For these observations, however, the gelling rate seemed to remain constant, independently of the alginate concentration.
A reduced gelling rate may therefore be obtained by using high M W alginates.
Our interpretation of the data presented here is that the most important factor influencing the gelling rate was the rate of gelling ion release from the particles.
The data shown in Figure 3 demonstrate both a higher gelling rate for the light alginate and that the gel stabilized at lower elasticity values.
Not surprisingly, the final gel strength was lowered in the presence of a strontium binding compound, hexametaphosphate, and this was also found to increase the gelling rate.
The gelling rate could be manipulated, e.g. through selection of the alginate type and molecular weight, particle sizes and the concentration of non-gelling ions.
For the smallest particle sizes (less than 25 μm) it should be noted that, because of the high gelling rate, some mechanical degradation of the gel probably occurred while the two components were still being displaced between the syringes.
The data also demonstrated that the use of calcium alginate particles gave a higher gelling rate compared to similar strontium alginate particles, which may reflect the difference in binding mechanisms.
Increasing the soluble alginate concentration in the formulation from 1.0%to2.0%0% resulted in an approximately two-fold increase in the storage modulus, but did not significantly change the gelling rate (3.0 vs. 2.6 minutes).
The final gel elasticity as well as gelling rate seemed to follow a similar pattern for both types of particles although the final storage modulus was several times higher and gelation half time generally shorter when using strontium alginate as the gelling ion donor.
