Abstract
Young's modulus of heat-denatured gels of calcium alginate and bovine
serum albumin (BSA) was determined and compared to the modulus of
BSA gels containing sodium alginate and to pure BSA gels. Ionic strength,
pH, and calcium concentration were varied. The BSA Ca-alginate gels
were either prepared with D-glucono-delta-lactone (GDL) and CaCO3
to induce alginate gelation before the gelation of BSA, or by soaking
heat-denatured BSA/Na-alginate gels in a CaCl2 solution. BSA/Ca-alginate
gels were stronger than BSA/Na-alginate gels at all conditions, and
stronger than pure BSA gels up to higher pH values and up to somewhat
higher ionic strengths than BSA/Na-alginate gels. The strength of
BSA/Ca-alginate gels was highly dependent on the strength of the
alginate gel. This was shown by variation of the calcium concentration
and by soaking the gels in EDTA, NaCl, and CaCl2 solutions. When
BSA/Na-alginate or BSA/Ca-alginate gels prepared at optimum conditions
were soaked in solutions of higher ionic strength or pH, no reduction
in gel strength was observed. Consequently, they were much stronger
than gels that were prepared directly at high pH or ionic strength.
The results may suggest that the alginate network in a BSA/Ca-alginate
gel increases the effectiveness of electrostatic BSA-alginate cross-links
or entanglements. However, other explanations are also possible.
(C) 1999 Elsevier Science Ltd. All rights reserved.
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