Delivery of therapeutics with amylose-based nanosystems: A review

Amylose represents water soluble, helical component of starch which shows resistance towards the enzymatic degradation and is mainly degraded by microbial fermentation by the colon microbiota. Owing to a lesser vulnerability towards enzyme hydrolysis, amylose has been investigated for colon-targeted drug delivery and in the designing of enteric coated tablets for facilitating a controlled slower release of the pharmaceuticals. A typical polysaccharide chain of V-amylose constitutes of a left-handed single helical structure containing 6 glucose units per turn with a pitch height of 7.91–8.17 Å which results in the generation of a central channel-like cavity. The presence of methylene groups and glycosidic linkers at the inside of helix provides hydrophobicity, whereas the abundance of glycosyl hydroxyl groups at the periphery of amylose helix provides hydrophilicity. This unique feature of amylose caters to the delivery of a wide range of pharmaceuticals and biologics either by encapsulation in the helical cavity, or by covalent/ physical conjugation at the helix periphery. Furthermore, the abundance of –OH groups offer chemical modification on V-amylose for providing supplemental characteristics aimed at improving the contemporary challenges countered by conventional drug delivery strategies. The chemically modified amylose also improves its inclusion complex formation ability which is restricted in native amylose owing to its low water solubility, due to the presence of multiple hydrogen bonds between the –OH groups in amylose, and the tendency of native amylose to retrograde. Eventually, the amylose-based drug delivery systems provide sustainable solutions by offering the advantages of conventional polysaccharide-based delivery systems, which includes low cytotoxicity, immunogenicity, and biodegradability. This review presents the intervention of amylose based nanosystems in the effective delivery of pharmaceutically important molecules by overcoming the conventional physiological barriers.