Soft Matter Composites Interfacing with Biomolecules, Cells, and Tissues - Bioinspired Approaches for Human-Centric Technologies - page 46

provided information concerning their viscoelastic properties. In addition, different
modalities for drug loading were analyzed with respect to drug homogeneous
distribution; testosterone was employed as model drug for transdermal admini-
stration. Finally, the performances of the produced transdermal patches were
studied, in terms of reproducibility and reliability, by determination of in vitro
drug release profiles.
Transdermal patches are usually formulated to assure a sustained systemic drug
release, from a few days up to a couple of weeks. In this respect, the accurate
rheological characterization performed on patches with different formulations had
the aim to select those presenting the best viscoelastic properties, allowing an easy
administration (i.e., skin application) and duration of use. As further objective
aimed to evaluate the drug product performance, specific tests for determining the
drug release from the produced patches were performed. Determination of drug or
metal ion (in the case of silver- or copper-based patches) release profiles from
transdermal medicines, although does not represent a measure of bioavailability,
gives important information on the drug release characteristics that have the
potential to alter the biological performance of the drug in the dosage form. As
an example to nanoparticle-laden hydrogels, silver nanocomposite hydrogels were
recently developed by using acrylamide and biodegradable gelatin (Reddy
et al. 2013 ). Silver nanoparticles were generated throughout the hydrogel networks
using in situ method by incorporating Ag + ions and the subsequent treatment with
sodium borohydride as shown in Fig. 2.10 . The effect of gelatin on the swelling
studies was investigated. The hydrogel synthesized silver nanocomposites were
also characterized. The biodegradable gelatin-based silver nanocomposite
hydrogels were tested for antibacterial properties and exhibited a strong anti-
bacterial activity against bacillus. These agents can easily find applications in
wound and burn dressings. Moreover, cross-linked gelatin-chondroitin sulfate
hydrogels exhibit excellent properties for the controlled release of small cationic
antibacterial proteins into wounds (Kuijpers et al. 2000 ). Combining chondroitin
sulfate with gelatin in a cross-linked gel increases the interaction between the
cationic protein and the hydrogel, causing an increased loading capacity and an
extended release time for wound treatment. As two different antibacterial proteins,
recombinant thrombocidin, rTC-1, and lysozyme, were used resulting in similar
release results, it is, hence, expected that such release systems can be used for a
broad range of cationic antibacterial proteins without major adaptations. The
effectiveness of these hydrogels in skin treatment was demonstrated on polyester
films (Dacron) coated with a skin-like tissue as seen in Fig. 2.11 . Finally, these
hydrogels are biocompatible and degrade almost completely within several weeks
of application, thus allowing tissue integration, which is advantageous for the
healing characteristics of porous biomaterials, and may improve the long-term
infection resistance of these materials.
Similar to alginic acid polymers, chitosan-based hydrogels have also received a
great deal of attention due to their well-documented biocompatibility, low toxicity,
and degradability by human enzymes and their natural antibacterial properties (Giri
et al. 2012 ; Bhattarai et al. 2010 ; Fiejdasz et al. 2013 ). These and other properties