Plasmon-enhanced autofluorescence imaging in Deep-UV for biological cells (Invited Paper)

Recently, we achieved highly sensitive autofluorescence imaging of living HeLa cells using deep-UV SPR with the Kretschmann-Raether configuration. A buffer solution, such as N-2-hydroxyethylpiperazine-N-ethanesulfonic acid (HEPES), is essential for observing living cells. Therefore, the refractive index of specimen layer is higher than that of the atmosphere. The commonly used quartz prism, which is generally used for exciting deep-UV SPR in the Kretschmann configuration, is not sufficient under aqueous conditions. In our research, we employed a high-refractive index prism made of sapphire. The deep-UV SPR excitation of an aluminum thin film through a sapphire prism was investigated theoretically and experimentally, revealing a 2.8-fold increase in fluorescence intensities. Deep-UV SPR enhanced the autofluorescence of cell structures, with yeast cells exhibiting particularly high sensitivity. Consequently, for water-immersed specimens, the sapphire prism-based Kretschmann configuration successfully excited SPR in the deep-UV.