Interfacial processes that modulate the kinetics of lipase-mediated catalysis using porous silica host particles

Abstract

Surface immobilised lipases are important bioactive materials that have a wide range of applications in the biotechnology, chemical and pharmaceutical industries. However, the interfacial mechanism of action and the interplay between material characteristics and lipase activity are not well understood. A quartz crystal microbalance with dissipation (QCM-D) was used to elucidate interfacial processes between lipases and lipid films deposited on silica surfaces with varying wettabilities. Adsorption of triglycerides onto a hydrophilic support at multilayer coverage resulted in fast lipolysis kinetics, while adsorption onto a hydrophobic support hindered lipase activity and delayed lipolysis, characterised by changes in frequency and the release of free fatty acids from the QCM-D cell. In parallel, porous silica carriers with varying hydrophilicities/phobicities were used to confine lipid substrate molecules and manipulate lipase-mediated reactions, i.e. hydrolysis and esterification of triglycerides, as monitored using a pH-stat titrator. The surface chemistry of the carrier particles played a critical role on lipase action, whereby hydrophilic silica particles promoted catalysis of the hydrolysis reaction and hydrophobic particles promoted the reverse, esterification reaction. Physical observations of lipid film hydrolysis in combination with biomaterial design of lipid loaded porous silica particles provided advancements in understanding the mechanism of lipase action, which can be harnessed to tailor the delivery of poorly water-soluble molecules and improve the synthesis process of organic esters.