Polymeric Supramolecular Hydrogels as Materials for Medicine - In-Situ Gelling Polymers: For Biomedical Applications - page 172

24 h, as shown in Fig. 19 . Cukierman and collaborators explained the high swelling
degree with the composition of the hydrogel: MS has a degree of functionalization
with ammonium moieties of 4 %, whereas KC has a degree of functionalization with
sulfate moieties of 50 %. The hydrogels were prepared using equimolar amounts
of functional groups, entailing a higher content of MS in the hydrogels than KC;
this leads to formation of crosslinked domains that do not disentangle. The steady
increase during the first hour of the experiment indicates that the polyionic complex is
not influenced by the surrounding acidic medium.
To determine the applicability for oral drug delivery, the tablets were loaded
with ibuprofen, a nonsteroidal anti-inflammatory drug, and investigated in regard
of their drug release. The conditions were similar to the swelling experiments:
during the first 2 h, the tablets were immersed within strongly acidic medium
at pH 1, followed by 6 h of storage at pH 6.8 phosphate buffered medium. The
granular mixture showed the same characteristics as in the swelling studies,
releasing the drug completely within 2 h. Samples prepared of the dried hydro-
gel of 50 or 100 mg, each loaded with 50 mg of ibuprofen, showed slow release
in the acidic stage that accelerated after change of the medium. After 6 h, the
tablet composed of 50 mg hydrogel released all its drug content, whereas the tab-
let with 100 mg hydrogel needed 8 h for complete drug release, as illustrated in
Fig. 20 . The slow release in the acidic phase can be explained by the poor solu-
bility of ibuprofen in acidic media. Fitting the data of these release experiments
to model predictions could show that the hydrogels release the drug with zero-
order kinetics.
In conclusion, Cukierman and coworkers presented a polyelectrolyte hydrogel
system for drug delivery. The hydrogels can be formulated as tablets that can be
loaded with drugs. The swelling degree and the release of ibuprofen with zero-
order kinetics could be shown.
Fig. 19 Comparison of the swelling degree of hydrogels based on starch and carageenan.
Tablets were composed of either a freeze-dried polyionic complex (IPEC; diamonds ) or a
granular mixture of dried polymers (phys. mix.; squares ). The swelling degree was determined
by comparison of the mass of swollen gel to dry gel. Reprinted from Cukierman et al. [ 159 ].
Copyright 2009 Elsevier