Based on their size and unique electrical properties, carbon nanotubes offer the exciting possibility of developing ultrasensitive, electrochemical biosensors. In this study, we describe construction amperometric biosensors based incorporation single-walled modified with enzyme into redox polymer hydrogels. The composite films were constructed by first incubating an in a nanotube (SWNTs) solution then cross-linking within poly[(vinylpyridine)Os(bipyridyl)2Cl2+/3+] film. Incorporation SWNTs,...

Adhesion and subsequent aggregation between neutrophils platelets is dependent upon the initial binding of P-selectin on activated to glycoprotein ligand 1 (PSGL-1) microvilli neutrophils. High speed, high resolution videomicroscopy flowing interacting with spread demonstrated that thin membrane tethers were pulled from in 32 ± 4% interactions. After capture by platelets, neutrophil (length 5.9 4.1 μm, n = 63) at an average rate 6–40 μm/s as wall shear was increased 100–250 s−1. The tether...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTScanning electrochemical microscopy. 24. Enzyme ultramicroelectrodes for the measurement of hydrogen peroxide at surfacesBenjamin R. Horrocks, David. Schmidtke, Adam. Heller, and Allen J. BardCite this: Anal. Chem. 1993, 65, 24, 3605–3614Publication Date (Print):December 15, 1993Publication History Published online1 May 2002Published inissue 15 December...

In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb redox enzyme glucose oxidase (GOX) onto single-walled carbon nanotubes (SWNT). By method, solutions dispersed and debundled SWNTs were prepared that remained stable for 30 days which retained 75% native enzymatic activity. We also demonstrate GOX-SWNT conjugates can be assembled into amperometric biosensors with poly[(vinylpyridine)Os(bipyridyl)2Cl2+/3+] polymer (PVP-Os) through layer-by-layer (LBL)...

An implantable 0.29 mm o.d. flexible wire electrode was designed for subcutaneous monitoring of glucose. The formed by sequentially depositing in a 0.09 deep shielded recess at the tip polyimide-insulated 0.25 gold "wired" glucose oxidase (GOX) sensing layer, mass transport limiting and nonfouling biocompatible layer. layer cross-linking (poly[(1-vinylimidazolyl)osmium(4,4'-dimethylbipyridine)2Cl] )+/2+(PVI13-dme - Os) GOX with poly(ethylene glycol) diglycidyl ether (PEG). restricting...

In this study, we describe the construction of glucose biosensors based on an electrostatic layer-by-layer (LBL) technique. Gold electrodes were initially functionalized with negatively charged 11-mercaptoundecanoic acid followed by alternate immersion in solutions a positively redox polymer, poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)], and enzyme, oxidase (GOX), or GOX solution containing single-walled carbon nanotubes (SWNTs). The LBL assembly multilayer films characterized UV-vis...

Leukocytes rolling on selectins extrude thin membrane tethers that might stabilize velocities despite marked alterations in wall shear stress. To test this hypothesis, we used differential interference contrast videomicroscopy to visualize formation and breakage of as neutrophils rolled P-selectin under flow. Neutrophils rapidly increased tether number stress rose decreased declined. Membrane invariably accompanied slower, more uniform steps translated into lower mean variances velocity....

Biofuel cells provide a safe and renewable means of powering small electronic devices. In this work, we demonstrate bioanode that is capable extracting four electrons from single molecule sucrose by way three-enzyme cascade. Invertase, fructose dehydrogenase glucose oxidase are immobilized in ferrocene-modified linear poly(ethylenimine) (LPEI) hydrogel onto the surface carbon electrode. Fuel sources generated polymer film (1) hydrolyzing into then (2) electroenzymatically oxidizing to...

The kinetics of the fall in subcutaneous fluid glucose concentration anesthetized rats ( n = 7) after intravenous injection insulin (0.5 units/kg) was studied by using 5 × 10 −4 cm 2 active area, <150-sec 10–90% response time, amperometric sensors. onset decline delayed and statistically different P < 0.001) from that blood (8.9 ± 2.1 min vs. 3.3 0.5 min). Similarly, rate drop between 6 20 for tissue (3.9 1.3 mg⋅dl −1 ⋅ ) (6.8 2.0 ⋅min 0.003). hypoglycemic nadir occurred 24.5 6.8...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesign, Characterization, and One-Point in vivo Calibration of a Subcutaneously Implanted Glucose ElectrodeElisabeth. Csoeregi, Chris P. Quinn, David W. Schmidtke, Sten-Eric. Lindquist, Michael V. Pishko, Ling. Ye, Ioanis. Katakis, Jeffrey A. Hubbell, Adam. HellerCite this: Anal. Chem. 1994, 66, 19, 3131–3138Publication Date (Print):October 1, 1994Publication History Published online1 May 2002Published inissue 1 October...

