Targeting Ultrasmall Gold Nanoparticles with cRGD Peptide Increases the Uptake and Efficacy of Cytotoxic Payload.

Cyclic arginyl-glycyl-aspartic acid peptide (cRGD) peptides show a high affinity towards αVß3 integrin, a receptor overexpressed in many cancers. We aimed to combine the versatility of ultrasmall gold nanoparticles (usGNP) with the target selectivity of cRGD peptide for the directed delivery of a cytotoxic payload in a novel design. usGNPs were synthesized with a modified Brust-Schiffrin method and functionalized via amide coupling and ligand exchange and their uptake, intracellular trafficking, and toxicity were characterized. Our cRGD functionalized usGNPs demonstrated increased cellular uptake by αVß3 integrin expressing cells, are internalized via clathrin-dependent endocytosis, accumulated in the lysosomes, and when loaded with mertansine led to increased cytotoxicity. Targeting via cRGD functionalization provides a mechanism to improve the efficacy, tolerability, and retention of therapeutic GNPs.

Absolute Quantification of Gold Nanoparticles with Femtomolar Accuracy Using Inductively Coupled Plasma Atomic Emission Spectroscopy.

Here we describe a label-free method for the detection and absolute quantification of gold nanoparticles (AuNPs). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) is used to detect less than a nanogram of AuNPs from complex unpurified biological samples. This corresponds to approximately femtomolar concentration range of AuNPs. ICP-AES is a nonoptical analytical technique which is unaffected by optically active molecules, opaque solutions, and organic or inorganic contaminants. It is therefore superior to traditional methods of detecting AuNPs based on the distinctive extinction peak in the visible spectrum. This method is compatible with high-throughput automated applications in life science and environmental research.