Surface Modification and Bioconjugation of Gold Nanorods

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0906838 PI: Hamad-Schifferli, Kimberly ORG: MIT Title: Surface Modification and Bioconjugation of Gold Nanorods INTELLECTUAL MERIT: Gold nanorods (NRs) possess unique physical properties, which have made them attractive for numerous biological applications such as drug delivery, photothermal therapy, sensing of biological binding events, and ultrasonic imaging contrast agents. The biggest barrier to widespread use of NRs in biological applications is their surface coating ligand. Synthesis of NRs requires the ligand cetyl trimethyl ammonium bromide (CTAB), which is amphiphilic and forms a bilayer on the NR surface. Because CTAB binds weakly to the NR, it is fluxional, and therefore there must be excess free CTAB for the NRs to remain soluble in water. The CTAB coating not only complicates NR use in triggered release for drug delivery, but also prevents interfacing to biology. While surface chemistry of spherical nanoparticles (NPs) can be routinely modified, and NP conjugation to DNA and proteins and other biological molecules is straightforward, analogous success with Au NRs has not yet been achieved. Thus, there is a need for a way to customize the surface chemistry of NRs. A method that completely replaces CTAB with a variety of molecules is desirable. Single phase methods cannot remove CTAB completely, so the PI proposes to explore two-phase ligand extraction to modify Au NRs surfaces. She will test a range of molecules that can be put on the surface in order to expand the versatility of the surface chemistry of the NRs. The ligand exchanged NRs will be characterized by FTIR, optical absorption, TEM, electrophoretic mobility, and dynamic light scattering. Stability of the ligand-exchanged NRs will be assayed in water and buffers. After ligand exchange the NRs will be functionalized with thiolated DNA oligonucleotides of varying lengths (15-50mers). The DNA function will be probed by quantifying its ability to hybridize to a complement and also by measuring the biophysical properties of the NR-DNA conjugates such as zeta potential and hydrodynamic radius. The stability of the NR-DNA conjugates will be assayed, and the conditions and surface chemistry that maximize DNA loading and function will be determined. BROADER IMPACTS: Potential applications of surface-modified NRs include use as drug delivery or photothermal devices triggered by highly penetrating infrared radiation in a wavelength range where water and tissue are generally transparent. Many imaging applications can also be envisaged for NRs targeted for specific tissues. The PI describes in detail a planned workshop designed to inform female (and male) students about successful strategies for negotiating a successful academic or scientific career while raising a family.