Diffuse Spectroscopy For Inhomogeneous Metal Nanoparticle Assays

By Prasant Potuluri, Michael E. Sullivan, Yanqia Wang, David J. Brady, Centice

A biosensor is a device, which enables molecular recognition. The application of biosensors is widespread in areas such as medical diagnostics, drug discovery, DNA detection, proteomics and environmental detection of biological agents. The goal of a biosensor is to detect molecules (referred to as target analytes) by creating a binding event between the analyte and a receptor element. The analyte-receptor coupling transduces a signal (such as electrical or optical), which contains the information such as concentration or the identity of the target molecule. The signals generated are measured by a detector and the concentration of the target molecule is estimated. The transduction can be accomplished in several ways, the most popular of which are optical methods such as absorbance, fluorescence, Raman and Surface Enhanced Raman Scattering (“SERS”). Metal nanoparticle assays based SERS is emerging as one of the most sensitive transduction modality among biosensors [1,2,3]. The use of nanoparticle assays to induce optical signatures for molecular binding is well known. Metal nanoparticles (gold or silver) are extremely sensitive to small changes in their surround dielectric environment. Hence, their surfaces can be chemically functionalized and used to provide highly sensitive and selective detection of biological targets.