title: Amperometric cholesterol biosensor based on the direct electrochemistry of cholesterol oxidase and catalase on a graphene/ionic liquid-modified glassy carbon electrode.
abstract: Cholesterol oxidase (ChOx) and catalase (CAT) were co-immobilized on a graphene/ionic liquid-modified glassy carbon electrode (GR-IL/GCE) to develop a highly sensitive amperometric cholesterol biosensor. The H2O2 generated during the enzymatic reaction of ChOx with cholesterol could be reduced electrocatalytically by immobilized CAT to obtain a sensitive amperometric response to cholesterol. The direct electron transfer between enzymes and electrode surface was investigated by cyclic voltammetry. Both enzymes showed well-defined redox peaks with quasi-reversible behaviors. An excellent sensitivity of 4.163 mA mM(-1)cm(-2), a response time less than 6s, and a linear range of 0.25-215 μM (R(2)>0.99) have been observed for cholesterol determination using the proposed biosensor. The apparent Michaelis-Menten constant (KM(app)) was calculated to be 2.32 mM. The bienzymatic cholesterol biosensor showed good reproducibility (RSDs<5%) with minimal interference from the coexisting electroactive compounds such as ascorbic acid and uric acid. The CAT/ChOx/GR-IL/GCE showed excellent analytical performance for the determination of free cholesterol in human serum samples.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran. Electronic address: mbgholivand@yahoo.com.
authors.forename: Mohammad Bagher
authors.initials: MB
authors.lastname: Gholivand
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khodadadian
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002244:Carbon; D002374:Catalase / Q000737:chemistry; D048271:Chitosan / Q000737:chemistry; D002784:Cholesterol / Q000302:isolation & purification*; D002789:Cholesterol Oxidase / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D006046:Gold / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry
chemical_list: D052578:Ionic Liquids; D002244:Carbon; D006046:Gold; D006108:Graphite; D048271:Chitosan; D002784:Cholesterol; D006861:Hydrogen Peroxide; D002789:Cholesterol Oxidase; D002374:Catalase
keywords: Catalase; Cholesterol; Cholesterol oxidase; Electrocatalysis; Graphene