Microfluidic-SERS sensing system based on dual signal amplification and aptamer for gastric cancer detection

Studies have found that matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6) play an important role in tumorigenesis. In order to detect MMP-9 and IL-6 concentrations with high sensitivity and specificity, an efficient microfluidic-SERS sensing system was prepared based on surface-enhanced Raman scattering (SERS). The aptamer recognition-release mechanism and the dual signal amplification strategy were applied in the sensing system. The sensor system was developed using two kinds of nanomaterials with excellent SERS properties, namely gold-coated iron tetroxide particles (Fe₃O₄@AuNPs) and gold nanocages (AuNCs). In addition, Fe₃O₄@AuNPs also has magnetic adsorption properties. In the sensing system, single-stranded DNA1 (ssDNA1) and aptamer were modified on Fe₃O₄@AuNPs. Single-stranded DNA2 (ssDNA2) and Raman tags were modified on AuNCs. When the target was present, the aptamer bound to the target and detached from the Fe₃O₄@AuNPs, and ssDNA2 bound to the exposed ssDNA1. At this time, the Fe₃O₄@AuNPs@AuNCs@SERS tag complex was formed, and the SERS signal was enhanced for the first time. Under the action of an external magnet on the microfluidic chip, the complex was magnetized and enriched. The SERS signal was enhanced for the second time. Due to the high affinity between the aptamer and the target object, the sensing system has a strong specificity. The double amplification of the SERS signal gave the system excellent sensitivity. The limit of detection (LOD) relative to MMP-9 and IL-6 were as low as 0.178 pg/mL and 0.165 pg/mL, respectively. The microfluidic-SERS sensing system has a feasible prospect in the early screening of gastric cancer.