Amperometric biosensors for glucose and hydrogen peroxide have been built by immobilizing oxidase (GOX) horseradish peroxidase (HRP) in cross-linked films of ferrocene-modified linear poly(ethylenimine). At pH 7, the sensors generated limiting catalytic current densities 1.2 mA/cm2. These are approximately 4 times higher than those with other ferrocene-based redox polymers comparable to highest reported values osmium-based GOX. Because high sensitivity these (73 nA/cm2·μM), concentrations...

Linear poly(ethylenimine) (, LPEI) was modified by attachment of 3-(dimethylferrocenyl)propyl groups to ca. 17% its nitrogen atoms form a new redox polymer for use as an anodic mediator in glucose/ biofuel cells. The electrochemical properties this were compared those 3-ferrocenylpropyl-modified LPEI . When or mixed with glucose oxidase and cross-linked ethylene glycol diglycidyl ether hydrogels on planar, glassy carbon electrodes, limiting catalytic bioanodic current densities up at...

The effect of mediator distance from the polymer backbone on redox behavior, electron transport, electrochemical stability, and electrical communication with enzymes was studied novel linear poly(ethylenimine) polymers. To measure these effects, we synthesized two new ferrocene polymers having a three-carbon (Fc-C3-LPEI) six-carbon (Fc-C6-LPEI) spacer to complement our previous (Fc-C1-LPEI) 1-carbon spacing. Increasing length either three or six carbons resulted in single peak behavior over...

Ferrocene redox polymers based on the coupling of ferrocenecarboxaldehyde to both linear and branched poly(ethylenimine) (PEI) have been prepared investigate effects pH, electrolyte, cross-linking electron charge transport film swelling. The behavior ferrocene-modified PEI was investigated by cyclic voltammetry, while diffusion coefficients reported for PEI-based were determined electrochemical impedance spectroscopy. In phosphate solutions at pH>7, cross-linked films exhibited multiple wave...

In this study, we describe the effects of incorporating single-walled carbon nanotubes (SWNTs) into redox polymer−enzyme hydrogels. The hydrogels were constructed by combining enzyme glucose oxidase with a polymer (Fc-C6-LPEI) in which ferrocene was attached to linear poly(ethylenimine) six-carbon spacer. Incorporation SWNTs these films changed their morphology and resulted significant increase enzymatic response at saturating concentrations (3 mA/cm2) as compared without (0.6 mA/cm2)....

Ferrocenylhexyl- and ferrocenylpropyl-modified linear poly(ethylenimine) (Fc-C6-LPEI, Fc-C3-LPEI) were used with periodate-modified glucose oxidase (p-GOX) in the layer-by-layer assembly of enzymatic bioanodes on gold. Fc-C6-LPEI/p-GOX Fc-C3-LPEI/p-GOX films 16 bilayers capable generating up to 381 ± 3 1417 63 μA cm(-2), respectively, response glucose. These responses are greater than those analogous fabricated using conventional cross-linking techniques extremely high for planar, low...

Following injury and refractive surgery, corneal wound healing can initiate a protracted fibrotic response that interferes with ocular function. This fibrosis is related, in part, to the myofibroblast differentiation of keratocytes transforming growth factor beta 1 (TGF- β 1). Previous studies have shown changes mechanical properties extracellular matrix (ECM) regulate this process, but mechanotransductive pathways govern stiffness-dependent keratocyte remain unclear. Here, we used...

The ability of platelets to tether and translocate on injured vascular endothelium relies the interaction between platelet glycoprotein receptor Ib alpha (GPIb/spl alpha/) A1 domain von Willebrand factor (vWF-A1). We now report that GPIb/spl alpha/-vWF-A1 bond displays similar kinetic attributes as selectins including: 1) requirement for a critical level flow initiate adhesion, 2) short-lived tethering events at sites injury in vivo, 3) fast intrinsic dissociation rate constant, k/sub...

The hypothesis of the feasibility one-point in vivo calibration intravenously implanted glucose sensors during periods rapid rise and decline venous blood concentration was tested. Miniature (5 × 10-4 cm2 mass transporting area) electrodes with 10−90% response times <2 min, that did not consume oxygen, were jugular veins systemically heparinized rats used 4-h experiments, which amperometrically monitored. made by electrically connecting ("wiring") reaction centers oxidase through an...