Cascading reaction of arginase and urease on a graphene-based FET for ultrasensitive, real-time detection of arginine

Herein, a biosensor based on a reduced graphene oxide field effect transistor (rGO-FET) functionalized with the cascading enzymes arginase and urease was developed for the detection of L-arginine. Arginase and urease were immobilized on the rGO-FET sensing surface via electrostatic layer-by-layer assembly using polyethylenimine (PEI) as cationic building block. The signal transduction mechanism is based on the ability of the cascading enzymes to selectively perform chemical transformations and prompt local pH changes, that are sensitively detected by the rGO-FET. In the presence of L-arginine, the transistors modified with (PEI/urease(arginase)) multilayers showed a shift in the Dirac point due to the change in the local pH close to the graphene surface, produced by the catalyzed urea hydrolysis. The transistors were able to monitor L-arginine in the 10–1000 μM linear range with a LOD of 10 μM, displaying a fast response and a good long-term stability. The sensor showed stereospecificity and high selectivity in the presence of non-target amino acids. Taking into account the label-free, real-time measurement capabilities and the easily quantifiable, electronic output signal, this biosensor offers advantages over state-of-the-art L-arginine detection methods.Fil: Berninger, Teresa. Austrian Institute Of Technology; AustriaFil: Bliem, Christina. Austrian Institute Of Technology; AustriaFil: Piccinini, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Knoll, Wolfgang. Austrian Institute Of Technology; Austri

Magnetic nanoparticle-enhanced SPR biosensor

AbstractWe report a new concept of surface plasmon resonance (SPR) biosensor for detection of chemical and biological analytes that holds potential for increased sensitivity and shorten detection time. It is based on magnetic nanoparticles (MNPs) assays in which the MNPs are employed to simultaneously serve as a) ‘carriers’ for efficient delivery of target analyte to the sensor surface and b) as labels that can dramatically increase refractive index changes associated with molecular binding events. We implemented this approach by using a sensor chip with diffraction grating and SPR-active gold and magnetic Co70Fe30 layers. A periodically modulated polymer sensor surface was coated by a magnetic Co70Fe30 layer for a rapid (and reversible) docking of MNPs followed by a deposition of a gold layer for diffraction-based excitation of surface plasmons. In conjunction with sandwich assays, this concept is expected to provide means for detection of molecular and biological analytes that is not hindered by their slow diffusion-controlled mass transport to the sensor surface

Integrated optics for the characterization of photoreactive organic thin films

Abstract Integrated optical techniques are introduced as a powerful approach for the investigation of thin organic films and their photo-physical and -chemical properties. Waveguide and surface plasmon spectroscopies and microscopies are shown to sensitively monitor optical and structural modifications in these ultrathin layers upon irradiation with light. After a short introduction into the field of evanescent-and guided wave-optics we will give various examples that are chosen so as to demonstrate where and when integrated optics offer analytical advantages over more classical techniques with plane waves, "normal" photons. Among the photo-chemical examples discussed are studies with various types of polysilane films that volatilize upon irradiation with W light. We compare, in particular, differences between films prepared by spin casting to those fabricated, layer by layer, by the Langmuir-Blodgett-Kuhn technique with their substantially higher internal order. An interesting structure / property relation is found for different polymer systems functionalized by photoisomerizing azobenzene chromophores. The systems investigated range from liquidcrystalline (LC), side group polymers in planar waveguide format to single monolayers acting as photo-responsive command layer for LC cells. I. Plasmon surface polaritons ("surface plasmons" or PSP for short) are surface electromagnetic modes associated with a polarization charge wave propagating along a metal-dielectric interface. Their field amplitudes decay exponentially, both into the dielectric and into the metal, respectively, with the maximum intensity being at the interface. As can be seen from the dispersion relation which, for a flat metal surface in air or vacuum, is given by 1

Nanoscale Architectures for Smart Bio-Interfaces: Advances and Challenges

Volcanology & seismolog

Functionalization Strategies of PEDOT and PEDOT:PSS Films for Organic Bioelectronics Applications

