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Research Paper

Stable Flexible Electrodes With Enzyme Cluster Decorated Carbon Nanotubes for Glucose-Driven Power Source in Biosensing Applications

[+] Author and Article Information
Thang Ho, Jamie A. Hestekin

Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701

Pratyush Rai, Jining Xie, Vijay K. Varadan

Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701

J. Nanotechnol. Eng. Med 1(4), 041013 (Nov 01, 2010) (8 pages) doi:10.1115/1.4002731 History: Received September 29, 2010; Revised October 06, 2010; Published November 01, 2010; Online November 01, 2010

Over the years, implantable sensor technology has found many applications in healthcare. Research projects have aimed at improving power supply lifetime for longevity of an implanted sensor system. Miniature power sources, inspired from the biofuel cell principle, can utilize enzymes (proteins) as catalysts to produce energy from fuel(s) that are perennial in the human body. Bio-nanocatalytic hierarchical structures, clusters made of enzyme molecules, can be covalently linked to the electrode’s surface to provide better enzyme loading and sustained activity. Carbon nanotube base electrodes, with high surface area for direct electron transfer, and enzyme clusters can achieve efficient enzymatic redox reaction. A redox pair of such bioelectrodes can make up a power source with improved performance. In this study, we have investigated high throughput processes for coupling enzyme catalysts with power harvesting mechanisms via a screen printing process and solution processing. The process incorporates enzyme (glucosse oxidase and catalase) micro-/nanocluster immobilization on the surface of carboxylated (functionalized) carbon nanotubes with screen printed electrodes. The 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide amide linkage chemistries were used to bind the enzyme molecules to nanotube surface, and bis[sulfosuccinimidyl] suberate (BS3) was used as the cross-linker between enzymes. Optimized enzyme cross-linking was obtained after 25 min at room temperature with 0.07 mmol BS3/nmol of enzymes, with which 44% of enzymes were immobilized onto the surface of the bioelectrode with only 24% enzyme activity lost. A cell, redox pair of bioelectrodes, was tested under continuous operation. It was able to maintain most of the enzyme activity for 7 days before complete deactivation at 16 days. Thus, the power harvesting mechanism was able to produce power continuously for 7 days. The results were also analyzed to identify impeding factors such as competitive inhibition by reaction byproduct and cathode design, and methods to rectify them have been discussed. Coupling this new and improved nanobiopower cell with a product removal mechanism and enzyme mutagenesis should provide enzyme protection and longevity. This would bring the research one step closer to development of compatible implantable battery technology for medical applications.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 3

Enzymes immobilization mechanism on carboxylated carbon nanotubes surface using EDC/NHS-BS3 immobilization method

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Figure 4

Effects of cross-linking time on enzyme activity (given as percentage of maximum activity or free enzyme activity)

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Figure 5

Effects of cross-linking time on amount of cross-linking enzymes (given as percentage of total enzyme added)

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Figure 6

Effects of BS3’s amount on enzyme activity (given as percentage of maximum activity or free enzyme activity)

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Figure 7

Effect of BS3’s amount on amount of cross-linking enzymes (given as percentage of total enzyme added)

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Figure 8

SEM images of a bioelectrode before and after EDC/NHS-BS3 immobilization, (a) carboxylated carbon nanotube surface of a bioelectrode, (b) bioelectrode surface after enzymes immobilization, and (c) close look at enzymes cluster size

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Figure 9

Enzyme stability study with time bound percentage of enzyme activity for three resident states of glucose oxidase: free enzyme (◆), EDC-NHS cross-linking (◼), EDC-NHS and BS3 (▲). Inset: gluconic acid concentration profile for EDC-NHS BS3 immobilized glucose oxidase over the same period of time.

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Figure 10

Power density of power harvesting system versus time

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Figure 2

CSTR setup for bioelectrodes cell testing

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Figure 1

Bionanopower cell architecture and power cell array for biobattery setup

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