Encapsulation of roxithromycin into gellan gum matrices and the impact of other natural polymers on drug release

Abstract

The aim of the work was to investigate the properties of polysaccharide matrices loaded with roxithromycin (ROX), made on the basis of low-acyl gellan and its blends with sodium alginate, pectin, karaya gum, methylcellulose, and κ-carrageenan. The obtained formulations were investigated as potential oral dosage forms with the ability to protect the drug from the acidic conditions of the stomach. Another desired feature of the obtained systems was the sustained release of the active ingredient allowing for potential shifting of the therapeutic effect to the colon. The morphology of the matrices was evaluated with optical and scanning electron microscopy. Moreover, Raman spectroscopy and thermal analysis were performed for ROX, polymers, ROX/polymers physical mixtures and the matrices. Next, the swelling behavior was examined. The matrices were evaluated for ROX content and encapsulation efficiency. The last stage concerned the drug release studies. All matrices after production revealed more or less oval shape with visible deformation most probably occurring during drying. Raman analysis and DSC confirmed the crystalline form of ROX and showed no evidence of interactions between the drug and the excipients. It was shown that the matrices containing gellan combined with methylcellulose or κ-carrageenan at pH = 7.4 released ROX slower than the other matrices which might be promising in terms of colonic drug delivery. Moreover, the polymer matrices remained physically stable at acidic pH similar to the environment of the stomach. However, in these conditions drug degradation was observed which indicates the necessity to further modify the applied technology.