(731e) Transport of Nucleic Acid Cargo Into Cells Using “Striped” Cell-Penetrating Gold Nanoparticles

A major challenge facing drug delivery is efficient targeting of bioactive cargo to specific cells or tissues. Delivery of macromolecular cargo (e.g., nucleic acids, proteins) to cells for example, is hindered by the inability of these cargos to escape membrane bound intra-cellular compartments (endosomes) during cell delivery/uptake, resulting in cargo degradation. Developing new clinically-relevant treatments requires drug delivery systems that are both biocompatible and that overcome such cellular delivery barriers. Gold nanoparticles (AuNPs) have become of great interest in drug delivery because these materials can be functionalized with a range of biological cargos with minimal toxicity, and can be efficiently cleared from the body. Highly ordered self-assembled monolayers can be assembled on the surface of small gold particles, and mixtures of hydrophobic and hydrophilic organic ligands packed on the surfaces of AuNPs via chemisorption can self-organize into nanoscale “striped” surface morphologies that can be exploited to control the interactions of AuNPs with cells.

We recently reported that highly water-soluble striped NPs that display amphiphilic mixed ligand shells composed of 11-mercapto-1-undecanesulphonateand 1-octanethiol are capable of penetrating the plasma membrane of cells, in contrast to AuNPs bearing the same hydrophilic/hydrophobic ligands in a disordered arrangement, which are taken up by endocytosis.  Here we describe a new strategy for endocytosis-independent (i.e. cell penetrating) delivery of large, membrane-impermeable macromolecular cargo (e.g., oligonucleotides) using striped cell-penetrating AuNP carriers. To determine whether striped AuNPs would retain their cell entry properties when conjugated to large polar drug cargos, the cellular uptake of striped NPs (and non-striped control particles) conjugated with thiol-terminated oligonucleotides was assessed. Strikingly, striped AuNPs conjugated to both single-stranded and double-stranded oligonucleotides were taken up by cells in vitro, even under conditions where active uptake processes (i.e., endocytosis) were blocked by incubation at 4 degrees C or through the use of pharmacological inhibitors. Control sulfonate-capped particles lacking the striped domains failed to promote oligonucleotide uptake when endocytic processes were blocked in cells, and were taken up at 50% lower levels at 37 degrees C compared to striped particles. Confocal microscopy confirmed cystosolic localization of particle-conjugated oligonucleotides carried into cells by striped AuNPs. Total oligonucleotide uptake was inversely related to oligonucleotide length for single-stranded oligonucleotides attached to striped particles, and uptake of double-stranded oligonucleotides linked to striped particles was significant but did not vary as a function of oligonucleotide length.  Together, these data suggest that striped AuNPs are of interest for intracellular delivery of membrane-impermeable drug cargos such as siRNA or immunostimulatory DNA, and ongoing studies are exploring the potential of these materials for modulating function in live cells.