Design and Preparation of Nanoparticle Dimers for SERS Detection

The overarching objectives of this proposal were to develop novel reagents for the detection and identification of various proteins, antibodies, and antigens, based on the remarkable sensitivity afforded by surface enhanced Raman spectroscopy (SERS). Metal nanoparticles dimers were synthesized that incorporate SERS reporters selectively at the junction between the two metallic spheres, where signal enhancement is at its maximum. The resulting dimeric structures incorporate aptamers (aptatags) or antibodies (antitags) as the recognition elements. Preparation of suitable sensing surfaces will enable target detection down to the level of a few molecules. Furthermore, by correlating the optical signatures of the reporting chromophore with the selectivity of the agent on the antitag or aptatag surface, it should be possible to develop a single sensing surface capable of identifying multiple proteins in complex mixtures. All of the objectives stated in the original proposal were achieved. Notable highlights include the fine-tuning of chemical steps to produce antitags with femtomolar detection thresholds and the demonstration of multiplexed assays with very high levels of selectivity. A key element for the design of these highly sensitive SERS reporters involve simple to carry out surface passivation chemistry using thiolated polyethyleneglycol prior to the purification steps.
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