title: Template-directed hierarchical self-assembly of graphene based hybrid structure for electrochemical biosensing.
abstract: A template-directed self-assembly approach, using functionalised graphene as a fundamental building block to obtain a hierarchically ordered graphene-enzyme-nanoparticle bioelectrode for electrochemical biosensing, is reported. An anionic surfactant was used to prepare a responsive, functional interface and direct the assembly on the surface of the graphene template. The surfactant molecules altered the electrostatic charges of graphene, thereby providing a convenient template-directed assembly approach to a free-standing planar sheet of sp(2) carbons. Cholesterol oxidase and cholesterol esterase were assembled on the surface of graphene by intermolecular attractive forces while gold nanoparticles are incorporated into the hetero-assembly to enhance the electro-bio-catalytic activity. Hydrogen peroxide and cholesterol were used as two representative analytes to demonstrate the electrochemical sensing performance of the graphene-based hybrid structure. The bioelectrode exhibited a linear response to H2O2 from 0.01 to 14 mM, with a detection limit of 25 nM (S/N=3). The amperometric response with cholesterol had a linear range from 0.05 to 0.35 mM, sensitivity of 3.14 µA/µM/cm(2) and a detection limit of 0.05 µM. The apparent Michaelis-Menten constant (Km(app)) was calculated to be 1.22 mM. This promising approach provides a novel methodology for template-directed bio-self-assembly over planar sp(2) carbons of a graphene sheet and furnishes the basis for fabrication of ultra-sensitive and efficient electrochemical biosensors.
authors.affiliation: Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden.
authors.forename: Onur
authors.initials: O
authors.lastname: Parlak
authors.forename: Atul
authors.initials: A
authors.lastname: Tiwari
authors.forename: Anthony P F
authors.initials: AP
authors.lastname: Turner
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Tiwari
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D001951:Brevibacterium / Q000201:enzymology; D002784:Cholesterol / Q000032:analysis*; D055664:Electrochemical Techniques / Q000379:methods; D004800:Enzymes, Immobilized / Q000378:metabolism; D006108:Graphite / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000032:analysis*; D057230:Limit of Detection; D011549:Pseudomonas / Q000201:enzymology
chemical_list: D004800:Enzymes, Immobilized; D006108:Graphite; D002784:Cholesterol; D006861:Hydrogen Peroxide
keywords: Biosensor; Graphene; Hierarchical self-assembly; Nano-biointerface; Template directed hybrid nanomaterial