Seaweed biomass is as an abundant and renewable source of complex polysaccharides, including alginate which has a variety of applications. A sustainable method for exploiting alginate towards the ...production of valuable oligosaccharides is through enzymatic processing, using alginate lyases. Industrial refinement methods demand robust enzymes. Metagenomic libraries from extreme environments are a new source of unique enzymes with great industrial potential. Herein we report the identification of a new thermostable alginate lyase with only 58 % identity to known sequences, identified by mining a metagenomic library obtained from the hydrothermal vents of the volcano Kolumbo in the Aegean Sea (Kolumbo Alginate Lyase, KAlLy). Sequence analysis and biochemical characterization of KAlLy showed that this new alginate lyase is a Polysaccharide Lyase of family 7 (PL7) enzyme with endo- and exo-action on alginate and poly-mannuronic acid, with high activity at 60°C (56 ± 8 U/mg) and high thermostability (half-life time of 30 h at 50°C). The response surface methodology analysis revealed that the reaction optimum conditions with poly-mannuronic acid as substrate are 44°C, pH of 5.5 with 440 mM NaCl. This novel alginate lyase is a valuable addition to the toolbox of alginate modifying enzymes, due to its diverse sequence and its good thermal stability.
In general, alginate hydrogels are considered to be biologically inert and are commonly used for biomedical purposes that require minimum inflammation. However, Ca2+, which is commonly used to ...crosslink alginate, is a critical second messenger in immune cell signaling, and little has been done to understand its effect on immune cell fate when delivered as a component of alginate gels. We found that dendritic cells (DCs) encapsulated in Ca2+-crosslinked alginate (calcium alginate) secreted at least fivefold more of the inflammatory cytokine IL-1β when compared to DCs encapsulated in agarose and collagen gels, as well as DCs plated on tissue-culture polystyrene (TCPS). Plating cells on TCPS with the alginate polymer could not reproduce these results, whereas culturing DCs on TCPS with increasing concentrations of Ca2+ increased IL-1β, MHC class II and CD86 expression in a dose-dependent manner. In agreement with these findings, calcium alginate gels induced greater maturation of encapsulated DCs compared to barium alginate gels. When injected subcutaneously in mice, calcium alginate gels significantly upregulated IL-1β secretion from surrounding tissue relative to barium alginate gels, and similarly, the inflammatory effects of LPS were enhanced when it was delivered from calcium alginate gels rather than barium alginate gels. These results confirm that the Ca2+ used to crosslink alginate gels can be immunostimulatory and suggest that it is important to take into account Ca2+’s bioactive effects on all exposed cells (both immune and non-immune) when using calcium alginate gels for biomedical purposes. This work may strongly impact the way people use alginate gels in the future as well as provide insights into past work utilizing alginate gels.
•New alternative and renewable adsorbents for the chromium removal were presented.•The XPS analysis indicated a complex biosorption process for Cr(VI).•Ion exchange mechanisms are predominating in ...the removal of Cr(III) by alginate.•The adsorption results encourage the use of the residue extraction as a sorbent.
The alginate extraction products from Brazilian brown seaweed Sargassum filipendula were studied for chromium biosorption. Batch experiments were conducted at pH 2 and 3 and 20°C to determine the sorption capacity of this biosorbents for chromium (VI) and (III). The biomass was characterized before and after metal binding by X-ray photoelectron spectroscopy (XPS) in order to determine the mechanisms of chromium biosorption. The residue has a high adsorption capacity, close the value obtained with seaweed and higher than that of alginate for both Cr(III) and Cr(VI). XPS analysis of the biosorbents revealed that carboxyl, amino and sulfonate groups are responsible for the binding of the metal ions. The analysis also indicated that the Cr(VI) bound to the biomass was reduced to Cr(III).
To improve drug delivery efficiency in cancer therapy, many researchers have recently concentrated on drug delivery systems that use anticancer drug loaded micro‐ or nanoparticles. In addition, ...induction methods, such as ultrasound, magnetic field, and infrared light, have been considered as active induction methods for drug delivery. Among these, focused ultrasound has been regarded as a promising candidate for the active induction method of drug delivery system because it can penetrate a deep site in soft tissue, and its energy can be focused on the targeted lesion. In this research, we employed focused ultrasound as an active induction method. For an anticancer drug loaded microparticles, we fabricated poly‐lactic‐co‐glycolic acid docetaxel (PLGA‐DTX) nanoparticle encapsulated alginate microbeads using the single‐emulsion technique and the aeration method. To select the appropriate operating parameter for the focused ultrasound, we measured the pressure and temperature induced by the focused ultrasound at the focal area using a needle‐type hydrophone and a digital thermal detector, respectively. Additionally, we conducted a simulation of focused ultrasound using COMSOL Multiphysics 4.3a. The experimental measurement results were compared with the simulation results. In addition, the drug release rates of the PLGA‐DTX‐encapsulated alginate microbeads induced by the focused ultrasound were tested. Through these experiments, we determined that the appropriate focused ultrasound parameter was peak pressure of 1 MPa, 10 cycle/burst, and burst period of 20 μSec. Finally, we performed the cell cytotoxicity and drug uptake test with focused ultrasound induction and found that the antitumor effect and drug uptake efficiency were significantly enhanced by the focused ultrasound induction. Thus, we confirmed that focused ultrasound can be an effective induction method for an anticancer drug delivery system.
