Date of Award

8-2007

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Polymer and Fiber Science

Advisor

Ke, Pu-Chun

Committee Member

Luo , Jian

Committee Member

Kornev , Konstantin G.

Abstract

ABSTRACT


This thesis intends to present, from the biophysical viewpoint, my study on understanding carbon nanomaterials in biological and environmental systems. Carbon nanotubes and fullerenes represent a major family of carbon nanoparticles which possess distinct electrical, optical and mechanical properties. However, the major hurdle for making carbon nanomaterials bioavailable lies in their tendency toward bundling, driven by hydrophobic interaction, van der Waals force, and pi-stacking. To overcome this problem, we used non-covalent binding of zwitterionic lysophopholipids (LPL) onto the external surfaces of single-walled carbon nanotubes (SWNTs). This method affords superior SWNT solubility in aqueous solution. The stability of SWNT-LPL complex has been found to be dependent on the pH of the solvent, but independent of solvent temperature. Based on this method, the translocation of rhodamine-lysophosphoethanolamine-SWNT (Rd-LPE-SWNT) complex across cell membranes, as well as the dissociation of Rd-LPE from SWNTs in the cellular environment was detected using the technique of fluorescence resonance energy transfer (FRET). Towards understanding the environmental impact of carbon nanomaterials, we have studied the biomodification of SWNT-lyso-phosphatidylcholine (SWNT-LPC) by aquatic organism Daphnia magna. Through normal feeding behavior, Daphnia magna ingested SWNT-LPC and stripped out the lipids as food source. SWNTs rebundled inside the guts of daphnia and were excreted into the water column. Acute toxicity was observed only in the highest test concentrations of 0.5 mg/L under starvation conditions. Regarding fullerenes, C70, the shortest 'SWNT', was solubilized in water by gallic acid, a natural anti-oxidant and anticancer agent. The suparmolecular complex of C70-gallic acid, assembled through pi-stacking, emitted green fluorescence in aqueous solution. Utilizing this optical property, we succeeded in labeling biological systems at cellular, tissue and living organism levels. We have further discovered that the fluorescence of C70 is far more resistant to photobleaching than calcein AM, a conventional dye for bioimaging. Using confocal fluorescence microscopy we have obtained the first real-time observation of nanoparticle translocation across cell membranes.
In summary, the objectives of this thesis are:
 Solubilizating SWNT in aqueous solution afforded by different solvating agents, including DOPA, sodium dodecyl sulfate (SDS) and LPC, and testing the stability of the solution at different temperatures, pH and ionic strengths;
 Using SWNT as a transporter for lipid delivery across cell membranes;
 Understanding the fate of SWNT in aquatic organism Daphnia magna; and
 Coating C70 with gallic acid and utilizing the optical properties of C70 for detecting its cell translocation.
The studies documented in this thesis further our understanding of the interactions between carbon nanomaterials and biological and environmental systems. Water soluble carbon nanomaterials enable future field studies in imaging, sensing, drug delivery, nanotoxicity, nanomedicine, and environmental science and engineering.

Share

COinS