Alginate gelling process: Use of bivalent ions rich microspheres

Abstract

A new approach for obtaining a controlled gelling process of sodium alginate, based on the use of bivalent ions rich alginate microbeads added as crosslinkers, is presented. Normally, calcium ions are used in the gelation of alginate solutions. In this article, alginate microspheres, obtained by electrospray, and enriched with different bivalent ions (Ca2+, Ba2+, and Mg2+) are described. Because of the solvent/non‐solvent system, it is possible to use also Mg2+ as a crosslinker for alginate, despite the fact that it had long been regarded as a nongelling bivalent ion. The morphology and the ions content of the microspheres are evaluated. Gels are characterized according to type and amount of the ions added to the alginate solution, using rheological measurements to assess the variation in the storage modulus (G′) and loss modulus (G″). The gel point is then detected using magnesium ions. The new approach guarantees a working system that could be easily applied in different fields. POLYM. ENG. SCI., 57:531–536, 2017. © 2017 Society of Plastics Engineers

Alginate and alginate/hyaluronic acid membranes generated by electrospinning in wet conditions: Relationship between solution viscosity and spinnability

“…Using wet conditions with a solution containing divalent ions, in which the newly formed fibers are collected, allows directly crosslinking the alginate during the membrane formation. The collecting solution (3 wt % of BaCl 2 in 60:40 water/EtOH) was created for two purposes: (1) to crosslink alginate with the presence of the barium salt, which worked as a gelling agent and was selected on the basis of its affinity with alginate, that is, Ba 2+ >Ca 2+ ≫ Mg 2+ ; (2) to avoid fibers dissolving in the aqueous environment. A 60:40 water/EtOH mixture was selected because ethanol is a non‐solvent for the alginate .…”

“…Only the G blocks of alginate are believed to participate in intermolecular crosslinking with divalent cations, because only the α‐ l ‐guluronic acid has an active role in the formation of the gel. The gelling proprieties are explained by the formation of cavities, thanks to the G blocks, which work as binding sites for the bivalent cations and arrange themselves all around creating a structure comparable to an “egg shell.” This reaction is instantaneous and the stability of the gel depends on the kind and quantity of the ions added to the alginate solution as well as on the length of the G blocks . This property has been used in many fields such as the pharmaceutical industry and tissue engineering…”

“…6 This reaction is instantaneous and the stability of the gel depends on the kind and quantity of the ions added to the alginate solution as well as on the length of the G blocks. 7,8 This property has been used in many fields such as the pharmaceutical industry and tissue engineering. 1 The hyaluronic acid (HA) is a high molecular weight biopolysaccharide consisting of units of N-acetlyl-D-glucosamine and Dglucuronic acid [ Figure 1(b)].…”

Influence of Process Parameters in Graphene Oxide Obtention on the Properties of Mechanically Strong Alginate Nanocomposites

“…Alginate is most commonly used in a water-soluble sodium alginate powder form, allowing physical cross-linking usually by the addition of divalent cations, such as Ca 2+ , Ba 2+ , and Zn 2+ [7]. These divalent cations form a chelated structure, according to the commonly called egg-box model, preferentially with the GG blocks, thereby creating a stable three-dimensional network [8]. Alginate has potential in applications such as biomedicine, pharmaceutics, food industry, textiles, and additive manufacturing [9].…”

Composite Central Face Design—An Approach to Achieve Efficient Alginate Microcarriers

“…Until now, there are some published works related to the formulation parameters on alginate MPs [3]. However, most of them are focused on the influence of the release profile [4], crosslinker, and its ratio [5,6], on the combination of some particular parameters of the MPs produced (like size and sphericity [7]), or in the use multimaterial particles [8]. The mainly applied technique for the MPs production is the extrusion dripping and, during this process, the alginate is extruded through a capillary/nozzle and dropwise into a multivalent ion solution [7].…”