Gellan Gum/Laponite Beads for the Modified Release of Drugs: Experimental and Modeling Study of Gastrointestinal Release

Abstract

In this study, gellan gum (GG), a natural polysaccharide, was used to fabricate spherical porous beads suitable as sustained drug delivery systems for oral administration. GG was cross-linked with calcium ions to prepare polymeric beads. Rheological studies and preliminary experiments of beads preparation allowed to identify the GG and the CaCl2 concentrations suitable for obtaining stable and spherical particles. GG beads were formed, through ionotropic gelation technique, with and without the presence of the synthetic clay laponite. The resultant beads were analyzed for dimensions (before and after freeze-drying), morphological aspects and ability to swell in different media miming biological fluids, namely SGF (Simulated Gastric Fluid, HCl 0.1 M) and SIF (Simulated Intestinal Fluid, phosphate buffer, 0.044 M, pH 7.4). The swelling degree was lower in SGF than in SIF and further reduced in the presence of laponite. The GG and GG-layered silicate composite beads were loaded with two model drugs having different molecular weight, namely theophylline and cyanocobalamin (vitamin B12) and subjected to in-vitro release studies in SGF and SIF. The presence of laponite in the bead formulation increased the drug entrapment efficiency and slowed-down the release kinetics of both drugs in the gastric environment. A moving-boundary swelling model with “diffuse” glassy-rubbery interface was proposed in order to describe the swelling behavior of porous freeze-dried beads. Consistently with the swelling model adopted, two moving-boundary drug release models were developed to interpret release data from highly porous beads of different drugs: drug molecules, e.g., theophylline, that exhibit a typical Fickian behavior of release curves and drugs, such as vitamin B12, whose release curves are affected by the physical/chemical interaction of the drug with the polymer/clay complex. Theoretical results support the experimental observations, thus confirming that laponite may be an effective additive for fabricating sustained drug delivery systems.

Laponite‐Based Nanomaterials for Drug Delivery

“…[ 94 ] Sustained drug delivery provides a continuous release of therapeutics at a predetermined ratio for a fixed period, [ 66 ] enabling stable plasma levels of drugs, less frequent dosing, reduced side effects, [ 95 ] increased efficacy, and prolonged delivery. [ 96 ]…”

Rheological and textural analysis as tools for investigation of drug-polymer and polymer–polymer interactions on the example of low-acyl gellan gum and mesalazine

“…The process is known as ionotropic gelation and in pharmaceutical technology can be used to prepare drug-loaded beads or in situ gelling fluids, both with the potential to modify the drug release according to the changing pH in the gastrointestinal tract (GIT). 21 In the case of the beads, the mixture of gellan and drug is instilled drop-wise to the solution of gelling cations. The ions form intermolecular junctions between the polymer chains.…”

Untitled

“…The gelation of deacetylated GG with the influence of di-/tri-valent metal cations is called ionotropicgelation of GG and the mechanism of this ionotropic gelation of deacetylated GG entails the arrangement of the double helical junction zones subsequently the aggregation of the double helical segments to structure 3-dimensional networking by the complexation with di-/tri-valent metal cations and the hydrogen bonding with the water molecules [27][28][29] . In the previous literature, blending of other plant polysaccharides with deacetylated GG in the formulation of ionotropically gelled GG beads have been reported for improving the preferred functional characteristics, such as drug encapsulations, drug releases, swelling, stability, etc.…”