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

Lactic acid is a simple and effective indicator for estimatingphysiological function. Rapid and sensitive detection of lactic acid is veryuseful in clinical diagnosis. However, the concentration of lactic acid in thephysiological state is too low to be detected using traditional Ramanspectroscopy. We applied silver colloidal nanoparticles-mediatedsurface- enhanced Raman spectroscopy (SERS) for rapid identification andquantification of lactic acid. The standard SERS spectra of lactic acid weredefined and the 1395 cm^-1 band intensity was used for quantificationfrom 0.3 to 2 mM (R² = 0.99). In clinical blood sample measurement,the ultrafiltration (cutoff value 5 kDa) can efficiently reduce backgroundfluorescence to improve SERS performance. We established identical and optimalprocedure by adjusting reaction time and volume ratio of serum and nanoparticlesto obtain high SERS reproducibility. Finally, we showed that silver colloidalnanoparticles-mediated SERS technique was successfully applied to detect lacticacid at physiological concentrations in the blood.