Biomedical Engineering Reference
In-Depth Information
satisfied by sulphated polysaccharides obtained from abundant and safer origin and Ulvan
can represent the ideal material for such purpose.
2.2.3 Immunomodulating activity
Some of the polysaccharides obtained from the cell walls of seaweeds appear to exert
immunomodulatory activities in mammals as they modify the activity of macrophages.
Most classes of carrageenans, sulphated polysaccharide obtained from red algae (Figure 1)
are known to induce potent macrophages activation (Nacife et al., 2004.).
The structure of the repeating unit mostly found in Ulvan, resembles that typical of
glycosaminoglycan, such as hyaluronic acid and chondroitin sulphate because they all
contain glucuronic acid and sulphate. Chondroitin sulphate based proteoglycans are known
to be produced by macrophages and human monocytes at inflammatory sites (Uhlin-
Hansen et al., 1993) and the structure similarity shared with most of sulphated
polysaccharides of algal origin and in particular with Ulvan could represent the trigger of
the immunomodulating activity of these materials. Indeed Ulvan from
Ulva rigida
has been
reported to modulate the activity of murine macrophages and the presence of sulphate
groups has demonstrated to be necessary (Leiro et al., 2007). On the other side, a deeper
insight into the structure-immunomodulating effect relationship of these polysaccharides
would provide the possibility to obtain an anti-inflammatory effect simply by properly
modifying their chemical structure.
2.2.4 Antihyperlipidemic activity
Ulvan is known to resist degradation by human endogeneous enzymes thus belonging to
the dietary fibers of “sea lattuce” (Taboada et al., 2010). Dietary fibers are considered to be
helpful in the prevention of pathologies related to intestinal transit dysfunctions because
they act as bulking agents due to their impressive water retention capacity (Bobin-Dubigeon
et al., 1997). Dietary fibers are also associated with their ability to lower cholesterol levels
(Brown et al., 1999) and the presence of ion charged groups along their structure has shown
to improve this beneficial activity (Guillon & Champ, 2000). The ionic groups are thought to
complex with bile acids and consequently increase fecal bile acid excretion thus promoting
blood cholesterol attenuation (Yu et al., 2003). Ulvan is reported to interact and binding
effectively with bile acids due to its high content of negatively charged groups (Lahaye,
1991) thus potentially contributing to the antihyperlipidemic action. Indeed Ulvan has been
demonstrated to effectively reduce the level of total and LDL-cholesterol concentrations in
the serum and induce an increase in the daily bile excretion in rats (Yu et al., 2003). This
activity has been shown to be strongly dependent on the molecular weight of the
polysaccharide because a decrease in the viscosity of these materials affected negatively the
interaction with bile acids.
3. Potential use of ulvan in biomedical applications
A material suitable for biomedical applications, namely tissue engineering, regenerative
medicine and drug delivery, is required to be biocompatible and biodegradable and its
products of degradation must be safe and easily cleared from the host organisms. Most of
the materials obtained from natural resources are able to fulfil these strict requirements but
