Gold Nanorod Mediated Mild Hyperthermia and PEGylated Human Serum Albumin Drug Delivery for Cancer Therapies

Jonathan G Mehtala, Purdue University

Abstract

Photothermally active gold nanorods were used to sensitize cells to chemotherapeutic agents by producing mildly hyperthermic effects (42-43 °C). We examined the synergistic effects of GNR-mediated mild hyperthermia (MHT) on cisplatin (CP) activity against SKOV3 ovarian cancer cells. In vitro studies were performed using CP at cytostatic concentrations (5 &mgr;M) and mPEG-stabilized GNRs (λmax 815 nm) with near-infrared laser excitation for MHT (or external heating as a positive control), followed by 72 hours incubation at 37 °C. The amount of PEG-GNRs needed for GNR-mediated MHT was determined to be 1 &mgr;g/mL, several times lower than the loadings used in tumor tissue ablation. A cell viability assay indicated 80% enhancement in CP-mediated cytotoxicity 3 days after GNR-mediated MHT relative to the projected additive effect. A pilot in vivo study showed preliminary results that cisplatin chemotherapy can be developed in combination with low loadings of GNR-mediated MHT for localized MHT to treat tumors. Stable aqueous dispersions of citrate-stabilized gold nanorods were prepared in scalable fashion by surfactant exchange from cetyltrimethylammonium bromide (CTAB)-stabilized GNRs, using sodium polystyrenesulfonate (PSS) as a detergent. Nanoparticle tracking analysis (NTA) was used to measure the size of the Cit-GNR dispersions, which provides particle sizing resolution several times better than that of dynamic light scattering (DLS). Cit-GNRs were further functionalized with human serum albumin (HSA) and thiols and dithiocarbamates (DTCs) of varying molecular weights. The quality of the Cit-GNR dispersions allows us to address fundamental questions relating GNR stabilization to surface adsorption, including insights into the formation of the protein corona in serum-containing media. Mono-PEGylated human serum albumin was synthesized to investigate its ability to improve the bioavailability of the ability of paclitaxel (PTX), a poorly soluble drug. Matrix assisted laser desportion/ionization mass spectrometry was used to confirm the formation of the mono-PEGylated adduct, and HPLC analysis revealed that 70% of native HSA was converted to HSA-mPEG. A cell viability assay with MCF-7 breast cancer cells was used to measure the enhancement of the therapeutic efficacy of a PTX formulation with HSA, HSA-mPEG 5 kDa, or HSA-mPEG 20 kDa compared to PTX in PBS in the absence of HSA. We observed that the therapeutic efficacy of PTX was maximized when it was formulated in a 10:1 molar ratio with HSA, and for intermediate PTX doses (3.3 and 6.6 nM) the therapeutic efficacy of PTX with HSA-mPEG 20 kDa was greater than that for HSA-mPEG 5 kDa. These results suggest that PTX can bind to PEGylated HSA, and that most of the drug can be released.

Degree

Ph.D.

Advisors

Wei, Purdue University.

Subject Area

Nanotechnology

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