SERS sensors for biomedical tubing

There is strong motivation for the development detection systems that can provide continuous analysis of fluids in medical tubing used to either deliver or remove fluids from a patient's body. Possible applications include systems that increase the safety of intravenous (IV) drug injection and point-of-care health monitoring during urinary catheterization. This talk will describe recent efforts in our group to develop nanostructured surfaces capable of performing Surface Enhanced Raman Spectroscopy (SERS) with high electromagnetic enhancement factors, while utilizing fabrication processes that enable SERS surfaces to be fabricated inexpensively on flexible plastic substrates over large areas. In particular, Glancing Angle Deposition (GLAD) has been used to provide densely packed arrays of dielectric-metal "post-cap" structures with 10-20 nm gaps between adjacent metal nanoparticles. We have also developed nanoreplica molding approaches for producing arrays of silver "nanodomes" with <10 nm gaps between domes. These two approaches are significant because they each provide a high density of electromagnetic "hot spots" for delivering strong SERS signals, while not requiring expensive, low throughput lithography processes to produce nanometer-scale surface features. The talk will describe the design, electromagnetic computer modeling, fabrication, and efforts to incorporate plastic-based SERS surfaces in-line with biomedical tubing. Using a custom-built detection instrument designed to excite SERS on the inner surface of the system, Raman spectra are gathered for typical IV-delivered pain medications and urinary metabolites, and kinetic measurements are used to track their concentrations within their clinically relevant concentration ranges. Distinct SERS peaks for each analyte are used to demonstrate co-detection of the analytes.