Insight into the ionotropic gelation of chitosan using tripolyphosphate and pyrophosphate as cross-linkers

Ionotropic gelation of chitosan by means of opposite charged ions represents an efficient alternativeto covalent reticulation because of milder condition of use and, in general, higher biocompatibility ofthe resulting systems. In this work 90◦light scattering (turbidimetry), circular dichroism (CD) and1HNMR measurements have been performed to study the interactions between the biopolymer and ioniccross-linkers tripolyphosphate (TPP) and pyrophosphate (PPi) in dilute solutions. Thereafter, a dialysis-based technique was exploited to fabricate tridimensional chitosan hydrogels based on both polyanions.Resulting matrices showed a different mechanical behavior because of their peculiar mesh-texture atmicro/nano-scale: in the present contribution we demonstrate that TPP and PPi favor the formation ofhomogeneous and inhomogeneous systems, respectively. The different texture of networks could beexploited in future for the preparation of systems for the controlled release of molecules