Ionically gelled alginate foams: physical properties controlled by type, amount and source of gelling ions.

A new and flexible method for preparation of dry macroporous alginate foams with the capability of absorbing physiological solutions has been developed, which may find use within areas such as wound healing, cell culture, drug delivery and tissue engineering. The present study demonstrates how the gelation rate of the alginate and degree of ionic crosslinking can be utilized to control the physical foam properties. The rate of released Ca(2+)/Sr(2+) gelling ions available for interaction with the alginate was influenced by the concentration and physical characteristics of CaCO3/SrCO3 particles. The method of preparation of such foams allows, as described herein, tailoring of the pore structure, hydration properties and mechanical integrity in a manner not possible by other techniques.

Ionically gelled alginate foams: physical properties controlled by operational and macromolecular parameters.

Alginates in the format of scaffolds provide important functions as materials for cell encapsulation, drug delivery, tissue engineering and wound healing among others. The method for preparation of alginate-based foams presented here is based on homogeneous, ionotropic gelation of aerated alginate solutions, followed by air drying. The method allows higher flexibility and better control of the pore structure, hydration properties and mechanical integrity compared to foams prepared by other techniques. The main variables for tailoring hydrogel properties include operational parameters such as degree of aeration and mixing times and concentration of alginate, as well as macromolecular properties such as the type of alginate (chemical composition and molecular weight distribution). Exposure of foams to γ-irradiation resulted in a dose-dependent (0-30 kGy) reduction in molecular weight of the alginate and a corresponding reduction in tensile strength of the foams.

Influence of high-M alginate on the growth and survival of Atlantic cod (Gadus morhua L.) and spotted wolffish (Anarhichas minor Olafsen) fry.

Atlantic cod and spotted wolffish fry were fed high-M alginate containing feed for 59 and 55 days, respectively. During this period the fry showed a higher specific growth rate compared to controls. Uptake and distribution of alginate was studied by inclusion of the (125)I-labelled molecule in the feed. The stomach and intestine contained the highest amount while the kidney, liver and spleen contained some, indicating that the alginate was taken up by the gut and transported to internal organs. Cod fry fed 0.06% and 0.1% high-M alginate showed a death rate of 51.4% and 53.3%, respectively. The lowest mortality, 48.1%, was found in fry fed 0.01% high-M alginate. Controls showed a mortality rate of 49.0%. Differences were, however, not statistically significant. Challenge of the immunostimulated fry (fed 0.02% and 0.06% alginate for 62 days) with atypical Aeromonas salmonicida bacteria resulted in accumulated mortalities of 56% and 49%, respectively, 47 days after infection. The group that received 0.06% alginate for a shorter period (47 days) and then control feed until challenged, and the group that received alginate by bath reached a cumulative mortality of 59% and 60%, respectively. Lowest mortality (44%) was seen in the control group. Numerous microabscesses were found in both immunostimulated and control fish in secondary lamellae of the gills, haematopoietic tissues of the kidneys, the submucosa and mucosa of the intestine, the spleen, the liver and the myocardium of the heart.