Detection of 5-fluorouracil in saliva using surface-enhanced Raman spectroscopy

The ability of a surface-enhanced Raman active capillary to extract and detect the chemotherapy drug 5-fluorouracil (5-FU) in saliva is presented. Several methods to isolate 5-FU from potential interfering chemical components of saliva, in particular thiocyanate, were explored. It was found that this and other anions that could potentially deactivate the Raman signal enhancing properties of silver could be removed by passing the sample through an ion retardation column. It was also found that pH adjustment of the sample and the surface-enhanced Raman active capillary yielded better results, and 50 μg of 5-FU in 1 mL saliva was easily measured with an estimated limit of detection of 2 μg/mL. The entire analysis, sample preparation and spectral acquisition, required less than 5 min. However, the success of either method is based on a very limited set of saliva samples and the requirements necessary to remove anions and other physiological chemicals in saliva have not been fully defined. Nevertheless, these measurements suggest that disposable SERS-active capillaries could be used to measure 5-FU concentrations in chemotherapy patient saliva, thereby providing metabolic data that would allow regulating dosage.