Entrapment and determination of lipase embedded in swellable organosilica, modeling particle aggregation and aging of colloidal sol-gels

Kemar Reid, The College of Wooster

Abstract

The immobilization of enzymes have been extensively cited for use as robust biocatalyst in industrial processes. Immobilization is typically directed towards reinforcing enzyme stability and extending the range of operating conditions over which enzymes remains catalytically active. Sol-gel encapsulation provides a convenient route to immobilize enzymes and other biologicals as a result of the low temperature chemistries required and the fine control over the fabrication of the material. However, conventional protocols for encapsulation involve pre-mixing enzymes in solutions that often lead to denaturation. Swellable organosilica may provide an alternate route to embedding enzymes in inorganic sca olds. In this work lipase was trapped within swellable organosilica post gel synthesis. Lipase was found to be active within the organosilica as determined by enzyme hydrolysis of 4-nitrophenyl butyrate. Organosilica that swell depend critically on morphologies of the aggregated structures that make up the gel network and pore collapse that occurs during aging of the colloidal gel. A model for particle aggregation and aging of colloidal gels was developed towards predicting and understanding the swellable properties of organosilicas that exhibit them. The model adapts and extends the DLCA model, used to describe the aggregation processes in colloidal gels, to account for gel shrinkage of the aged gel. Model validation against physical quantities suggested that flexibilities in the aggregating structures and rearrangements of the aggregates during aging of the gel are important to the display of swellable properties.