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.