Real-Time Monitoring of Lipolysis Based on Polystyrene Inverse Opal Layer by Optical Interferometry

Real-time monitoring of interfacial lipolysis is critical for understanding lipid metabolism and food digestion but remains challenging for traditional analytical techniques due to the complexity of heterogeneous lipid-aqueous interfaces. Here, a label-free optical interferometric method based on three-dimensional ordered polystyrene inverse opal (PS-IO) films for the dynamic analysis of lipolysis was reported. The PS-IO films, featuring higher porosity and hydrophobicity, serve as a high-specific-surface-area host for triglyceride immobilization, forming a sensitive optical layer for interferometric biosensing. As lipase enters the layer and hydrolyzes lipids, the mass fluctuation induces a shift in Fabry-Pérot fringes, which was captured and converted to a change in optical thickness by self-developed ordered porous layer interferometry (OPLI). Using an optimized lipolysis model, the analytical system exhibited a linear response to lipase concentrations ranging from 1 to 200 U/L. Furthermore, the high temporal resolution of the system enabled the derivation of Michaelis-Menten kinetic parameters. The optical interferometry platform was successfully applied to discriminate the digestion of triglycerides with varying degrees of unsaturation and commercial edible oils, revealing that unsaturation correlates with lipolysis rates due to the steric structure of lipid molecules at the interface. This methodology provides an effective and quantitative tool for probing the lipolysis of triglycerides with different unsaturation and evaluating the digestion behavior of edible oil in the food industry and physiological systems.