Organic bioelectronics involves the connection of organic semiconductors with living organisms, organs, tissues, cells, membranes, proteins, and even small molecules. In recent years, this field has received great interest due to the development of all kinds of devices architectures, enabling the detection of several relevant biomarkers, the stimulation and sensing of cells and tissues, and the recording of electrophysiological signals, among others. In this review, we discuss recent func-tionalization approaches for PEDOT and PEDOT:PSS films with the aim of integrating biomolecules for the fabrication of bioelectronics platforms. As the choice of the strategy is determined by the conducting polymer synthesis method, initially PEDOT and PEDOT:PSS films preparation methods are presented. Later, a wide variety of PEDOT functionalization approaches are discussed, together with bioconjugation techniques to develop efficient organic-biological interfaces. Finally, and by making use of these approaches, the fabrication of different platforms towards organic bioelectronics devices is reviewed.Fil: Fenoy, Gonzalo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Knoll, Wolfgang. Ait Austrian Institute of Technology Gmbh; Austria. Danube Private University; AustriaFil: Marmisollé, Waldemar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Highly sensitive urine glucose detection with graphene field-effect transistors functionalized with electropolymerized nanofilms

We introduce a new approach for glucose oxidase (GOx) immobilization on graphene field-effect transistors (gFETs) to fabricate highly sensitive glucose sensors. The strategy relies on the electropolymerization of a layer of the copolymer poly(3-amino-benzylamine-co-aniline) (PABA) on graphene-based transistors. The synthesized polymer film provides the suitable electrostatic charge and non-denaturing environment for enzyme immobilization without the need of any chemical primer. Then, the local pH changes triggered by the enzyme-catalyzed oxidation produce a shift in the Dirac potential of the gFETs to more negative values, which is evidenced by the differences in the graphene channel conductivity and constitutes the signal transduction mechanism of the sensing devices. The assembled biosensors revealed a low LOD of 4.1 μM and were capable of detecting glucose in the range from 10 to 1000 μM in a flow configuration. Moreover, they showed sensitivity of −24.9 μA per decade of glucose concentration and a fast response time, with an average value of 190 seconds, while allowing the operation at small gate-source and drain-source voltages. Finally, the biosensors were able to successfully monitor the analyte in urine samples, showing their potential towards the fabrication of point-of-care glucose testing devices.Fil: Fenoy, Gonzalo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Marmisollé, Waldemar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Knoll, Wolfgang. AIT Austrian Institute of Technology; Austria. Danube Private University; AustriaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Reversible Switching of the Dirac Point in Graphene Field-Effect Transistors Functionalized with Responsive Polymer Brushes

The reversible control of the graphene Dirac point using external chemical stimuli is of major interest in the development of advanced electronic devices such as sensors and smart logic gates. Here, we report the coupling of chemoresponsive polymer brushes to reduced graphene oxide (rGO)-based field-effect transistors to modulate the graphene Dirac point in the presence of specific divalent cations. Poly[2-(methacryloyloxy)ethyl] phosphate (PMEP) brushes were grown on the transistor channel by atom transfer radical polymerization initiated from amine-pyrene linkers noncovalently attached to rGO surfaces. Our results show an increase in the Dirac point voltage due to electrostatic gating effects upon the specific binding of Ca2+ and Mg2+ to the PMEP brushes. We demonstrate that the electrostatic gating is reversibly controlled by the charge density of the polymer brushes, which depends on the divalent cation concentration. Moreover, a theoretical formalism based on the Grahame equation and a Langmuir-type binding isotherm is presented to obtain the PMEP–cation association constant from the experimental data.Fil: Piccinini, Esteban. Facultad de Ciencias Exactas, Universidad Nacional de la Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Bliem, Christina. Austrian Institute of Technology; AustriaFil: Giussi, Juan Martín. Facultad de Ciencias Exactas, Universidad Nacional de la Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Knoll, Wolfgang. Austrian Institute of Technology; AustriaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

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 (20.3 µA/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 500 mV) and were able to monitor urea in the range of 1–1000 µm, with a limit of detection (LOD) down to 1 µm, 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 10 nM) was performed in aqueous solution by taking advantage of the urease specific inhibition.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta