Laser-Activated Microfluidic SERS Substrates

The development of automated microfluidic systems for ultrasensitive detection of biomaterials via surface-enhanced Raman spectroscopy (SERS) represents one of the most promising areas in current research. Within this field, special attention is directed toward SERS-based detection and analysis of extracellular vesicles, aimed at identifying disease biomarkers either in the form of microRNA and mRNA or membrane-bound proteins. However, practical applications of SERS detection systems, particularly those employing silver-based SERS substrates, are significantly limited due to their temporal instability caused by surface contamination and oxidation. In this work, we propose a fabrication method and operational concept for SERS substrates that are activated immediately prior to experimentation, serving as a basis for integration into chip-based spectral recording chambers within automated microfluidic systems. The nonactivated SERS substrates described herein can be embedded into microfluidic chips and stored for extended periods without loss of functionality, being activated just before the start of experimental procedures. A theoretical model was developed to evaluate local electromagnetic field enhancement in such SERS substrates. The sensitivity of these substrates was determined experimentally, demonstrating the feasibility of rapid detection of individual extracellular vesicles from HEK293T cells as well as their clusters.