Functionalized Vertically Aligned Carbon Nanofibers as Scaffolds for Immobilization and Electrochemical Detection of Redox-Active Proteins

Abstract

We have investigated the functionalization of vertically aligned carbon nanofibers with the redox-active protein cytochrome c and have characterized the resulting chemical and electrochemical activity. A comparison of monolayers with different terminal groups shows that those exposing carboxylic acid groups are most effective at binding active cytochrome c to carbon nanofibers. Cyclic voltammetry (CV) measurements reveal redox peaks due to electrochemical activity of the nanofiber-bound protein. CV and chemical measurements of enzymatic activity both show that nanofibers modified with cytochrome c yield approximately 10 times more activity than similarly modified surfaces of glassy carbon and gold. However, cytochrome c-modified nanofibers yield a high capacitive background, reducing the signal-to-noise ratio of the electrical measurements. We attribute this in part to inhomogeneous functionalization of the nanofibers at edge-plane versus basal-plane sites on the nanofiber surface, leading to leaky monolayers that yield increased capacitance. Our results demonstrate the ability to link chemically and electrochemically active proteins to nanofibers in a manner that preserves their activity and provide insight into the nanometer-scale factors that control the resulting chemical and electrochemical properties of biologically modified nanostructured electrodes.

Surface functionalization of thin-film diamond for highly stable and selective biological interfaces

“…While the surface chemistry of carbon is relatively unexplored, in recent work we have shown that photochemical grafting of organic alkenes can provide an extremely robust way to link functional organic molecules to surfaces of carbon, including diamond (22)(23)(24)(25)(26), amorphous carbon (23,27,28), glassy carbon (29), and carbon nanofibers (30,31). Carbon surfaces functionalized in this manner have shown excellent stability, even at elevated temperatures (32).…”

Fabrication of three dimensional layered vertically aligned carbon nanotube structures and their potential applications

“…34 Another approach is to attach functional groups such as carboxylic acid groups to the nanotube ends as anchoring sites for other molecules. 35 The growth of a layer--by--layer forest structure would potentially allow for each layer to be functionalised differently, increasing the versatility of functionalised nanotubes for novel applications. A limitation of this method is that functionalization in one layer would need to be preserved during the high temperatures required for CVD of the second layer; however CVD production of carbon nanotubes has recently been demonstrated at lower temperatures (~400 °C) and so this limitation may be avoided by this technique.…”

Improved Direct Electrochemistry for Proteins Adsorbed on a UV/Ozone-Treated Carbon Nanofiber Electrode

“…These results implied that the reversibility is significantly improved and the treated CNF-modified electrode exhibited faster electron-transfer compared with its untreated counterpart. Since edge planes and defect sites have been suggested to be the primary electron-transfer regions in carbon materials, 25 the improved electrochemical behavior at a treated CNF-modified ECR electrode is mainly attributed to the large increases in edge-plane defect sites, and the effective surface area. In Figs.…”

“…vertically aligned carbon nanofiber (VACNF) modified electrode. The CNF was modified by the reaction of liquid-phase molecules containing an alkene group induced by irradiating ultraviolet light for around 16 h. 25 Li's group also obtained the DET of hemoglobin (Hb) by using a hydrophilic organic-inorganic composite consisting of CNFs and Nafion, and then developed a Hb-based biosensor. 24 These previous reports suggest that hydrophilic CNFs with a sufficient number of functionalized surface groups are very significant for achieving DET.…”