden hydrogels with high accuracy. Notably, these alginate-based bioinks were shown to be capable of modulating proliferation and spreading of hADSCs without affecting the structure integrity of the lattice structures (except the highly degradable one) after 8days in culture. This research lays a foundation for the development of alginate-based bioink for tissue-specific tissue engineering applications.
Alginate lyases play a vital role in the degradation of alginate, an important marine carbon source. Alginate is a complex macromolecular substrate, and the synergy of alginate lyases is important ...for the alginate utilization by microbes and the application of alginate lyases in biotechnology. Although many studies have focused on the synergy between different alginate lyases, the synergy between two alginate lyase domains of one alginate lyase has not been reported. Here, we report the synergism between the two catalytic domains of a novel alginate lyase, AlyC6', from the marine alginate-degrading bacterium
sp. NC2. AlyC6' contains two PL7 catalytic domains (CD1 and CD2) that have no sequence similarity. While both CD1 and CD2 are endo-lyases with the highest activity at 30°C, pH 8.0, and 1.0 M NaCl, they also displayed some different properties. CD1 was PM-specific, but CD2 was PG-specific. Compared with CD2, CD1 had higher catalytic efficiency, but lower substrate affinity. In addition, CD1 had a smaller minimal substrate than CD2, and the products from CD2 could be further degraded by CD1. These distinctions between the two domains enable them to synergize intramolecularly in alginate degradation, resulting in efficient and complete degradation of various alginate substrates. The bioinformatics analysis revealed that diverse alginate lyases have multiple catalytic domains, which are widespread, especially abundant in
and
, which may secret multimodular alginate lyases for alginate degradation. This study provides new insight into bacterial alginate lyases and alginate degradation and is helpful for designing multimodular enzymes for efficient alginate depolymerization.
Alginate is a major component in the cell walls of brown algae. Alginate degradation is carried out by alginate lyases. Until now, while most characterized alginate lyases contain one single catalytic domain, only a few have been shown to contain two catalytic domains. Furthermore, the synergy of alginate lyases has attracted increasing attention since it plays important roles in microbial alginate utilization and biotechnological applications. Although many studies have focused on the synergy between different alginate lyases, the synergy between two catalytic domains of one alginate lyase has not been reported. Here, a novel alginate lyase, AlyC6', with two functional alginate lyase domains was biochemically characterized. Moreover, the synergism between the two domains of AlyC6' was revealed. Additionally, the distribution of the alginate lyases with multiple alginate lyase domains was investigated based on the bioinformatics analysis. This study provides new insight into bacterial alginate lyases and alginate degradation.
Uronic acid in extracellular polymeric substances is a primary but often ignored factor related to the difficult hydrolysis of waste-activated sludge (WAS), with alginate as a typical polymer. ...Previously, we enriched alginate-degrading consortia (ADC) in batch reactors that can enhance methane production from WAS, but the enzymes and metabolic pathway are not well documented. In this work, two chemostats in series were operated to enrich ADC, in which 10 g/L alginate was wholly consumed. Based on it, the extracellular alginate lyase (∼130 kD, EC 4.2.2.3) in the cultures was identified by metaproteomic analysis. This enzyme offers a high specificity to convert alginate to disaccharides over other mentioned hydrolases. Genus Bacteroides (>60%) was revealed as the key bacterium for alginate conversion. A new Entner–Doudoroff pathway of alginate via 5-dehydro-4-deoxy-d-glucuronate (DDG) and 3-deoxy-d-glycerol-2,5-hexdiulosonate (DGH) as the intermediates to 2-keto-3-deoxy-gluconate (KDG) was constructed based on the metagenomic and metaproteomic analysis. In summary, this work documented the core enzymes and metabolic pathway for alginate degradation, which provides a good paradigm when analyzing the degrading mechanism of unacquainted substrates. The outcome will further contribute to the application of Bacteroides-dominated ADC on WAS methanogenesis in the future.
Droplet‐based microfluidics‐assisted fabrication of alginate microgels has extensive applications in biomaterials, biomedicines, and related fields. This approach is typically achieved by ...crosslinking droplets of an aqueous solution of sodium alginate with various divalent and trivalent ions, such as Ca2+, Ba2+, Sr2+, etc. Despite the exceptional features exhibited by bulk alginate hydrogels when using iron ions as the crosslinking reagent, including stimulus responsiveness and complex chemistry, no attention has been given to studying the fabrication of Fe‐alginate microgels through droplet microfluidics. In this work, a facile method is presented for fabricating Fe‐alginate microgels using single emulsion droplets as templates and an off‐chip crosslinking technique to solidify the droplets. The morphologies of the resulting microgels can be systematically adjusted by manipulating different parameters such as viscosities and ionic strength of the collecting solutions. It should be noted that these resulting microgels undergo a color change from light brown to dark brown due to presumed self‐oxidation of iron ions within their skeleton structure. Furthermore, these Fe‐alginate microgels are functionalized by decorating them with a positively charged linear polymer via electrostatic interactions to impart them with stable fluorescent property. These functionalized Fe‐alginate microgels may find potential applications in drug delivery carriers and biomimetic structures.
