title: Implantable hollow fiber bioreactor as a potential treatment for hypercholesterolemia: characterization of the catalytic unit.
abstract: Previous studies have shown that the modification of low density lipoprotein (LDL) by the enzyme phospholipase A(2)(PLA(2))results in a reduction of cholesterol levels in the plasma of hypercholesterolemic rabbits, due to accelerated clearance of the modified LDL. In the current study, we established techniques and optimized the ratio of enzyme to support for the immobilization of PLA(2) on a polymeric support. Hollow fiber bioreactors made from polytetrafluoroethylene (PTFE) polymers were used to encapsulate immobilized PLA(2). This design was adopted to eliminate hemolysis of red blood cells by the enzyme. Characterization of the resulting immobilized enzyme in terms of its activity, Michaelis-Menten kinetic constants, and the variation of its activity with incubation time is presented. The enzyme activity was not significantly altered upon incubation at 37 degrees C in lipoprotein-deficient serum (LPDS), over the course of 2 months. The Michaelis-Menten kinetics constants are K(M) = 8.9 mM, V(max) = 6434.2 for the free enzyme and K(app) (M) = 16.7 mM, V(app) (max) = 619.7 for the immobilized enzyme. These data suggest that a system based on immobilized PLA(2) in conjunction with hollow fiber bioreactors (HFBs) may be a good candidate for lowering LDL levels in plasma.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, E-25 Room 342, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Shefer
authors.forename: V
authors.initials: V
authors.lastname: Rosenberger
authors.forename: G
authors.initials: G
authors.lastname: Vahanian
authors.forename: W T
authors.initials: WT
authors.lastname: Wong
authors.forename: R
authors.initials: R
authors.lastname: Langer