title: Advances in oral macromolecular drug delivery.
abstract: BACKGROUND
  Various macromolecules including polypeptides, proteins, genes and polysaccharides have been drawing attention for their therapeutic potential. The passage through intestinal epithelium is the major barrier for the oral delivery of macromolecules, by either paracellular or transcellular pathways. However, most macromolecules are poorly absorbed in oral route due to their high molecular weight and low stability in the gastrointestinal (GI) tract. Nonetheless, advancing in oral macromolecular drug delivery will be significant in expanding the clinical use of therapeutic macromolecules.
  
  
  METHODS
  Technologies using chemical conjugation, absorption enhancers and nano-/micro-particulate systems have been developed to improve oral bioavailability of macromolecules, and some of them are in the process of clinical trials. In this review, they are discussed in the context of their progression states, hurdles and modes of action.
  
  
  CONCLUSIONS
  According to the better understanding of receptor or transporter structure and transport mechanisms in the GI tract, the progress ineffective oral delivery systems for therapeutic macromolecules is anticipated over the next decades. In addition, the advent of numerous particulate systems will also speed up the development of novel drug delivery technologies. This offers an optimistic perspective on the potential clinical usage of oral macromolecular drugs.
authors: Chosun University, College of Pharmacy , Gwangju 501-759 , Republic of Korea.
authors: Seung Rim
authors: SR
authors: Hwang
authors: Youngro
authors: Y
authors: Byun
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D006801:Humans; D007408:Intestinal Absorption; D046911:Macromolecular Substances / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D046911:Macromolecular Substances
keywords: absorption enhancer; chemical conjugation; macromolecular drug; oral delivery; particle