K+ and Na+ effects on the gelation properties of κ-Carrageenan

Relation between structural and release properties in a polysaccharide gel system

“…In fact, these cations play a different and specific role in the κ-carrageenan gelation pathway: the K + induces a coil?double helix transition preceding and promoting the formation of an ordered gel, whereas the Na + ion does not promote the coil?double helix transition, but takes part in the aggregation process probably through a phase separation mechanism. In this case the resulting structure is more disordered with respect to that one obtained in the presence of K + [10]. Both different gelation mechanisms (i.e.…”

“…In the case of κ-carrageenan, K + and Na + ions play a fundamental role in establishing the gelation pathway [9][10]. Previous studies, performed on gels without drug [10], have shown that it is possible, by using an…”

“…The use of the sodium salt form at 2.5% w/w determines a contribution of approximately 100 mM of Na + ions which is sufficient to appreciably affect the aggregation process [10].…”

“…Previous studies on κ-carrageenan gels have shown that the internal structure of the gel can be easily and opportunely modulated using different proportions of K + and Na + ions [9][10]. In fact, these cations play a different and specific role in the κ-carrageenan gelation pathway: the K + induces a coil?double helix transition preceding and promoting the formation of an ordered gel, whereas the Na + ion does not promote the coil?double helix transition, but takes part in the aggregation process probably through a phase separation mechanism.…”

“…Both different gelation mechanisms (i.e. the formation and lengthening of the helices induced by K + ions, or coil aggregation induced through phase separation by Na + ions) can compete when the two cations are both present in solution depending on the K + /Na + ratio and temperature [10]. The gelation pathway can be modulated to produce gels with different texture.…”