Permeability of a sol-gel synthesized aminopropyl-silicate-titanate hybrid membrane for the microcapsule-shaped bioartificial pancreas

The aminopropyl-silicate-titanate hybrid membrane was successfully synthesized onto a Ca-alginate gel bead by the sol-gel method, from two kinds of organometallic compound precursors, tetraethyl orthotitanate (TEOTi) [Ti(OC₂H₅)₄] and 3-aminopropyltrimethyl orthosilicate (APTrMOS) [(CH₃O)₃Si(CH₂)₃NH₂]. APTrMOS acted as a binding agent between inorganic titanate and alginate polymer via electrostatic interaction between amino groups of APTrMOS and carboxyl groups of alginate. From the measurements of the diffusion of ovalbumin and γ-globulin through the aminopropyl-silicate-titanate hybrid membrane, it was found that the molecular permeability of the membrane could be controlled by changing the amount of each precursor. The molecular weight cutoff point required for immunoisolation, less than 150kDa, was achieved under the condition that the amount of APTrMOS was 3.40 mmol/ (10 ml of Ca-alginate) and TEOTi was more than 1.42 mmol. The islets encapsulated in the membrane showed almost the same insulin secretion viability as the free islets.