•Fabrication of nanofibrous hydrogel made of oxidized alginate/gelatin/silk fibroin.•Evaluation of the structure-property relationship in prepared scaffolds.•Fabrication of 3D silk fibroin ...electrospun and engineering extracellular structure.•Evaluation of the composition-property relationship in prepared scaffolds.•Investigation of the stem cell-scaffold interaction.
In the article, a bilayer nanocomposite scaffold made of oxidized alginate (OAL), gelatin (G), and silk fibroin (SF) has been prepared via combining electrospinning, in situ gas foaming, in situ crosslinking and freeze drying methods. The physicochemical and mechanical properties, as well as thermal stability of the proposed composite, have been investigated by SEM, FTIR, XRD, tensile, and TGA analysis. The data indicate that structure and degree of crosslinking play a vital role in adjusting the physical and mechanical properties of composite scaffolds. Further, the authors find a favorable adipose-derived mesenchymal stem cell’s (AMSC) attachment and distribution within this novel hydrogel-electrospun composite. Such a nanocomposite structure with its promising properties and cell-material interaction may be considered as a new scaffold for different tissue engineering applications.
Here, we report two methods that chemically modify alginate to achieve neutral–basic pH sensitivity of the resultant hydrogel. The first method involves direct amide bond formation between alginate ...and 4-(2-aminoethyl)benzoic acid. The second method that arose out of the desire to achieve better control of the degradation rate of the alginate hydrogel involves reductive amination of oxidized alginate. The products of both methods result in a hydrogel vehicle for targeted delivery of encapsulated payload under physiological conditions in the gastrointestinal tract. Two-dimensional diffusion-ordered spectroscopy and internal and coaxial external nuclear magnetic resonance standards were used to establish chemical bonding and percent incorporation of the modifying groups into the alginate polymer. The hydrogel made with alginate modified by each method was found to be completely stable under acidic pH conditions while disintegrating within minutes to hours in neutral–basic pH conditions. We found that, while alginate oxidation did not affect the β-d-mannuronate/α-l-guluronate ratio of alginate, the rate of disintegration of the hydrogel made with oxidized alginate was dependent upon the degree of oxidation.
Connective tissue growth factor (CTGF) holds great promise for enhancing the wound healing process; however, its clinical application is hindered by its low stability and the challenge of maintaining ...its effective concentration at the wound site. Herein, we developed novel double-emulsion alginate (Alg) and heparin-mimetic alginate sulfate (AlgSulf)/polycaprolactone (PCL) nanoparticles (NPs) for controlled CTGF delivery to promote accelerated wound healing. The NPs’ physicochemical properties, cytocompatibility, and wound healing activity were assessed on immortalized human keratinocytes (HaCaT), primary human dermal fibroblasts (HDF), and a murine cutaneous wound model. The synthesized NPs had a minimum hydrodynamic size of 200.25 nm. Treatment of HaCaT and HDF cells with Alg and AlgSulf2.0/PCL NPs did not show any toxicity when used at concentrations <50 µg/mL for up to 72 h. Moreover, the NPs’ size was not affected by elevated temperatures, acidic pH, or the presence of a protein-rich medium. The NPs have slow lysozyme-mediated degradation implying that they have an extended tissue retention time. Furthermore, we found that treatment of HaCaT and HDF cells with CTGF-loaded Alg and AlgSulf2.0/PCL NPs, respectively, induced rapid cell migration (76.12% and 79.49%, P<0.05). Finally, in vivo studies showed that CTGF-loaded Alg and AlgSulf2.0/PCL NPs result in the fastest and highest wound closure at the early and late stages of wound healing, respectively (36.49%, P<0.001 on day 1; 90.45%, P<0.05 on day 10), outperforming free CTGF. Double-emulsion NPs based on Alg or AlgSulf represent a viable strategy for delivering heparin-binding GF and other therapeutics, potentially aiding various disease treatments.
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•Alginate-hyaluronate hybrid can be synthesized via ethylenediamine linkage.•Alginate-hyaluronate hybrid forms hydrogels in the presence of calcium ions.•Alginate-hyaluronate hybrid gels have ...potential in cartilage regeneration.•Defined polymer composition and gel stiffness are critical for tissue regeneration.
Alginate is a typical biomaterial that forms hydrogels in the presence of calcium ions and has often been utilized in tissue engineering approaches. However, it lacks biofunctionality in the form of interactions with cells and proteins. Hyaluronate, a main component of glycosaminoglycans, provides CD44-specific interactions with chondrocytes but typically requires chemical cross-linking agents to fabricate hydrogels, which may cause unexpected side effects in the body. In this study, we propose the design and fabrication of a hybrid structure of alginate and hyaluronate useful for cartilage regeneration. Alginate was used as a backbone, and hyaluronate with a low molecular weight was introduced to the backbone to fabricate alginate-hyaluronate hybrid coupled by ethylenediamine. We hypothesized that alginate-hyaluronate hybrid (AH) could maintain its ability to form gels in the presence of calcium ions and could be useful for cartilage regeneration as an injectable system. Characteristics of AH hydrogels containing various composition ratios of hyaluronate to alginate were investigated, and the chondrogenic potential of ATDC5 cells encapsulated within AH hydrogels was evaluated in vitro. Consequently, AH hydrogels having a defined polymer composition and mechanical stiffness were useful to successfully regulate chondrogenic differentiation and to maintain the chondrocytic cell phenotype, which may lead to many useful applications in cartilage regeneration.
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