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Science and Technology of Bioadhesive-Based Targeted Oral Delivery Systems
Novel hydrophobic bioadhesive polymers and dosage designs are now available to effectively achieve tailored release kinetics of a broad range of drugs to meet the clinical needs.
Nov 2, 2008 By:
Avinash Nangia, PhD Pharmaceutical Technology
Volume 32,
Issue 11,
pp. 100-121
Figure 11: A schematic comparing a bioadhesive microsphere and a microfabricated bioadhesive flat chip. The flat chip allows
maximum contact area with the mucosa. It incorporates two drug reservoirs for unidirectional release (59). (ALL FIGURES AND
TABLES ARE COURTESY OF THE AUTHOR.)
Recent work has shown that hydrophobic bioadhesive polymers can prolong the residence time of orally administered insulin
microspheres by enhancing the uptake of particles. Suppression of blood glucose levels was demonstrated in Type 1 diabetic
rats and dogs (56). To evaluate the possibility of increasing the potential for greater oral uptake of bioadhesive nanoparticles
of paclitaxel (BCS Class IV), formulations were prepared and tested in rats via oral gavage. Figure 10 shows the effect of
Spheromer particles on the oral uptake of paclitaxel, in comparison with micronized (stock) paclitaxel and non-bioadhesive
paclitaxel. In contrast with micronized paclitaxel with no oral bioavailability, the uptake of bioadhesive nanoparticles resulted
in a significant increase (approximately 12 fold) in AUC compared to non-bioadhesive polylactide-co-glycolide coated nanoparticles
(57).
In a recent in vivo study, the efficacy of gliadin bioadhesive nanoparticles containing amoxicillin was evaluated to eradicate Helicobacter pylori in the GIT. When compared with an amoxicillin suspension, the bioadhesive system resulted in the complete clearance of infection
as a result of prolonged residence time attributed to bioadhesion (58).
Figure 12: Schematic showing the adherence of trilayer bioadhesive tablet to the mucosal surface of stomach. The trilayer
tablet consists of a middle slow eroding core laminated with outer bioadhesive layers. (ALL FIGURES AND TABLES ARE COURTESY
OF THE AUTHOR.)
Although spherical particles have been commonly used over the years, bioadhesive microdevices are being explored as a viable
platform for improved residence time (59). These microdevices or microreservoirs, in the shape of thin, flat, disk-like structures
are modified on one surface with a bioadhesive agent (see Figure 11). This type of asymmetric coating orients the delivery
system toward the target intestinal lining and thus provides maximum contact time because of a large surface area with minimum
resistance to passing fluids. The reservoir, which may be filled with drugs or biomolecules, provides unidirectional drug
release. These structures can be further complemented with various lectins that can make site-specific interactions (60).
Although this technology is at an early stage for drug delivery, the application of these nano-platforms has tremendous potential
in developing new therapeutic modalities. They can be used to deliver drugs, and various absorption enhancers–enzyme inhibitors
can be coreleased from the dosage form in a regulated manner, which can further increase the effectiveness of incorporated
drugs.
Figure 13: Cross-section view of BIOROD system for two-pulse delivery. (ALL FIGURES AND TABLES ARE COURTESY OF THE AUTHOR.)
Bioadhesive tablets. Bioadhesive polymer-based monolithic matrix tablets (61, 62), multilayered tablets (36), or BIOROD (BIOadhesive Rate-controlled
Oral Dosage) systems (Spherics, Mansfield, MA) with various geometrical configurations (63) offer several advantages for controlled
drug release. Bioadhesive polymers are easily mixed with drugs and compressed into matrix tablets. In the multilayer tablet
design, the layers can be configured such that the bioadhesive layer is in contact with the mucosa and independent of drug
release that occurs from the peripheral ends (see Figure 12). By modifying the surface texture and hydration rate of the compressed
bioadhesive layers, the system can be kept at the target site over an extended duration.
Avinash Nangia, PhD, is senior vice-president of research and development at Spherics, Inc., 375 Forbes Blvd., Mansfield, MA 02048, tel. 508.452.7000, fax 508.452.7070.
Articles by Avinash Nangia, PhD
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