Nano Res (2008) 1: 203212

Nano-Graphene Oxide for Cellular Imaging and Drug Delivery

ABSTRACT

Two-dimensional graphene offers interesting electronic, thermal, and mechanical properties that are currently being explored for advanced electronics, membranes, and composites. Here we synthesize and explore the biological applications of nano-graphene oxide (NGO), i.e., single-layer graphene oxide sheets down to a few nanometers in lateral width. We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments. We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions. The intrinsic photoluminescence (PL) of NGO is used for live cell imaging in the near-infrared (NIR) with little background. We found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Owing to its small size, intrinsic optical properties, large speci c surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological

and medical applications.

KEYWORDS

Graphene oxide, pegylation, size separation, cellular imaging, drug delivery

Introduction

The interesting physical properties of graphene, a novel one-atom-thick two-dimensional graphitic carbon system, have led to much excitement in recent years in material science and condensed-matter physics [16]. Potential applications of graphene for nanoelectronics [1, 3], sensors, and nanocomposites [4, 5] have been actively pursued [6]. The biological applications of graphene and graphene oxide (GO) remain unexplored and wide-open, however. There are several prerequisites for biological applications for a new material. First, rational functionalization

Address correspondence to hdai@stanford.edu

chemistry is needed to impart graphene with aqueous solubility and biocompatibility. GO and its chemically converted derivatives form stable suspensions in pure water but generally aggregate in salt or other biological solutions [6]. Second, graphene sheets with suitable sizes are desired. Size control or size separation on various length scales is necessary to suitably interface with biological systems in vitro or in vivo. Graphene and GO samples obtained thus far are typically microns or larger in size. Lastly, little is known experimentally about the properties of graphene with molecular dimensions, on the order of