Cholesterol Oxidase Immobilization on Carbon Nanofiber Electrode
- Paper number
IAC-11,B3,5,10,x11196
- Author
Ms. Dámaris Suazo-Dávila, NASA Harriet Jenkins Pre-Doctoral Fellowship, University of Puerto Rico, Puerto Rico
- Author
Ms. Johary Rivera, University of Puerto Rico, Puerto Rico
- Author
Dr. Jessica Koehne, National Aeronautics and Space Administration (NASA), United States
- Author
Dr. Meyya Meyyappan, National Aeronautics and Space Administration (NASA), United States
- Author
Dr. Carlos R. Cabrera, University of Puerto Rico, Puerto Rico
- Year
2011
- Abstract
The development of new health monitoring technologies is imperative to ensure the safety of astronauts during long space missions. The alarming rise in clinical disorders due to abnormal blood cholesterol levels have motivated the development of reliable cholesterol sensors. We are using a carbon nanofiber (CNF) embedded in silicon dioxide nanoelectrode array platform, developed by the Nanotechnology group at NASA-Ames Research Center. In our approach, the CNF electrodes are used to immobilize cholesterol oxidase that was previously modified by glycosylation chemistry. Cholesterol oxidase chemical modification and immobilization on CNFs is new to the scientific community. The protein is covalently bound to the tips of the CNFs by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxy-sulfo-succinimide (sulfo-NHS) forming an amide linkage between the proteins’ amine residues and carboxylic acid groups on the CNFs tips. Cyclic voltammograms (CV) of CNFs fully encapsulated in silicon dioxide showed no current for the oxidation and reduction of the redox couple Fe(CN)6(-3/-4) ; on the contrary, the samples in which the silicon dioxide was polished to exposed CNF tips produced quasireversible redox peaks. Moreover, a CV of the polished sample in a solution of 11 mM H2O2 in 0.1 M PBS at pH 7.5 showed a change in current at 500 mV (Ag/AgCl). In the absence of H2O2, no current peak was observed within the same potential window. Atomic force microscopy characterization of the polished CNF electrodes indicated that the CNFs had a mean diameter of 100 nm and protruded 12 nm from the silicon dioxide. X-ray photoelectron spectroscopy (XPS) was utilized to compare the polished CNF sample modified with the EDC/sulfo-NHS and the protein to the unmodified CNF surface. As expected, peaks corresponding to the EDC/sulfo-NHS molecules were observed in the N (1s) and S(2p) region. On the contrary, the unmodified surface does not show binding energy peaks in these same energy regions. After the addition of the protein, no peak was observed in the S(2p) binding energy region. In contrast, the peak from the N(1s) region increased due the protein’s presence on the surface of the chemically modified CNF electrodes. Electrochemical measurements have been done to determine the activity of the protein for cholesterol. The research to be presented is innovative because it aims to unite different techniques, such as chemical glycosylation, covalent immobilization of enzymes and CNF growth on metal substrates.
- Abstract document
- Manuscript document
(absent)