Polysaccharidic microsystem for intestinal uptake

Purpose: Preparation of a polysaccharidic microsystem for the intestinal uptake by Peyer’s patches of antibiotics showing a low oral bioavailability. Methods: The spray-drying technique was applied to sodium alginate and antibiotic aqueous solutions to obtain microparticles. The microparticles were crosslinked with calcium ions and chitosan (CS). The obtained microsystem was evaluated for morphological and dimensional properties by SEM. The antibiotic content was determined by spectrophotometric method. The in vitro drug release studies were carried out in gastric fluid (pH 3.0) and subsequently in intestinal fluid (pH 7.4) for 1 and 4 h, respectively. The microsystem intestinal uptake by Peyer’s patches was evaluated by ex vivo technique using fluorescent samples. The antibacterial activity of the drug in the Peyer’s patches was tested by microbiological assay. Results: Alginate/antibiotic microparticles with size less than 5 m were obtained by spray-drying technique. In order to formulate microsystems with suitable drug loading and crosslinking degree it was necessary to modulate alginate/crosslinking agent ratio during the gelation process. The in vitro drug release profile of the microsystem showed a slow phase at gastric pH value and a burst effect followed by a sustained phase at intestinal pH value. The uptake of the microsystem by Peyer’s patches was demonstrated by ex vivo technique. Moreover, the samples extracted from Peyer’s patches showed antibacterial activity. Conclusion: This study revealed the suitability of the spray-drying technique to provide microparticles with a size of less than 5 m as a carrier for an antimicrobial agent poorly absorbed by the oral route. In fact, the microparticles were able to be taken up intact by the M cells of Peyer’s patches and to show antibacterial activity. The development of such a microsystem could represent a strategy to increase bioavailability by means of intestinal uptake