Biomedical Engineering Reference
In-Depth Information
In order to be employed in biomedical applications such as tissue engineering, regenerative
medicine and drug delivery, Ulvan needs to be converted into an insoluble material under
physiological conditions and to have mechanical properties suitable for the end application.
The preparation of physically crosslinked Ulvan hydrogels has been reported since long
times, but their weak mechanical properties and uncontrolled dissolution in presence of
physiological fluids make them unsuitable for biomedical uses, where a scaffolding role is
required
A novel method for covalent crosslinking of Ulvan through the UV mediated radical
polymerization of activated macromers by double bond conjugated moieties, revealed to be
promising in the preparation of chemically crosslinked Ulvan hydrogels. The conjugation of
methacryloyl group to Ulvan through the reaction with methacrylic anhydride under
slightly basic conditions gave the best results in terms of product yield and substitution
degree. The hydrogels obtained after their exposure to UV light seemed to be very stable in
physiological conditions.
The crosslinking of the Ulvan macromer precursors is usually not complete because is
hampered both by its aggregative behaviour in solution that limits the availability of the
(meth)acryloyl groups and very presumably by the radical quenching activity of the
polysaccharide during the UV exposure thus negatively affecting the mechanical properties
of the final hydrogels. Nevertheless the antioxidant activity of Ulvan could make this
material a good candidate as a matrix for cell encapsulation due to the possible protection
against the radicals produced during UV crosslinking (Fedorovich et al., 2009). The use of
these materials as a base for cytocompatible scaffolds is also promoted by the softness
related to partial crosslinking of these macromers, since it is known that cell spreading
within hydrogels is influenced by matrix stiffness and soft matrices interestingly are
expected to promote cell spreading (Liu & Chan-Park, 2009).
Moreover the possibility of preparing Ulvan based hydrogels by a straightforward
technique such as UV crosslinking makes the use of Ulvan in biomedical fields even more
attractive. Indeed UV photopolymerization allows the spatial and temporal control over the
crosslinking and the fabrication of hydrogels in situ with the possibility of forming complex
architectures that adhere and conform to tissue structure.
5. Acknowledgment
The present work was performed within the framework of NOE project Expertissues
(NMP3-CT 2004-500328) and Expertissues Miniproject NATCOM.
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