Synergistic effect of divalent cations in improving technological properties of cross-linked alginate beads

Zinc and Calcium Cations Combination in the Production of Floating Alginate Beads as Prednisolone Delivery Systems

“…As previously reported in our study [22], in fact, the co-presence of calcium (Ca 2+ ) and zinc (Zn 2+ ) could have a synergistic effect during the external ionotropic gelation, significantly improving the technological properties (i.e., encapsulation efficiency and drug release control) of the resulting cross-linked alginate beads. This effect is because of both the ability of Ca 2+ to establish quicker electrostatic interactions with guluronic groups and the ability of Zn 2+ to bond in covalent-like manner carboxylate groups of guluronic and mannuronic moieties of alginate.…”

“…Although some studies have been focused on the production of floating alginate beads with calcium in the gelling solution, few data are available on the simultaneous use of two different cations as cross-linking agents [22,23]. Moreover, no results have been reported on the exploitation of two different cations in a double simultaneous gelation mechanism, that is, external, promoted by zinc ions in the gelling solution, and internal, promoted by calcium ions in prilling the feed solution.…”

“…In this paper, a double internal-external alginate gelation approach was investigated, verifying the combined effect of Ca 2+ in the feed and Zn 2+ in the gelling medium on the final beads' performance. With this in mind, floating Ca-Zn alginate beads were designed as potential oral prolonged delivery systems of prednisolone as a model SAID, taking advantage of the efficient prilling/ionotropic gelation in the presence of zinc ions [22], widely known as the promoter of the external alginate gelation, and the pore-generating ability of calcium carbonate. Among different gas-generating agents employed for the formulation of floating beads [24,25], calcium carbonate was selected for its capability to interact with alginate guluronic groups, potentially responsible for an additional internal gelation when added in the feed.…”

“…Drug/alginate solutions (alginate 2.5% w/v and drug/polymer ratio 1:5) [22] were opportunely combined with calcium carbonate and processed by prilling to obtain hollow gel beads, after drip into the zinc acetate solution. CO 2 exploited during the particle manufacturing gave a porous alginate matrix with good results in terms of the encapsulation efficiency and morphology of the beads.…”

Pectin and Zinc Alginate: The Right Inner/Outer Polymer Combination for Core-Shell Drug Delivery Systems

“…As a consequence, several innovative drug delivery systems have been developed to achieve a selective drug delivery to the inflamed tissues [6][7][8][9]. With this aim, several approaches can be followed, i.e., the use of prodrugs becoming active after the hydrolysis by specific colon enzymes [10], bioadhesive delivery systems [11], timed-dependent delivery systems [12] and drug coating with pH dependent polymers [13,14]. In this case, the use of pH-sensitive polymers protects the drug from the early release in the acidic pH of the stomach and small intestine, increasing the amount of active compound in the colon region.…”