Clinical Probe Utilizing Surface-Enhanced Raman Scattering (SERS) for In-Situ Molecular Imaging Applications

Abstract

In this research, a clinical probe utilizing Surface-Enhanced Raman Scattering (SERS) is developed for molecular imaging application which is a visualizing technology to support early diagnosis by providing images in molecular level. In addition to other molecular imaging applications using magnetic resonance, light, and ultrasound, Raman spectroscopy has great potential in terms of non-invasiveness, safety, imaging agent-free, and scanning multiple molecules at a time. However, the critical limitation of Raman spectroscopy using in-vivo molecular imaging application is the inherent low sensitivity of Raman effect. The challenge is overcome by employing SERS enhancing Raman scattering with concentrated electromagnetic oscillation in nanometallic structures. This phenomenon gives normal Raman spectroscopy more capabilities for diverse applications, especially for a clinical Raman probe of molecular imaging. The imaging apparatus is composed of three parts: SERS substrate with nanostructures, probe with gradient index (GRIN) lens, and signal transmission system from the spectrometer and the probe. For a transparent SERS substrate, electrochemically etched porous silicon (PS) is employed as a master mold from which a transparent UV epoxy is cast, and different thicknesses of gold (Au) are sputtered over the cast nanostructures. Rhodamine 6G solutions on the transparent SERS substrates are characterized and analyzed with various aspects in a fluidic cell. In addition to the transparent SERS substrate, a clinical probe is customized with the optical analysis of gradient-index (GRIN) lens in order to focus laser beam on SERS substrate. A transmission system, called “articulated arm” is built with multiple rotating joints which reflect laser light 90 degree. The clinical probe is assembled with transmission system, and the scanned Raman signals are transmitted from the target specimen to the Raman spectrometer. Some measurement results of a gelatin block contains Rhodamine 6G demonstrate that the developed remote probe using SERS and articulated arm show promising remote Raman detections for molecular imaging applications.