Novel Liposome-Based Surface-Enhanced Raman Spectroscopy (SERS) Substrate

Although great strides have been made in recent years toward making highly enhancing surface-enhanced Raman spectroscopy (SERS) substrates, the biological compatibility of such substrates remains a crucial problem. To address this issue, liposome-based SERS substrates have been constructed in which the biological probe molecule is encapsulated inside the aqueous liposome compartment, and metallic elements are assembled using the liposome as a scaffold. Therefore, the probe molecule is not in contact with the metallic surfaces. Herein we report our initial characterization of these novel nanoparticle-on-mirror substrates, both experimentally and theoretically, using finite-difference time-domain calculations. The substrates are shown to be structurally stable to laser irradiation, the liposome compartment does not rise above 45 °C, and they exhibit an analytical enhancement factor of 8 × 10⁶ for crystal violet encapsulated in 38 liposomes sandwiched between a 40 nm planar gold mirror and 80 nm gold colloid.