Chimeric siRNA-DNA Surfactants for the Enhanced Delivery and Sustained Cytotoxicity of a Gold(III) Metallodrug

Using a recently developed nucleic acid delivery platform, we demonstrate the effective delivery of metallodrug [Au^IIIBr₂(SSC-Inp-OEt)] (AP228; Inp = isonipecotic moiety), a hydrophobic, low solubility gold complex cytotoxic to cancer cells. It is shown that AP228 is delivered more effectively into HeLa cells using micellular surfactant assemblies compared to that of a more polar derivative [Au^IIIBr₂(SSC-Inp-GlcN1)] (AP209; GlcN1 = (α,β)-d-glucosamino moiety). When AP228 is codelivered with siRNA targeting Bcl-2, a key regulator of apoptosis, the overall cytotoxic therapeutic effects of the drug are maximized. The optimized delivery and distribution of the compound is monitored by both fluorescence microscopy and inductively coupled plasma mass spectrometry. We show that codelivery of the AP228 and Bcl-2 targeting siRNA results in a substantial increase in drug efficacy, wherein the cytotoxic therapeutic effects of the drug are maximized, reducing the IC₅₀ from 760 nM to 11 nM. This hybrid small molecule drug and therapeutic nucleic acid delivery vehicle is shown to enable both the improved solubility and uptake of the gold(III) metallodrugs and the delivery of chemically unmodified siRNA, resulting in enhanced cytotoxic effects.