Abstract 2889: Development of a novel nanoconstruct for tumor hypoxia photothermal therapy
Authors: Xie Huan , Bian Xiaomei , Deorukhkar Amit Anil , Krishnan Sunil 
Published: August 2012

Abstract
PURPOSE: Hypoxia is a common feature of solid tumors that occurs across a wide variety of malignancies and significantly reduces tumor sensitivity to radiation and chemotherapy. Carbonic anhydrase IX (CAIX), an extracellular protein that is overexpressed in hypoxic zones within many human tumors, has emerged as a promising biomarker. To pursue focal targeted therapy of tumor hypoxia, we prepared and characterized a novel nanoconstruct composed of gold nanorods (GNR), which show superior capability to assist tumor photothermal ablation, and anti-CAIX antibody (CAIX-Ab), which binds specifically to CAIX. EXPERIMENTS: GNR with aspect ratio (length 24 nm to width 8nm) of 3 were conjugated to CAIX-Ab through bifunctional polyethylene glycol (PEG). The conjugates were characterized by monitoring the absorption peak shift as well as size and zeta potential changes for each step of the preparation. The stabilities of the GNR, GNR-PEG and GNR/CAIX-Ab were challenged by 1X PBS. The binding affinity and specificity of the GNR/CAIX-Ab were evaluated with ELISA using CAIX protein and cell adhesion assay using HT29 human colorectal cells (overexpresing CAIX) and NIH-3T3 cells (no expressing CAIX, control). The photothermal cell ablation was performed on HT29 cells treated with medium (control), GNR-PEG (control) and GNR/CAIX-Ab. RESULTS: Obvious shifts of the absorption peaks of GNR at the NIR region and particle size and surface charge changes suggested the success of the conjugation. After challenging by 1XPBS, bare GNR formed aggregations and lost the peak at 745 nm while GNR-PEG and GNR/CAIX-Ab remained stable as their absorption peaks around 750 nm were preserved. This is an important finding suggesting that our conjugated GNR will be stable for in vivo work. From the sandwich ELISA study, we obtained a standard linear curve of absorbance vs. CAIX-Ab concentration with R2 of 0.997 and linear curve of absorbance vs. GNR/CAIX-Ab concentration with R2 of 0.999. And we found that the negative control GNR-PEG had no binding to the CAIX protein. We calculated the number of CAIX-Ab per GNR to be 1.47 ± 0.2. In cell adhesion assay, neither GNR-PEG nor GNR/CAIX-Ab had detectable binding to 3T3 cells; but with HT29 cells, GNR-PEG still showed no binding while GNR/CAIX-Ab bound specifically and avidly to the cells. Photothermal ablation of HT29 cells revealed complete cell death after treatment of GNR/CAIX-Ab while the cells remained alive when treated with medium or GNR-PEG. CONCLUSION: These findings suggested that GNR/CAIX-Ab is a stable and effective nanoconstruct appropriate for focal targeting and photothermal ablation of tumor hypoxia. This new photothermal therapy has the great potential as an alternative or complementary approach for standard cancer treatment to eliminate residual or recurrent tumor cells, especially within the hypoxic areas that are resistant to traditional therapies.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2889. doi:1538-7445.AM2012-2889