QCM-D and ToF-SIMS Investigation to Deconvolute the Relationship between Lipid Adsorption and Orientation on Lipase Activity.
Quartz crystal microbalance with dissipation (QCM-D) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to provide insights into the relationship between lipid adsorption kinetics and molecular behavior in porous silica particles of varying hydrophobicities on lipase activity. Lipase (an interfacial enzyme that cleaves ester bonds to break down lipids to fatty acids and monoglycerides) activity was controlled by loading triglycerides at different surface coverages in hydrophilic and hydrophobic porous silica particles. The rate of lipid adsorption increased 2-fold for the hydrophobic surface compared to the hydrophilic surface. However, for submonolayer lipid coverage, the hydrophilic surface enhanced lipase activity 4-fold, whereas the hydrophobic surface inhibited lipase activity 16-fold, compared to lipid droplets in water. A difference in lipid orientation for low surface coverage, evidenced by ToF-SIMS, indicated that lipid adsorbs to hydrophilic silica in a conformation promoting hydrolysis. Multilayer coverage on hydrophobic and hydrophilic surfaces was indistinguishable with ToF-SIMS analysis. Increased lipid adsorption for both substrates facilitated digestion kinetics comparable to a conventional emulsion. Improved understanding of the interfacial adsorption and orientation of lipid and its digestibility in porous silica has implications in improving the uptake of pharmaceuticals and nutrients from lipid-based delivery systems.
School of Pharmacy and Medical Sciences, University of South Australia , Playford Building P4-04, City East Campus, Adelaide, South Australia 5001, Australia.
Paul
P
Joyce
Future Industries Institute, University of South Australia , Mawson Lakes Campus, Mawson Lakes, South Australia 5095, Australia.
Ivan
I
Kempson
School of Pharmacy and Medical Sciences, University of South Australia , Playford Building P4-04, City East Campus, Adelaide, South Australia 5001, Australia.
Clive A
CA
Prestidge
D000327:Adsorption; D057927:Hydrophobic and Hydrophilic Interactions; D008049:Lipase / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry; D058525:Quartz Crystal Microbalance Techniques; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties
D008055:Lipids; D012822:Silicon Dioxide; D008049:Lipase