Introduction: Collagen is the most abundant protein of animal connective
tissues, found in skins, bones or cartilages, which turn it into one of
the key polymers to be considered for biomedical applications, namely
tissue engineering and drug delivery.
Current industrial procedures to extract collagen involves bovine and
porcine as main sources. However, due to religious factors and the risk
of transmitting diseases to humans, the search for new sources has been
growing.Marine origin is one of the alternatives that has been explored,
particularly, through by-products of fish processing, such as skins, scales
or spines, with both economic and environmental benefits [1].
In this work, collagen was extracted from shark Scyliorhinus canicula
skin. The collagen was processed and further evaluated as alternative
for dermal membranes, regarding sustained release of drugs.
Materials and methods: Extraction of collagen: Skins of shark (Scyliorhinus
canicula) were treated with 0.1 M NaHO to remove non-collagenous
proteins, cleaned with distilled water and then collagen was
extracted with 0.5 M acetic acid, overnight. After centrifugation, the
supernatant was purified by dialysis and the resultant collagen solution
was freeze-dried. The produced collagen was characterized by FTIR,
SDS-PAGE, aminoacid composition and l-DSC.
Preparation of membranes: Collagen was dissolved in 0.5 M acetic
acid to obtain 1% (w/v) solution. Then, a 5% (v/v) hexamethylene
diisocyanate (HMDI) was added at a ratio of 1% and 5% with respect
to collagen, and allowed to react for 24 h. The mixture was cast in Petri
dish, and let to dry at room temperature. Non-crosslinked membranes
were prepared as reference. In order to prepare membranes for drug
delivery assessment, dexamethasone was added to the collagen solutions
and membranes were prepared as described. Collagen membranes
were characterized by determining water contact angle, mechanical
properties and stability in PBS. Furthermore, the release profile of dexamethasone
was also determined.
Results: SDS-Page analysis indicates that the extracted collagen from
shark skin is mainly of type I. l-DSC analysis indicates a denaturation
temperature of about 33°C, lower than mammalian collagen. The aminoacid
analysis confirmed the presence of hydroxyproline and the high
quantity of glycine, characteristic of collagen.
Collagen membranes showed more stability in PBS as long as the
degree of crosslinking is higher, which also influences their mechanical
properties. Moreover, the crosslinking degree also affects the hydrophobicity
of the membranes. The release profile of dexamethasone was
evaluated, with the drug being released in a progressive and sustained
manner.
Discussion and conclusions: Collagen has been successfully extracted
from shark skins and used on the preparation of membranes by solvent
casting. The properties of the collagen membranes can be tunned,
according to crosslinking degree, revealing a promising potential for
application in biomedical field, namely as dermal membranes for controlled
drug release.
Acknowledgments: Funding is acknowledged from projects IBEROMARE,
MARMED and POLARIS. FCT Post-doc fellowship (JMS) is also
acknowledged