Flexible 2D S-CNF/Au NSs substrate for detection of malondialdehyde in serum of gastric cancer patients

A two-dimensional (2D) substrate composed of nanocellulose-gold nanostars (S-CNF/Au NSs) was prepared, which exhibited remarkable homogeneity and stability. P-aminothiophenol (PATP) was modified on the S-CNF/Au NSs substrate by Au–S bonds. The amino group of PATP was utilized to react with the aldehyde group of malondialdehyde (MDA) in a Schiff base reaction, resulting in a new Raman peak at 1655 cm⁻¹ attributed to C = N vibration. Since the intensity of the Raman peak at 1078 cm⁻¹ was hardly affected under acidic conditions, the ratio of the characteristic peak of C = N (1655 cm⁻¹) to the peak intensity at 1078 cm⁻¹ was used as a characterization of the MDA concentration. The precision of signal intensity was further corrected to improve confidence of the results. The developed SERS sensing system displayed satisfactory sensitivity with a linear detection range of 1 × 10^–9 ~ 2.5 × 10^–2 mM and a limit of detection (LOD) of 1.29 × 10^–11 mM. The S-CNF/Au NSs 2D substrate was able to sensitively differentiate serum from gastric cancer patients and healthy individuals by SERS analysis (p < 0.0001), which was superior to colorimetric analysis (p < 0.01). This result suggests that the proposed S-CNF/Au NSs 2D substrate has potential for MDA detection and can be used for early diagnosis of gastric cancer.