Binding characteristics of bovine serum albumin encapsulated in sol-gel glasses: An alternative for protein interaction studies

Silica glasses doped with 500–700 μg of bovine serum albumin were prepared by the sol-gel method; two pH conditions (pH 5 and 7) were assayed for protein encapsulation. Both biomaterials showed a highly porous structure, with pore sizes in the range 5–28 nm. Columns packed with the ground biogels were on-line coupled to a C18 HPLC column for evaluation of the entrapped protein binding properties using propranolol. Binding capacities (at saturation) were ∼3.7 and 7.1 μg of propranolol (drug–protein molar ratios 1.4 and 2.7) for the biogels prepared at pH 5 and 7, respectively. The significant difference indicates increased albumin denaturation upon encapsulation at pH 5. A frontal analysis study was then performed in cartridges packed with biogel prepared at pH 7 to evaluate the protein interaction with naproxen at low concentrations (⩽2 μg/ml). Up to 6.2 μg of naproxen was bound; the estimated neffKass (functional binding sites per albumin molecule × association constant) was 4 × 105 M−1. Results corroborate the excellent preservation of native protein in sol-gel matrices, which, with low cost, simple preparation, and repeatable batch to batch characteristics, make these biomaterials an interesting alternative for studying solute–protein interactions.