Pectin Nanoporous Structures Prepared via Salt-Induced Phase Separation and Ambient Azeotropic Evaporation Processes.

Polysaccharide nanoporous structures are suitable for various applications, ranging from biomedical scaffolds to adsorption materials, owing to their biocompatibility and large surface areas. Pectin, in particular, can create 3D nanoporous structures in aqueous solutions by binding with calcium cations and creating nanopores by phase separation; this process involves forming hydrogen bonds between alcohols and pectin chains in water and alcohol mixtures and the resulting penetration of alcohols into calcium-bound pectin gels. However, owing to the dehydration and condensation of polysaccharide chains during drying, it has proven to be challenging to maintain the 3D nanoporous structure without using a freeze-drying process or supercritical fluid. Herein, we report a facile method for creating polysaccharide-based xerogels, involving the co-evaporation of water with a nonsolvent (e.g., a low-molecular-weight hydrophobic alcohol such as isopropyl or n-propyl alcohol) at ambient conditions. Experiments and coarse-grained molecular dynamics simulations confirmed that salt-induced phase separation and hydrogen bonding between hydrophobic alcohols and pectin chains were the dominant processes in mixtures of pectin, water, and hydrophobic alcohols. Furthermore, the azeotropic evaporation of water and alcohol mixed in approximately 1:1 molar ratios was maintained during the natural drying process under ambient conditions, preventing the hydration and aggregation of the hydrophilic pectin chains. These results introduce a simple and convenient process to produce 3D polysaccharide xerogels under ambient conditions.

Microencapsulation by pectin for multi-components carriers bearing both hydrophobic and hydrophilic active agents.

Oil/water microencapsulation by microfluidic systems has been a prominent delivery method to prepare functional microcapsules in the food, cosmetic, and pharmaceutical industries because it is an easy way to control the shape and size of structures and functionalities. We prepared biocompatible and multi-component microcapsules using the precipitation and ionic crosslinking of pectin in a poor solubility environment and with multivalent cations, respectively. When the aqueous solution (including calcium ions and ethanol) in a sheath flow met the flow of a pectin aqueous solution containing oil droplets, ethanol-gelation and ionic cross-linking occurred, enclosing the inner oil phase droplets by solidified pectin shells. Furthermore, the resulting microcapsules stabilized by pectin shells exhibited functionalities using a hydrophobic agent and nanoparticles of a hydrophilic species that were dissolved and dispersed, respectively, in the oil phase.