Oral Delivery of Proteins and Peptides: Concepts and Applications - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 513

of mucosal immunoglobulin (Ig) A antibody responses to protein antigens [230] .
A comparative evaluation of influenza virus antigen entrapped in proteinoid micro-
spheres and free antigen was done and found that the antigen entrapped in proteinoid
microspheres was able to induce a significant IgG response as early as 2 weeks after
the administration of the dose, whereas free antigen showed no detectable antibody
response [231] . Polylactic- co -glycolic acid (PLGA) microspheres are a striking car-
rier for oral delivery of antigens because of their higher lipophilicity and protection
of the entrapped antigen from proteolytic enzymes [197-232] .
10.9 Conclusion
Therapeutic peptides and proteins can now be successfully delivered through oral
route. We have a better understanding of the para- and transcellular routes of absorp-
tion and proteolytic enzyme activity that may potentially degrade therapeutic peptides
as well as the simultaneous degradation of compounds during the mucosal transport
process. Oral delivery of therapeutic peptides and proteins is only successfully attained
if the peptides and proteins bypass the various penetration or enzymatic barriers at each
stage. The goal is to increase typical bioavailability from less than 1% to at least 10%
to 20%. Methods to increase drug flux without associated toxicity (e.g., by the use of
permeation enhancers) seeks to minimize proteolytic degradation and chemical modi-
fication. Innovative approaches with regard to mucoadhesive dosage forms and tar-
geted as well as controlled drug delivery will be employed to improve oral peptide and
protein delivery. Several methods are employed to study oral absorption using these
approaches. Promising results have begun to appear, and oral delivery of insulin is cur-
rently in clinical trials.
Acknowledgment
The authors acknowledge the financial assistance from the Indian Council of Medical
Research and TIFAC CORE in Novel Drug Delivery Systems (NDDS), Department
of Science and Technology, Government of India, New Delhi, for providing research
facilities to the team.
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