| Interfacing nanomaterials and biomolecules has led to rapid advances in a variety of different fields including cellular and tissue imaging, biomaterials, cellular delivery, diagnostics, and sensing. Though various methods have been developed to prepare conjugates of proteins with nanomaterials, few researchers have addressed the question: "how does a nanomaterial alter the structure and function of a protein interfaced with it?" This research work is focused on studying the behavior of proteins on a wellcharacterized class of nanomaterial, namely, carbon nanotubes. The broad goals of this work are: (1) To lay the ground-work required for addressing important questions regarding protein interactions with carbon nanotubes at the structural and functional level and, (2) at the same time begin to explore the practical utility of these interesting hybrid materials.; In the first in-depth study of its kind, we used enzyme kinetics in conjunction with analysis using atomic force microscopy (AFM) and FTIR spectroscopy to elucidate the structure and function of enzymes adsorbed onto single-walled carbon nanotubes (SWNTs). Investigation of the stability of these adsorbed enzymes led to the discovery of a novel property of nanomaterials---their ability to enhance protein activity and stability. We found that proteins adsorbed onto SWNTs are more stable in strongly denaturing environments (e.g. at high temperatures and in organic solvents) relative to those adsorbed on macroscopic supports. Highly active and stable conjugates of enzymes and carbon nanotubes were prepared by covalently attaching a variety of enzymes with multi-walled carbon nanotubes (MWNTs). These water-soluble carbon nanotube-enzyme conjugates represent novel preparations that possess the virtues of both soluble and immobilized enzymes, thus providing a unique combination of useful attributes such as low mass transfer resistance, high activity and stability, and reusability. We recently reported a simple method to prepare aqueous solutions of SWNTs using commercially available proteins. Characterization using UV-Vis spectroscopy, Raman spectroscopy, and AFM revealed the presence of individually dispersed SWNTs in solution. Solubilization of SWNTs using proteins provides a simple, one-step method for preparing biocompatible solutions of SWNTs and may also find use in approaches for functionalization and assembly of carbon nanotubes. |
