pH-Dependent Behavior of Novel Gellan Beads Loaded with Naproxen

Oral administration of non-selective COX inhibitors involves the risk of serious side-effects. In the case of naproxen (NPX), the most frequent are those related to malfunctioning of the gastric mucosa. On the other hand, NPX and other NSAIDs are extensively studied in terms of colorectal cancer (CRC) prevention and inhibition, since it has been evidenced that COX-2 corresponds with the risk of the tumor occurrence and growth. Both side-effects in the stomach and possible antitumor activity of NPX justify the attempts to search for novel carriers for NPX with the site specific release in the colon. Thus, the aim of the work was to design, formulate and characterize low-acyl gellan gum (GG) macro beads as potential carriers for the delivery of NPX to the distal parts of the gastrointestinal tract.

The beads were obtained by the ionotropic gelation technique. CaCl2 solution was used as a cross-linking medium. After production, the beads were dried and used for further experiments. First, pure NPX and the beads were evaluated by Raman spectroscopy and DSC studies. The surface and morphology of the beads were analyzed by SEM. Next, the drug encapsulation efficiency and content in the beads were determined. The swelling and degradation behavior of the beads were evaluated in four simulated gastrointestinal fluids at different pH (1.2; 4.5; 6.8 and 7.4). The NPX in vitro release studies were conducted on USP I apparatus (rotating basket) at pH=7.4 and compared to the commercial enteric tablet.

The polymer content of 0.5 % was considered as too low to obtain spherical beads in the dried form. Raman spectra confirmed that NPX did not undergo structural changes during production process. DSC studies showed that thermal decomposition at lower temperatures was observed for formulations with the lowest amount of GG. It turned out that the most important factor which determined the morphology of the beads was the amount of gellan gum in the initial mixture. The beads revealed 13.9- 39.9% of drug loading and 75.3-99.7% drug encapsulation efficiency. Swelling of the beads was pHdependent as the beads remained stable in the acidic environment but started to absorb water. In pH=7.4 after 3 hours, the beginning of the physical decomposition of the polymer matrix was observed. The drug release studies showed that in pH=7.4 the commercial tablets released 90% of the drug after 45 minutes while the amount of NPX released from pellets after the same time was 40-80%.

In general, it can be stated that gellan macro beads may be regarded as suitable for site specific delivery of NPX to the colon. However, these simple to obtain beads can be potentially used as carriers for many different drugs whenever it is necessary to omit the stomach.