A combined surface-enhanced Raman spectroscopy (SERS)/colorimetric approach for the sensitive detection of malondialdehyde in biological samples.

Variations of malondialdehyde (MDA) level in biological samples often induce pathological changes, which is associated with various diseases. Here, we developed a combined surface-enhanced Raman spectroscopy (SERS) and colorimetric strategy for MDA quantitation. The methodology is based on the condensation reaction between 4-aminothiophenol (4-ATP)-modified Au nanoflowers (Au NFs) with the aldehyde groups of MDA, which causes the aggregation of the Au NFs and a concomitant change in the solution color from purple to blue and shifts in the local surface plasmon resonance band to longer wavelengths compared with monodisperse NFs. Additionally, after the condensation reaction, a new Raman peak ascribable to the CN vibration appeared at 1630 cm-1. The intensity of this peak was directly related to the concentration of MDA in solution, which allowed establishing the quantitative measurement of MDA based on SERS. The developed SERS assay displayed satisfactory sensitivity and selectivity with a broad linear range from 1.0 × 10-12 to 1.0 × 10-7 M and a low detection limit (∼3.6 × 10-13 M), outperforming other reported optical and electrochemical methods. Furthermore, the use of 4-ATP-modified Au NF probes to monitor MDA in human serum demonstrates the applicability of this combined SERS/colorimetric approach in a real environment.