Controlling Porosity of Calcium Alginate Hydrogels by Interpenetrating Polyvinyl Alcohol–Diboronate Polymer Network

The high porosity of calcium alginate hydrogels was controlled by its treatment with polyvinyl alcohol followed by cross-linking with diboronic acids, which blocks larger pores in calcium alginate. Low molecular weight (11-31 kDa) polyvinyl alcohol selectively diffuses into larger pores of calcium alginate hydrogels, and the subsequent cross-linking with 1,3-benzenediboronic acid is highly efficient, providing stoichiometry of one 1,3-benzenediboronic acid per four OH groups of polyvinyl alcohol. Cross-linking blocks larger pores in calcium alginate hydrogels, decreasing leaching of model bovine serum albumin, insulin, and myoglobin proteins physically entrapped in calcium alginate hydrogels by 20-30 fold. Internal pore blockage was confirmed by scanning electron microscopy and surface pore closure by liquid atomic force microscopy.