RNA binding proteins such as HuR are becoming recognized as potential mediators of cardiac physiology and pathology, but this class of proteins has traditionally been considered to be “un‐druggable” targets. Recent work from our laboratory using a cardiomyocyte‐specific HuR‐deficient mouse model has identified HuR as a novel therapeutic target for heart failure. Specifically, deletion of HuR preserves cardiac function and decreases pathological ventricular remodeling in a mouse model of heart failure. In order to identify novel HuR inhibitors, we are collaborating with the Sagle laboratory, which has significant expertise in localized surface plasmon resonance (LSPR) biosensing and recently developed a nanoparticle fabrication technique applicable to high‐throughput drug screening. Thus, the objective of this study is to adapt a multiplexed plasmonic nanoparticle platform developed by the Sagle laboratory for the development of a novel plasmonic nanoparticle‐based drug screening assay to identify small molecule inhibitors of HuR.

Gold nanoparticle arrays, 100 nm in diameter and 60 nm in height, were fabricated and thiolated DNA was covalently bound to the surface of the gold. Next, a single‐stranded RNA containing a HuR target binding site was hybridized to the nanoparticle‐bound DNA. We are then able to detect HuR protein binding to its target site within the RNA by observing a LSPR shift induced by the increased mass bound to the gold nanoparticle surface. For each step of the assembly, a significant LSPR absorbance shift was observed with the addition of DNA, RNA, and HuR protein to the nanoparticle surface. Importantly, we are able to quantitatively demonstrate a reversal of HuR‐RNA binding in the presence an experimental new inhibitor.

Our results describe a novel multiplexed plasmonic nanoparticle‐based assay suitable for high‐throughput screening of drug candidates to inhibit RNA binding proteins through a simple colorimetric (LSPR) detection method. Here we demonstrate the initial application of this approach to specifically screen for inhibitors of the RNA binding protein HuR, but this assay provides a flexible platform applicable to many RNA binding proteins by simply changing the RNA target sequence.