Enhanced solubility and self-assembly of amphiphilic sulfasalazine-PEG-OMe (S-PEG) conjugate into core-shell nanostructures useful for colonic drug delivery

Abstract

Recently, several studies have been undertaken to formulate drugs in soluble state leading to enhanced bioavailability as well as to provide controlled drug release. Because of their distinct advantages, such systems have attracted increasing attention of the researchers. Here, sulfasalazine, a drug used to treat inflammatory bowel disease, was conjugated with a low molecular weight polyethylene glycol monomethyl ether (750 Da) to obtain amphiphilic sulfasalazine-polyethylene glycol (S-PEG) conjugate, which not only showed enhanced solubility but also, on self-assembly, generated core-shell type micellar nanostructures with hydrophobic core and hydrophilic shell. Post-physicochemical characterization, these micellar nanostructures were used to entrap hydrophobic drug molecules, ornidazole and sulfasalazine. The drug-entrapped S-PEG nanoformulations showed controlled release of drugs at pH 7.2 making these nanoformulations ideal for colon-targeted drug delivery. Further, azo-moiety bearing sulfasalazine conjugate showed responsiveness to a chemical reductant, sodium dithionite, which mimics azoreductase enzymes present in the colonic microflora. Drug release in the presence of sodium dithionite increased significantly ensuring the potential of these formulations for colon-targeted drug delivery.