Characterization of time-dependent viscoelastic behaviors of alginate-calcium chloride hydrogels for bioprinting applications.

Alginate is known to readily aggregate and form a physical gel when exposed to cations, making it a promising material for bioprinting applications. Alginate and its derivatives exhibit viscoelastic behavior due to the combination of solid and fluid components, necessitating the characterization of both elastic and viscous properties. However, a comprehensive investigation into the time-dependent viscoelastic properties of alginate hydrogels specifically optimized for bioprinting is still lacking. In this study, we investigated and quantified the time-dependent viscoelastic properties (elastic modulus, shear modulus, and viscosity) of calcium chloride (CaCl₂) crosslinked-alginate hydrogels across 5 different alginate concentrations under 2 environmental conditions and 3 indentation depths using the Prony series. Moreover, we evaluated the printability of alginate solutions at different concentrations through bioprinted-filament collapse and fusion tests to assess their potential for bioprinting applications. The results demonstrated significant effects of alginate concentration, indentation depth, and environmental conditions on the viscoelastic behavior of alginate-based hydrogels. Furthermore, we identified 5% alginate as the optimal concentration for bioprinting. This study establishes a foundational workflow for characterizing various biomaterials, enabling their assessment for suitability in bioprinting and other tissue engineering applications.