Kinetic-mechanistic studies of P. cepacia lipase catalyzed corona charge selective micelle degradation

Abstract

The polyester cores of micelles that self-assemble from poly(caprolactone)-poly(ethylene oxide) block copolymers (HO-PCL-b-PEO-X) are substrates for P. cepacia lipase-catalyzed hydrolytic degradation. The charge on the micelle corona can be modified by varying the PEO end group (X) with neutral (CH2CHCH2,OMe), positively charged (NH3+), or negatively charged (CO2−, SO3−) groups. The latter set of substrates has the added benefit that the corona charge can be changed by varying the pH. P. cepacia lipase has isoforms that manifest highly selective catalytic degradation of micelles depending on the corona charge. One isoform or group of isoforms (L(I)) selectively hydrolyze micelles with neutral or negatively charged coronas, whereas a second isoform or group of isoforms (L(II)) selectively hydrolyze micelles with neutral or positively charged coronas. The L(I) isoform was selectively inhibited, exposing the activity of the L(II) form. The occurrence of P. cepacia isoforms that was initially revealed by kinetic studies has been confirmed by two-dimensional gel electrophoresis with isoelectric focusing. Micelle surface charge could be employed as a strategy in the design of micelles for control of the transport and release of therapeutic substances.