Application of Chitosan-Based Gels in Pharmaceuticals - Chitosan Based Hydrogels: Functions and Applications - page 328

Comparing the capacities of chitosan versus cellulose membranes, Sawayanagi et al. [98]
found that the diffusion constant for acidic substances such as nonsteroidal antiinflammatory
drugs was two to three times larger through the chitosan membrane.
Regarding the kinetic characteristics of several films described in the literature, it can be
seen that permeability coefficients are affected by different parameters, including the
degree of cross-linking [94,96], the acid or base nature of the drug [98], the molecular vol-
ume of the drug [98], the pH of the environmental medium [99], and the thickness of the
membrane [97].
Until now, little information has been available concerning the influence of the site of
application of such systems. Furthermore, most of the literature consists of in vitro release
tests, which provides information on pharmacokinetic parameters affected by the biopoly-
meric membrane solely. It could be interesting to conduct in vitro skin permeation tests
using excised skin mounted on a diffusion cell such as the Franz diffusion apparatus [100].
This type of test could provide useful indications of the pharmaceutical flux from the
membrane to the skin sample, which in turn may provide information on in vivo perfor-
mance of the transdermal system [101].
7.5 Conclusions
Chitosan has the desired properties for safe use as a pharmaceutical excipient. This has
prompted accelerated research activities worldwide on chitosan micro- and nanoparticles
as drug delivery vehicles. These systems have great utility in controlled release and target-
ing studies of almost all classes of bioactive molecules as discussed in this review. Recently,
chitosan is also extensively explored in studies of gene delivery. However, studies on the
optimization of process parameters and scale-up from the laboratory to pilot plant and
then to production level are yet to be undertaken. Most of the studies carried out so far are
only under in vitro conditions. More in vivo studies need to be carried out. Chemical modi-
fications of chitosan are important for obtaining the desired physicochemical properties
such as solubility, hydrophilicity, and so on. The published literature indicates that in the
near future, chitosan-based particulate systems will have more commercial status in the
market than in the past.
References
1. Agnihotri, S. A., Mallikarjuna, N. N., and Aminabhavi, T. M. 2004. Recent advances on chitosan-
based micro- and nanoparticles in drug delivery. J Control Release 100: 5-28.
2. Kumar, M. N. V. R., Muzzarelli, R. A. A., Muzzarelli, C., Sashiwa, H., and Domb, A. J. 2004.
Chitosan chemistry and pharmaceutical perspectives. Chem Rev 104: 6017-6084.
3. Akbuga, J. and Durmaz, G. 1994. Preparation and evaluation of cross-linked chitosan micro-
spheres containing furosemide. Int J Pharm 111: 217-222.
4. Nishimura, K., Nishimura, S., Seo, H., Nishi, N., Tokura, S., and Azuma, I. 1986. Macrophage
activation with multi-porous beads prepared from partially deacetylated chitin. J Biomed Mater
Res 20: 1359-1372.