Study on binding phenomenon of lipase enzyme with tributyrin on the surface of graphene oxide array using surface plasmon resonance

The performance of biological sensors can be significantly improved by understanding the interaction phenomena at the sensing interfaces. Graphene oxide (GO) surface, has oxygen containing functional groups that strongly interact with the enzyme as well as affect the binding phenomenon. This paper reports an SPR-based approach for the development of lipase (LIP) enzyme based triglyceride (TG) biosensor using the graphene oxide (GO) platform, covalently linked on self-assembled monolayer. The GO flakes, prepared by Hummer's modified process was covalently bonded with self-assembled monolayer of 4-amino thiophenol (4-ATP) on gold (Au) to fabricate GO/4-ATP/Au SPR surface. The LIP was covalently immobilized with the carboxylic acid group of GO sheet (LIP/GO/4-ATP/Au) to construct sensing platform (LIP/GO/4-ATP/Au) for the detection of TG using SPR. The SPR angle is found to vary linearly with the concentration of tributyrin (tbn) within a range of 20 mg dL(-1) to 350 mg dL(-1). The value of association equilibrium constant (K-A) is 3.4 mM. This shows that SPR signal is sensitive to detect low concentration of TG i.e. 20 mg dL(-1). The LIP/GO/4-ATP/Au bioelectrode is also fabricated to conduct the cyclic voltammetric (CV) study as supportive information and found to have a linear range of 50 to 350 mg dL(-1) and low K-m value of 0.88 mmol. The SPR surface provides wider linearity, low detection limit than the electrochemical platform and high affinity towards the tbn but suffers from non-specific interaction by the serum substances which provides useful information for commercialization of LIP and GO nano sheet combination based TG biosensors.