Simultaneous detection of alkaline phosphatase and beta-galactosidase activity using SERRS

Surface enhanced resonance Raman scattering (SERRS) is an alternative to fluorescence for use in bioanalysis however due to the different optical mechanism it requires specifically designed reporters. Recently we have reported the use of 8-hydroxyquinolinyl azo dyes and their ester derivatives as reporters of lipase activity using SERRS. Acylation of the 8-hydroxy moiety significantly reduces surface enhancement of the Raman response and subsequent lipase catalysed ester hydrolysis enables the analyte to bind to silver nanoparticles, thus providing surface enhancement and the SERRS signal is 'switched on'. By following this principle, phosphorylated and galactosylated analogues of 8-hydroxyquinolinylazo dyes were prepared and shown to act as reporters of enzymatic activity for alkaline phosphatase and beta-galactosidase respectively when using SERRS.