4-Thiobenzoic acid-functionalized nanocomposite probes for surface-enhanced raman spectroscopy-based detection of CA19-9 in colorectal adenocarcinoma

This study presents a novel surface-enhanced Raman spectroscopy (SERS) method for detecting CA19-9 in colorectal adenocarcinoma using 4-thiobenzoic acid (4-TBA) functionalized gold nanoparticles (nanospheres). The optimized SERS probes exhibited a maximum enhancement at pH 7 and 50 mu M 4-TBA concentration, with stable signal achieved after 2 hours of incubation. The assay demonstrated a wide dynamic range of 1-100 U/mL, with a lower limit of quantification of 1.0 U/mL. Excellent selectivity was observed against common serum interferents, with normalized SERS intensities within 10 % of CA19-9 alone. Recovery studies in spiked serum samples yielded results ranging from 94.5 % to 105.2 %, indicating minimal matrix effects. Clinical validation using 70 serum samples (50 colorectal adenocarcinoma patients, 20 healthy volunteers) showed strong agreement with a commercial ELISA kit (Pearson's r = 0.987, p < 0.0001). Bland-Altman analysis revealed a mean bias of -0.37 U/mL between SERS and ELISA methods. The SERS-based approach offers advantages including rapid analysis (<1 hour), small sample volume requirements (5-10 mu L), and potential for multiplexing. This method shows promise for early detection, disease monitoring, and treatment response evaluation in colorectal adenocarcinoma, with potential applications in both clinical and research settings.