Surface-enhanced Raman spectroscopy for quantitative measurement of lactic acid at physiological concentration in human serum

Lactic acid is a simple and effective indicator for estimating physiological function. Rapid and sensitive detection of lactic acid is very useful in clinical diagnosis. However, the concentration of lactic acid in the physiological state is too low to be detected using traditional Raman spectroscopy. We applied silver colloidal nanoparticles-mediated surface-enhanced Raman spectroscopy (SERS) for rapid identification and quantification of lactic acid. The standard SERS spectra of lactic acid were defined and the 1395 cm(-1) band intensity was used for quantification from 0.3 to 2 mM (R(2) = 0.99). In clinical blood sample measurement, the ultrafiltration (cutoff value 5 kDa) can efficiently reduce background fluorescence to improve SERS performance. We established identical and optimal procedure by adjusting reaction time and volume ratio of serum and nanoparticles to obtain high SERS reproducibility. Finally, we showed that silver colloidal nanoparticles-mediated SERS technique was successfully applied to detect lactic acid at physiological concentrations in the blood. Copyright (C) 2010 John Wiley & Sons, Ltd.