Gold hybrid nanoparticles for targeted phototherapy and cancer imaging

Abstract

Gold and iron oxide hybrid nanoparticles (HNPs) synthesized by the thermaldecomposition technique are bio-functionalized with a single chain antibody, scFv,that binds to the A33 antigen present on colorectal cancer cells. The HNP–scFvconjugates are stable in aqueous solution with a magnetization value of 44 emu g − 1 and exhibit strong optical absorbance at 800 nm. Here we test this material in targeting,imaging and selective thermal killing of colorectal cancer cells. Cellular uptakestudies showed that A33-expressing cells take up the A33scFv-conjugated HNPs ata rate five times higher than cells that do not express the A33 antigen. Laserirradiation studies showed that approximately 53% of the A33-expressing cellsexposed to targeted HNPs are killed after a six-minute laser treatment at 5.1 W cm − 2 using a 808 nm continuous wave laser diode while < 5% of A33-nonexpressing cells are killed. At a higher intensity, 31.5 W cm − 2, the thermal destruction increases to 99 and 40% for A33-expressing cellsand A33 nonexpressing cells, respectively, after 6 min exposure. Flowcytometric analyses of the laser-irradiated A33 antigen-expressing cells showapoptosis-related cell death to be the primary mode of cell death at 5.1 W cm − 2, with increasing necrosis-related cell death at higher laser power. These results suggestthat this new class of bio-conjugated hybrid nanoparticles can potentially serve as aneffective antigen-targeted photothermal therapeutic agent for cancer treatment as well as aprobe for magnetic resonance-based imaging.