Bioelectrocatalytic generation of directly readable code: harnessing cathodic current for long-term information relayw

نویسندگان

  • Guinevere Strack
  • Heather R. Luckarift
  • Robert Nichols
  • Kristofor Cozart
  • Evgeny Katz
  • Glenn R. Johnson
چکیده

Digital paradigms have been applied to chemical and biochemical systems with a variety of outcomes, for example, information processing, encryption, and security systems. Another form of chemical/biochemical-based digital information conveyance is the unconventional barcode. Several bar codes serving as medical diagnostic models or multiplexed bioanalytical assays have been developed with applications ranging from the detection of multiple proteins to single molecules of DNA. In addition, unconventional barcodes serving as encryption tags were demonstrated with metallic nanowires and quantum dots. Although not all of the given examples are considered digital sequences, the commonality is the directly readable information providing medically relevant diagnostic or other encoded information within a single-use report. An unexplored approach to the unconventional barcode is the generation of continuous digital information though a bioelectronic interface. In this concept, the biocatalytic electrode can control current density in a selfpowered device and/or decipher received signals from a variety of chemical/biochemical sources with an intrinsic write rewrite function. Practical application of enzyme-based electronics and fuel cells requires that the biocatalysts withstand environmental fluctuations and continually catalyze redox reactions. Enzyme-based Boolean logic has been demonstrated to control biofuel cells by coupling signal-responsive materials and soluble redox mediators for electron transfer. To render selfpowered bioelectronic devices fit for sustained built-in information processing under continuous flow, the present work uses a laccasefunctionalized architecture that responds directly to a continuous input chemical signal (i.e., dissolved O2) and generates an amperometric output response. Refined control of the input conditions extends the utility of the platform to generate commonly recognized code. For optimal electrode fabrication, hierarchically ordered carbon nanomaterials that are scalable and manufacturable provide a clear advantage for subsequent development. In this study, electrodes were composed entirely of a multiwall carbon nanotube (CNT) material commonly referred to as ‘‘buckypaper’’ (CNT-BP) providing a flexible and highly electrically conductive (51.2 S cm ) surface area for enzyme immobilization. A heterobifunctional cross-linker, 1-pyrenebutanoic acid, succinimidyl ester (PBSE), was used to effectively link laccase to CNT-BP. The connection occurs by virtue of a succinimidyl residue that provides covalent bonding to protein amines, and an aromatic pyrenyl moiety that interacts with CNT through p–p stacking. The PBSE-modified CNT-BP alone shows capacitive current and an open circuit potential (OCP) of 0.22 V, but lacks any Faradaic current within the given potential range. CNT-BP electrodes functionalized with laccase reduce O2 at an onset potential of 0.635 0.016 V; n = 6, and an OCP of 0.627 0.01 V; n = 5 (vs. Ag/AgCl), in good agreement with previous reports showing oxygen reduction with direct electron transfer (DET) processes (Fig. 1, inset). Measurements of O2-free electrolytes by cyclic voltammetry (CV) lack the catalytic cathodic peak. The quasi-reversible process at 0.029 V was likely the oxidation and reduction of coppercontaining active centers in the enzyme, no such response was observed in the absence of laccase. Aerobic potentiostatic and galvanostatic polarization data demonstrated current densities in excess of 100 mA cm 2 indicating that the CNT-BP provides an excellent support for laccase-catalyzed O2 reduction (Fig. 1). Potentiostatic polarization data in N2-saturated electrolyte exhibited minimal current density, as expected in the absence of O2. Sustained DET between enzymes and electrodes is influenced by several factors, in particular enzyme stability and effective electron transfer from electron donor to the terminal a Air Force Research Laboratory, Airbase Sciences Division, Tyndall Air Force Base, Florida, 32403, USA. E-mail: Glenn.Johnson@tyndall.af.mil Universal Technology Corporation, 1270 N. Fairfield Road, Dayton, Ohio, 45432, USA. E-mail: Heather.Luckarift.ctr@tyndall.af.mil Applied Research Associates, 430 West 5th St, Panama City, Florida, 32401, USA Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York, 13699, USA w Electronic supplementary information (ESI) available: Experimental details for the enzyme and electrode preparation, electrochemical measurements and barcode generation. See DOI: 10.1039/c1cc11475a ChemComm Dynamic Article Links

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Bioelectrocatalytic generation of directly readable code: harnessing cathodic current for long-term information relay.

Here we present an exceptionally stable bioelectrocatalytic architecture for electrocatalytic oxygen reduction using a carbon nanotube electrode as the electron donor and a fungal enzyme as electrocatalyst. Controlling oxygen content in the electrolyte enables generation of a directly readable barcode from monitoring the enzyme response.

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تاریخ انتشار 2011