The bioconjugation mechanism of purine cross-linkers affects microstructure and cell response to ultra rapidly gelling purine–chitosan sponges

Abstract

C-NMR revealed the formation of a quadruplex structure among the four GDP molecules confined between the chitosan backbone. This resulted from the ability of guanine to form intermolecular hydrogen bonds, while adenosine in ADP lacks this capacity. The formation of a more organized structure in GDP-chitosan sponges also increased the crystallinity of the sponge as shown by X-ray diffraction data. Further, physicochemical analyses with SEM and μCT indicated a more open-pore architecture and increased porosity. Although an active population of encapsulated cells was maintained in all chitosan sponges overtime, the GDP-based sponges provided a 6-fold increase in the activity of MC-3T3 cells and significantly enhanced their proliferation due to a more appropriate microstructure. Overall, these findings suggest that slight changes in the chemical structure of the cross-linker in the preparation of chitosan-based biomaterials will have a significant impact on the structural properties of the chitosan. This important parameter can be utilized to modulate cell response and to understand the cell signaling pathway of chitosan-based biomaterials in the context of their applications in tissue engineering.