Self-directed Transport on Nanostructured Plasmonic Sensors

Abstract

Analytical sensors using varying detection strategies have been widely and successfully employed for advances in areas such as drug discovery, disease diagnosis and study of biological systems. Many of these sensors utilize plasmonic metallic nanostructures which can concentrate electromagnetic fields in nanoscale regions leading to many fold enhancement in optical signal obtained from the molecules. They employ techniques including fluorescence, surface plasmon resonance (SPR)-based refractive index sensing, surface-enhanced Raman spectroscopy (SERS) and other forms of vibrational spectroscopy for molecular characterization. However, the performance of these devices relies on effective transport of the target molecules to these nanoscale detection sites. Guided transport is extremely important for fast detection in cases where the concentration of molecules is really low and for accurate measurements of protein–protein binding kinetics. In this chapter, we discuss nanostructured biosensing substrates which can spontaneously direct the flow of molecules in solution towards the sensing hotspots. These devices demonstrate improved detection sensitivity, while minimizing the limitations and complexity imposed upon the system. Additionally, they can trap biological particles such as organelles and liposomes on the sensor surface, facilitating on-chip analysis of single particles. This chapter discusses a few methods which have been utilized for concentration of molecules on plasmonic sensing surfaces, without the application of external power sources.

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