~ nm. Nanomaterials in Bio-Sensors. Carbon Nanomaterials in Bio-Sensors. Stabilization in Confined Spaces. Stabilization: Protein and Cage Size

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1 Nanomaterials in Bio-Sensors Nanomaterials must have unique and novel physical and/or chemical characteristics which can aid in the design of bio-sensors with improved analytical characteristics: High surface ratio Novel electro-optical properties Increased catalytic activity Enhanced electron transfer Nanomaterials in Bio-Sensors Materials for Immobilization and stabilization Nanotubes Immobilization and Stabilization matrices, Mediators, Transduction platforms Nanoporous Nanofibers Stabilization in Confined Spaces Effect of confinement on the folding free energy as a function of the cage size Stabilization: Protein and Cage Size Maximum stabilization of proteins in spherical cages with diameter of 2 to 6 times the diameter of the native protein Active Surface Ν = 100 Ν = 200 The radius of the protein in the native state (a N ) was given by 3.73N 1/3 Cage size (in units of 2a N ) is given on a log scale. H.X. Zhou, K.A. Dill Biochemistry, 2001, 40 (38), Gluconic Acid ~7 nm ~ nm with polyelectrolyte 1

2 Porous Pesticide Biosensor Nanotubes Mutant (E69Y, Y71D) Drosophila melanogaster AChE +350 mv 25 o C Continuous Operation Calibration Curve Pt Transducer Gluconic acid % Remaining Activity free m-ache m-ache in carbon nanopores % Inhibition dichlorvos paraoxon e - Oxidase time (hr) log[pesticide], M The carbon nanotubes were grown by the CVD method on a platinum substrate, thus providing an array of MWNT, microns long and with an internal diameter of 150nm. S. Sotiropoulou, N.A. Chaniotakis, Biosens.Bioelectron. 2005, 20, 2347 S. Sotiropoulou, N.A. Chaniotakis, Anal.Chim. Acta 2005, 530, 199 Nanotubes Nanotube Biosensor Linear range: M Sensitivity: 93.9 ± 0.4 µa mm -1 cm -2 (µα) Ι [glucose] (mm) 2

3 Nanofiber Biosensor Nanofiber Biosensor Table 1. nanofiber physical characteristics Nanofiber Grade LHT HTE GFE Diameter (nm) N2 Surface Area (m 2 /g) > 50 Density (g/cm 3 ) > Heat treatment ( o C) Metal Content (wt. %) < 0.50 < 0.50 < 0.01 Electrical Resistivity (Ohm/cm) < 10-3 < 10-3 < 10-3 SEM image of HTE Nanofibers mean diameter ~ 110 nm length ~ tenths of nanometers Nanofibers Nanotubes Nanofiber BioSensor Structures as Mediators Stability Study ing Activity % Remaini GFE HTE LHT NANOTUBES GRAPHITE t (hours) Reproducibility: RSD value < 1% (N = 3) 3

4 Structures as Mediators Fullerene C 60 multiple redox states low solubility in aqueous solutions stable in many redox forms +350 mv Mediator (red) oxidase FAD S. Licht et al./ Solar Energy Materials and Solar Cells 51 (1998) 9-19 e- Mediator (ox) FADH Gluconic acid +100mV +350mV Fullerene Mediator Oxidase FAD Hydrodynamic voltammogram for the glucose biosensors constructed using carbonincubatedfor:0( ),4( ),5( ) cycles in the toluene-c 60 solution Calibration curve of the glucose biosensor containing 1.7µg C 60 /mg of electrode material. Measurements were performed in 10mM phosphate buffer, ph=7.5 under argon, at +350mV vs. Ag/AgCl. e - FADH Gluconic acid Flowchart of the processes involved in a light induced fullerene mediated electrochemical biosensor. The operating potential has dropped to +100 mv. V. Gavalas, N.A. Chaniotakis, Anal. Chim. Acta 2000, 409, 131 4

5 Structures as Mediators Ι (µα Α) Light ON Light OFF [], mm S. Licht et al./ Solar Energy Materials and Solar Cells 51 (1998) 9-19 Conclusions-Future Directions nanomaterials have unique properties that are ideal for the development of highly stable, reproducible, and sensitive chemical sensors and biosensors 5