Immunoconjugates of carbon nanostructures
Ashcroft, Jared Mark
Wilson, Lon J.
Doctor of Philosophy
For the first time, carbon nanostructures have been designed and synthesized to form immunoconjugates with monoclonal antibodies (mAb) for use in cell-targeted cancer diagnosis and therapy. The immunoconjugates are derived from various nanoscale carbon-based building blocks, specifically fullerenes (C60 ), gadofullerenes (M C60) and ultra-short carbon nanotubes (US-tubes). The exterior of each nanostructure has been derivatized with water-solubilizing addends using Bingel-type (nucleophilic cyclopropanation) addition chemistry to facilitate biocompatibility. Initially, conjugation to the murine anti-gp240 melanoma antibody (ZME-018 mAb) was completed with two different water-soluble C60 derivatives, only one of which had the potential to covalently attach to the ZME-018 mAb. After conjugation, this covalently linked C 60-SPDP conjugate incorporated 15 C60 moieties per antibody, while retaining 80% of the antibody's target specificity. In a second experiment a non-covalently linked C60-Ser conjugate incorporated 38 fullerenes per antibody but retained only 4% of the antibody's target specificity. These findings suggest that covalent attachment of C60 derivatives to antibodies may not be essential for the development of fullerene immunotherapy (FIT), although the ratio of C60: antibody may need to be minimized so as not to inhibit antibody targeting. To study the cell internalization characteristics of the fullerene immunoconjugates, two water-soluble Gd C60 derivatives, which allowed for Gd 3+ monitoring by inductively-coupled plasma mass spectrometry (ICP-MS) at concentrations <10 ppb, have been utilized. These studies have provided evidence that the fullerene-based immunoconjugates retain the ability to effectively internalize into target cells, with approximately 20% of the available Gd 3+ internalizing into the A375m melanoma cells. These results suggest that immunoconjugates derived from C60-based chemotherapeutics may become new-targeted therapies against cancer. Of the carbon-based nanomaterials studied in this work, US-tubes are perhaps the most attractive candidates for nanomedicine platforms, due to the possibility of internally loading medically interesting materials, such as Gd3+ ions for magnetic imaging resonance (MRI) or iodine (I2) for computed tomography (CT). Toward this end, single-molecule US-tubes have been isolated by chemical reduction of the US-tubes, followed by immediate functionalization using Bingel chemistry to produce debundled and derivatized US-tube materials. Three different malonate addends have been attached to the US-tubes, including serinol, polyethylene glycol (PEG) and amide malonates. Each of the US-tube derivatives exhibited varying degrees of solubilities in water ranging from 0.25 mg/mL to 1.00 mg/mL. An n-octanol/water partition coefficient has also been determined for each derivative, with values ranging from 0.25 to 1.20, which suggest that these derivatized nanocapsules might readily internalize into cells. Loaded internally with medically-useful materials such as Gd3+ ions, I2 or radionuclides for imaging and therapeutic applications, these biocompatible carbon nanocapsules may be engineered into a universal platform for the containment and delivery of an array of medical agents in vivo.