Title : The effects of drug encapsulation into gellan gum matrix by the example of roxithromycin, naproxen and meloxicam Tomasz Osmalek
Gellan gum is a linear, anionic biopolymer produced by the bacteria Sphingomonas elodea. Its chain consists of a tetrasaccharide repeating unit of L-rhamnose, D-glucose and D-glucuronate. Due to the unique structure and beneficial properties, gellan is broadly described as a potent multifunctional additive for various pharmaceutical products. There are two main types of gellan gum in use, native (high-acyl, HAG), which contains acyl substituents and deacetylated (low-acyl, LAG). Both are soluble in hot water (>70°C). As a result of temperature decrease, HAG hot solution forms soft and deformable gels, whereas LAG gives hard and brittle ones. The gelation of LAG can be accelerated by the presence of cations. Rapid gelation of LAG solution after instillation to salt solutions is called ionotropic gelation and can be applied in the encapsulation of drugs or other actives. The obtained formulations (beads, capsules, matrices) show the evidence of pH-sensitivity as they are stable in the acidic environment and start to absorb water and degrade during the pH increase. Therefore the matrices based on LAG can be used to shift the drug release to the distal parts of the gastrointestinal tract.
The presented work aimed at the preparation of gellan beads loaded with three different drugs and to evaluate their macroscopic and physicochemical properties, especially regarding pH-dependent behavior. Naproxen, meloxicam and roxithromycin were used as the active compounds. The beads were obtained by ionotropic gelation technique with CaCl2 solution used as a cross-linking medium. Gellan alone or its mixtures with other naturally derived polysaccharides, i.e. carrageenans, guar gum, cellulose sulfate, dextran sulfate, were used for the preparation of the formulations. First, the surface and morphology of the dried beads were analyzed with scanning electron microscopy (SEM). Pure drugs and the beads were also evaluated with Raman spectroscopy and differential scanning calorimetry (DSC) technique. Next, the drug encapsulation efficiency and drug content were determined. The swelling and degradation behavior was evaluated in four simulated gastrointestinal fluids at different pH (1.2; 4.5; 6.8 and 7.4). The last step included in vitro drug release studies.
The work was funded by National Science Center (Poland) grant ID 370652, PUMS grants No. 502-14-03314429-09983 and 502-01-033-14-429-03439 and 502-05-03314429-09983.
Audience take away:
• The presentation will be the source of information concerning the potential application of low-acyl gellan gum as a pH-sensitive carrier for various drugs in oral delivery.
• The presented material will indicate some important aspects that have to be considered during the design and manufacturing of gellan beads.
• Both the advantages and limitations of ionotropic drug encapsulation will be discussed.