Polysaccharide coated niosomes for oral drug delivery: formulation and in vitro stability studies

Non-ionic surfactant vesicles (niosomes) were prepared and appended with a polysaccharide cap using hydrophobic anchors. Hydrophobized polysaccharides , O-palmitoyl pullulan (OPPu) and cholesteroyl pullulan (CHPu) were anchore d onto propranolol . HCl containing preformed niosomes. The coated niosomes were characterized for average vesicle size, size distribution, shape, enc apsulation efficiency and in vitro release profile and were compared with t heir uncoated counterparts. No significant difference was observed in % enc apsulation (P > 0.05 in a rank sum test) of polysaccharide coated and uncoa ted vesicles. In vitro release studies however, revealed a significant lowe ring (P < 0.01) of drug release for the coated systems in simulated gastric and intestinal fluids with a biphasic release profile. The influence of th e hydrophobized polysaccharide cap on niosomal membrane integrity and stabi lization against harsh bio-environment conditions was also investigated. Th e parameters investigated include detergent and bile (bile salts and fresh- pooled rat bile) challenge, freeze-thaw cycling, osmotic stress, and long t erm and shelf stability studies. It was seen that at higher bile salt conce ntrations and detergent content, uncoated niosomes underwent bilayer solubi lization into intermediate micellar structures, whereas coated niosomes wer e able to maintain their structural integrity as reflected from their highe r % latency for the entrapped water soluble agent. Similarly, freeze-thaw c ycling could not bring any fusion or collapse of the niosomal membrane (unl ike uncoated ones). Furthermore, the exceptional shelf stability of the coa ted vesicles both at 37 +/- 1 degrees and at 4 +/- 1 degreesC establishes t he potential of polysaccharide coated niosomes as an oral delivery system f or water-soluble agents. Results from OPPu and CHPu coated niosomal systems for their oral stability potential are compared.