Preserving the activity of enzymes under harsh oxidizing conditions: Sol-gel entrapped alkaline phosphatase exposed to bromine

Chemically reactive sol-gel matrices hold the ability of protecting entrapped enzymes from destruction by external harsh chemicals. We show this concept by exposing alkaline phosphatase (AlP) to a strong oxidizing agent - bromine. In solution, AlP is immediately destroyed by this oxidant. When AlP was entrapped in hybrid silica sol-gel materials carrying double bonds, the reactivity of AlP was preserved after exposure to bromine under conditions which totally destroy it in solution. The matrices studied were vinylated and allylated silicas, and their protectability was compared to n-alkylated silicas and to silica itself. For instance, the reactivity of AlP entrapped in allylated silica after exposure to 25.6 mM bromine solution is 40 times higher than its reactivity when entrapped in pure silica; and in solution the enzyme is totally destroyed at this concentration. Molecular level mechanisms for these observations are proposed.