Gold colloid-bienzyme conjugates for glucose detection utilizing surface-enhanced Raman scattering

It is difficult to detect glucose by surface-enhanced Raman spectroscopy (SERS) due to the small normal Raman cross-section and the weak adsorption of glucose molecules on the surface of noble metal. A simple and fast method is proposed in this paper for the detection of glucose based on SERS signal of the enzyme reaction product and the difficulties have been circumvented. Gold colloids modified by horseradish peroxidase and glucose oxidase (HRP/GOD-gold colloids) are added to the mixture of o-phenylenediamine and glucose, and the resulting solution is allowed to react at room temperature for 5 min. Azoaniline, an azo compound with strong Raman scattering, is generated and the Raman scattering of this reaction product is enhanced when adsorbed on gold colloids. The intensity of the SERS spectrum is used for assessment of glucose content. The dynamic signal range provided by this analytical system is 0.50-32 mM, which covers the normal clinical range for glucose in blood from 3.5 to 6.1 mM. The detection limit is about 0.46 mM. The interference effect of several proteins on glucose detection is also investigated and has shown to have no effect on the measurement of glucose by the described technique.