30 mL of 0.1% (w/v) of chitosan dispersion for 30 s. Periodically, the buccal cells
were harvested from the cheek and suspended in 0.25 M sucrose solution. Buccal
cells harvested from the cheeks of human subjects who received no treatment were
used as control. The results showed that chitosan formulation was able to adhere to
the human buccal cells for at least 1 h.
Chitosan microspheres, prepared by spray-drying, were loaded with
cholorohexidine, a drug that is used for treating chronic candida infection. The
microspheres along with mannitol and sodium alginate as excipients were compressed into tablets by direct compression. Tablets containing 40 mg of the drug
were administered buccally to human subjects. The control group rinsed with a
commercial mouthwash (DentosanR) containing 0.2% (w/v) chorohexidine. For the
control group, the salivary drug concentrations were very low and no drug was
detected after 2 h whereas the drug was still detected even after 3 h in the saliva of
the test group [54].
6.2.1 Chitosan Beads, Microcapsules and Microspheres for Gastrointestinal
Delivery Systems
Many gastric retentive devices have been developed such as high-density systems,
expandable systems, superporous hydrogel systems, intragastric floating systems
and mucoadhesive systems. In view of recent problems concerned with
Helicobacter pylori infection, causing ulcerations, many researchers have been
trying to make effective sustained release antibacterial therapy. Tetracycline-loaded
chitosan microspheres have been developed for stomach-specific delivery. The
microspheres prepared by ionic precipitation with sulfate were spherical in shape
with an average diameter of 2–3 μm and were 55% drug-loaded. It was found that
only about 60% of the entrapped tetracycline was released in 2 h into the medium of
pH 3.5 whereas the microspheres were instantly dissolved at pH 1.2–2.0. Another
study examined the gastric residence time of chitosan microspheres following oral
administration in fasted gerbils. Because of the instant dissolution of those
microspheres at pH 1.2–2.0, the effect of acid suppression on the chitosan microsphere residence time and on the tetracycline concentrations in stomach was also
examined. Similar results were obtained as in vitro. As a result of these studies,
chemically crosslinked glyoxal chitosan microspheres were developed that showed
increased stability even at pH 1.2–2.0. These microparticles were settled and adhere
to gastric mucosa by electrostatic interaction. A large fraction of the administered
chitosan microsphere dose was found in the colon after 6 h. The tetracycline
concentration in the stomach from the crosslinked chitosan microspheres was higher
than that of the non-crosslinked microspheres for all times of administration.
Chitosan is a promising polymer for colon delivery because it can be biodegraded
by the colonic microflora and it has mucoadhesive character. A thorough study has
been carried out on chitosan beads obtained by ionotropic gelation with alginate or
tripolyphosphate. The aim was to develop, using natural polymers, a controlled
release system that would resist the conditions in the stomach and release its drug
288
A.K. Anal and A. Tuladhar
were harvested from the cheek and suspended in 0.25 M sucrose solution. Buccal
cells harvested from the cheeks of human subjects who received no treatment were
used as control. The results showed that chitosan formulation was able to adhere to
the human buccal cells for at least 1 h.
Chitosan microspheres, prepared by spray-drying, were loaded with
cholorohexidine, a drug that is used for treating chronic candida infection. The
microspheres along with mannitol and sodium alginate as excipients were compressed into tablets by direct compression. Tablets containing 40 mg of the drug
were administered buccally to human subjects. The control group rinsed with a
commercial mouthwash (DentosanR) containing 0.2% (w/v) chorohexidine. For the
control group, the salivary drug concentrations were very low and no drug was
detected after 2 h whereas the drug was still detected even after 3 h in the saliva of
the test group [54].
6.2.1 Chitosan Beads, Microcapsules and Microspheres for Gastrointestinal
Delivery Systems
Many gastric retentive devices have been developed such as high-density systems,
expandable systems, superporous hydrogel systems, intragastric floating systems
and mucoadhesive systems. In view of recent problems concerned with
Helicobacter pylori infection, causing ulcerations, many researchers have been
trying to make effective sustained release antibacterial therapy. Tetracycline-loaded
chitosan microspheres have been developed for stomach-specific delivery. The
microspheres prepared by ionic precipitation with sulfate were spherical in shape
with an average diameter of 2–3 μm and were 55% drug-loaded. It was found that
only about 60% of the entrapped tetracycline was released in 2 h into the medium of
pH 3.5 whereas the microspheres were instantly dissolved at pH 1.2–2.0. Another
study examined the gastric residence time of chitosan microspheres following oral
administration in fasted gerbils. Because of the instant dissolution of those
microspheres at pH 1.2–2.0, the effect of acid suppression on the chitosan microsphere residence time and on the tetracycline concentrations in stomach was also
examined. Similar results were obtained as in vitro. As a result of these studies,
chemically crosslinked glyoxal chitosan microspheres were developed that showed
increased stability even at pH 1.2–2.0. These microparticles were settled and adhere
to gastric mucosa by electrostatic interaction. A large fraction of the administered
chitosan microsphere dose was found in the colon after 6 h. The tetracycline
concentration in the stomach from the crosslinked chitosan microspheres was higher
than that of the non-crosslinked microspheres for all times of administration.
Chitosan is a promising polymer for colon delivery because it can be biodegraded
by the colonic microflora and it has mucoadhesive character. A thorough study has
been carried out on chitosan beads obtained by ionotropic gelation with alginate or
tripolyphosphate. The aim was to develop, using natural polymers, a controlled
release system that would resist the conditions in the stomach and release its drug
288
A.K. Anal and A. Tuladhar