ABSTRACT
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The oral absorption of biological macromolecules is one of the most challenging and exten-
sively studied topics in drug delivery research. The main obstacles associated with oral
administration and absorption of therapeutic macromolecules are the gastrointestinal (GI)
membrane impermeability to the large hydrophilic molecules and their susceptibility to
inactivation by GI enzymes. Various formulation approaches have been investigated to
enhance GI delivery of biological macromolecules including permeability of GI membrane
by use of surfactants, inhibition of enzymatic cleavage (reviewed in Chapter 5), enhancement
of tight junction permeability, and use of carrier molecules and systems. This chapter will
review tight junction modulators and various carriers used in oral drug delivery with a
particular focus on the enhancing effects of surfactants on GI delivery.