Droplet microfluidics produced spherical droplets of an aqueous solution of sodium alginate can be deformed and generate Fe‐alginate/Ca‐alginate microgels with different morphologies and color intensities when collected in aqueous solutions with different concentrations of glycerol, CaCl2, and FeCl3. The microgels can be further endowed with stable fluorescence property when reacted with a linear pNIPAAm‐co‐Ru(bpy)3 polymer simply via the electrostatic interaction.
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•Alginate and methacrylated dECM (Ma-dECM) based composite bioink was prepared.•Optimal processing condition of the composite bioink was selected with printabilty and in situ cell ...viability.•Outstanding osteogenic differentiation of the hASCs-laden composite structure was observed, compared to that of the hASCs-laden alginate structure.
Alginate bioink has been widely employed to fabricate 3D cell-laden structures because of its low toxicity, appropriate biocompatibility, and easy/fast cross-linking ability. However, the low bioactivity of the hydrogel is a main shortcoming, so that physical or chemical modification with bioactive components is a promising strategy to efficiently increase the biological activity of alginate hydrogel. The present study proposes a new method to obtain bioactive alginate-based bioink by supplementing it with methacrylated (Ma)-decellularized extracellular matrix (dECM) derived from bone tissues. We demonstrate that the appropriate processing conditions and concentration of Ma-dECM in the bioink offer not only reasonable printability for fabricating 3D cell-laden structures, but also meaningful cell viability of the printed cell-laden construct. Moreover, the biologically improved microenvironment of alginate-based cell-laden structures formed using our method demonstrated a substantial effect on the osteogenic differentiation of the human adipose derived stem cells that were laden in the bioink.
Brown algae, as the main source of alginate, are a type of marine biomass with a very high output. Alginate, a polysaccharide composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G), has great ...potential for applications in the food, cosmetic and pharmaceutical industries. Alginate lyases (Alys) can degrade alginate polymers into oligosaccharides or monosaccharides, resulting in a broad application field. Alys can be used for both the production of alginate oligosaccharides and the biorefinery of brown algae. In view of their important functions, an increasing number of Alys have been isolated and characterized. For better application, a comprehensive understanding of Alys is essential. Therefore, in this paper, we summarized recently discovered Alys, discussed their characteristics, and introduced their structural properties, degradation patterns and biological roles in alginate-degrading organisms. In addition, applications of Alys have been illustrated with examples. This paper provides a relatively comprehensive description of Alys, which is significant for Alys exploration and application.
•Recently characterized alginate lyases are summarized and discussed•Various degradation patterns of alginate lyases are introduced in details•Alginate lyases are crucial for alginate high-value utilization
Double‐network hydrogels based on calcium alginate are extensively exploited. Unfortunately, their low strength and unstable constitution to open environments limit their application potential. ...Herein, a new type of double‐network organohydrogel (OHG) is proposed. By solvent exchange, a stable physical network is established based on dimethyl sulfoxide (DMSO)‐alginate in the presence of a polyacrylamide network. The DMSO content endows tunable mechanical properties, with a maximum tensile strength of ≈1.7 MPa. Importantly, the OHG shows much better environmental stability compared to the conventional double‐network hydrogels. Due to the reversible association of hydrogen bonds, the OHG possesses some unique properties, including free‐shapeability, shape‐memory, and self‐adhesion, that offers several promising ways to utilize alginate‐based gels for wide applications.
An innovative alginate‐based double‐network organohydrogel from polymers forming dimethyl sulfoxide (DMSO)‐alginate‐based hydrogen bonding and covalent bonding crosslinked networks is proposed and established by solvent exchange. This gel shows enhanced mechanical properties and better environmental stability compared to conventional double‐network hydrogels based on calcium alginate, which improves the potential application of alginate‐based gels.
Objectives
Bifunctional alginate lyase can efficiently saccharify alginate biomass and prepare functional oligosaccharides of alginate.
Results
A new BP-2 strain that produces alginate lyase was ...screened and identified from rotted
Sargassum
. A new alginate lyase, Alg17B, belonging to the polysaccharide lyase family 17, was isolated and purified from BP-2 fermentation broth by freeze-drying, dialysis, and ion exchange chromatography. The enzymatic properties of the purified lyase were investigated. The molecular weight of Alg17B was approximately 77 kDa, its optimum reaction temperature was 40–45 °C, and its optimum reaction pH was 7.5–8.0. The enzyme was relatively stable at pH 7.0–8.0, with a temperature range of 25–35 °C, and the specific activity of the purified enzyme reached 4036 U/mg. A low Na
+
concentration stimulated Alg17B enzyme activity, but Ca
2+
, Zn
2+
, and other metal ions inhibited it. Substrate specificity analysis, thin-layer chromatography, and mass spectrometry showed that Alg17B is an alginate lyase that catalyses the hydrolysis of sodium alginate, polymannuronic acid (polyM) and polyguluronic acid to produce monosaccharides and low molecular weight oligosaccharides. Alg17B is also bifunctional, exhibiting both endolytic and exolytic activities toward alginate, and has a wide substrate utilization range with a preference for polyM.
Conclusions
Alg17B can be used to saccharify the main carbohydrate, alginate, in the ethanolic production of brown algae fuel as well as in preparing and researching oligosaccharides.
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