SERS nano-imaging probes for characterizing extracellular surfaces

Abstract

Across extracellular surfaces, lipid rafts are believed to be an important organizing membrane microdomain component, facilitating specific protein-protein interactions by selectively excluding or including proteins into them. The lipid-based sorting mechanism of these microdomains has been implicated in many cellular processes including; membrane trafficking, signal transduction and cell growth regulation. However, since individual rafts are estimated to range in size from the nanoscale to the microscale, in many cases, they cannot be easily monitored by conventional imaging techniques. We have developed surface enhanced Raman scattering (SERS)-based nanoimaging probes for nanoscale imaging of biochemical species on and within extracellular environments. These probes synergistically combine the qualitative and quantitative information of SERS with the nanoscale imaging capabilities of tapered fiber optic bundles, potentially allowing for chemical imaging of extracellular components and chemical exchange events across cellular surfaces. These probes are fabricated from coherent fiber optic bundles containing 30,000 individual fiber elements that have been tapered to have diameters as small as 140 nm, thus allowing for image magnification and submicron spatial resolution. Due to the uniformly roughened surface features across the probe's imaging surface onto which silver island arrays are fabricated, these probes exhibit less than 3% RSD in SERS signal across the imaging area. In this work, tunability, multiplex detection capabilities and an application of these SERS nanoimaging probes to biological systems are demonstrated.