Biomedical Engineering Reference
In-Depth Information
Particle uptake via M-cells
Mucus
O
Peyer's patch
Epithelium
Lymph capillary
Mesenteric lymph vessels
Thoracic duct
Systemic circulation
SCHEME 7.1
Particle uptake pathway.
particles (10 μm or less) by oral route [28]. Depending on the nature of the polymer involved,
these systems are reported to exhibit interesting properties, which can be exploited for developing
oral delivery systems. For instance, polymeric nano/microparticles consisting of hydrophobic
biodegradable polymers have been shown to translocate across the intestinal mucosa and hence
can facilitate the absorption of peptides and proteins from the gut lumen (Scheme 7.1). M-cells,
which are located on the surface of the Peyer's patches, are a possible pathway for transporting
the nanoparticles through the epithelium of the gut [29]. On the other hand, particles composed
of hydrophilic polymers have restricted movement across the intestinal epithelium under normal
circumstances. Some of these materials are effective in enhancing the intestinal permeability and
thereby improving the peptide absorption [30]. Net surface charge of the system is also regarded as
a factor in deciding the fate of an oral delivery system. Using natural polymers as carriers is another
promising prospect in oral peptide delivery. Chitosan, starch, alginate, dextran, and the like, are
widely investigated for developing as drug-delivery systems.
Despite of the encouraging potential of polymeric nano/microparticles, formulating a
marketable peptide-delivery system still remains a major challenge. In this chapter, we have
attempted to review the prospects and problems associated with polymeric nano/microparticles
toward oral peptide delivery. Polymers are classifi ed under three different categories: (1) synthetic
biodegradable polymers, (2) synthetic nonbiodegradable polymers, and (3) natural- and protein-
based polymers (Table 7.2).
