Surface-enhanced Raman of dopamine and neurotransmitters using sol-gel substrates and polymer-coated fiber-optic probes

Surface-enhanced Raman spectroscopy (SERS) is used to detect catecholamines -viz., dopamine, norepinephrine, epinine, and isoproterenol-using a new sub strate prepared with sol-gel technology. Catecholamines are complexed at th e surface by iron(III) ions, which were introduced during the reduction of the silver ions embedded inside the sol-gel matrix. With the use of a He-Ne laser at a power of only 12 mW, it is possible to measure dopamine in the micromolar concentration range. A single-fiber SERS probe system was also i ntroduced that has great potential for sampling in micro-environment applic ations such as in vivo measurements of dopamine. In this microprobe design both excitation and SERS signals are transmitted through the same fiber sim ultaneously. The tips of tapered fibers were coated with a polyvinyl alcoho l polymer doped with metallic silver particles. The potential of the SERS m ethod and microprobes for medical diagnostics is discussed.