Development of a graphene oxide-based PEGylated fluorescent aptasensor with ultrahigh-sensitivity and anti-fouling properties for the detection of serum carcinoembryonic antigen levels.

The specificity and sensitivity of aptamer-based serum biomarker assays can be compromised by nonspecific adsorption of proteins. In this study, we used the carcinoembryonic antigen (CEA) aptamer as a model to develop a fluorescent aptasensor capable of specifically and sensitively detecting serum biomarkers. This aptasensor employs the good antifouling capability of polyethylene glycol 2000 (P2K) to enhance specificity and the good fluorescence resonance energy transfer capability of graphene oxide (GO) to improve sensitivity. The aptasensor was applied to determine pure CEA protein and CEA in clinical serum and demonstrated that the P2K-modified fluorescent aptasensor exhibited significantly superior performance in CEA detection compared with the unmodified aptasensor, including accuracy, precision, linear range, antifouling properties, and selectivity. In the detection of CEA levels in clinical serum samples, the P2K-modified fluorescent aptasensor exhibited a lower limit of detection (LOD) (1.31 vs. 1.90 ng/mL), a wider linear range (1-256 vs. 1-64 ng/mL), better recovery (92.4%-103.6% vs. 73.3%-124.1%), and a smaller relative standard deviation (RSD) (0.7%-2.5% vs. 2.0%-6.4%). The aptasensor is capable of determining CEA levels within 90 min using only 1 µL of serum, with advantages of requiring no prefabrication of sensors, measuring fluorescence intensity in a conventional microplate reader, operating experimentally at room temperature, and high-throughput detection. Conclusively, this study successfully developed a GO-based P2K-modified fluorescent aptasensor capable of specifically, sensitively, and conveniently detecting CEA levels in clinical serum samples and with potential for clinical application.