Enzyme-polyelectrolyte multilayer assemblies on reduced graphene oxide field-effect transistors for biosensing applications.
We present the construction of layer-by-layer (LbL) assemblies of polyethylenimine and urease onto reduced-graphene-oxide based field-effect transistors (rGO FETs) for the detection of urea. This versatile biosensor platform simultaneously exploits the pH dependency of liquid-gated graphene-based transistors and the change in the local pH produced by the catalyzed hydrolysis of urea. The use of an interdigitated microchannel resulted in transistors displaying low noise, high pH sensitivity (20.3µA/pH) and transconductance values up to 800 µS. The modification of rGO FETs with a weak polyelectrolyte improved the pH response because of its transducing properties by electrostatic gating effects. In the presence of urea, the urease-modified rGO FETs showed a shift in the Dirac point due to the change in the local pH close to the graphene surface. Markedly, these devices operated at very low voltages (less than 500mV) and were able to monitor urea in the range of 1-1000µm, with a limit of detection (LOD) down to 1µm, fast response and good long-term stability. The urea-response of the transistors was enhanced by increasing the number of bilayers due to the increment of the enzyme surface coverage onto the channel. Moreover, quantification of the heavy metal Cu2+(with a LOD down to 10nM) was performed in aqueous solution by taking advantage of the urease specific inhibition.
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata - CONICET, Suc. 4, CC 16, La Plata, Argentina.
Esteban
E
Piccinini
Centre of Electrochemical Surface Technology (CEST), Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria.
Christina
C
Bliem
AIT Austrian Institute of Technology, Donau City Straße 1, 1220 Vienna, Austria.
Ciril
C
Reiner-Rozman
INQUIMAE, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina.
Fernando
F
Battaglini
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata - CONICET, Suc. 4, CC 16, La Plata, Argentina. Electronic address: azzaroni@inifta.unlp.edu.ar.
Omar
O
Azzaroni
AIT Austrian Institute of Technology, Donau City Straße 1, 1220 Vienna, Austria.
Wolfgang
W
Knoll
D015374:Biosensing Techniques / Q000295:instrumentation*; D032449:Canavalia / Q000201:enzymology; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D057230:Limit of Detection; D010087:Oxides / Q000737:chemistry*; D000071228:Polyelectrolytes / Q000737:chemistry*; D014173:Transistors, Electronic; D014508:Urea / Q000032:analysis / Q000097:blood*; D014510:Urease / Q000737:chemistry
D004800:Enzymes, Immobilized; D010087:Oxides; D000071228:Polyelectrolytes; D006108:Graphite; D014508:Urea; D014510:Urease
Biosensors; Chemical sensors; Field-effect transistors; Graphene