Versatile preparation of spherically and mechanically controllable liquid-core-shell alginate-based bead through interfacial gelation.

Developing alginate-based beads with liquid-core-shell structure is highly appealing for industrial applications as a promising delivery matrix material. Herein, based on the reaction-diffusion mechanism, a facile method that includes dissolving natural polymer in calcium ion core solution followed by dripping it to alginate shell bath is proposed through interfacial gelation. By facilely tuning the viscosity and surface tension, the boundary condition for forming spherical beads with applicable mechanical properties was obtained. The universal viscosity-boundary relationship was independent of the type or charge condition of polymers in liquid-core. However, chitosan in the core solution significantly affected mechanical properties due to polyelectrolyte interaction with alginate, based on FTIR and SEM analyses. Moreover, a larger spherical zone was obtained by adding a surfactant into the shell bath. By varying calcium ion concentration and reaction time, beads of superior mechanical properties were obtained with an increase in shell membrane compactness.