Resolutions in Branched Alkanes using Lipase in Beads


Principal Investigator: S H Neau
Abstract: The long-term goals of this research are to investigate and characterize fresh and freeze-dried macromolecule-loaded polysaccharide-based hydrogel beads for applications in chemical reactions, and their application in macromolecule delivery for therapeutic purposes. The use of these beads for therapeutic peptide and protein delivery will be pursued, in particular for site specific delivery of these agents to the colon following oral administration. Various chemical reactions can be investigated using entrapped enzymes. The long-term goals include applications of these beads in reactions where the catalysis is well characterized, such that the bead performance (and not the reaction) is studied. The proposed research incorporates lipase into these beads for easy recovery and subsequent delivery. The solvents are straight chain and methyl-branched alkanes to test the hypothesis that branching can enhance the activity and enantioselectivity of lipase. The short-term goal is the resolution of the pharmacologically active enantiomer of a drug that is a racemic mixture, ibuprofen, by enantioselective esterification by a lipase that is free or entrapped in the chitosan bead. Isolation of the active, enantiomer will become a regulatory requirement because administration of only the active enantiomer can reduce the toxicity and dose. Resolution using an entrapped lipase offers a rapid, enantioselective reaction; repeated applications since the enzyme can be recovered; and economical terminal resolution in the synthesis sequence. In the first study, the solvent system, consisting of water at a known activity in an alkane, will be optimized for the fastest reactions and the highest enantioselectivity. Michaelis-Menten parameters will be evaluated and compared. In the second study, lipase-loaded chitosan hydrogel beads are fabricated. The successful rugged, spherical matrix can entrap the enzyme, minimally interfere with activity, and allow substrate and product diffusion. Permeability of the bead will be investigated by measuring the substrate diffusion coefficient within the bead. Reaction parameters of the entrapped enzyme will be compared to those of the free enzyme in the third study. The stability of the bead, the efficiency of the lipase entrapment, and the reduction in lipase activity as a function of repeated applications will also be evaluated in the third study.
Funding Period: 2002-08-01 - 2006-07-31
more information: NIH RePORT