Biomedical Engineering Reference
In-Depth Information
Figure 11.10 SEM micrographs of the cross-section of Cu 2+
- alginate aerogel dried after 22 h of ageing of the
hydrogel: (a) section of the crust; (b) cross-section normal to the shaft; (c) detail of the shaft wall
indicating an anisotropic contraction of the gel away from the shaft axis. The aerogel volume is
nearly half of the volume of the hydrogel. Adapted with permission from Di Renzo et al.( 2005 )
© 2005 American Chemical Society.
11.3.2.3
Amphiphilic alginate beads
Controlled-release properties are of considerable interest for numerous pharmaceutical
and medical applications (Leonard et al., 2004 ; Rastello de Boisseson et al., 2004 ). In the
selection of a gel network for a given application, properties such as modulus, swelling
ratio and porosity needed to be matched via appropriate formulations. In addition,
knowledge of gel stability is essential as it is directly related to gel performance with
time. A novel way to gel alginates is to transform them into amphiphilic derivatives that
then form networks by associating in water ( Chapter 6 ).
Such amphiphilic Na + or Ca 2+ alginate gels were prepared by Rastello de Boisseson et al.
( 2004 ). Their objective was to control properties such as mechanical strength, porosity or
stability through the introduction of covalently bound hydrophobic alkyl chains. The
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